document_title: Human leg

question_text: the back of the leg is called what

question_tokens: the back of the leg is called what

text: Human leg

text: Structure[edit]

text: In human anatomy, the lower leg is the part of the lower limb that lies between the knee and the ankle. The thigh is between the hip and knee and makes up the rest of the lower limb. The term lower limb or "lower extremity" is commonly used to describe all of the leg. This article generally follows the common usage.

text: The leg from the knee to the ankle is called the crus or cnemis /ˈniːmɪs/. The calf is the back portion, and the tibia or shinbone together with the smaller fibula make up the front of the lower leg.

text: Evolution has provided the human body with two distinct features: the specialization of the upper limb for visually guided manipulation and the lower limb's development into a mechanism specifically adapted for efficient bipedal gait. While the capacity to walk upright is not unique to humans, other primates can only achieve this for short periods and at a great expenditure of energy. The human adaption to bipedalism is not limited to the leg, however, but has also affected the location of the body's center of gravity, the reorganisation of internal organs, and the form and biomechanism of the trunk. In humans, the double S-shaped vertebral column acts as a shock-absorber which shifts the weight from the trunk over the load-bearing surface of the feet. The human legs are exceptionally long and powerful as a result of their exclusive specialization to support and locomotion — in orangutans the leg length is 111% of the trunk; in chimpanzees 128%, and in humans 171%. Many of the leg's muscles are also adapted to bipedalism, most substantially the gluteal muscles, the extensors of the knee joint, and the calf muscles.[7]

text: Skeleton[edit]

text: The major bones of the leg are the femur (thigh bone), tibia (shin bone), and adjacent fibula, and these are all long bones. The patella (kneecap) is the sesamoid bone in front of the knee. Most of the leg skeleton has bony prominences and margins that can be palpated and some serve as anatomical landmarks that define the extent of the leg. These landmarks are the anterior superior iliac spine, the greater trochanter, the superior margin of the medial condyle of tibia, and the medial malleolus.[8] Notable exceptions to palpation are the hip joint, and the neck and body, or shaft of the femur.

text:
Usually, the large joints of the lower limb are aligned in a straight line, which represents the mechanical longitudinal axis of the leg, the Mikulicz line. This line stretches from the hip joint (or more precisely the head of the femur), through the knee joint (the intercondylar eminence of the tibia), and down to the center of the ankle (the ankle mortise, the fork-like grip between the medial and lateral malleoli). In the tibial shaft, the mechanical and anatomical axes coincide, but in the femoral shaft they diverge 6°, resulting in the femorotibial angle of 174° in a leg with normal axial alignment. A leg is considered straight when, with the feet brought together, both the medial malleoli of the ankle and the medial condyles of the knee are touching. Divergence from the normal femorotibial angle is called genu varum if the center of the knee joint is lateral to the mechanical axis (intermalleolar distance exceeds 3 cm), and genu valgum if it is medial to the mechanical axis (intercondylar distance exceeds 5 cm). These conditions impose unbalanced loads on the joints and stretching of either the thigh's adductors and abductors.[9]
The angle of inclination formed between the neck and shaft of the femur, (collodiaphysial angle), varies with age—about 150° in the newborn, it gradually decreases to 126-128° in adults, to reach 120° in old age. Pathological changes in this angle results in abnormal posture of the leg: A small angle produces coxa vara and a large angle in coxa valga; the latter is usually combined with genu varum and coxa vara leads genu valgum. Additionally, a line drawn through the femoral neck superimposed on a line drawn through the femoral condyles forms an angle, the torsion angle, which makes it possible for flexion movements of the hip joint to be transposed into rotary movements of the femoral head. Abnormally increased torsion angles results in a limb turned inward and a decreased angle in a limb turned outward; both cases resulting in a reduced range of a persons mobility.[10]

text: Muscles[edit]

text: Hip[edit]

text:
Function of hip muscles[11]

Movement
Muscles(In order ofimportance)

Lateralrotation

•Sartorius
•Gluteus maximus
•Quadratus femoris
•Obturator internus
•Gluteus medius and minimus
•Iliopsoas (with psoas major♣)
•Obturator externus
•All functional adductors
except gracilis* and pectineus
•Piriformis

Medialrotation

•Gluteus medius andminimus (anterior fibers)
•Tensor fasciae latae*
•Adductor magnus(long medial fibers)
•Pectineus (with leg abducted)

Extension

•Gluteus maximus
•Gluteus medius and  minimus (dorsal fibers)
•Adductor magnus
•Piriformis
•Semimembranosus*
•Semitendinousus*
•Biceps femoris*(long head)

Flexion

•Iliopsoas (with psoas major♣)
•Tensor fasciae latae*
•Pectineus
•Adductor longus
•Adductor brevis
•Gracilis*
•Rectus femoris*
•Sartorius*

Abduction

•Gluteus medius
•Tensor fasciae latae*
•Gluteus maximus(fibers to fascia lata)
•Gluteus minimus
•Piriformis
•Obturator internus

Adduction

•Adductor magnus (with adductor minimus)
•Adductor longus
•Adductor brevis
•Gluteus maximus (fibersto gluteal tuberosity)
•Gracilis
•Pectineus
•Quadratus femoris
•Obturator externus
•Semitendinosus*

Notes
♣ Also act on vertebral joints. * Also act on knee joint.

tag: table

text: There are several ways of classifying the muscles of the hip: (1) By location or innervation (ventral and dorsal divisions of the plexus layer); (2) by development on the basis of their points of insertion (a posterior group in two layers and an anterior group); and (3) by function (i.e. extensors, flexors, adductors, and abductors).[12]

text: Some hip muscles also act on either the knee joint or on vertebral joints. Additionally, because the area of origin and insertion of many of these muscles are very extensive, these muscles are often involved in several very different movements. In the hip joint, lateral and medial rotation occur along the axis of the limb; extension (also called dorsiflexion or retroversion) and flexion (anteflexion or anteversion) occur along a transverse axis; and abduction and adduction occur about a sagittal axis.[11]

text: The anterior dorsal hip muscles are the iliopsoas, a group of two or three muscles with a shared insertion on the lesser trochanter of the femur. The psoas major originates from the last vertebra and along the lumbar spine to stretch down into the pelvis. The iliacus originates on the iliac fossa on the interior side of the pelvis. The two muscles unite to form the iliopsoas muscle which is inserted on the lesser trochanter of the femur. The psoas minor, only present in about 50 per cent of subjects, originates above psoas major to stretch obliquely down to its insertion on the interior side of the major muscle.[13]

text: The posterior dorsal hip muscles are inserted on or directly below the greater trochanter of the femur. The tensor fasciae latae, stretching from the anterior superior iliac spine down into the iliotibial tract, presses the head of the femur into the acetabulum but also flexes, rotates medially, and abducts to hip joint. The piriformis originates on the anterior pelvic surface of the sacrum, passes through the greater sciatic foramen, and inserts on the posterior aspect of the tip of the greater trochanter. In a standing posture it is a lateral rotator, but it also assists extending the thigh. The gluteus maximus has its origin between (and around) the iliac crest and the coccyx from where one part radiates into the iliotibial tract and the other stretches down to the gluteal tuberosity under the greater trochanter. The gluteus maximus is primarily an extensor and lateral rotator of the hip joint, and it comes into action when climbing stairs or rising from a sitting to standing posture. Furthermore, the part inserted into the fascia latae abducts and the part inserted into the gluteal tuberosity adducts the hip. The two deep glutei muscles, the gluteus medius and minimus, originate on the lateral side of the pelvis. The medius muscle is shaped like a cap. Its anterior fibers act as a medial rotator and flexor; the posterior fibers as a lateral rotator and extensor; and the entire muscle abducts the hip. The minimus has similar functions and both muscles are inserted onto the greater trochanter.[14]

