document_title: Retina

question_text: where do the blood vessels that supply the retinal cells lie

text: Retina

text: Structure[edit]

text: Inverted versus non-inverted retina[edit]

text: The vertebrate retina is inverted in the sense that the light sensing cells are in back of the retina, so that light has to pass through layers of neurons and capillaries before it reaches the rods and cones. In contrast, in the cephalopod retina the photoreceptors are in front, with processing neurons and capillaries behind them. Because of this, cephalopods do not have a blind spot.

text: The overlying neural fibre layer does not degrade vision in the inverted retina. The neurons are transparent and the accompanying glial cells have been shown to act as fibre-optic channels to transport photons directly to the photoreceptors.[4][5] In any case, the fovea centralis, the part of the retina with the highest resolution, does not have a layer of blood vessels and nerve cells over it, so there is no possibility of image degradation here.

text: The cephalopods have a non-inverted retina which is comparable in resolving power to the eyes of many vertebrates. Squid eyes do not have an analog of the vertebrate retinal pigment epithelium (RPE). Although their photoreceptors contain a protein, retinochrome, that recycles retinal and replicates one of the functions of the vertebrate RPE, one could argue that cephalopod photoreceptors are not maintained as well as in vertebrates and that, as a result, the useful lifetime of photoreceptors in invertebrates is much shorter than in vertebrates.[6] Having easily replaced stalk-eyes (some lobsters) or retinae (some spiders, such as Deinopis[7]) rarely occurs.

text: The cephalopod retina does not originate as an outgrowth of the brain, as the vertebrate one does. It is arguable that this difference shows that vertebrate and cephalopod eyes are not homologous but have evolved separately. From an evolutionary perspective, a more complex structure such as the inverted retina can generally come about as a consequence of two alternate processes: (a) an advantageous "good" compromise between competing functional limitations, or (b) as a historical maladaptive relic of the convoluted path of organ evolution and transformation. Vision is an important adaptation in higher vertebrates.

text: Retinal layers[edit]

text: The vertebrate retina has ten distinct layers.[9] From closest to farthest from the vitreous body:

text:
Inner limiting membrane – basement membrane elaborated by Müller cells.
Nerve fibre layer – axons of the ganglion cell nuclei (note that a thin layer of Müller cell footplates exists between this layer and the inner limiting membrane).
Ganglion cell layer – contains nuclei of ganglion cells, the axons of which become the optic nerve fibres for messages and some displaced amacrine cells.[2]
Inner plexiform layer – contains the synapse between the bipolar cell axons and the dendrites of the ganglion and amacrine cells.[2]
Inner nuclear layer – contains the nuclei and surrounding cell bodies (perikarya) of the amacrine cells, bipolar cells, and horizontal cells.[2]
Outer plexiform layer – projections of rods and cones ending in the rod spherule and cone pedicle, respectively. These make synapses with dendrites of bipolar cells.[2] In the macular region, this is known as the Fiber layer of Henle.
Outer nuclear layer – cell bodies of rods and cones.
External limiting membrane – layer that separates the inner segment portions of the photoreceptors from their cell nucleus.
Layer of rods and cones – layer of rod cells and cone cells.
Retinal pigment epithelium – single layer of cuboidal cells (with extrusions not shown in diagram). This is closest to the choroid.

text: These layers can be grouped into 4 main processing stages: photoreception; transmission to bipolar cells; transmission to ganglion cells, which also contain photoreceptors, the photosensitive ganglion cells; and transmission along the optic nerve. At each synaptic stage there are also laterally connecting horizontal and amacrine cells.

text: The optic nerve is a central tract of many axons of ganglion cells connecting primarily to the lateral geniculate body, a visual relay station in the diencephalon (the rear of the forebrain). It also projects to the superior colliculus, the suprachiasmatic nucleus, and the nucleus of the optic tract. It passes through the other layers, creating the optic disc in primates.[10]

text: Additional structures, not directly associated with vision, are found as outgrowths of the retina in some vertebrate groups. In birds, the pecten is a vascular structure of complex shape that projects from the retina into the vitreous humour; it supplies oxygen and nutrients to the eye, and may also aid in vision. Reptiles have a similar, but much simpler, structure.[11]

text: In adult humans, the entire retina is approximately 72% of a sphere about 22 mm in diameter. The entire retina contains about 7 million cones and 75 to 150 million rods. The optic disc, a part of the retina sometimes called "the blind spot" because it lacks photoreceptors, is located at the optic papilla, where the optic-nerve fibres leave the eye. It appears as an oval white area of 3 mm². Temporal (in the direction of the temples) to this disc is the macula, at whose centre is the fovea, a pit that is responsible for our sharp central vision but is actually less sensitive to light because of its lack of rods. Human and non-human primates possess one fovea, as opposed to certain bird species, such as hawks, who are bifoviate, and dogs and cats, who possess no fovea but a central band known as the visual streak.[citation needed] Around the fovea extends the central retina for about 6 mm and then the peripheral retina. The farthest edge of the retina is defined by the ora serrata. The distance from one ora to the other (or macula), the most sensitive area along the horizontal meridian is about 32 mm.[clarification needed]

text: In section, the retina is no more than 0.5 mm thick. It has three layers of nerve cells and two of synapses, including the unique ribbon synapse. The optic nerve carries the ganglion cell axons to the brain, and the blood vessels that supply the retina. The ganglion cells lie innermost in the eye while the photoreceptive cells lie beyond. Because of this counter-intuitive arrangement, light must first pass through and around the ganglion cells and through the thickness of the retina, (including its capillary vessels, not shown) before reaching the rods and cones. Light is absorbed by the retinal pigment epithelium or the choroid (both of which are opaque).

text: The white blood cells in the capillaries in front of the photoreceptors can be perceived as tiny bright moving dots when looking into blue light. This is known as the blue field entoptic phenomenon (or Scheerer's phenomenon).

text: Between the ganglion cell layer and the rods and cones there are two layers of neuropils where synaptic contacts are made. The neuropil layers are the outer plexiform layer and the inner plexiform layer. In the outer neuropil layer, the rods and cones connect to the vertically running bipolar cells, and the horizontally oriented horizontal cells connect to ganglion cells.

text: The central retina predominantly contains cones, while the peripheral retina predominantly contains rods. In total, there are about seven million cones and a hundred million rods. At the centre of the macula is the foveal pit where the cones are narrow and long, and, arranged in a hexagonal mosaic, the most dense. At the foveal pit the other retinal layers are displaced, before building up along the foveal slope until the rim of the fovea, or parafovea, is reached, which is the thickest portion of the retina. The macula has a yellow pigmentation, from screening pigments, and is known as the macula lutea. The area directly surrounding the fovea has the highest density of rods converging on single bipolar cells. Since its cones have a much lesser convergence of signals, the fovea allows for the sharpest vision the eye can attain.[2]

text: Though the rod and cones are a mosaic of sorts, transmission from receptors, to bipolars, to ganglion cells is not direct. Since there are about 150 million receptors and only 1 million optic nerve fibres, there must be convergence and thus mixing of signals. Moreover, the horizontal action of the horizontal and amacrine cells can allow one area of the retina to control another (e.g. one stimulus inhibiting another). This inhibition is key to lessening the sum of messages sent to the higher regions of the brain. In some lower vertebrates (e.g. the pigeon), there is a "centrifugal" control of messages – that is, one layer can control another, or higher regions of the brain can drive the retinal nerve cells, but in primates this does not occur.[2]

text: Layers imagable with Optical Coherence Tomography (OCT)[edit]

text: On OCT there are 18 layers that can be identified in the retina. The layers and anatomical correlation are as follows:[12][13][14]

text: From innermost to outermost, the layers identifiable by OCT are as follows:

text:
#
OCT Layer / Conventional Label
Anatomical Correlate
Reflectivity
on OCT

Specific
anatomical
boundaries?

Additional
references

1
Posterior cortical vitreous
Posterior cortical vitreous
Hyper-reflective
Yes
[13]

2
Preretinal space
In eyes where the vitreous has fully or partially detached from the retina, this is the space created between the posterior cortical vitreous face and the internal limiting membrane of the retina.
Hypo-reflective

[13]

3
Internal limiting membrane (ILM)
Formed by Müller cell endfeet
(unclear if it can be observed on OCT)

Hyper-reflective
No
[13]

Nerve fiber layer (NFL)
Ganglion cell axons travelling towards the optic nerve

4
Ganglion cell layer (GCL)
Ganglion cell bodies (and some displaced amacrine cells)
Hypo-reflective

[13]

5
Inner plexiform layer (IPL)
Synapses between bipolar, amacrine and ganglion cells
Hyper-reflective

[13]

6
Inner nuclear layer (INL)
a) Horizontal, bipolar and amacrine cell bodies
b) Müller cell nuclei

Hypo-reflective

[13]

7
Outer plexiform layer (OPL)
Synapses between photoreceptor, bipolar and horizontal cells
Hyper-reflective

[13]

8
(Inner half) Henle’s nerve fiber layer (HL)
Photoreceptor axons
(obliquely orientated fibres; not present in mid-peripheral or peripheral retina)

Hypo-reflective
No
[13]

(Outer half) Outer nuclear layer (ONL)
The photoreceptor cell bodies

9
External limiting membrane (ELM)
Made of zonulae adherens between Müller cells and photoreceptor inner segments
Hyper-reflective

[13]

10
Myoid zone (MZ)
The innermost portion of the photoreceptor inner segment (IS) containing:

Smooth and rough endoplasmic reticulum
Ribosomes
Golgi bodies
Microtubules
(rarely: mitochondria)

Hypo-reflective
No
[15][16]

11
Ellipsoid zone (EZ)
The outermost portion of the photoreceptor inner segment (IS) packed with mitochondria
Very Hyper-reflective
No
[17][18][19] [20][21][22]

IS/OS junction or Photoreceptor integrity line (PIL)
The photoreceptor connecting cilia which bridge the inner and outer segments of the photoreceptor cells.

