The semitendinosus is a long superficial muscle in the back of the thigh. It is so named because it has a long tendon of insertion, it lies posteromedially in the thigh, superficial to the semimembranosus. The semitendinosus, remarkable for the great length of its tendon of insertion, is situated at the posterior and medial aspect of the thigh, it arises from the lower and medial impression on the upper part of the tuberosity of the ischium, by a tendon common to it and the long head of the biceps femoris. The muscle is fusiform and ends a little below the middle of the thigh in a long round tendon which lies along the medial side of the popliteal fossa; the semitendinosus is more superficial than the semimembranosus. However, because the semimembranosus is wider and flatter than the semitendinosus, it is still possible to palpate the semimembranosus directly. At its insertion it gives off from its lower border a prolongation to the deep fascia of the leg and lies behind the tendon of the sartorius, below that of the gracilis, to which it is united.
These three tendons form what is known as the pes anserinus, so named because it looks like the foot of a goose. A lower motor neuron exits to the sacral plexus exiting through the spinal levels L5-S2. From the sacral plexus, the lower motor neuron travels down the sciatic nerve; the sciatic nerve branches into the deep fibular nerve and the tibial nerve. The tibial nerve innervates the semitendinosus as well as the other hamstring muscles, the semimembranosus and biceps femoris; the semitendinosus muscle is one of three hamstring muscles that are located at the back of the thigh. The other two are the biceps femoris; the semitendinosus muscle lies between the other two. These three muscles work collectively to extend the hip; the muscle helps to medially rotate the tibia on the femur when the knee is flexed and medially rotate the femur when the hip is extended. It counteracts forward bending at the hips as well. Semimembranosus Biceps femoris This article incorporates text in the public domain from page 479 of the 20th edition of Gray's Anatomy Anatomy photo:14:st-0410 at the SUNY Downstate Medical Center Cross section image: pembody/body18b—Plastination Laboratory at the Medical University of Vienna knee/surface/surface4 at the Dartmouth Medical School's Department of Anatomy PTCentral
The fascia lata is the deep fascia of the thigh. It encloses the thigh muscles and forms the outer limit of the fascial compartments of thigh, which are internally separated by intermuscular septa; the fascia lata is thickened at its lateral side where it forms the iliotibial tract, a structure that runs to the tibia and serves as a site of muscle attachment. The fascia lata is an investment for the whole of the thigh, but varies in thickness in different parts, it is thicker in the upper and lateral part of the thigh, where it receives a fibrous expansion from the gluteus maximus, where the tensor fasciae latae is inserted between its layers. The fascia lata surrounds the tensor fasciae latae muscle, it is a fibrous sheath. This encircling of the muscle allows the muscles to be bound together tightly; the fascia lata is attached and behind, to the back of the sacrum and coccyx. From its attachment to the iliac crest it passes down over the gluteus medius to the upper border of the gluteus maximus, where it splits into two layers, one passing superficial to and the other beneath this muscle.
Laterally, the fascia lata receives the greater part of the tendon of insertion of the gluteus maximus, becomes proportionately thickened. The portion of the fascia lata attached to the front part of the iliac crest, corresponding to the origin of the tensor fasciae latae, extends down the lateral side of the thigh as two layers, one superficial to and the other beneath this muscle; this band is continued downward under the name of the iliotibial band and is attached to the lateral condyle of the tibia. The part of the iliotibial band which lies beneath the tensor fasciae latae is prolonged upward to join the lateral part of the capsule of the hip joint. Below, the fascia lata is attached to all the prominent points around the knee joint, viz. the condyles of the femur and tibia, the head of the fibula. On either side of the kneecap it is strengthened by transverse fibers from the lower parts of the vasti muscles which are attached to and support this bone. Of these the lateral are the stronger, are continuous with the iliotibial band.
The deep surface of the fascia lata gives off two strong intermuscular septa, which are attached to the whole length of the linea aspera and its prolongations above and below. Besides these there are numerous smaller septa, separating the individual muscles, enclosing each in a distinct sheath; the deep fascia of the lower leg is a continuation of the fascia lata. Since the 1920s fasciae latae from deceased donors have been used in reconstructive surgery. In 1999 preserved mashed fasciae latae became FDA-approved as a tissue product designed to replace areas of lost fascia or collagen; the fascia lata performs the function of encircling and tightening the muscles in the thigh. Because of this function, it has been used as grafts for patients with facial paralysis; the fascia lata offers supports to the muscles that make up the face and this support increases the recovery of the facial muscles. The surgeons use the fascia lata as a sort of facial sling to support up the paralyzed face and loops the fascia lata around the center of the lower lip, the corner of the mouth and the center of the upper lip.