text: The ventral hip muscles function as lateral rotators and play an important role in the control of the body's balance. Because they are stronger than the medial rotators, in the normal position of the leg, the apex of the foot is pointing outward to achieve better support. The obturator internus originates on the pelvis on the obturator foramen and its membrane, passes through the lesser sciatic foramen, and is inserted on the trochanteric fossa of the femur.  "Bent" over the lesser sciatic notch, which acts as a fulcrum, the muscle forms the strongest lateral rotators of the hip together with the gluteus maximus and quadratus femoris. When sitting with the knees flexed it acts as an abductor. The obturator externus has a parallel course with its origin located on the posterior border of the obturator foramen. It is covered by several muscles and acts as a lateral rotator and a weak adductor. The inferior and superior gemelli represent marginal heads of the obturator internus and assist this muscle. The three muscles have been referred to as the triceps coxae. The quadratus femoris originates at the ischial tuberosity and is inserted onto the intertrochanteric crest between the trochanters. This flattened muscle act as a strong lateral rotator and adductor of the thigh.[15]

text: The adductor muscles of the thigh are innervated by the obturator nerve, with the exception of pectineus which receives fibers from the femoral nerve, and the adductor magnus which receives fibers from the tibial nerve. The gracilis arises from near the pubic symphysis and is unique among the adductors in that it reaches past the knee to attach on the medial side of the shaft of the tibia, thus acting on two joints. It share its distal insertion with the sartorius and semitendinosus, all three muscles forming the pes anserinus. It is the most medial muscle of the adductors, and with the thigh abducted its origin can be clearly seen arching under the skin. With the knee extended, it adducts the thigh and flexes the hip. The pectineus has its origin on the iliopubic eminence laterally to the gracilis and, rectangular in shape, extends obliquely to attach immediately behind the lesser trochanter and down the pectineal line and the proximal part of the linea aspera on the femur. It is a flexor of the hip joint, and an adductor and a weak medial rotator of the thigh. The adductor brevis originates on the inferior ramus of the pubis below the gracilis and stretches obliquely below the pectineus down to the upper third of the linea aspera. Except for being an adductor, it is a lateral rotator and weak flexor of the hip joint.[16] The adductor longus has its origin at superior ramus of the pubis and inserts medially on the middle third of the linea aspera. Primarily an adductor, it is also responsible for some flexion. The adductor magnus has its origin just behind the longus and lies deep to it. Its wide belly divides into two parts: One is inserted into the linea aspera and the tendon of the other reaches down to adductor tubercle on the medial side of the femur's distal end where it forms an intermuscular septum that separates the flexors from the extensors. Magnus is a powerful adductor, especially active when crossing legs. Its superior part is a lateral rotator but the inferior part acts as a medial rotator on the flexed leg when rotated outward and also extends the hip joint. The adductor minimus is an incompletely separated subdivision of the adductor magnus. Its origin forms an anterior part of the magnus and distally it is inserted on the linea aspera above the magnus. It acts to adduct and lateral rotate the femur.[17]

text: Thigh[edit]

text:
Function of knee muscles[18]

Movement
Muscles(In order ofimportance)

Extension

•Quadriceps femoris
•Tensor fasciae latae*

Flexion

•Semimembranosus
•Semitendinosus
•Biceps femoris
•Gracilis
•Sartorius
•Popliteus
•Gastrocnemius

Medialrotation

•Semimembranosus
•Semitendinosus
•Gracilis
•Sartorius
•Popliteus

Lateralrotation

•Biceps femoris
•Tensor fasciae latae*

*Insignificant assistance.

text: The muscles of the thigh can be classified into three groups according to their location: anterior and posterior muscles and the adductors (on the medial side). All the adductors except gracilis insert on the femur and act on the hip joint, and so functionally qualify as hip muscles. The majority of the thigh muscles, the "true" thigh muscles, insert on the leg (either the tibia or the fibula) and act primarily on the knee joint. Generally, the extensors lie on anterior of the thigh and flexors lie on the posterior. Even though the sartorius flexes the knee, it is ontogenetically considered an extensor since its displacement is secondary.[12]

text: Of the anterior thigh muscles the largest are the four muscles of the quadriceps femoris: the central rectus femoris, which is surrounded by the three vasti, the vastus intermedius, medialis, and lateralis. Rectus femoris is attached to the pelvis with two tendons, while the vasti are inserted to the femur. All four muscles unite in a common tendon inserted into the patella from where the patellar ligament extends it down to the tibial tuberosity. Fibers from the medial and lateral vasti form two retinacula that stretch past the patella on either sides down to the condyles of the tibia. The quadriceps is the knee extensor, but the rectus femoris additionally flexes the hip joint, and articular muscle of the knee protects the articular capsule of the knee joint from being nipped during extension. The sartorius  runs superficially and obliquely down on the anterior side of the thigh, from the anterior superior iliac spine to the pes anserinus on the medial side of the knee, from where it is further extended into the crural fascia. The sartorius acts as a flexor on both the hip and knee, but, due to its oblique course, also contributes to medial rotation of the leg as one of the pes anserinus muscles (with the knee flexed), and to lateral rotation of the hip joint.[19]

text:
There are four posterior thigh muscles. The biceps femoris has two heads: The long head has its origin on the ischial tuberosity together with the semitendinosus and acts on two joints. The short head originates from the middle third of the linea aspera on the shaft of the femur and the lateral intermuscular septum of thigh, and acts on only one joint. These two heads unite to form the biceps which inserts on the head of the fibula. The biceps flexes the knee joint and rotates the flexed leg laterally — it is the only lateral rotator of the knee and thus has to oppose all medial rotator. Additionally, the long head extends the hip joint. The semitendinosus and the semimembranosus share their origin with the long head of the biceps, and both attaches on the medial side of the proximal head of the tibia together with the gracilis and sartorius to form the pes anserinus. The semitendinosus acts on two joints; extension of the hip, flexion of the knee, and medial rotation of the leg. Distally, the semimembranosus' tendon is divided into three parts referred to as the pes anserinus profondus. Functionally, the semimembranosus is similar to the semitendinosus, and thus produces extension at the hip joint and flexion and medial rotation at the knee.[20]
Posteriorly below the knee joint, the popliteus stretches obliquely from the lateral femoral epicondyle down to the posterior surface of the tibia. The subpopliteal bursa is located deep to the muscle. Popliteus flexes the knee joint and medially rotates the leg.[21]

text: Crus and foot[edit]

text:
Function of foot muscles[22]

Movement
Muscles(In order ofimportance)

Dorsi-flexion

•Tibialis anterior
•Extensor digitorumlongus
•Extensor hallucislongus

Plantarflexion

•Triceps surae
•Peroneus longus
•Peroneus brevis
•Flexor digitorumlongus
•Tibialis posterior

Eversion

•Peroneus longus
•Peroneus brevis
•Extensor digitorumlongus
•Peroneus tertius

Inversion

•Triceps surae
•Tibialis posterior
•Flexor hallucislongus
•Flexor digitorumlongus
•Tibialis anterior

text: With the popliteus (see above) as the single exception, all muscles in the leg are attached to the foot and, based on location, can be classified into an anterior and a posterior group separated from each other by the tibia, the fibula, and the interosseous membrane. In turn, these two groups can be subdivided into subgroups or layers — the anterior group consists of the extensors and the peroneals, and the posterior group of a superficial and a deep layer. Functionally, the muscles of the leg are either extensors, responsible for the dorsiflexion of the foot, or flexors, responsible for the plantar flexion. These muscles can also classified by innervation, muscles supplied by the anterior subdivision of the plexus and those supplied by the posterior subdivision.[23]  The leg muscles acting on the foot are called the extrinsic foot muscles whilst the foot muscles located in the foot are called intrinsic.