12
Photoreceptor outer segments (OS)
The photoreceptor outer segments (OS) which contain disks filled with opsin, the molecule that absorbs photons.
Hypo-reflective

[23][13]

13
Interdigitation zone (IZ)
Apices of the RPE cells which encase part of the cone OSs.
Poorly distinguishable from RPE. Previously: "cone outer segment tips line" (COST)

Hyper-reflective
No

14
RPE/Bruch’s complex
RPE phagosome zone
Very Hyper-reflective
No
[24][13]

RPE melanosome zone
Hypo-reflective

RPE mitochondria zone + Junction between the RPE & Bruch's membrane
Very Hyper-reflective

15
Choriocapillaris
Thin layer of moderate reflectivity in inner choroid
No
[13]

16
Sattler’s layer
Thick layer of round or ovalshaped hyperreflective profiles, with hyporeflective cores in mid-choroid

[13]

17
Haller’s layer
Thick layer of oval-shaped hyperreflective profiles, with hyporeflective cores in outer choroid

[13]

18
Choroidal-scleral juncture
Zone at the outer choroid with a marked change in texture, in which large circular or ovoid profiles abut a
homogenous region of variable reflectivity

[13]

text: Development[edit]

text: Retinal development begins with the establishment of the eye fields mediated by the SHH and SIX3 proteins, with subsequent development of the optic vesicles regulated by the PAX6 and LHX2 proteins.[25] The role of Pax6 in eye development was elegantly demonstrated by Walter Gehring and colleagues, who showed that ectopic expression of Pax6 can lead to eye formation on Drosophila antennae, wings, and legs.[26] The optic vesicle gives rise to three structures: the neural retina, the retinal pigmented epithelium, and the optic stalk. The neural retina contains the retinal progenitor cells (RPCs) that give rise to the seven cell types of the retina. Differentiation begins with the retinal ganglion cells and concludes with production of the Muller glia. Although each cell type differentiates from the RPCs in a sequential order, there is considerable overlap in the timing of when individual cell types differentiate.[25] The cues that determine a RPC daughter cell fate are coded by multiple transcription factor families including the bHLH and homeodomain factors.[27]

text: In addition to guiding cell fate determination, cues exist in the retina to determine the dorsal-ventral (D-V) and nasal-temporal (N-T) axes. The D-V axis is established by a ventral to dorsal gradient of VAX2, whereas the N-T axis is coordinated by expression of the forkhead transcription factors FOXD1 and FOXG1. Additional gradients are formed within the retina that aid in proper targeting of RGC axons that function to establish the retinotopic map.[25]

text: Blood supply[edit]

text:
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text: The retina is stratified into distinct layers, each containing specific cell types or cellular compartments[28] that have metabolisms with different nutritional requirements.[29] To satisfy these requirements, the ophthalmic artery bifurcates and supplies the retina via two distinct vascular networks: the choroidal network, which supplies the choroid and the outer retina, and the retinal network, which supplies the retina's inner layer.[30]

text: Circulatory mechanisms[edit]

text: At first glance, one may think that the vertebrate retina is "wired wrongly" or "badly designed"; but in fact, the retina could not function if it were not inverted. The photoreceptor layer must be embedded in the retinal pigment epithelium (RPE), which performs at least seven vital functions,[31] one of the most obvious being to supply oxygen and other necessary nutrients needed for the photoreceptors to function. These nutrients include glucose, fatty acids, and retinal. The mammalian photoreceptor amplification process uses large quantities energy for vision in photopic conditions (requiring less under scotopic conditions) and, thus, requires the large supply nutrients supplied by the blood vessels in the choroid, which lies beyond the RPE. The choroid supplies about 75% of these nutrients to the retina and the retinal vasculature only 25%.[32]

text: When light strikes 11-cis-retinal (in the disks in the rods and cones), 11-cis-retinal changes to all-trans-retinal which then triggers changes in the opsins. Now, the outer segments do not regenerate the retinal back into the cis- form once it has been changed by light. Instead the retinal is pumped out to the surrounding RPE where it is regenerated and transported back into the outer segments of the photoreceptors. This recycling function of the RPE protects the photoreceptors against photo-oxidative damage[33][34] and allows the photoreceptor cells to have decades-long useful lives.

text: In birds[edit]

text: The bird retina is devoid of blood vessels, perhaps to give unobscured passage of light for forming images, thus giving better resolution. It is, therefore, a considered view that the bird retina depends for nutrition and oxygen supply on a specialized organ, called the "pecten" or pecten oculi, located on the blind spot or optic disk. This organ is extremely rich in blood vessels and is thought to supply nutrition and oxygen to the bird retina by diffusion through the vitreous body. The pecten is highly rich in alkaline phosphatase activity and polarized cells in its bridge portion – both befitting its secretory role.[35] Pecten cells are packed with dark melanin granules, which have been theorized to keep this organ warm with the absorption of stray light falling on the pecten. This is considered to enhance metabolic rate of the pecten, thereby exporting more nutritive molecules to meet the stringent energy requirements of the retina during long periods of exposure to light.[36]

text: Biometric identification and diagnosis of disease[edit]

text: The bifurcations and other physical characteristics of the inner retinal vascular network are known to vary among individuals,[37] and these individual variances have been used for biometric identification and for early detection of the onset of disease. The mapping of vascular bifurcations is one of the basic steps in biometric identification.[38] Results of such analyses of retinal blood vessel structure can be evaluated against the ground truth data[39] of vascular bifurcations of retinal fundus images that are obtained from the DRIVE dataset.[40] In addition, the classes of vessels of the DRIVE dataset have also been identified,[41] and an automated method for accurate extraction of these bifurcations is also available.[42] Changes in retinal blood circulation are seen with aging[43] and exposure to air pollution,[44] and may indicate cardiovascular diseases such as hypertension and atherosclerosis.[45][46][47] Determining the equivalent width of arterioles and venules near the optic disc is also a widely used technique to identify cardiovascular risks.[48]

text: Function[edit]

text: The retina translates an optical image into neural impulses by the patterned excitation of the colour-sensitive pigments of its rods and cones, the retina's photoreceptor cells. The excitation is processed by the neural system and various parts of the brain working in parallel to form a representation of the external environment in the brain.

text: The cones respond to bright light and mediate high-resolution colour vision during daylight illumination (also called photopic vision). The rods are saturated at daylight levels and don't contribute to pattern vision. However, rods do respond to dim light and mediate lower-resolution, monochromatic vision under very low levels of illumination (called scotopic vision). The illumination in most office settings falls between these two levels and is called mesopic vision. At mesopic light levels, both the rods and cones are actively contributing pattern information. What contribution the rod information makes to pattern vision under these circumstances is unclear.

text: The response of cones to various wavelengths of light is called their spectral sensitivity. In normal human vision, the spectral sensitivity of a cone falls into one of three subtypes, often called blue, green, or red but more accurately known as short, medium, or long wavelength-sensitive cone subtypes. It is a lack of one or more of the cone subtypes that causes individuals to have deficiencies in colour vision or various kinds of colour blindness. These individuals are not blind to objects of a particular colour but are unable to distinguish between colours that can be distinguished by people with normal vision. Humans have this trichromatic vision, while most other mammals lack cones with red sensitive pigment and therefore have poorer dichromatic colour vision. However, some animals have four spectral subtypes, e.g. the trout adds an ultraviolet subgroup to short, medium, and long subtypes that are similar to humans. Some fish are sensitive to the polarization of light as well.

text: In the photoreceptors, exposure to light hyperpolarizes the membrane in a series of graded shifts. The outer cell segment contains a photopigment. Inside the cell the normal levels of cyclic guanosine monophosphate (cGMP) keep the Na+ channel open, and thus in the resting state the cell is depolarised. The photon causes the retinal bound to the receptor protein to isomerise to trans-retinal. This causes the receptor to activate multiple G-proteins. This in turn causes the Ga-subunit of the protein to activate a phosphodiesterase (PDE6), which degrades cGMP, resulting in the closing of Na+ cyclic nucleotide-gated ion channels (CNGs). Thus the cell is hyperpolarised. The amount of neurotransmitter released is reduced in bright light and increases as light levels fall. The actual photopigment is bleached away in bright light and only replaced as a chemical process, so in a transition from bright light to darkness the eye can take up to thirty minutes to reach full sensitivity.

text: When thus excited by light, the photoceptor sends a proportional response synaptically to bipolar cells which in turn signal the retinal ganglion cells. The photoreceptors are also cross-linked by horizontal cells and amacrine cells, which modify the synaptic signal before it reaches the ganglion cells, the neural signals being intermixed and combined. Of the retina's nerve cells, only the retinal ganglion cells and few amacrine cells create action potentials.

text: In the retinal ganglion cells there are two types of response, depending on the receptive field of the cell. The receptive fields of retinal ganglion cells comprise a central, approximately circular area, where light has one effect on the firing of the cell, and an annular surround, where light has the opposite effect. In ON cells, an increment in light intensity in the centre of the receptive field causes the firing rate to increase. In OFF cells, it makes it decrease. In a linear model, this response profile is well described by a difference of Gaussians and is the basis for edge detection algorithms. Beyond this simple difference, ganglion cells are also differentiated by chromatic sensitivity and the type of spatial summation. Cells showing linear spatial summation are termed X cells (also called parvocellular, P, or midget ganglion cells), and those showing non-linear summation are Y cells (also called magnocellular, M, or parasol retinal ganglion cells), although the correspondence between X and Y cells (in the cat retina) and P and M cells (in the primate retina) is not as simple as it once seemed.

text: In the transfer of visual signals to the brain, the visual pathway, the retina is vertically divided in two, a temporal (nearer to the temple) half and a nasal (nearer to the nose) half. The axons from the nasal half cross the brain at the optic chiasma to join with axons from the temporal half of the other eye before passing into the lateral geniculate body.