It is named from its great extent. "Latus" give the superlative "Latissimus" meaning widest. This article incorporates text in the public domain from page 468 of the 20th edition of Gray's Anatomy
The gracilis muscle is the most superficial muscle on the medial side of the thigh. It is thin and flattened, broad above and tapering below, it arises by a thin aponeurosis from the anterior margins of the lower half of the symphysis pubis and the upper half of the pubic arch. The muscle's fibers run vertically downward; this tendon passes behind the medial condyle of the femur, curves around the medial condyle of the tibia where it becomes flattened, inserts into the upper part of the medial surface of the body of the tibia, below the condyle. For this reason, the muscle is a lower limb adductor. At its insertion the tendon is situated above that of the semitendinosus muscle, its upper edge is overlapped by the tendon of the sartorius muscle, which it joins to form the pes anserinus; the pes anserinus is separated from the medial collateral ligament of the knee-joint by a bursa. A few of the fibers of the lower part of the tendon are prolonged into the deep fascia of the leg. By its inner or superficial surface gracilis is in relation with the fascia lata, below with the sartorius and internal saphenous nerve.
By its outer or deep surface with the adductor longus and magnus, the internal lateral ligament of the knee-joint, from which it is separated by a synovial bursa common to the tendons of the gracilis and semitendinosus. The obturator nerve innervates the gracilis muscle via the lumbar spinal vertebrae; the muscle adducts, medially rotates, laterally rotates, flexes the hip as above, aids in flexion of the knee. The gracilis muscle is used as a flap in microsurgery. According to the classification of Mathes and Nahai, it presents a type II blood supply, allowing it to be transferred on its artery derived from the medial circumflex femoral artery; this artery enters the muscle about 10 cm from the pubic symphysis. At this point the nerve enters. Gracilis muscle is used in reconstructive surgery, either as a pedicled flap or as a free microsurgical flap. Both pedicled and free flaps can be musculocutaneos; as a pedicled flap, gracilis muscle can be used in perineal and vaginal reconstruction, after oncological surgery, in the treatment of recurrent anovaginal and rectovaginal fistulas as well in the coverage of the neurovascular bundle after vascular surgery.
As a functioning pedicled flap, the gracilis muscle can be transferred for the treatment of anal incontinence. This technique called graciloplasty was described in the 1950s by Pickrell and was revolutionized in the late 1980s by the introduction of chronic muscle electro-stimulation; the gracilis microsurgical free flap is used in the reconstruction of upper and lower limbs, in breast reconstruction and – as a free functioning flap – to restore forearm function or in dynamic reconstruction of facial paralysis. Gracilis Muscles Clinical Role The muscle may be split to reduce bulk for facial reanimation, as well as to repair hand muscles, it can be used to fashion an external anal sphincter. This article incorporates text in the public domain from page 471 of the 20th edition of Gray's Anatomy Anatomy figure: 12:02-07 at Human Anatomy Online, SUNY Downstate Medical Center - "Muscles of the anterior compartment of the thigh." Anatomy figure: 14:02-02 at Human Anatomy Online, SUNY Downstate Medical Center - "Muscles that form the superficial boundaries of the popliteal fossa."
Cross section image: pembody/body18b—Plastination Laboratory at the Medical University of Vienna
Anatomical terms of muscle
Muscles are described using unique anatomical terminology according to their actions and structure. There are three types of muscle tissue in the human body: skeletal and cardiac. Skeletal striated muscle, or "voluntary muscle" joins to bone with tendons. Skeletal muscle maintains posture. Smooth muscle tissue is found in parts of the body; the majority of this type of muscle tissue is found in the digestive and urinary systems where it acts by propelling forward food and feces in the former and urine in the latter. Other places smooth muscle can be found are within the uterus, where it helps facilitate birth, the eye, where the pupillary sphincter controls pupil size. Cardiac muscle is specific to the heart, it is involuntary in its movement, is additionally self-excitatory, contracting without outside stimuli. As well as anatomical terms of motion, which describe the motion made by a muscle, unique terminology is used to describe the action of a set of muscles. Agonist muscles and antagonist muscles refer to muscles that inhibit a movement.
Agonist muscles cause a movement to occur through their own activation. For example, the triceps brachii contracts, producing a shortening contraction, during the up phase of a push-up. During the down phase of a push-up, the same triceps brachii controls elbow flexion while producing a lengthening contraction, it is still the agonist, because while resisting gravity during relaxing, the triceps brachii continues to be the prime mover, or controller, of the joint action. Agonists are interchangeably referred to as "prime movers," since they are the muscles considered responsible for generating or controlling a specific movement. Another example is the dumbbell curl at the elbow; the "elbow flexor" group is the agonist. During the lowering phase the "elbow flexor" muscles lengthen, remaining the agonists because they are controlling the load and the movement. For both the lifting and lowering phase, the "elbow extensor" muscles are the antagonists, they shorten during the dumbbell lowering phase.
Here it is important to understand that it is common practice to give a name to a muscle group based on the joint action they produce during a shortening contraction. However, this naming convention does not mean; this term describes the function of skeletal muscles. Antagonist muscles are the muscles that produce an opposing joint torque to the agonist muscles; this torque can aid in controlling a motion. The opposing torque can slow movement down - in the case of a ballistic movement. For example, during a rapid discrete movement of the elbow, such as throwing a dart, the triceps muscles will be activated briefly and to accelerate the extension movement at the elbow, followed immediately by a "burst" of activation to the elbow flexor muscles that decelerates the elbow movement to arrive at a quick stop. To use an automotive analogy, this would be similar to pressing your gas pedal and immediately pressing the brake. Antagonism is not an intrinsic property of a particular muscle group. During slower joint actions that involve gravity, just as with the agonist muscle, the antagonist muscle can shorten and lengthen.