text: Dorsiflexion (extension) and plantar flexion occur around the transverse axis running through the ankle joint from the tip of the medial malleolus to the tip of the lateral malleolus. Pronation (eversion) and supination (inversion) occur along the oblique axis of the ankle joint.[22]

text: Extrinsic[edit]

text:
Three of the anterior muscles are extensors. From its origin on the lateral surface of the tibia and the interosseus membrane, the three-sided belly of the tibialis anterior extends down below the superior and inferior extensor retinacula to its insertion on the plantar side of the medial cuneiform bone and the first metatarsal bone. In the non-weight-bearing leg, the anterior tibialis dorsal flexes the foot and lifts the medial edge of the foot. In the weight-bearing leg, it pulls the leg towards the foot. The extensor digitorum longus has a wide origin stretching from the lateral condyle of the tibia down along the anterior side of the fibula, and the interosseus membrane. At the ankle, the tendon divides into four that stretch across the foot to the dorsal aponeuroses of the last phalanges of the four lateral toes. In the non-weight-bearing leg, the muscle extends the digits and dorsiflexes the foot, and in the weight-bearing leg acts similar to the tibialis anterior. The extensor hallucis longus has its origin on the fibula and the interosseus membrane between the two other extensors and is, similarly to the extensor digitorum, is inserted on the last phalanx of big toe ("hallux"). The muscle dorsiflexes the hallux, and acts similar to the tibialis anterior in the weight-bearing leg.[24]
Two muscles on the lateral side of the leg form the peroneal group. The peroneus longus and brevis both have their origins on the fibula and they both pass behind the lateral malleolus where their tendons pass under the peroneal retinacula. Under the foot, the longus stretches from the lateral to the medial side in a groove, thus bracing the transverse arch of the foot. The brevis is attached on the lateral side to the tuberosity of the fifth metatarsal. Together the two peroneals form the strongest pronators of the foot.[25] The peroneus muscles are highly variable and several variants can occasionally be present.[26]

text: Of the posterior muscles three are in the superficial layer. The major plantar flexors, commonly referred to as the triceps surae, are the soleus, which arises on the proximal side of both leg bones, and the gastrocnemius, the two heads of which arises on the distal end of the femur. These muscles unite in a large terminal tendon, the Achilles tendon, which is attached to the posterior tubercle of the calcaneus. The plantaris closely follows the lateral head of the gastrocnemius. Its tendon runs between those of the soleus and gastrocnemius and is embedded in the medial end of the calcaneus tendon.[27]

text: In the deep layer, the tibialis posterior has its origin on the interosseus membrane and the neighbouring bone areas and runs down behind the medial malleolus. Under the foot it splits into a thick medial part attached to the navicular bone and a slightly weaker lateral part inserted to the three cuneiform bones. The muscle produces simultaneous plantar flexion and supination in the non-weight-bearing leg, and approximates the heel to the calf of the leg. The flexor hallucis longus arises distally on the fibula and on the interosseus membrane from where its relatively thick muscle belly extends far distally. Its tendon extends beneath the flexor retinaculum to the sole of the foot and finally attaches on the base of the last phalanx of the hallux. It plantarflexes the hallux and assists in supination. The flexor digitorum longus, finally, has its origin on the upper part of the tibia. Its tendon runs to the sole of the foot where it forks into four terminal tendon attached to the last phalanges of the four lateral toes. It crosses the tendon of the tibialis posterior distally on the tibia, and the tendon of the flexor hallucis longus in the sole. Distally to its division, the quadratus plantae radiates into it and near the middle phalanges its tendons penetrate the tendons of the flexor digitorum brevis. In the non-weight-bearing leg, it plantar flexes the toes and foot and supinates. In the weight-bearing leg it supports the plantar arch.[21] (For the popliteus, see above.)

text: Intrinsic[edit]

text:
The intrinsic muscles of the foot, muscles whose bellies are located in the foot proper, are either dorsal (top) or plantar (sole).
On the dorsal side, two long extrinsic extensor muscles are superficial to the intrinsic muscles, and their tendons form the dorsal aponeurosis of the toes. The short intrinsic extensors and the plantar and dorsal interossei radiates into these aponeuroses.
The extensor digitorum brevis and extensor hallucis brevis have a common origin on the anterior side of the calcaneus, from where their tendons extend into the dorsal aponeuroses of digits 1-4. They act to dorsiflex these digits.[28]

text: The plantar muscles can be subdivided into three groups associated with three regions: those of the big digit, the little digit, and the region between these two. All these muscles are covered by the thick and dense plantar aponeurosis, which, together with two tough septa, form the spaces of the three groups. These muscles and their fatty tissue function as cushions that transmit the weight of the body downward. As a whole, the foot is a functional entity.[29]

text:
The abductor hallucis stretches along the medial edge of the foot, from the calcaneus to the base of the first phalanx of the first digit and the medial sesamoid bone. It is an abductor and a weak flexor, and also helps maintain the arch of the foot. Lateral to the abductor hallucis is the flexor hallucis brevis, which originates from the medial cuneiform bone and from the tendon of the tibialis posterior. The flexor hallucis has a medial and a lateral head inserted laterally to the abductor hallucis. It is an important plantar flexor which comes into prominent use in classical ballet (i.e. for pointe work).[29]
The adductor hallucis has two heads; a stronger oblique head which arises from the cuboid and lateral cuneiform bones and the bases of the second and third metatarsals; and a transverse head which arises from the distal ends of the third-fifth metatarsals. Both heads are inserted on the lateral sesamoid bone of the first digit. The muscle acts as a tensor to the arches of the foot, but can also adduct the first digit and plantar flex its first phalanx.[30]

text: The opponens digiti minimi originates from the long plantar ligament and the plantar tendinous sheath of peroneus longus and is inserted on the fifth metatarsal. When present, it acts to plantar flex the fifth digit and supports the plantar arch. The flexor digiti minimi arises from the region of base of the fifth metatarsal and is inserted onto the base of the first phalanx of the fifth digit where it is usually merged with the abductor of the first digit. It acts to plantar flex the last digit. The largest and longest muscles of the little toe is the abductor digiti minimi. Stretching from the lateral process of the calcaneus, with a second attachment on the base of the fifth metatarsal, to the base of the fifth digit's first phalanx, the muscle forms the lateral edge of the sole. Except for supporting the arch, it plantar flexes the little toe and also acts as an abductor.[30]

text: The four lumbricales have their origin on the tendons of the flexor digitorum longus, from where they extend to the medial side of the bases of the first phalanx of digits two-five. Except for reinforcing the plantar arch, they contribute to plantar flexion and move the four digits toward the big toe. They are, in contrast to the lumbricales of the hand, rather variable, sometimes absent and sometimes more than four are present. The quadratus plantae arises with two slips from margins of the plantar surface of the calcaneus and is inserted into the tendon(s) of the flexor digitorum longus, and is known as the "plantar head" of this latter muscle. The three plantar interossei arise with their single heads on the medial side of the third-fifth metatarsals and are inserted on the bases of the first phalanges of these digits. The two heads of the four dorsal interossei arise on two adjacent metatarsals and merge in the intermediary spaces. Their distal attachment is on the bases of the proximal phalanges of the second-fourth digits. The interossei are organized with the second digit as a longitudinal axis; the plantars act as adductors and pull digits 3-5 towards the second digit; while the dorsals act as abductors. Additionally, the interossei act as plantar flexors at the metatarsophalangeal joints. Lastly, the flexor digitorum brevis arises from underneath the calcaneus to insert its tendons on the middle phalanges of digit 2-4. Because the tendons of the flexor digitorum longus run between these tendons, the brevis is sometimes called perforatus. The tendons of these two muscles are surrounded by a tendinous sheath. The brevis acts to plantar flex the middle phalanges.[31]

text: Flexibility[edit]

text: Flexibility can be simply defined as the available range of motion (ROM) provided by a specific joint or group of joints.[32] For the most part, exercises that increase flexibility are performed with intentions to boost overall muscle length, reduce the risks of injury and to potentially improve muscular performance in physical activity.[33] Stretching muscles after engagement in any physical activity can improve muscular strength, increase flexibility, and reduce muscle soreness.[34] If limited movement is present within a joint, the “insufficient extensibility” of the muscle, or muscle group, could be restricting the activity of the affected joint.[35]

text: Stretching[edit]

text: Stretching prior to strenuous physical activity has been thought to increase muscular performance by extending the soft tissue past its attainable length in order to increase range of motion.[32] Many physically active individuals practice these techniques as a “warm-up” in order to achieve a certain level of muscular preparation for specific exercise movements. When stretching, muscles should feel somewhat uncomfortable but not physically agonizing.