text: Although there are more than 130 million retinal receptors, there are only approximately 1.2 million fibres (axons) in the optic nerve. So, a large amount of pre-processing is performed within the retina. The fovea produces the most accurate information. Despite occupying about 0.01% of the visual field (less than 2° of visual angle), about 10% of axons in the optic nerve are devoted to the fovea. The resolution limit of the fovea has been determined to be around 10,000 points.[clarification needed] The information capacity is estimated at 500,000 bits per second (for more information on bits, see information theory) without colour or around 600,000 bits per second including colour.[citation needed]

text: Spatial encoding[edit]

text: When the retina sends neural impulses representing an image to the brain, it spatially encodes (compresses) those impulses to fit the limited capacity of the optic nerve. Compression is necessary because there are 100 times more photoreceptor cells than ganglion cells. This is done by "decorrelation", which is carried out by the "centre–surround structures", which are implemented by the bipolar and ganglion cells.

text: There are two types of centre–surround structures in the retina – on-centres and off-centres. On-centres have a positively weighted centre and a negatively weighted surround. Off-centres are just the opposite. Positive weighting is more commonly known as excitatory, and negative weighting as inhibitory.

text: These centre–surround structures are not physical apparent, in the sense that one cannot see them by staining samples of tissue and examining the retina's anatomy. The centre–surround structures are logical (i.e., mathematically abstract) in the sense that they depend on the connection strengths between bipolar and ganglion cells. It is believed that the connection strengths between cells is caused by the number and types of ion channels embedded in the synapses between the bipolar and ganglion cells.

text: The centre–surround structures are mathematically equivalent to the edge detection algorithms used by computer programmers to extract or enhance the edges in a digital photograph. Thus, the retina performs operations on the image-representing impulses to enhance the edges of objects within its visual field. For example, in a picture of a dog, a cat and a car, it is the edges of these objects that contain the most information. In order for higher functions in the brain (or in a computer for that matter) to extract and classify objects such as a dog and a cat, the retina is the first step to separating out the various objects within the scene.

text: As an example, the following matrix is at the heart of the computer algorithm that implements edge detection. This matrix is the computer equivalent to the centre–surround structure. In this example, each box (element) within this matrix would be connected to one photoreceptor. The photoreceptor in the centre is the current receptor being processed. The centre photoreceptor is multiplied by the +1 weight factor. The surrounding photoreceptors are the "nearest neighbors" to the centre and are multiplied by the -1/8 value. The sum of all nine of these elements is finally calculated. This summation is repeated for every photoreceptor in the image by shifting left to the end of a row and then down to the next line.

text:
-1/8
-1/8
-1/8

-1/8
+1
-1/8

-1/8
-1/8
-1/8

text: The total sum of this matrix is zero, if all the inputs from the nine photoreceptors are of the same value. The zero result indicates the image was uniform (non-changing) within this small patch. Negative or positive sums mean the image was varying (changing) within this small patch of nine photoreceptors.

text: The above matrix is only an approximation to what really happens inside the retina. The differences are:

text:
The above example is called "balanced". The term balanced means that the sum of the negative weights is equal to the sum of the positive weights so that they cancel out perfectly. Retinal ganglion cells are almost never perfectly balanced.
The table is square while the centre–surround structures in the retina are circular.
Neurons operate on spike trains traveling down nerve cell axons. Computers operate on a single floating point number that is essentially constant from each input pixel. (The computer pixel is basically the equivalent of a biological photoreceptor.)
The retina performs all these calculations in parallel while the computer operates on each pixel one at a time. The retina performs no repeated summations and shifting as would a computer.
Finally, the horizontal and amacrine cells play a significant role in this process, but that is not represented here.

text: Here is an example of an input image and how edge detection would modify it.

text: Once the image is spatially encoded by the centre–surround structures, the signal is sent out along the optic nerve (via the axons of the ganglion cells) through the optic chiasm to the LGN (lateral geniculate nucleus). The exact function of the LGN is unknown at this time. The output of the LGN is then sent to the back of the brain. Specifically, the output of the LGN "radiates" out to the V1 primary visual cortex.

text: Simplified signal flow: Photoreceptors → Bipolar → Ganglion → Chiasm → LGN → V1 cortex

text: Clinical significance[edit]

text: There are many inherited and acquired diseases or disorders that may affect the retina. Some of them include:

text:
Retinitis pigmentosa is a group of genetic diseases that affect the retina and cause the loss of night vision and peripheral vision.
Macular degeneration describes a group of diseases characterized by loss of central vision because of death or impairment of the cells in the macula.
Cone-rod dystrophy (CORD) describes a number of diseases where vision loss is caused by deterioration of the cones and/or rods in the retina.
In retinal separation, the retina detaches from the back of the eyeball. Ignipuncture is an outdated treatment method. The term retinal detachment is used to describe a separation of the neurosensory retina from the retinal pigment epithelium.[49] There are several modern treatment methods for fixing a retinal detachment: pneumatic retinopexy, scleral buckle, cryotherapy, laser photocoagulation and pars plana vitrectomy.
Both hypertension and diabetes mellitus can cause damage to the tiny blood vessels that supply the retina, leading to hypertensive retinopathy and diabetic retinopathy.
Retinoblastoma is a cancer of the retina.
Retinal diseases in dogs include retinal dysplasia, progressive retinal atrophy, and sudden acquired retinal degeneration.
Lipemia retinalis is a white appearance of the retina, and can occur by lipid deposition in lipoprotein lipase deficiency.

text: Diagnosis[edit]

text: A number of different instruments are available for the diagnosis of diseases and disorders affecting the retina. Ophthalmoscopy and fundus photography have long been used to examine the retina. Recently, adaptive optics has been used to image individual rods and cones in the living human retina, and a company based in Scotland has engineered technology that allows physicians to observe the complete retina without any discomfort to patients.[50]

text: The electroretinogram is used to non-invasively measure the retina's electrical activity, which is affected by certain diseases. A relatively new technology, now becoming widely available, is optical coherence tomography (OCT). This non-invasive technique allows one to obtain a 3D volumetric or high resolution cross-sectional tomogram of the fine structures of the retina, with histologic quality.

text: Treatment[edit]

text: Treatment depends upon the nature of the disease or disorder.

text: Common treatment modalities[edit]

text: The following are commonly modalities of management for retinal disease:

text:
Intravitreal medication, such as anti-VEGF or corticosteroid agents
Vitreoretinal surgery
Use of nutritional supplements
Modification of systemic risk factors for retinal disease

text: Uncommon treatment modalities[edit]

text:
showRare or uncommon methods of treatment for retinal disease

Retinal gene therapy
Main article: Adeno associated virus and gene therapy of the human retina
Gene therapy holds promise as a potential avenue to cure a wide range of retinal diseases. This involves using a non-infectious virus to shuttle a gene into a part of the retina. Recombinant adeno-associated virus (rAAV) vectors possess a number of features that render them ideally suited for retinal gene therapy, including a lack of pathogenicity, minimal immunogenicity, and the ability to transduce postmitotic cells in a stable and efficient manner.[51] rAAV vectors are increasingly utilized for their ability to mediate efficient transduction of retinal pigment epithelium (RPE), photoreceptor cells and retinal ganglion cells. Each cell type can be specifically targeted by choosing the appropriate combination of AAV serotype, promoter, and intraocular injection site.
Several clinical trials have already reported positive results using rAAV to treat Leber's congenital amaurosis, showing that the therapy was both safe and effective.[52][53] There were no serious adverse events, and patients in all three studies showed improvement in their visual function as measured by a number of methods. The methods used varied among the three trials, but included both functional methods such as visual acuity[53][54][55] and functional mobility[54][55][56] as well as objective measures that are less susceptible to bias, such as the pupil's ability to respond to light[52][57] and improvements on functional MRI.[58] Improvements were sustained over the long-term, with patients continuing to do well after more than 1.5 years.[52][53]
The unique architecture of the retina and its relatively immune-privileged environment help this process.[59] Tight junctions that form the blood retinal barrier separate the subretinal space from the blood supply, thus protecting it from microbes and most immune-mediated damage, and enhancing its potential to respond to vector-mediated therapies. The highly compartmentalized anatomy of the eye facilitates accurate delivery of therapeutic vector suspensions to specific tissues under direct visualization using microsurgical techniques.[60] In the sheltered environment of the retina, AAV vectors are able to maintain high levels of transgene expression in the retinal pigmented epithelium (RPE), photoreceptors, or ganglion cells for long periods of time after a single treatment. In addition, the eye and the visual system can be routinely and easily monitored for visual function and retinal structural changes after injections with noninvasive advanced technology, such as visual acuities, contrast sensitivity, fundus auto-fluorescence (FAF), dark-adapted visual thresholds, vascular diameters, pupillometry, electroretinography (ERG), multifocal ERG and optical coherence tomography (OCT).[61]
This strategy is effective against a number of retinal diseases that have been studied, including neovascular diseases that are features of age-related macular degeneration, diabetic retinopathy and retinopathy of prematurity. Since the regulation of vascularization in the mature retina involves a balance between endogenous positive growth factors, such as vascular endothelial growth factor (VEGF) and inhibitors of angiogenesis, such as pigment epithelium-derived factor (PEDF), rAAV-mediated expression of PEDF, angiostatin, and the soluble VEGF receptor sFlt-1, which are all antiangiogenic proteins, have been shown to reduce aberrant vessel formation in animal models.[62] Since specific gene therapies cannot readily be used to treat a significant fraction of patients with retinal dystrophy, there is a major interest in developing a more generally applicable survival factor therapy. Neurotrophic factors have the ability to modulate neuronal growth during development to maintain existing cells and to allow recovery of injured neuronal populations in the eye. AAV encoding neurotrophic factors such as fibroblast growth factor (FGF) family members and GDNF either protected photoreceptors from apoptosis or slowed down cell death.[62]
Organ transplantation Transplantation of retinas has been attempted, but without much success. At MIT, The University of Southern California, RWTH Aachen University, and the University of New South Wales, an "artificial retina" is under development: an implant which will bypass the photoreceptors of the retina and stimulate the attached nerve cells directly, with signals from a digital camera.