text:
Plantar flexion: One of the most popular lower leg muscle stretches is the step standing heel raises, which mainly involves the gastrocnemius, soleus, and the Achilles tendon.[36] Standing heel raises allow the individual to activate their calf muscles by standing on a step with toes and forefoot, leaving the heel hanging off the step, and plantar flexing the ankle joint by raising the heel. This exercise is easily modified by holding on to a nearby rail for balance and is generally repeated 5-10 times.
Dorsiflexion: In order to stretch the anterior muscles of the lower leg, crossover shin stretches work well.[37] This motion will stretch the dorsiflexion muscles, mainly the anterior tibialis, extensor hallucis longus and extensor digitorum longus, by slowly causing the muscles to lengthen as body weight is leaned on the ankle joint by using the floor as resistance against the top of the foot.[37] Crossover shin stretches can vary in intensity depending on the amount of body weight applied on the ankle joint as the individual bends at the knee. This stretch is typically held for 15–30 seconds.
Eversion and inversion: Stretching the eversion and inversion muscles allows for better range of motion to the ankle joint.[33] Seated ankle elevations and depressions will stretch the peroneus and tibilalis muscles that are associated with these movements as they lengthen. Eversion muscles are stretched when the ankle becomes depressed from the starting position. In like manner, the inversion muscles are stretched when the ankle joint becomes elevated. Throughout this seated stretch, the ankle joint is to remain supported while depressed and elevated with the ipsilateral (same side) hand in order to sustain the stretch for 10–15 seconds. This stretch will increase overall eversion and inversion muscle group length and provide more flexibility to the ankle joint for larger range of motion during activity.[32][33]

text: Blood supply[edit]

text: The arteries of the leg are divided into a series of segments.

text: In the pelvis area, at the level of the last lumbar vertebra, the abdominal aorta, a continuation the descending aorta, splits into a pair of common iliac arteries. These immediately split into the internal and external iliac arteries, the latter of which descends along the medial border of the psoas major to exits the pelvis area through the vascular lacuna under the inguinal ligament.[38]

text: The artery enters the thigh as the femoral artery which descends the medial side of the thigh to the adductor canal. The canal passes from the anterior to the posterior side of the limb where the artery leaves through the adductor hiatus and becomes the popliteal artery. On the back of the knee the popliteal artery runs through the popliteal fossa to the popliteal muscle where it divides into anterior and posterior tibial arteries.[38]

text: In the lower leg, the anterior tibial enters the extensor compartment near the upper border of the interosseus membrane to descend between the tibialis anterior and the extensor hallucis longus. Distal to the superior and extensor retinacula of the foot it becomes the dorsal artery of the foot. The posterior tibial forms a direct continuation of the popliteal artery which enters the flexor compartment of the lower leg to descend behind the medial malleolus where it divides into the medial and lateral plantar arteries, of which the posterior branch gives rise to the fibular artery.[38]

text:
For practical reasons the lower limb is subdivided into somewhat arbitrary regions:[39]
The regions of the hip are all located in the thigh: anteriorly, the subinguinal region is bounded by the inguinal ligament, the sartorius, and the pectineus and forms part of the femoral triangle which extends distally to the adductor longus. Posteriorly, the gluteal region corresponds to the gluteus maximus. The anterior region of the thigh extends distally from the femoral triangle to the region of the knee and laterally to the tensor fasciae latae. The posterior region ends distally before the popliteal fossa. The anterior and posterior regions of the knee extend from the proximal regions down to the level of the tuberosity of the tibia. In the lower leg the anterior and posterior regions extend down to the malleoli. Behind the malleoli are the lateral and medial retromalleolar regions and behind these is the region of the heel. Finally, the foot is subdivided into a dorsal region superiorly and a plantar region inferiorly.[39]

text: Veins[edit]

text: The veins are subdivided into three systems. The deep veins return approximately 85 percent of the blood and the superficial veins approximately 15 percent. A series of perforator veins interconnect the superficial and deep systems. In the standing posture, the veins of the leg have to handle an exceptional load as they act against gravity when they return the blood to the heart. The venous valves assist in maintaining the superficial to deep direction of the blood flow.[40]

text: Superficial veins:

text:
Greater saphenous vein
Small saphenous

text: Deep veins:

text:
Femoral vein
Popliteal vein
Anterior tibial vein
Posterior tibial vein
Fibular vein

text: Innervation[edit]

text: The sensory and motor innervation to the lower limb is supplied by the lumbosacral plexus, which is formed by the ventral rami of the lumbar and sacral spinal nerves with additional contributions from the subcostal nerve (T12) and coccygeal nerve (Co1). Based on distribution and topography, the lumbosacral plexus is subdivided into the lumbar plexus (T12-L4) and the Sacral plexus (L5-S4); the latter is often further subdivided into the sciatic and pudendal plexuses:[41]

text: The lumbar plexus is formed lateral to the intervertebral foramina by the ventral rami of the first four lumbar spinal nerves (L1-L4), which all pass through psoas major. The larger branches of the plexus exit the muscle to pass sharply downward to reach the abdominal wall and the thigh (under the inguinal ligament); with the exception of the obturator nerve which pass through the lesser pelvis to reach the medial part of the thigh through the obturator foramen. The nerves of the lumbar plexus pass in front of the hip joint and mainly support the anterior part of the thigh.[41]

text: The iliohypogastric (T12-L1) and ilioinguinal nerves (L1) emerge from the psoas major near the muscle's origin, from where they run laterally downward to pass anteriorly above the iliac crest between the transversus abdominis and abdominal internal oblique, and then run above the inguinal ligament. Both nerves give off muscular branches to both these muscles. Iliohypogastric supplies sensory branches to the skin of the lateral hip region, and its terminal branch finally pierces the aponeurosis of the abdominal external oblique above the inguinal ring to supply sensory branches to the skin there. Ilioinguinalis exits through the inguinal ring and supplies sensory branches to the skin above the pubic symphysis and the lateral portion of the scrotum.[42]

text: The genitofemoral nerve (L1, L2) leaves psoas major below the two former nerves, immediately divides into two branches that descends along the muscle's anterior side. The sensory femoral branch supplies the skin below the inguinal ligament, while the mixed genital branch supplies the skin and muscles around the sex organ. The lateral femoral cutaneous nerve (L2, L3) leaves psoas major laterally below the previous nerve, runs obliquely and laterally downward above the iliacus, exits the pelvic area near the iliac spine, and supplies the skin of the anterior thigh.[42]

text: The obturator nerve (L2-L4) passes medially behind psoas major to exit the pelvis through the obturator canal, after which it gives off branches to obturator externus and divides into two branches passing behind and in front of adductor brevis to supply motor innervation to all the other adductor muscles. The anterior branch also supplies sensory nerves to the skin on a small area on the distal medial aspect of the thigh.[43] The femoral nerve (L2-L4) is the largest and longest of the nerves of the lumbar plexus. It supplies motor innervation to iliopsoas, pectineus, sartorius, and quadriceps; and sensory branches to the anterior thigh, medial lower leg, and posterior foot.[43]

text:
The nerves of the sacral plexus pass behind the hip joint to innervate the posterior part of the thigh, most of the lower leg, and the foot.[41]  The superior (L4-S1) and inferior gluteal nerves (L5-S2) innervate the gluteus muscles and the tensor fasciae latae. The posterior femoral cutaneous nerve (S1-S3) contributes sensory branches to the skin on the posterior thigh.[44]  The sciatic nerve (L4-S3), the largest and longest nerve in the human body, leaves the pelvis through the greater sciatic foramen. In the posterior thigh it first gives off branches to the short head of the biceps femoris and then divides into the tibial (L4-S3) and common fibular nerves (L4-S2). The fibular nerve continues down on the medial side of biceps femoris, winds around the fibular neck and enters the front of the lower leg. There it divides into a deep and a superficial terminal branch. The superficial branch supplies the peroneus muscles and the deep branch enters the extensor compartment; both branches reaches into the dorsal foot. In the thigh, the tibial nerve gives off branches to semitendinosus, semimembranosus, adductor magnus, and the long head of the biceps femoris. The nerve then runs straight down the back of the leg, through the popliteal fossa to supply the ankle flexors on the back of the lower leg and then continues down to supply all the muscles in the sole of the foot.[45]
The pudendal (S2-S4) and coccygeal nerves (S5-Co2) supply the muscles of the pelvic floor and the surrounding skin.[46]

text: The lumbosacral trunk is a communicating branch passing between the sacral and lumbar plexuses containing ventral fibers from L4. The coccygeal nerve, the last spinal nerve, emerges from the sacral hiatus, unites with the ventral rami of the two last sacral nerves, and forms the coccygeal plexus.[41]

text: Lower leg and foot[edit]

text: The lower leg and ankle need to keep exercised and moving well as they are the base of the whole body. The lower extremities must be strong in order to balance the weight of the rest of the body, and the gastrocnemius muscles take part in much of the blood circulation.

text: Exercises[edit]

text: Isometric and standard[edit]

text: There are a number of exercises that can be done to strengthen the lower leg. For example, in order to activate plantar flexors in the deep plantar flexors one can sit on the floor with the hips flexed, the ankle neutral with knees fully extended as they alternate pushing their foot against a wall or platform. This kind of exercise is beneficial as it hardly causes any fatigue.[47]  Another form of isometric exercise for the gastrocnemius would be seated calf raises which can be done with or without equipment. One can be seated at a table with their feet flat on the ground, and then plantar flex both ankles so that the heels are raised off the floor and the gastrocnemius flexed.[48] An alternate movement could be heel drop exercises with the toes being propped on an elevated surface—as an opposing movement this would improve the range of motion.[49] One-legged toe raises for the gastrocnemius muscle can be performed by holding one dumbbell in one hand while using the other for balance, and then standing with one foot on a plate. The next step would be to plantar flex and keep the knee joint straight or flexed slightly. The triceps surae is contracted during this exercise.[50] Stabilization exercises like the BOSU ball squat are also important especially as they assist in the ankles having to adjust to the ball’s form in order to balance.[51]

text: Clinical significance[edit]

text: Lower leg injury[edit]

text: Lower leg injuries are common while running or playing sports. About 10% of all total injuries involve the lower extremities in athletes.[52]  The majority of athletes sprain their ankles, which are mainly caused by the increased loads onto the feet when they move into the foot down or in an outer ankle position. All areas of the foot, which are the forefoot, midfoot, and rearfoot, absorb various forces while running and can lead to injuries as well.[53] Running and various activities can cause stress fractures, tendinitis, musculotendinous injuries, or any chronic pain to our lower extremities such as the tibia.[52]

text: Types of activities[edit]

text: Injuries to quadriceps or hamstrings are caused by the constant impact loads to the legs during activities, such as kicking a ball. While doing this type of motion, 85% of that shock is absorbed to the hamstrings which can cause strain to those muscles.[53]

text:
Jumping – is another risk because if the legs do not land properly after an initial jump, there may be damage to the meniscus in the knees, sprain to the ankle by everting or inverting the foot, or damage to the Achilles tendon and gastrocnemius if there is too much force while plantar flexing.[53]
Weight lifting – such as the improperly performed deep squat, is also dangerous to the lower limbs, because the exercise can lead to an overextension, or an outstretch, of our ligaments in the knee and can cause pain over time.[53]
Running – the most common activity associated with lower leg injury. There is constant pressure and stress being put on the feet, knees, and legs while running by gravitational force. Muscle tears in our legs or pain in various areas of the feet can be a result of poor biomechanics of running.

text: Running[edit]

text: The most common injuries in running involve the knees and the feet. Various studies have focused on the initial cause of these running related injuries and found that there are many factors that correlate to these injuries. Female distance runners who had a history of stress fracture injuries had higher vertical impact forces than non-injured subjects.[54] The large forces onto the lower legs were associated with gravitational forces, and this correlated with patellofemoral pain or potential knee injuries.[54]  Researchers have also found that these running related injuries affect the feet as well because runners with previous injuries showed more foot eversion and over pronation while running than non-injured runners.[55] This causes more loads and forces on the medial side of the foot, causing more stress on the tendons of the foot and ankle (peroneal tendons).[55] Most of these running injuries are caused by overuse and that running at longer distances weekly for a long duration is a risk for injuring the lower legs.[56]

text: Prevention tools[edit]

text: Voluntary stretches to the legs, such as the wall stretch, condition the hamstrings and the calf muscle to various movements before vigorously working them.[57] But a study has shown that Kinesiology tape gives more promising effect in hamstring extensibility to produce more fluid movement.[58] Thirty previously injured males showed a greater advantage of hamstring extensibility in longer durations with Kinesiology tape, or elastic therapeutic tape. However, they were more advantageous in the beginning of the exercise with a voluntary, static stretch or proprioceptive neuromuscular facilitation, which are stretching techniques specific to optimize the range of motion of the limb.[58] This shows that stretches do help in the immediate time frames, whereas Kinesiology tape helps in long durations to prevent any future injuries from occurring. The environment and surroundings, such as uneven terrain, can cause the feet to position in an unnatural way, so wearing shoes that can absorb forces from the ground’s impact and allow for stabilizing the feet can prevent some injuries while running as well. Shoes should be structured to allow friction-traction at the shoe surface, space for different foot-strike stresses, or for comfortable, regular arches for the feet.[53]

text: Summary[edit]

text: The chances of damaging our lower extremities will be reduced by having knowledge about some activities associated with lower leg injury and developing a correct form of running, such as not over pronating the foot or overusing the legs. Preventative measures, such as taping, various stretches, and wearing appropriate footwear, will reduce injuries from occurring as well.[59]

text: Fracture[edit]

text: A fracture of the leg can be classified according to the involved bone into:

text: Femoral fracture (in the upper leg)

text: Crus fracture (in the lower leg).

text: Pain management[edit]

text: Lower leg and foot pain management is critical in reducing the progression of further injuries, uncomfortable sensations and limiting alterations while walking and running. Most individuals suffer from various pains in their lower leg and foot due to different factors. Muscle inflammation, strain, tenderness, swelling and muscle tear from muscle overuse or incorrect movement are several conditions often experienced by athletes and the common public during and after high impact physical activities. Therefore, suggested pain management mechanisms are provided to reduce pain and prevent the progression of injury.

text: Plantar fasciitis[edit]

text: A plantar fasciitis foot stretch is one of the recommended methods to reduce pain caused by plantar fasciitis (Figure 1). To do the plantar fascia stretch, while sitting in a chair place the ankle on the opposite knee and hold the toes of the impaired foot, slowly pulling back. The stretch should be held for approximately ten seconds, three times per day[60]

text: Medial tibial stress syndrome (shin splint)[edit]

text: Several methods can be utilized to help control pain caused by shin splints. Placing ice on the affected area prior to and after running will aid in reducing pain. In addition, wearing orthotic devices including a neoprene sleeve (Figure 2) and wearing appropriate footwear such as a foot arch can help to eliminate the condition. Stretching and strengthening of the anterior tibia or medial tibia by performing exercises of plantar and dorsi flexors such as calf  stretch can also help in easing the pain[61]

text: Achilles tendinopathy[edit]

text: There are numerous appropriate approaches to handling pain resulting from Achilles tendinitis. The primary action is to rest. Activities that do not provide additional stress to the affected tendon are also recommended. Wearing orthothics or prostheses will provide cushion and will prevent the affected Achilles tendon from experiencing further stress when walking and performing therapeutic stretches. A few stretch modalities or eccentric exercises such as toe extension and flexion and calf and heel stretch are beneficial in lowering pain with Achilles tendinopathy patients (Figure 4)[62]

text: Society and culture[edit]

text: Adolescent and adult women in many Western cultures often remove the hair from their legs. Toned, tanned, shaved legs are sometimes perceived as a sign of youthfulness and are often considered attractive in these cultures.