text: Notable researchers and discoveries[edit]

text: In 1894, Santiago Ramón y Cajal published the first major characterization of retinal neurons in Retina der Wirbelthiere (The Retina of Vertebrates).[63]

text: George Wald, Haldan Keffer Hartline, and Ragnar Granit won the 1967 Nobel Prize in Physiology or Medicine for their scientific research on the retina.[64]

text: A recent University of Pennsylvania study calculated that the approximate bandwidth of human retinas is 8.75 megabits per second, whereas a guinea pig's retinal transfer rate is 875 kilobits per second.[65]

text: MacLaren & Pearson and colleagues at University College London and Moorfields Eye Hospital in London, in 2006, showed that photoreceptor cells could be transplanted successfully in the mouse retina if donor cells were at a critical developmental stage.[66] Recently Ader and colleagues in Dublin showed, using the electron microscope, that transplanted photoreceptors formed synaptic connections.[67]

text: In 2012, Sebastian Seung and his laboratory at MIT have launched EyeWire, an online Citizen science game where players trace neurons in the retina.[68] The goals of the EyeWire project are to identify specific cell types within the known broad classes of retinal cells, and to map the connections between neurons in the retina, which will help to determine how vision works.[69][70]

text: Additional images[edit]

text:
The structures of the eye labeled

Another view of the eye and the structures of the eye labeled

Illustration of image as 'seen' by the retina independent of optic nerve and striate cortex processing.


document_title: The Vampire Diaries (season 2)

question_text: when does elijah first appear in vampire diaries

root

text: The Vampire Diaries (season 2)

text: Cast[edit]

text: Main[edit]

text:
Nina Dobrev as Elena Gilbert (22 episodes) / Katherine Pierce (18 episodes)
Paul Wesley as Stefan Salvatore (22 episodes)
Ian Somerhalder as Damon Salvatore (22 episodes)
Steven R. McQueen as Jeremy Gilbert (17 episodes)
Sara Canning as Jenna Sommers (15 episodes)
Kat Graham as Bonnie Bennett (17 episodes)
Candice Accola as Caroline Forbes (20 episodes)
Zach Roerig as Matt Donovan (15 episodes)
Michael Trevino as Tyler Lockwood (15 episodes)
Matt Davis as Alaric Saltzman (17 episodes)

tag: ul

text: Recurring[edit]

text:
Susan Walters as Carol Lockwood (13 episodes)
Daniel Gillies as Elijah Mikaelson (alias Smith) (12 episodes)
Marguerite MacIntyre as Sheriff Elizabeth "Liz" Forbes (8 episodes)
Taylor Kinney as Mason Lockwood (8 episodes)
David Anders as John Gilbert (7 episodes)
Bryton James as Luka Martin (7 episodes)
Randy J. Goodwin as Dr. Jonas Martin (6 episodes)
Michaela McManus as Jules (6 episodes)
Lauren Cohan as Rosemary "Rose" (5 episodes)
Dawn Olivieri as Andie Starr (4 episodes)
Joseph Morgan as Klaus Mikaelson (4 episodes)
Gino Anthony Pesi as Maddox (4 episodes)

text: Guest[edit]

text:
Tiya Sircar as Aimee Bradley (3 episodes)
Lisa Tucker as Greta Martin (3 episodes)
Maiara Walsh as Sarah (2 episodes)
Trevor Peterson as Slater (1 episodes)
Stephen Amell as Brady (2 episodes)
B.J. Britt as Carter (1 episodes)
Mia Kirshner as Isobel Flemming (2 episodes)
Courtney Ford as Vanessa Monroe (1 episodes)
Simon Miller as George Lockwood (1 episodes)
Natashia Williams as Lucy Bennett (1 episodes)
Trent Ford as Trevor (3 episodes)
Bree Condon as Alice (1 episodes)
James Harvey Ward as Cody Webber (1 episodes)
Ahna O'Reilly as Jessica Cohen (1 episodes)
Arielle Kebbel as Alexia "Lexi" Branson (1 episodes)
Bianca Lawson as Emily Bennett (voice only) (1 episodes)
Malese Jow as Annabelle "Anna"(1 episodes)
Kayla Ewell as Vicki Donovan (uncredited)(1 episodes)

text: Episodes[edit]

text:
No.
overall
No. in
season
Title
Directed by
Written by
Original air date
Prod.
code
U.S. viewers
(millions)

23
1
"The Return"
J. Miller Tobin
Kevin Williamson & Julie Plec
September 9, 2010 (2010-09-09)
2J5251
3.28[5]

Picking up where the first season left off, Elena arrives home to discover the fates of Uncle John and Jeremy. Jeremy has not transitioned into a vampire, because he did not take enough drugs to die and Anna's blood overcame the overdose. Damon, Bonnie, and Elena agree that Caroline needs Damon's blood to survive. Damon realizes that Katherine has returned and is impersonating Elena. Tyler is surprised when his uncle, Mason Lockwood, arrives in town to console him. Katherine and Damon nearly sleep together, but Katherine tells Damon, "it will always be Stefan". Distraught, Damon goes to see Elena, who resists his attempt to kiss her. Angry that Elena also loves Stefan, Damon snaps Jeremy's neck. Jeremy survives because he is wearing a Gilbert ring, which protects the wearer from death from supernatural causes. Katherine goes to the hospital and smothers Caroline with a pillow. Before Caroline dies, Katherine gives her a message for the Salvatore brothers: "Game on."

24
2
"Brave New World"
John Dahl
Brian Young
September 16, 2010 (2010-09-16)
2J5252
3.05[6]

Caroline has become a vampire and awakens in the hospital craving blood. Tyler catches Mason searching for a moonstone, which is a family heirloom. At the carnival, Damon compels a boy named Carter to pick a fight with Tyler to provoke one of Tyler's bursts of anger. Mason breaks up the fight using his supernatural abilities, proving that he is a werewolf. Caroline confronts Damon about his abusive treatment, and he realizes that she is a vampire. He alerts Elena and Stefan, while a ravenous Caroline drains Carter. Stefan promises Caroline he will guide her journey as a vampire. Tyler retrieves the moonstone Mason has been seeking. Matt notices Caroline's erratic behavior but admits that he loves her.

25
3
"Bad Moon Rising"
Patrick Norris
Andrew Chambliss
September 23, 2010 (2010-09-23)
2J5253
3.57[7]

Elena, Damon, and Alaric head to Isobel's old office at Duke University, where it is revealed that vampires and werewolves used to roam freely until a shaman uttered a curse to limit their powers, after which the werewolves were servants of the moon and vampires became the slaves of the sun. Stefan teaches Caroline how to control herself and hunt animals. Bonnie makes Caroline a daylight ring so that she will not be burned by the sun. In werewolf form, Mason encounters Stefan and Caroline. Tyler saves them by shouting at the werewolf; he later finds Mason in the woods and realises what has happened. Unable to control herself, Caroline feeds on Matt. She compels him to forget it, but ends their relationship to keep him safe from her. Damon tells Elena Katherine's real name, Katerina Petrova, to aid Elena with her research. Alaric reaffirms his romantic interest in Jenna, and Caroline finds Katherine in her bedroom.

26
4
"Memory Lane"
Rob Hardy
Caroline Dries
September 30, 2010 (2010-09-30)
2J5254
3.18[8]

Katherine tells Stefan that she will kill Elena unless he ends his relationship with her, and as a result, Elena realizes that Caroline is working for Katherine. Elena and Katherine finally meet, but Katherine ignores Elena's questions. Damon stabs Mason with a silver knife, but Mason says it is only a myth that silver hurts werewolves. They are now enemies. Katherine remembers how in 1864, after Stefan and Damon were shot in an attempt to save her, she had kissed Stefan, declaring her love and saying they would be together again one day. Stefan and Elena stage a fake break-up to prevent Katherine from hurting anybody.

27
5
"Kill or Be Killed"
Jeff Woolnough
Mike Daniels
October 7, 2010 (2010-10-07)
2J5255
3.47[9]

At the Mystic Falls picnic, Mason Lockwood tells Sheriff Liz Forbes that Stefan and Damon are vampires. Liz and her fellow police officers shoot Stefan and Damon. Caroline and Elena reach the Salvatore's before Liz can kill them, but Caroline's identity as a vampire is exposed to her mother. Liz rejects Caroline as her daughter, and Stefan drinks Elena's blood to gain strength. Caroline confesses to Elena that Katherine had threatened to kill Matt if Caroline didn't spy on Elena and Stefan for her; Elena forgives Caroline. Jeremy and Tyler start to bond when Tyler learns that Jeremy knows about the curse. Tyler almost kills a girl, feeling for a second that he wants her to die. He then tells Mason that he wants nothing to do with the curse, and gives him the moonstone. It is revealed that Mason is working for Katherine, who wants the moonstone, and that they are lovers.

28
6
"Plan B"
John Behring
Elizabeth Craft & Sarah Fain
October 21, 2010 (2010-10-21)
2J5256
3.62[10]

Liz accepts Caroline, and Caroline compels her mother to forget that she is a vampire. Bonnie incapacitates Mason by giving him an aneurysm. Damon then questions and tortures Mason who, believing that Katherine loves him, refuses to talk. Telling Mason that Katherine is using him, Damon eventually kills him. Bonnie has a vision of the moonstone's location in a well. Stefan discovers that the well is full of vervain, which burns him. Caroline and Bonnie help Elena rescue Stefan and retrieve the moonstone. Katherine compels Jenna to stab herself. Fearful of what else Katherine might do, Elena breaks up with Stefan for good. Needing another werewolf, Katherine compels Matt to attack Tyler, so that Tyler will kill Matt and become a werewolf.