text: Men generally do not shave their legs in any culture. However, leg-shaving is a generally accepted practice in modeling.[63] It is also fairly common in sports where the hair removal makes the athlete appreciably faster by reducing drag; the most common case of this is competitive swimming. It is also practiced in other sports such as cycling,[64] in which skin injuries are common: the absence of grown hair makes nicks, scratches and bruises heal faster because of the reduced microbial population on shaved skin.[citation needed]

text: Image gallery[edit]

text:
Surface anatomy of human leg

Muscles of the gluteal and posterior femoral regions.

Small saphenous vein and its tributaries.

The popliteal, posterior tibial, and peroneal arteries.

Nerves of the right lower extremity Posterior view.

Leg Bones


document_title: List of Catholic dioceses in Australia

question_text: what is the name of our diocese in sydney

root

text: List of Catholic dioceses in Australia

text: List of dioceses[edit]

text: Australian Catholic Bishops Conference[edit]

text: Ecclesiastical Province of Adelaide[edit]

text:
Archdiocese of Adelaide

Diocese of Darwin
Diocese of Port Pirie

tag: ul

text: Ecclesiastical Province of Brisbane[edit]

text:
Archdiocese of Brisbane

Diocese of Cairns
Diocese of Rockhampton
Diocese of Toowoomba
Diocese of Townsville

text: Ecclesiastical Province of Melbourne[edit]

text:
Archdiocese of Melbourne

Diocese of Ballarat
Eparchy of Saints Peter and Paul
Eparchy of Saint Thomas the Apostle
Diocese of Sale
Diocese of Sandhurst

text: Ecclesiastical Province of Perth[edit]

text:
Archdiocese of Perth

Diocese of Broome
Diocese of Bunbury
Diocese of Geraldton

text: Ecclesiastical Province of Sydney[edit]

text:
Archdiocese of Sydney

Diocese of Armidale
Diocese of Bathurst
Diocese of Broken Bay
Diocese of Lismore
Diocese of Maitland-Newcastle
Diocese of Parramatta
Diocese of Wagga Wagga
Diocese of Wilcannia-Forbes
Diocese of Wollongong

text: Sui iuris jurisdictions[edit]

text:
Archdiocese of Canberra and Goulburn
Archdiocese of Hobart
Diocese of Saint Maron of Sydney
Diocese of Saint Michael’s of Sydney
Diocese of Saint Thomas the Apostle of Sydney
Military Ordinariate of Australia
Personal Ordinariate of Our Lady of the Southern Cross


document_title: U-boat

question_text: when were u boats first used in ww1

question_tokens: when were u boats first used in ww1

text: U-boat

text: Early U-boats (1850-1914)[edit]

text: The first submarine built in Germany, the three-man Brandtaucher, sank to the bottom of Kiel harbor on 1 February 1851 during a test dive.[2][3] The inventor and engineer Wilhelm Bauer had designed this vessel in 1850, and Schweffel & Howaldt constructed it in Kiel. Dredging operations in 1887 rediscovered Brandtaucher; it was later raised and put on historical display in Germany.

tag: p

text: There followed in 1890 the boats WW1 and WW2, built to a Nordenfelt design. In 1903 the Friedrich Krupp Germaniawerft dockyard in Kiel completed the first fully functional German-built submarine, Forelle,[4] which Krupp sold to Russia during the Russo-Japanese War in April 1904.[5] The SM U-1 was a completely redesigned Karp-class submarine and only one was built. The Imperial German Navy commissioned it on 14 December 1906.[6] It had a double hull, a Körting kerosene engine, and a single torpedo tube. The 50%-larger SM U-2 (commissioned in 1908) had two torpedo tubes. The U-19 class of 1912–13 saw the first diesel engine installed in a German navy boat. At the start of World War I in 1914, Germany had 48 submarines of 13 classes in service or under construction. During that war the Imperial German Navy used SM U-1 for training. Retired in 1919, it remains on display at the Deutsches Museum in Munich.[7]

text: World War I (1914-1918)[edit]

text: On 5 September 1914, HMS Pathfinder was sunk by SM U-21, the first ship to have been sunk by a submarine using a self-propelled torpedo. On 22 September, U-9 sank the obsolete British warships HMS Aboukir, HMS Cressy and HMS Hogue (the "Live Bait Squadron") in a single hour.

text: In the Gallipoli Campaign in early 1915 in the eastern Mediterranean, German U-boats, notably the U-21, prevented close support of allied troops by 18 pre-Dreadnought battleships by sinking two of them.[8]

text: For the first few months of the war, U-boat anticommerce actions observed the "prize rules" of the time, which governed the treatment of enemy civilian ships and their occupants. On 20 October 1914, SM U-17 sank the first merchant ship, the SS Glitra, off Norway.[9] Surface commerce raiders were proving to be ineffective, and on 4 February 1915, the Kaiser assented to the declaration of a war zone in the waters around the British Isles. This was cited as a retaliation for British minefields and shipping blockades. Under the instructions given to U-boat captains, they could sink merchant ships, even potentially neutral ones, without warning.

text: In February 1915, a submarine U-6 (Lepsius) was rammed and both periscopes were destroyed off Beachy Head by the collier SS Thordis commanded by Captain John Bell RNR after firing a torpedo.[10] On 7 May 1915, SM U-20 sank the liner RMS Lusitania. The sinking claimed 1,198 lives, 128 of them American civilians, and the attack of this unarmed civilian ship deeply shocked the Allies. According to the ship's manifest, Lusitania was carrying military cargo, though none of this information was relayed to the citizens of Britain and the United States who thought that the ship contained no ammunition or military weaponry whatsoever and it was an act of brutal murder. Munitions that it carried were thousands of crates full of ammunition for rifles, 3-inch artillery shells, and also various other standard ammunition used by infantry. The sinking of the Lusitania was widely used as propaganda against the German Empire and caused greater support for the war effort. A widespread reaction in the U.S was not seen until the sinking of the ferry SS Sussex. The sinking occurred in 1915 and the United States entered the war in 1917.

text: The initial U.S. response was to threaten to sever diplomatic ties, which persuaded the Germans to issue the Sussex pledge that reimposed restrictions on U-boat activity. The U.S. reiterated its objections to German submarine warfare whenever U.S. civilians died as a result of German attacks, which prompted the Germans to fully reapply prize rules. This, however, removed the effectiveness of the U-boat fleet, and the Germans consequently sought a decisive surface action, a strategy that culminated in the Battle of Jutland.

text: Although the Germans claimed victory at Jutland, the British Grand Fleet remained in control at sea. It was necessary to return to effective anticommerce warfare by U-boats. Vice-Admiral Reinhard Scheer, Commander in Chief of the High Seas Fleet, pressed for all-out U-boat war, convinced that a high rate of shipping losses would force Britain to seek an early peace before the United States could react effectively.

text: The renewed German campaign was effective, sinking 1.4 million tons of shipping between October 1916 and January 1917. Despite this, the political situation demanded even greater pressure, and on 31 January 1917, Germany announced that its U-boats would engage in unrestricted submarine warfare beginning 1 February. On 17 March, German submarines sank three American merchant vessels, and the U.S. declared war on Germany in April 1917.