29
7
"Masquerade"
Charles Beeson
Kevin Williamson & Julie Plec
October 28, 2010 (2010-10-28)
2J5257
3.55[11]

Stefan, Damon, Bonnie, Jeremy, Alaric, and Caroline plan to kill Katherine at the Lockwoods' masquerade ball. Katherine is visited by Lucy, a witch who is to help her retrieve the moonstone. Under Katherine's compulsion, Matt fights Tyler. Caroline breaks up the fight, but Sarah, who is also compelled, stabs Tyler, and he accidentally breaks her neck. Tyler's eyes turn yellow, showing that the curse has been triggered. Stefan and Damon try to kill Katherine, but they stop when Jeremy tells them that every time they stake her, Elena is wounded. Katherine reveals that she had Lucy put a spell on Elena and herself, which linked them. Lucy, who is Bonnie's cousin, lifts the spell and incapacitates Katherine, who collapses. Damon traps Katherine in the underground tomb. As Elena heads home she is intercepted by a masked stranger.

30
8
"Rose"
Liz Friedlander
Brian Young
November 4, 2010 (2010-11-04)
2J5258
3.63[12]

A vampire named Trevor takes Elena to an abandoned house, where she meets Rose, another vampire. When Tyler witnesses Caroline's abilities, she reveals that she is a vampire. Elena overhears Rose and Trevor arguing about a vampire named Elijah. Using a spell, Bonnie locates Elena. Elena tries to extract information from Rose, who tells her that Elijah is one of the "original" vampires. Rose and Trevor are using Elena, the Petrova doppelgänger who is the key to breaking the curse, as a bargaining chip. Elijah arrives, and Rose offers him Elena in exchange for their pardon. Elijah agrees but kills Trevor. Elena tries to stall Elijah by saying that she knows where the moonstone is, but he compels her to tell him its location. Stefan and Damon arrive to fight with Elijah and stake him. Elena's vervain necklace remains at the house. Later that night, Damon is in Elena's bedroom with her vervain necklace in his hand. He tells her that he loves her but doesn't deserve her, and that Stefan does. Then he compels her to forget what he said. In the abandoned house, Elijah pulls the wooden stake out of his chest.

31
9
"Katerina"
J. Miller Tobin
Andrew Chambliss
November 11, 2010 (2010-11-11)
2J5259
3.50[13]

This episode's plot summary may be too long or excessively detailed. Please help improve it by removing unnecessary details and making it more concise. (November 2016) (Learn how and when to remove this template message)

The episode begins in Bulgaria in 1490 and shows Katherine giving birth to a baby girl. Her father says that she has shamed their family and takes the baby away. In the present, Elena goes to the tomb, where she offers Katherine blood in exchange for the truth - that a doppelgänger from the Petrova line can be used to break the curse. As Katherine's descendant, Elena is the current Petrova doppelgänger. Katherine reveals that she was expelled from Bulgaria and fled to England, where Elijah and Trevor found her. They recognized her as the Petrova doppelgänger and Elijah tried to kill her, but Trevor helped her to escape. She became a vampire so that she could not be used to break the curse. Katherine came to Mystic Falls to offer Klaus what he needed to lift the curse: the current doppelgänger, a witch, a werewolf, a vampire, and the moonstone. She hoped that Klaus would spare her life in exchange for this. Bonnie meets a warlock named Luka and his father. Jeremy is jealous of Bonnie's attraction to Luka. Damon and Rose seek information about Klaus from Rose's vampire friend, Slater, but a healed Elijah overhears them. Damon and Rose sleep together, and Elijah compels Slater to stake himself. It is revealed that Luka and his father are working for Elijah.

32
10
"The Sacrifice"
Ralph Hemecker
Caroline Dries
December 2, 2010 (2010-12-02)
2J5260
3.46[14]

Elena and Rose go to ask Slater about Klaus, but they find his staked corpse. Elena uses information from Slater's computer to get Klaus's attention, saying she wants to surrender. Caroline and Tyler discover Mason's journal and the video diary that he used to document his transformations. Bonnie plans to lift the spell from the tomb and incapacitate Katherine so that Stefan can grab the moonstone, but Jeremy goes ahead with the plan alone and is captured by Katherine, who feeds on him. Stefan saves Jeremy but is trapped himself. Three vampires confront Damon, Rose, and Elena. Elijah kills the three vampires and then departs. Back home, a trapped Stefan makes Damon promise to protect Elena. Elijah informs Luka's father that Damon and Stefan will protect Elena, which is Elijah's goal.

33
11
"By the Light of the Moon"
Elizabeth Allen
Mike Daniels
December 9, 2010 (2010-12-09)
2J5261
3.16[15]

As the full moon approaches, Caroline helps Tyler prepare for his transformation. Stefan asks Katherine to prove that there is good in her, and she advises him to ask Isobel for help in finding Klaus. Bonnie seeks Luka's help to destroy the moonstone; they cast a spell, but Luka gives the moonstone to his father. Jules, a friend of Mason, arrives in Mystic Falls looking for him. Damon and Alaric try to trick her into having a drink mixed with wolfsbane. She reveals that she is a werewolf and tells Damon that he has been marked. Elijah makes a deal with Elena: she has to keep herself safe from Klaus (so that Elijah can use her as bait to kill Klaus) and in return, Elijah will protect her friends and family and free Stefan from the tomb. Caroline reunites with Tyler. At the Salvatore mansion, Jules, in wolf form, tries to attack Damon but instead bites Rose's shoulder, which becomes infected.

34
12
"The Descent"
Marcos Siega
Elizabeth Craft & Sarah Fain
January 27, 2011 (2011-01-27)
2J5262
3.55[16]

Stefan tries to contact Isobel and gets in touch with John Gilbert, who comes home. While Damon tries to get Jules to tell him how to cure the werewolf bite, he asks Elena to keep an eye on Rose, who becomes delirious and mistakes her for Katherine. Caroline and Matt confess their love for each other. Tyler's reaction to Caroline's generosity surprises her. Rose escapes from the Salvatore house and goes on a killing spree. Damon finds her and brought her back to the Salvatore's house, he then stakes her, while giving her a peaceful death by giving her a dream about her old home. He confesses to a stranger that he misses being human. He lets her go, but bites her soon after. Jules informs Tyler that she knows that he and Mason are werewolves. She tells him that more werewolves are coming.

35
13
"Daddy Issues"
Joshua Butler
Kevin Williamson & Julie Plec
February 3, 2011 (2011-02-03)
2J5263
3.22[17]

Tyler is furious that Caroline has kept Mason's death secret from him. Jenna becomes upset over the revelation that John is Elena's biological father. Jules meets her wolf-lover Brady and tells him she wants to leave town and take Tyler with them. Caroline asks Stefan to reason with Tyler, while Jules takes Caroline hostage. Jules tells Stefan to bring Tyler to her in exchange for Caroline. Stefan tries to make peace, but he fails, and Damon offers his "bloodier" method. Jules then calls on her wolf friends, and although Damon and Stefan are outnumbered, they kill most of the wolves. Tyler releases Caroline from the cage, but watches as Jules has Caroline at gunpoint. As Stefan and Damon are about to get staked, Jonas, on Elijah's behalf, incapacitates the remaining wolves. Tyler tries to apologize to Caroline, but she tells him they are no longer friends. Tyler tells Jules and Brady that Mason was probably killed because he found the moonstone. John says that he returned to protect Elena, and that the only way to kill an Original is with a dagger dipped in ash from a white oak as old as the Originals. John is shown to be still working with Katherine and trying to get her out of the tomb.

36
14
"Crying Wolf"
David Von Ancken
Brian Young
February 10, 2011 (2011-02-10)
2J5264
2.78[18]

Stefan and Elena spend a weekend at the Gilbert lakehouse, unaware that they've been followed by Tyler and Brady. Jenna worries that Alaric isn't being honest about his past. Jules and Brady explain the sun and moon curse to Tyler and lure him into helping them. Bonnie performs a hypnosis spell on Luka in order to get information. Luka reveals that Elijah plans to kill Klaus by making him vulnerable after he sacrifices Elena. He also reveals that Klaus has his sister, so he and his father are working for Elijah to help him kill Klaus. Jules and her friends torture Damon for information about the moonstone, but Elijah intervenes, kills most of the wolves, and saves Damon. Brady finds Stefan and shoots him with a wooden bullet, leaving Tyler to guard him. When Tyler learns that Elena has to die for the curse to be broken, he lets Stefan go. Stefan kills Brady to save Elena. Meanwhile, Jeremy and Bonnie confess their feelings for each other and kiss. Realising that Elena knew about Elijah's real plan for her, Stefan tells her that she is behaving like a martyr. Tyler tells Matt that he has feelings for Caroline but knows that Caroline loves Matt. The episode ends with Jules and Tyler leaving town.

37
15
"The Dinner Party"
Marcos Siega
Andrew Chambliss
February 17, 2011 (2011-02-17)
2J5265
3.07[19]

Elena reads one of Jonathan Gilbert's journals about a night when Stefan attacked him and killed two of the Fells. Stefan admits that he had been brutal and inhuman until Lexi showed him the path of love and humanity. Damon invites Elijah to the boarding house for a dinner party, intending to kill him. Jonathan Gilbert's journal reveals that if a vampire uses the dagger to kill an Original, both will die. After Stefan sends a warning, Alaric stabs and kills Elijah, but the body later disappears. Elena reads in the journal that if the dagger is removed, the Original will come back to life. John blackmails Alaric into returning his ring. Elijah shows up at the lake house telling Elena that the deal is off, but Elena threatens to kill herself and become a vampire so that she will no longer be useful to him. Elijah calls her out on a bluff, but Elena stabs herself. Elijah begs Elena to let him heal her, and she agrees, but then stabs him with the dagger, killing him again. Damon returns home to find Katherine there. Elijah's compulsion on her has worn off with his death, and she says she intends to help them.

38
16
"The House Guest"
Michael Katleman
Caroline Dries
February 24, 2011 (2011-02-24)
2J5266
2.98[20]

Discovering that Katherine is free, Elena is upset. Stefan and Bonnie try to persuade Jonas and Luka to work with them, but Jonas wants Elijah alive again. He performs a ritual that puts Luka in the boarding house in invisible form. Luka tries to remove the dagger from Elijah's body, but Katherine stops him. Luka then stakes Katherine, but Damon uses a flamethrower to prevent the removal of the dagger. Luka is fatally burned, and Jonas vows to avenge him by killing Elena. Bonnie tells Elena about her relationship with Jeremy and is surprised by Elena's positive response. Jonas appears at the Grill, looking for Elena. Bonnie tries to stop him, but he disables her; Matt intervenes, but Jonas stabs him. Caroline sees Matt dying and forces him to drink her blood to save his life. Jonas attacks Elena, but she proves to be Katherine, and she bites him. Alaric tells Jenna that he loves her. Bonnie reveals that Jonas has restored her powers and told her how to kill Klaus. Caroline tells Matt that she is a vampire, but he takes the news badly. Isobel shows up at Elena's house and tells Jenna that she is Elena's mother.

39
17
"Know Thy Enemy"
Wendey Stanzler
Mike Daniels
April 7, 2011 (2011-04-07)
2J5267
2.73[21]

Elena and Alaric become angry with John when Isobel's arrival devastates Jenna. Alaric is abducted by Maddox, a warlock from Klaus's inner circle. Meanwhile, Bonnie works with Jeremy and Damon to find the spell they need to gather the power of the witches killed in the massacre. Damon takes them to the site where the witches were burned. Matt demands to know what happened to Vicki. After Caroline tells him and then compels him to forget, it is revealed that Matt's involvement was a setup by Sheriff Forbes to find out everything about the vampires. Matt has drunk vervain, so the compulsion does not work. Isobel kidnaps Elena and then receives a phone call from Maddox, who tells her that she has finished what Klaus compelled her to do and is free to let Elena go. Isobel apologizes to Elena for being a disappointment as a mother, removes her necklace, and burns to death in the sun. Stefan and Damon realize that Bonnie is their new secret weapon since she now has tremendous power. Jeremy is upset because, if Bonnie uses too much power, she will die. Katherine, who had been set up by Isobel and taken by Maddox, wakes up to see Klaus take control of Alaric's body.

40
18
"The Last Dance"
John Behring
Michael Narducci
April 14, 2011 (2011-04-14)
2J5268
2.81[22]

Klaus (in Alaric's body) compels Katherine to tell him how the others plan to kill him. He then finds out that Bonnie has obtained power that could threaten his life. At the school dance, Jeremy confronts Bonnie about why she wants to kill herself for Elena, and Damon overhears. Jeremy goes to Stefan for help, and Stefan tells Elena about Bonnie's plans. Elena finally guesses who "Alaric" really is. Bonnie fights Klaus with her powers and appears to die. As Elena grieves, Damon tells her that Klaus must believe Bonnie is dead, but her death was faked. Realizing that Bonnie intends to endanger herself to defeat Klaus, Elena pulls the dagger out of Elijah's heart.

41
19
"Klaus"
Joshua Butler
Kevin Williamson & Julie Plec
April 21, 2011 (2011-04-21)
2J5269
2.70[23]

After Elena removed the dagger, Elijah wakes, and Elena makes another deal with him. In a flashback to 1492 England, Katherine meets Elijah and Klaus for the first time. Elijah and Klaus were raised as brothers, but Klaus was the result of their mother's affair with a man from a werewolf bloodline. Elijah's father hunted down the man and had him and his family killed, beginning the schism between werewolves and vampires. As a vampire/werewolf hybrid, Klaus can only be killed by a witch. The sun and moon curse was fake – the real curse is that Klaus's werewolf side had been forced into dormancy by witches. Jenna finally finds out about the vampires from Stefan and Klaus/Alaric. Elsewhere, Katherine is being held captive by Klaus. Damon finds her and gives her a vial of vervain to protect her from further compulsion. At the end of the episode, Maddox and Greta (Luka's sister) perform a ritual to release Klaus's spirit from Alaric's body and put it back into his own.

42
20
"The Last Day"
J. Miller Tobin
Andrew Chambliss & Brian Young
April 28, 2011 (2011-04-28)
2J5270
2.68[24]

Elijah tells Elena that the way to break the curse involves sacrifice a vampire and a werewolf. Maddox injures Carol Lockwood to make Tyler return to town, after which he and Greta kidnap Caroline and Tyler. Damon forces Elana to drink his blood so she will "survive" the sacrifice. Alaric returns as himself and gives the message from Klaus that the ritual will happen that night. Jenna forgives him. Damon realizes that if Klaus doesn't have a werewolf, he will be unable to complete the ritual, and Elena will have another month. He rescues Caroline and Tyler from the tomb and kills Maddox. Klaus takes Elena from the boarding house to begin the ritual. Damon informs Klaus that he has rescued the vampire and werewolf he needs for the ritual, but Klaus says he has backups. At the site of the ritual, Elena realizes that Klaus has turned Jenna and is using her as the vampire. Katherine makes Damon aware of a wolf bite he got from Tyler during his transformation.

43
21
"The Sun Also Rises"
Paul M. Sommers
Caroline Dries & Mike Daniels
May 5, 2011 (2011-05-05)
2J5271
2.84[25]

Matt and Caroline are in the Lockwood cellar while Tyler, in wolf form, attacks them, and they hide. Meanwhile, Greta the witch feeds Jenna her blood, completing Jenna's transformation into a vampire. Elijah is revealed to be seeking revenge on Klaus for killing his family and burying their bodies at sea. Klaus begins the ritual and kills Jules, the werewolf. Stefan offers to switch places with Jenna, but Klaus refuses and kills her. Bonnie performs a spell that can bring someone back to life by joining two people's souls, binding John and Elena. At the ritual grounds, Klaus drains Elena's blood and begins to transform. However, Bonnie uses her powers to weaken him while Damon kills Greta. Before Elijah can rip out his heart, Klaus says he didn't bury the bodies at sea and if he is killed, Elijah will never find them. Elijah listens to him and flees with Klaus. When Elena comes back to life, John dies. At Jenna's and John's funeral, Damon reveals to Stefan that he was bitten by Tyler and asks him to not tell Elena.

44
22
"As I Lay Dying"
John Behring
Turi Meyer & Al Septien & Michael Narducci
May 12, 2011 (2011-05-12)
2J5272
2.86[26]

This episode's plot summary may be too long or excessively detailed. Please help improve it by removing unnecessary details and making it more concise. (November 2016) (Learn how and when to remove this template message)

Damon apologizes to Elena for feeding her his blood. At home, he tries to kill himself by taking off his ring and walking into sunlight but is stopped by Stefan and locked in a cell. Klaus has completed the transformation into a wolf and awakens to find Elijah waiting for him. He makes Klaus remember his deal: he must reunite Elijah with their family, and Klaus does so by staking Elijah. Stefan seeks Klaus for a cure for Damon. Klaus then bites Katherine and feeds her his blood, revealing the cure for a werewolf bite. In exchange for a vial of his blood, Klaus wants Stefan to become a ripper again and leave Mystic Falls with him. Stefan drinks human blood to prove himself. Klaus gives Katherine the cure for Damon and allows her to leave. Sheriff Forbes, who wants to kill Damon, accidentally frees him from his cell. She later tracks him down and shoots at him but strikes and kills Jeremy instead. Bonnie begs the witches to bring Jeremy back to life saying that she loves him, and they do, warning of "consequences." Elena finds a delirious Damon, brings him home, and kisses him after he confesses his love. Katherine interrupts with Klaus's cure for the werewolf bite. Klaus tests Stefan, asking him to kill someone. Once Stefan does, Klaus says that they can leave Mystic Falls. At the Gilbert house, Jeremy finds his deceased vampire ex-girlfriends Anna and Vicki.

tag: table

text: Production[edit]

text: On February 16, 2010, The CW officially renewed The Vampire Diaries for a full 22-episode second season.[1] It premiered on Thursday September 9, 2010, at 8 pm ET.[2] The season finale aired on May 12, 2011.[27]

tag: p

text: Cast[edit]

text: On July 9, 2010, Entertainment Weekly announced Taylor Kinney would join the cast in a recurring role as Tyler's uncle Mason, a werewolf who comes to town after his brother dies. Katherine sends Mason to Mystic Falls to get the moonstone for her. He succeeds, but Damon and Stefan find out that he works with Katherine, and Damon kills him. Mason has been described as a "cool" uncle, sexy and athletic.[28] Lauren Cohan joined the cast as Rose, a 500-year-old vampire and possible love interest for Damon. She kidnaps Elena to hand her over to Elijah, but Elena is saved by Stefan and Damon. She then becomes their ally and even starts a small romantic relationship with Damon. She dies after being bitten by werewolf Jules.[29]

text: Michaela McManus joined the cast in a guest role as a werewolf who comes to town looking for answers about Mason's death.[30] She helps Tyler deal with the discovery that he is a werewolf, but is later killed during the sacrifice. Bryton James portrays warlock Luka Martin in season two. He befriends Bonnie, but it is later revealed that he and his father work for Elijah. When he tries to save Elijah invisibly, Damon burns him to death. His father Jonas Martin, played by Randy J. Goodwin in season two, is introduced as a friend of Elijah. He is a warlock who, in order to save his daughter Greta, is willing and able to help defeat Klaus.[31] He is later killed by Katherine, who is protecting the Salvatore brothers.[32]

text: Gino Anthony Pesi portrays Maddox at the end of season two, a warlock who works for Klaus. Matt shoots him to death when he tries to overcome Damon. On February 18, 2011, it was announced that British actor Joseph Morgan had signed on to play original vampire Klaus.[33]

text: Storylines[edit]

text: This section's plot summary may be too long or excessively detailed. Please help improve it by removing unnecessary details and making it more concise. (October 2011) (Learn how and when to remove this template message)

text: The second season focuses mainly on the arrival of Elena's doppelgänger Katherine Pierce and on her reasons for returning to Mystic Falls. It also introduces werewolves. Tyler's werewolf uncle, Mason Lockwood, arrives after the death of Tyler's father and tells Tyler about the so-called "Lockwood curse" in their family. To activate the werewolf gene, the person must kill someone. Katherine turns Caroline into a vampire, so as to have a spy against Stefan and Elena. Katherine's main reason for returning to Mystic Falls is to find the moonstone, with the help of Mason, who is killed by Damon. Katherine calls in a favor from a witch named Lucy to get the stone. Lucy casts a spell so that when Katherine is hurt, it also affects Elena.