text: Unrestricted submarine warfare in early 1917 was initially very successful, sinking a major part of Britain-bound shipping. Nevertheless, with the introduction of escorted convoys, shipping losses declined and in the end the German strategy failed to destroy sufficient Allied shipping. An armistice became effective on 11 November 1918 and all surviving German submarines were surrendered. Of the 360 submarines that had been built, 178 were lost, but more than 11 million tons of shipping had been destroyed. Of the 178 submarines destroyed, SM U-103 was sunk when the troopship RMS Olympic rammed it as it attempted to crash-dive, killing all on board.

text: Classes[edit]

text:
Körting kerosene-powered boats

Type U 1, Type U 2, Type U 3, Type U 5, Type U 9, Type U 13, Type U 16, Type U 17

Mittel-U MAN diesel boats

Type U 19, Type U 23, Type U 27, Type U 31, Type U 43, Type U 51, Type U 57, Type U 63, Type U 66, Type Mittel U

U-Cruisers and Merchant U-boats

Type U 139, Type U 142, Type U 151, Type UD 1

UB coastal torpedo attack boats

Type UB I, Type UB II, Type UB III, Type UF, Type UG

UC coastal minelayers

Type UC I, Type UC II, Type UC III

UE ocean minelayers

Type UE I, Type UE II

text: Surrender of the fleet[edit]

text: Under the terms of armistice, all U-boats were to immediately surrender. Those in home waters sailed to the British submarine base at Harwich. The entire process was done quickly and in the main without difficulty, after which the vessels were studied, then scrapped or given to Allied navies. Stephen King-Hall wrote a detailed eyewitness account of the surrender.[11]

text: Interwar years (1919-1939)[edit]

text: At the end of World War I, as part of the Paris Peace Conference, 1919, the Treaty of Versailles restricted the total tonnage of the German surface fleet. The treaty also restricted the independent tonnage of ships and forbade the construction of submarines. However, a submarine design office was set up in the Netherlands and a torpedo research program was started in Sweden. Before the start of World War II, Germany started building U-boats and training crews, labeling these activities as "research" or concealing them using other covers. When this became known, the Anglo-German Naval Agreement limited Germany to parity with Britain in submarines. When World War II started, Germany already had 65 U-boats, with 21 of those at sea, ready for war.[citation needed]

text: World War II (1939-1945)[edit]

text: During World War II, U-boat warfare was the major component of the Battle of the Atlantic, which lasted the duration of the war. Germany had the largest submarine fleet of the revived German War Navy (Kriegsmarine) since 1935 into World War II (1939-1945), since the Armistice of November 11th, 1918, scuttled most of the old Imperial German Navy from the First World War and the following Treaty of Versailles of 1919, had limited the surface navy of Germany's new Weimar Republic to only six battleships (of less than 10,000 tons each), six cruisers, and 12 destroyers.[12] British Prime Minister Winston Churchill later wrote "The only thing that really frightened me during the war was the U-boat peril."

text: In the early stages of the war the U-boats were extremely effective in destroying Allied shipping due to the large gap in mid-Atlantic air cover. Cross-Atlantic trade in war supplies and food was extensive and critical for Britain's survival. The continuous action surrounding British shipping became known as the Battle of the Atlantic, as the British developed technical defences such as ASDIC and radar, and the German U-boats responded by hunting in what were called "wolfpacks" where multiple submarines would stay close together, making it easier for them to sink a specific target. Britain's vulnerable shipping situation existed until 1942, when the tides changed as the U.S. merchant marine and Navy entered the war, drastically increasing the amount of tonnage of supplies sent across the Atlantic. The combination of increased tonnage and increased naval protection of shipping convoys made it much more difficult for U-boats to make a significant dent in British shipping. Once the United States entered the war, U-boats ranged from the Atlantic coast of the United States and Canada to the Gulf of Mexico, and from the Arctic to the west and southern African coasts and even as far east as Penang. The U.S. military engaged in various tactics against German incursions in the Americas; these included military surveillance of foreign nations in Latin America, particularly in the Caribbean, to deter any local governments from supplying German U-boats.

text: Because speed and range were severely limited underwater while running on battery power, U-boats were required to spend most of their time surfaced running on diesel engines, diving only when attacked or for rare daytime torpedo strikes. The more ship-like hull design reflects the fact that these were primarily surface vessels that could submerge when necessary. This contrasts with the cylindrical profile of modern nuclear submarines, which are more hydrodynamic underwater (where they spend the majority of their time), but less stable on the surface. While U-boats were faster on the surface than submerged, the opposite is generally true of modern submarines. The most common U-boat attack during the early years of the war was conducted on the surface and at night. This period, before the Allied forces developed truly effective antisubmarine warfare tactics, which included convoys, was referred to by German submariners as "die glückliche Zeit" or The First Happy Time[13]

text: Torpedoes[edit]

text: The U-boats' main weapon was the torpedo, though mines and deck guns (while surfaced) were also used. By the end of the war, almost 3,000 Allied ships (175 warships; 2,825 merchant ships) were sunk by U-boat torpedoes.[14] Early German World War II torpedoes were straight runners, as opposed to the homing and pattern-running torpedoes that were fielded later in the war. They were fitted with one of two types of pistol triggers: impact, which detonated the warhead upon contact with a solid object, and magnetic, which detonated upon sensing a change in the magnetic field within a few meters.

text: One of the most effective uses of magnetic pistols would be to set the torpedo's depth to just beneath the keel of the target. The explosion under the target's keel would create a detonation shock wave, which could cause a ship's hull to rupture under the concussive water pressure. In this way, even large or heavily armored ships could be sunk or disabled with a single, well-placed hit.

text: In practice, however, the depth-keeping equipment and magnetic and contact exploders were notoriously unreliable in the first eight months of the war. Torpedoes often ran at an improper depth, detonated prematurely, or failed to explode altogether—sometimes bouncing harmlessly off the hull of the target ship. This was most evident in Operation Weserübung, the invasion of Norway, where various skilled U-boat commanders failed to inflict damage on British transports and warships because of faulty torpedoes. The faults were largely due to a lack of testing. The magnetic detonator was sensitive to mechanical oscillations during the torpedo run, and to fluctuations in the Earth's magnetic field at high latitudes. These were eventually phased out, and the depth-keeping problem was solved by early 1942.[15]

text: Later in the war, Germany developed an acoustic homing torpedo, the G7/T5. It was primarily designed to combat convoy escorts. The acoustic torpedo was designed to run straight to an arming distance of 400 m and then turn toward the loudest noise detected. This sometimes ended up being the U-boat itself; at least two submarines may have been sunk by their own homing torpedoes. Additionally, these torpedoes were found to be only effective against ships moving at greater than 15 knots (28 km/h). The Allies countered acoustic torpedoes with noisemaker decoys such as Foxer, FXR, CAT and Fanfare. The Germans, in turn, countered this by introducing newer and upgraded versions of the acoustic torpedoes, like the late-war G7es, and the T11 torpedo. However, the T11 torpedoes did not see active service.[16]

text: U-boats also adopted several types of "pattern-running" torpedoes that ran straight out to a preset distance, then traveled in either a circular or ladder-like pattern. When fired at a convoy, this increased the probability of a hit if the weapon missed its primary target.

text: U-boat developments[edit]

text: During World War II, the Kriegsmarine produced many different types of U-boats as technology evolved. Most notable is the Type VII, known as the "workhorse" of the fleet, which was by far the most-produced type, and the Type IX boats, which were larger versions of the VII designed for long-range patrols, some traveling as far as Japan and the east coast of the United States.

text: With the increasing sophistication of Allied detection and subsequent losses, German designers began to fully realise the potential for a truly submerged boat. The Type XXI "Elektroboot" was designed to favor submerged performance, both for combat effectiveness and survival. It was the first true submersible. The Type XXI featured an evolutionary design that combined several different strands of the U-Boat development program, most notably from the Walter U-boats, the Type XVII, which featured an unsuccessful yet revolutionary hydrogen peroxide air-independent propellant system. These boats featured a streamlined hull design, which formed the basis of the later USS Nautilus nuclear submarine, and was adapted for use with more conventional propulsion systems. The larger hull design allowed for a greatly increased battery capacity, which enabled the XXI to cruise submerged for longer periods and reach unprecedented submerged speeds for the time.

text: Throughout the war, an arms race evolved between the Allies and the Kriegsmarine, especially in detection and counterdetection. Sonar (ASDIC in Britain) allowed Allied warships to detect submerged U-boats (and vice versa) beyond visual range, but was not effective against a surfaced vessel; thus, early in the war, a U-boat at night or in bad weather was actually safer on the surface. Advancements in radar became particularly deadly for the U-boat crews, especially once aircraft-mounted units were developed. As a countermeasure, U-boats were fitted with radar warning receivers, to give them ample time to dive before the enemy closed in, as well as more anti aircraft guns. However, by early to mid-1943, the Allies switched to centimetric radar (unknown to Germany), which rendered the radar detectors ineffective. U-boat radar systems were also developed, but many captains chose not to use them for fear of broadcasting their position to enemy patrols and lack of sufficient electronic countermeasures.

text: Early on, the Germans experimented with the idea of the Schnorchel (snorkel) from captured Dutch submarines, but saw no need for them until rather late in the war. The Schnorchel was a retractable pipe that supplied air to the diesel engines while submerged at periscope depth, allowing the boats to cruise and recharge their batteries while maintaining a degree of stealth. It was far from a perfect solution, however. Problems occurred with the device's valve sticking shut or closing as it dunked in rough weather; since the system used the entire pressure hull as a buffer, the diesels would instantaneously suck huge volumes of air from the boat's compartments, and the crew often suffered painful ear injuries. Waste disposal was a problem when the U-boats spent extended periods without surfacing, as it is today. Speed was limited to 8 knots (15 km/h), lest the device snap from stress. The Schnorchel also had the effect of making the boat essentially noisy and deaf in sonar terms. Finally, Allied radar eventually became sufficiently advanced that the Schnorchel mast could be detected beyond visual range.

text: Several other pioneering innovations included acoustic- and electro-absorbent coatings to make them less of an ASDIC or RADAR target. The Germans also developed active countermeasures such as facilities to release artificial chemical bubble-making decoys, known as Bold, after the mythical kobold.

text: Classes[edit]

text:
Type I: first prototypes
Type II: small submarines used for training purposes
Type V: uncompleted experimental midget submarines
Type VII: the "workhorse" of the U-boats, with 700 active in World War II
Type IX: these long-range U-boats operated as far as the Indian Ocean with the Japanese (Monsun Gruppe), and the South Atlantic
Type X: long-range minelayers and cargo transports
Type XI: uncompleted experimental artillery boats
Type XIV: used to resupply other U-boats; nicknamed the Milchkuh ("Milk Cow")
Type XVII: small coastal submarines powered by high-test peroxide propulsion systems
Type XXI: known as the Elektroboot; first subs to operate primarily submerged
Type XXIII: smaller version of the XXI used for coastal operations
Midget submarines, including Biber, Hai, Molch, and Seehund
Uncompleted U-boat projects

text: Countermeasures[edit]

text: Advances in convoy tactics, high-frequency direction finding (referred to as "Huff-Duff"), radar, active sonar (called ASDIC in Britain), depth charges, ASW spigot mortars (also known as "hedgehog"), the intermittent cracking of the German Naval Enigma code, the introduction of the Leigh light, the range of escort aircraft (especially with the use of escort carriers), the use of mystery ships, and the full entry of the U.S. into the war with its enormous shipbuilding capacity, all turned the tide against the U-boats. In the end, the U-boat fleet suffered extremely heavy casualties, losing 793 U-boats and about 28,000 submariners (a 75% casualty rate, the highest of all German forces during the war).

text: At the same time, the Allies targeted the U-boat shipyards and their bases with strategic bombing.

text: Enigma machine[edit]

text: The British had a major advantage in their ability to read some German naval Enigma codes. An understanding of the German coding methods had been brought to Britain via France from Polish code-breakers. Thereafter, code books and equipment were captured by raids on German weather ships and from captured U-boats. A team including Alan Turing used special purpose "Bombes" and early computers to break new German codes as they were introduced. The speedy decoding of messages was vital in directing convoys away from wolf packs and allowing interception and destruction of U-boats. This was demonstrated when the Naval Enigma machines were altered in February 1942 and wolf-pack effectiveness greatly increased until the new code was broken.

text: The German submarine U-110, a Type IXB, was captured in 1941 by the Royal Navy, and its Enigma machine and documents were removed. U-559 was also captured by the British in October 1942; three sailors boarded her as she was sinking, and desperately threw all the code books out of the submarine so as to salvage them. Two of them, Able Seaman Colin Grazier and Lieutenant Francis Anthony Blair Fasson, continued to throw code books out of the ship as it went under water, and went down with it. Further code books were captured by raids on weather ships. U-744 was boarded by crew from the Canadian ship HMCS Chilliwack on 6 March 1944, and codes were taken from her, but by this time in the war, most of the information was known.[17] The U-505, a Type IXC, was captured by the United States Navy in June 1944. It is now a museum ship in Chicago at the Museum of Science and Industry.

text: Battle of Bell Island[edit]

text: Two events in the battle took place in 1942 when German U-boats attacked four allied ore carriers at Bell Island, Newfoundland. The carriers SS Saganaga and SS Lord Strathcona were sunk by U-513 on 5 September 1942, while the SS Rosecastle and PLM 27 were sunk by U-518 on 2 November with the loss of 69 lives. When the submarine launched a torpedo at the loading pier, Bell Island became the only location in North America to be subject to direct attack by German forces in World War II.

text: Operation Deadlight[edit]

text: "Operation Deadlight" was the code name for the scuttling of U-boats surrendered to the Allies after the defeat of Germany near the end of the war. Of the 154 U-boats surrendered, 121 were scuttled in deep water off Lisahally, Northern Ireland, or Loch Ryan, Scotland, in late 1945 and early 1946.

text: Memorial[edit]

text: Möltenort U-Boat Memorial

text: Post–World War II and Cold War (after 1945)[edit]

text: From 1955, the West German Bundesmarine was allowed to have a small navy. Initially two sunken Type XXIIIs and a Type XXI were raised and repaired. In the 1960s, the Federal Republic of Germany (West Germany) re-entered the submarine business. Because West Germany was initially restricted to a 450 tonne displacement limit, the Bundesmarine focused on small coastal submarines to protect against the Soviet Union (Russian) threat in the Baltic Sea. The Germans sought to use advanced technologies to offset the small displacement, such as amagnetic steel to protect against naval mines and magnetic anomaly detectors.

text: The initial Type 201 was a failure because of hull cracking; the subsequent Type 205, first commissioned in 1967, was a success, and 12 were built for the German navy. To continue the U-boat tradition, the new boats received the classic U designation starting with the U-1.

text: With the Danish government's purchase of two Type 205 boats, the West German government realized the potential for the submarine as an export. Three of the improved Type 206 boats were later sold to the Israeli Navy, becoming the Gal-class. The German Type 209 diesel-electric submarine was the most popular export-sales submarine in the world from the late 1960s into the first years of the 21st century. With a larger 1,000–1,500 tonne displacement, the class was very customizable and has seen service with 14 navies with 51 examples being built as of 2006.

text: Germany has brought the U-boat name into the 21st century with the new Type 212. The 212 features an air-independent propulsion system using hydrogen fuel cells. This system is safer than previous closed-cycle diesel engines and steam turbines, cheaper than a nuclear reactor and quieter than either. While the Type 212 is also being purchased by Italy, the Type 214 has been designed as the follow-on export model and has been sold to Greece, South Korea and Turkey.

text: In July 2006, Germany commissioned its newest U-boat, the U-34, a Type 212.