text: When Lucy finds out that another Bennett is at the party and that Katherine had deceived her, she puts a spell on the moonstone, injuring Katherine. Damon then leaves her in the original tomb where she is trapped until the spell has been removed from the tomb. She tells him that her reason for not killing Elena is that she is in danger. Elena is later kidnapped by a masked individual and held hostage by vampires Rose and Trevor, who have been on the run from the Originals (the first generation of vampires). Rose reveals to Elena that she is the Petrova doppelgänger and needs to be sacrificed to break the sun and moon curse. Katherine was also a Petrova doppelgänger, who used Trevor to help her escape from the Originals and Rose to turn her into a vampire to save herself. Elena is rescued by Stefan and Damon by stabbing Elijah with a sharp wooden pole and they escape.

text: Klaus, one of the original vampires, arrives and is now hunting Elena. His brother Elijah has made a deal with Elena to protect her loved ones, because he wants to use her as bait to lure Klaus and kill him. Jules, a friend of Mason, tells the Lockwoods that Mason never came back to Florida and is missing. Alaric is suspicious of Jules and calls Damon to the Grill (local town hangout). Jules reveals that she is a werewolf. Damon tells Jules she won't find Mason and to leave town. Jules breaks into the Salvatore mansion in wolf form and attacks Damon, but Rose pushes him out of the way, getting bitten on the shoulder instead (werewolf bites are lethal to vampires). As Rose succumbs to the effects of the bite, Damon stakes her in a glorious dream they share, giving her a peaceful death.

text: Uncle John returns to Mystic Falls and comes as an unpleasant surprise to Elena, Damon, Jenna, and Alaric. John reveals to Damon that the only way to kill an Original is with a dagger dipped in white ash wood. A boy named Luka settle in the town with his father (they are both warlocks) and reveals that they are working for Elijah because Klaus has his sister Greta and they want him (Luka) dead as well. Luka becomes friends with Bonnie and tells her that Klaus will be weakened by the sacrificial ritual, meaning that Elena has to die so that Elijah can kill him and free his sister. John gives Damon the special dagger to kill Elijah.

text: Elena finds out that if a vampire uses the dagger, that vampire will die. Stefan warns Damon and Alaric stabs Elijah, but he pulls the dagger out and tells Elena their deal is off. Elena stabs herself in the stomach, and Elijah begs her to let him heal her. She stabs him with the dagger and leaves it in him. Elijah's death means that Katherine is no longer compelled to stay in the tomb. She helps kill the Martin witches. When Isobel returns to town, Katherine double-crosses the Salvatores by kidnapping Elena and stealing the moonstone for Klaus in exchange for her freedom. But it is revealed that Klaus wanted Katherine and compelled Isobel to get her and the moonstone.

text: Klaus enters Alaric's body and compels Katherine to stay in Alaric's house. Bonnie and Jeremy find the site of the a witch massacre and Bonnie channels all the power. Alaric/Klaus blends with Stefan, Damon, and Elena and finds out that Bonnie has her powers. Damon tells Bonnie to put on a protection spell and make Alaric/Klaus believe that she is dead. Elena does not want Bonnie to die, so she pulls the dagger out of Elijah's heart. After Elijah comes to life, Elena learns the full history of Klaus. The Aztec curse is fake and there is a curse on Klaus, as he is a vampire born in a werewolf bloodline. There is a ritual that involves killing a vampire and a werewolf and a Petrova doppelganger, that will unearth the werewolf side of Klaus making him a hybrid.

text: Elena realizes that the real curse is on Klaus, who therefore wants to kill her. But Elijah says he has an elixir that can save Elena from dying. Elena believes Elijah, but Damon says that there is another way to save her life and feeds her his blood. Stefan tries to stop him, but he stabs in the chest with the wooden dagger. Elena then cries that she will be a vampire against her will. Maddox kidnaps Tyler and Caroline. Damon frees them and is bitten. Then he goes to Klaus to tell him that he does not have a werewolf and witch, as he killed Maddox. Klaus says that he has backups. Klaus takes Elena from Stefan. Elena sees Jenna, who thinks she is dead, but Greta tells her she is transitioning. Damon asks Katherine about the vampire, and she says that Jenna is the backup vampire. He then checks his arm and sees that Tyler has bitten him.

text: In the season's finale, Klaus is working on the ritual out in the woods and is near completion when he is about to kill Elena, but Stefan tries to work a deal with him. Klaus agrees to have Stefan work for him in exchange for Damon's protection. Elena is "killed" in the ritual but is shown to have survived. Regardless, Klaus's werewolf side is unleashed and he becomes the first hybrid, half vampire half werewolf. Bonnie arrives and subdues Klaus with her powers, giving Elijah the opportunity to strike, but Klaus talks him down offering to help find their siblings. Elena's survival is revealed as John had Bonnie cast a spell that had him die in Elena's place. The next morning John succumbs and dies. At his funeral, Elena reads a note from John saying he will always love her and she will always be his daughter, even if she becomes a vampire. Damon also shows where he was bitten and walks away.

text: Reception[edit]

text: Ken Tucker of Entertainment Weekly wrote, "The throbbing red heart of The Vampire Diaries remains the tension between Damon and Paul Wesley's Stefan, and their mutual attraction to whomever Dobrev is embodying at the time."[34] Mark A. Perigard of the Boston Herald said, "The triangle – quadrangle? – becomes more twisted by episode's end. It leads to shocking violence against outsiders that deepens the tragedy and the mythology at the core of the show. "Game on" just might be the two most chilling words uttered this season."[34] Matt Roush of TV Guide commented, "The Vampire Diaries is the sort of show where 'never say die' is written into the mythology – a good thing for several of the opening hour's apparent victims. I don't know how much longer The Vampire Diaries can keep churning stories at this feverish rate, but if this is your sort of guilty pleasure, you'd be crazy not to bite."[34]

text: Ratings[edit]

text: DVR viewers[edit]

text:
No.
Title
Air date
18–49 rating (Live + SD)
Viewers
(millions) increase
Total 18-49 increase
Total viewers
(millions)
Ref

02
"Brave New World"
September 16, 2010 (2010-09-16)
1.4
0.91
1.9
3.96
[35]

03
"Bad Moon Rising"
September 23, 2010 (2010-09-23)
1.4
0.92
1.9
4.49
[36]

04
"Memory Lane"
September 30, 2010 (2010-09-30)
1.2
0.95
1.8
4.13
[37]

06
"Plan B"
October 21, 2010 (2010-10-21)
1.7
1.04
2.2
4.66
[38]

07
"Masquerade"
October 28, 2010 (2010-10-28)
1.7
0.85
2.2
4.40
[39]

08
"Rose"
November 4, 2010 (2010-11-04)
1.6
1.12
2.1
4.75
[40]

09
"Katerina"
November 11, 2010 (2010-11-11)
1.6
1.01
2.0
4.51
[41]

10
"The Sacrifice"
December 2, 2010 (2010-12-02)
1.6
1.07
2.1
4.53
[42]

11
"By the Light of the Moon"
December 9, 2010 (2010-12-09)
1.3
0.97
1.7
4.13
[43]

12
"The Descent"
January 27, 2011 (2011-01-27)
1.6
1.10
2.1
4.65
[44]

16
"The House Guest"
February 24, 2011 (2011-02-24)
1.3
1.13
1.8
4.11
[45]

17
"Know Thy Enemy"
April 7, 2011 (2011-04-07)
1.2
1.14
1.7
3.87
[46]

18
"The Last Dance"
April 14, 2011 (2011-04-14)
1.3
1.06
1.8
3.87
[47]

19
"Klaus"
April 21, 2011 (2011-04-21)
1.2
1.35
1.8
4.05
[48]

20
"The Last Day"
April 28, 2011 (2011-04-28)
1.2
1.34
1.8
4.02
[49]

21
"The Sun Also Rises"
May 5, 2011 (2011-05-05)
1.3
1.07
1.8
3.91
[50]

22
"As I Lay Dying"
May 12, 2011 (2011-05-12)
1.4
1.02
1.9
3.88
[51]

text: Accolades[edit]

text: For its second season The Vampire Diaries won five Teen Choice Awards, one People's Choice Award, and a nomination in Saturn Awards.

text: Home media[edit]

text: The Vampire Diaries Season 2 was made available on DVD and Blu-ray on August 30, 2011.[52] In region B, it was released on August 22, 2011.[53]


document_title: Spanish colonization of the Americas

question_text: who made the first spanish landing on the mainland of north america

text: Spanish colonization of the Americas

text: Conquests[edit]

text: The Catholic Monarchs Isabella of Castile, Queen of Castile and her husband King Ferdinand, King of Aragon, pursued a policy of joint rule of their kingdoms and created a single Spanish monarchy. Even though Castile and Aragon were ruled jointly by their respective monarchs, they remained separate kingdoms. The Catholic Monarchs gave official approval for the plans of Genoese mariner Christopher Columbus for a voyage to reach India by sailing West. The funding came from the queen of Castile, so the profits from Spanish expedition flowed to Castile. In the extension of Spanish sovereignty to its overseas territories, authority for expeditions of discovery, conquest, and settlement resided in the monarchy.[1]

text: West Indies[edit]

text: Columbus made four voyages to the West Indies as the monarchs granted Columbus the governorship of the new territories, and financed more of his trans-Atlantic journeys. He founded La Navidad on the island later named Hispaniola (now divided into Haiti and the Dominican Republic), in what is the present-day Haiti on his first voyage. After its destruction by the indigenous Taino people, the town of Isabella was begun in 1493, on his second voyage. In 1496 his brother, Bartholomew, founded Santo Domingo. By 1500, despite a high death rate, there were between 300 and 1000 Spanish settled in the area. The local Taíno people continued to resist, refusing to plant crops and abandoning their Spanish-occupied villages. The first mainland explorations were followed by a phase of inland expeditions and conquest. In 1500 the city of Nueva Cádiz was founded on the island of Cubagua, Venezuela, followed by the founding of Santa Cruz by Alonso de Ojeda in present-day Guajira peninsula. Cumaná in Venezuela was the first permanent settlement founded by Europeans in the mainland Americas,[2] in 1501 by Franciscan friars, but due to successful attacks by the indigenous people, it had to be refounded several times, until Diego Hernández de Serpa's foundation in 1569. The Spanish founded San Sebastian de Uraba in 1509 but abandoned it within the year. There is indirect evidence that the first permanent Spanish mainland settlement established in the Americas was Santa María la Antigua del Darién.[3]

text: Mexico[edit]

text: The Spanish conquest of Mexico is generally understood to be the Spanish conquest of the Aztec Empire (1519–21) which was the base for later conquests of other regions. Later conquests were protracted campaigns with less spectacular results than the conquest of the Aztecs. The Spanish conquest of Yucatán, the Spanish conquest of Guatemala, the war of Mexico's west, and the Chichimeca War in northern Mexico expanded Spanish control over territory and indigenous populations.[4][5][6] But not until the Spanish conquest of Peru was the conquest of the Aztecs matched in scope by the victory over the Inca empire in 1532.

text: The Spanish conquest of the Aztec empire was led by Hernán Cortés. The victory over the Aztecs was relatively quick, from 1519 to 1521, and aided by his Tlaxcala and other allies from indigenous city-states or altepetl. These polities allied against the Aztec empire, to which they paid tribute following conquest or threat of conquest, leaving the city-states' political hierarchy and social structure in place.

text: The Spanish conquest of Yucatán was a much longer campaign, from 1551 to 1697, against the Maya peoples in the Yucatán Peninsula of present-day Mexico and northern Central America. Hernán Cortés' landing ashore at present day Veracruz and founding the Spanish city there on April 22, 1519 marked the beginning of 300 years of Spanish hegemony over the region. The assertion of royal control over the Kingdom of New Spain and the initial Spanish conquerors took over a decade, with importance of the region meriting the creation of the Viceroyalty of New Spain. Established by Charles V in 1535, the first viceroy was Don Antonio de Mendoza.

text: Spain colonized and exerted control of Alta California through the Spanish missions in California until the Mexican secularization act of 1833.

text: Peru[edit]

text: In 1532 at the Battle of Cajamarca a group of Spaniards under Francisco Pizarro and their indigenous Andean Indian auxiliaries native allies ambushed and captured the Emperor Atahualpa of the Inca Empire. It was the first step in a long campaign that took decades of fighting to subdue the mightiest empire in the Americas. In the following years Spain extended its rule over the Empire of the Inca civilization.

text: The Spanish took advantage of a recent civil war between the factions of the two brothers Emperor Atahualpa and Huáscar, and the enmity of indigenous nations the Incas had subjugated, such as the Huancas, Chachapoyas, and Cañaris. In the following years the conquistadors and indigenous allies extended control over Greater Andes Region. The Viceroyalty of Perú was established in 1542. The last Inca stronghold was conquered by the Spanish in 1572.

text: Río de la Plata and Paraguay[edit]

text: European explorers arrived in Río de la Plata in 1516. Their first Spanish settlement in this zone was the Fort of Sancti Spiritu established in 1527 next to the Paraná River. Buenos Aires, a permanent colony, was established in 1536 and in 1537 Asunción was established in the area that is now Paraguay. Buenos Aires suffered attacks by the indigenous peoples that forced the settlers away, and in 1541 the site was abandoned. A second (and permanent) settlement was established in 1580 by Juan de Garay, who arrived by sailing down the Paraná River from Asunción (now the capital of Paraguay). He dubbed the settlement "Santísima Trinidad" and its port became "Puerto de Santa María de los Buenos Aires." The city came to be the head of the Governorate of the Río de la Plata and in 1776 elevated to be the capital of the new Viceroyalty of the Río de la Plata.

text: New Granada[edit]

text: Between 1537 and 1543, six[citation needed] Spanish expeditions entered highland Colombia, conquered the Muisca Confederation, and set up the New Kingdom of Granada (Spanish: Nuevo Reino de Granada). Gonzalo Jiménez de Quesada was the leading conquistador with his brother Hernán second in command.[7] It was governed by the president of the Audiencia of Bogotá, and comprised an area corresponding mainly to modern-day Colombia and parts of Venezuela. The conquistadors originally organized it as a captaincy general within the Viceroyalty of Peru. The crown established the audiencia in 1549. Ultimately, the kingdom became part of the Viceroyalty of New Granada first in 1717 and permanently in 1739. After several attempts to set up independent states in the 1810s, the kingdom and the viceroyalty ceased to exist altogether in 1819 with the establishment of Gran Colombia.[8]

text: Governance[edit]

text: Spain's administration of its colonies in the Americas was divided into the Viceroyalty of New Spain 1535 (capital, Mexico City), and the Viceroyalty of Peru 1542 (capital, Lima). In the 18th century the additional Viceroyalty of New Granada 1717 (capital, Bogotá), and Viceroyalty of Rio de la Plata 1776 (capital, Buenos Aires) were established from portions of the Viceroyalty of Peru. The change diminished the political and economic power of the viceroyalty and opened formal connections between the mining district of Upper Peru and the port of Buenos Aires.

text: The system of crown rule evolved from the era of the Catholic Monarchs, which established the Council of the Indies, to the establishment of viceroyalties in Mexico and Peru following their conquests in the Hapsburg era, and then into an Intendant system in the eighteenth century as part of the Bourbon Reforms. The reform was aimed at increasing crown control over its colonies, raising more revenue, and promoting greater efficiency.

text: Dominions[edit]

text: North America, Central America[edit]

text:
Viceroyalty of New Spain (1535–1821)

Las Californias
Nuevo Reino de León
Nuevo Santander
Nueva Vizcaya
Santa Fe de Nuevo México
Nueva Extremadura
Nueva Galicia
Captaincy General of Guatemala

Captaincy General of the Philippines (administered by New Spain from 1565 to 1821, then after Mexican independence transferred to and directly administered by Madrid until 1898)
Captaincy General of Cuba (until 1898) – Included in this captaincy general until 1819 was Florida.
Captaincy General of Puerto Rico (until 1898)
Santo Domingo (last Spanish rule 1861–1865)

text: South America[edit]

text:
Viceroyalty of Perú (1542–1824)
Captaincy General of Chile (1541–1818)
Viceroyalty of New Granada (1717–1819)
Captaincy General of Venezuela
Viceroyalty of the Río de la Plata (1776–1814)

text: 19th century[edit]

text: During the Napoleonic Peninsular War in Europe between France and Spain, assemblies called juntas were established to rule in the name of Ferdinand VII of Spain. The Libertadores (Spanish and Portuguese for "Liberators") were the principal leaders of the Spanish American wars of independence. They were predominantly criollos (Americas-born people of European ancestry, mostly Spanish or Portuguese), bourgeois and influenced by liberalism and in some cases with military training in the mother country.

text: In 1809 the first declarations of independence from Spanish rule occurred in the Viceroyalty of New Granada. The first two were in present-day Bolivia at Sucre (May 25), and La Paz (July 16); and the third in present-day Ecuador at Quito (August 10). In 1810 Mexico declared independence, with the Mexican War of Independence following for over a decade. In 1821 Treaty of Córdoba established Mexican independence from Spain and concluded the War. The Plan of Iguala was part of the peace treaty to establish a constitutional foundation for an independent Mexico.

text: These began a movement for colonial independence that spread to Spain's other colonies in the Americas. The ideas from the French and the American Revolution influenced the efforts. All of the colonies, except Cuba and Puerto Rico, attained independence by the 1820s. The British Empire offered support, wanting to end the Spanish monopoly on trade with its colonies in the Americas.

text: In 1898, the United States achieved victory in the Spanish–American War with Spain, ending the Spanish colonial era. Spanish possession and rule of its remaining colonies in the Americas ended in that year with its sovereignty transferred to the United States. The United States took occupation of Cuba, the Philippines, and Puerto Rico. Puerto Rico continues to be a possession of the United States, now officially continues as a self-governing unincorporated territory.

text: Demographic impact[edit]

text: It has been estimated that over 1.86 million Spaniards emigrated to Latin America in the period between 1492 and 1824, with millions more continuing to immigrate following independence.[9]

text: In Hispaniola, the indigenous Taíno pre-contact population before the arrival of Columbus of several hundred thousand had declined to sixty thousand by 1509. Although population estimates vary, Dominican friar Bartolomé de las Casas, the "Defender of the Indians" estimated there were 6 million (6,000,000) Taíno and Arawak in the Caribbean at the time of Columbus's arrival in 1492.[citation needed]

text: The population of the Native Amerindian population in Mexico declined by an estimated 90% (reduced to 1–2.5 million people) by the early 17th century. In Peru the indigenous Amerindian pre-contact population of around 6.5 million declined to 1 million by the early 17th century.[citation needed] The overwhelming cause of the decline in both Mexico and Peru was infectious diseases, although the brutality of the Encomienda also played a significant part in the population decline.

text: Of the history of the indigenous population of California, Sherburne F. Cook (1896–1974) was the most painstakingly careful researcher. From decades of research he made estimates for the pre-contact population and the history of demographic decline during the Spanish and post-Spanish periods. According to Cook, the indigenous Californian population at first contact, in 1769, was about 310,000 and had dropped to 25,000 by 1910. The vast majority of the decline happened after the Spanish period, during the Mexican and US periods of Californian history (1821–1910), with the most dramatic collapse (200,000 to 25,000) occurring in the US period (1846–1910).[10][11][12]