Using the example above of the triceps brachii during a push-up, the elbow flexor muscles are the antagonists at the elbow during both the up phase and down phase of the movement. During the dumbbell curl, the elbow extensors are the antagonists for both the lifting and lowering phases. Antagonist and agonist muscles occur in pairs, called antagonistic pairs; as one muscle contracts, the other relaxes. An example of an antagonistic pair is the triceps. "Reverse motions" need antagonistic pairs located in opposite sides of a joint or bone, including abductor-adductor pairs and flexor-extensor pairs. These consist of an extensor muscle, which "opens" the joint and a flexor muscle, which does the opposite by decreasing the angle between two bones. However, muscles don't always work this way. Sometimes during a joint action controlled by an agonist muscle, the antagonist will be activated, naturally; this occurs and is not considered to be a problem unless it is excessive or uncontrolled and disturbs the control of the joint action.
This serves to mechanically stiffen the joint. Not all muscles are paired in this way. An example of an exception is the deltoid. Synergist muscles help perform, the same set of joint motion as the agonists. Synergists muscles act on movable joints. Synergists are sometimes referred to as "neutralizers" because they help cancel out, or neutralize, extra motion from the agonists to make sure that the force generated works within the desired plane of motion. Muscle fibers can only contract up to 40% of their stretched length, thus the short fibers of pennate muscles are more suitable where power rather than range of contraction is required. This limitation in the range of contraction affects all muscles, those that act over several joints may be unable to shorten sufficiently to produce
In human anatomy, the thigh is the area between the hip and the knee. Anatomically, it is part of the lower limb; the single bone in the thigh is called the femur. This bone is thick and strong, forms a ball and socket joint at the hip, a modified hinge joint at the knee; the femur is the only bone in the thigh and serves for an attachment site for all muscles in the thigh. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates with the tibia and kneecap forming the knee. By most measures the femur is the strongest bone in the body; the femur is the longest bone in the body. The femur is categorised as a long bone and comprises a diaphysis, the shaft and two epiphysis or extremities that articulate with adjacent bones in the hip and knee. In cross-section, the thigh is divided up into three separate compartments, divided by fascia, each containing muscles; these compartments use the femur as an axis, are separated by tough connective tissue membranes.
Each of these compartments has its own blood and nerve supply, contains a different group of muscles. Medial fascial compartment of thigh, adductor Posterior fascial compartment of thigh, hamstring Anterior fascial compartment of thigh, extensionAnterior compartment muscles of the thigh include sartorius, the four muscles that comprise the quadriceps muscles- rectus femoris, vastus medialis, vastus intermedius and vastus lateralis. Posterior compartment muscles of the thigh are the hamstring muscles, which include semimembranosus and biceps femoris. Medial compartment muscles are pectineus, adductor magnus, adductor longus and adductor brevis, gracilis; because the major muscles of the thigh are the largest muscles of the body, resistance exercises of them stimulate blood flow more than any other localized activity. The arterial supply is by the obturator artery; the lymphatic drainage follows the arterial supply and drains to the lumbar lymphatic trunks on the corresponding side, which in turn drains to the cisterna chyli.
The deep venous system of the thigh consists of the femoral vein, the proximal part of the popliteal vein, various smaller vessels. The venae perfortantes connect the deep and the superficial system, which consists of the saphenous veins. Thigh weakness can result in a positive Gowers' sign on physical examination; the thigh meat of some animals such as chicken and cow is consumed as a food in many parts of the world
The inguinal ligament is a band running from the pubic tubercle to the anterior superior iliac spine. It forms the base of the inguinal canal; the inguinal ligament runs from the anterior superior iliac crest of the ilium to the pubic tubercle of the pubic bone. It is formed by the external abdominal oblique aponeurosis and is continuous with the fascia lata of the thigh. There is some dispute over the attachments. Structures that pass deep to the inguinal ligament include: Psoas major, pectineus Femoral nerve and vein Lateral cutaneous nerve of thigh Lymphatics The ligament serves to contain soft tissues as they course anteriorly from the trunk to the lower extremity; this structure demarcates the superior border of the femoral triangle. It demarcates the inferior border of the inguinal triangle; the midpoint of the inguinal ligament, halfway between the anterior superior iliac spine and pubic tubercle, is the landmark for the femoral nerve. The mid-inguinal point, halfway between the anterior superior iliac spine and the pubic symphysis, is the landmark for the femoral artery.
It is referred to as Poupart's ligament, because François Poupart gave it relevance in relation to hernial repair, calling it "the suspender of the abdomen". It is sometimes termed the Fallopian ligament. Colles' ligament is reflex ligament not inguinal ligament. Pelvis Anatomy figure: 12:03-02 at Human Anatomy Online, SUNY Downstate Medical Center - "Deep muscles of the anterior thigh." Anatomy photo:35:os-0107 at the SUNY Downstate Medical Center - "Anterior Abdominal Wall: Osteology and Surface Anatomy " Anatomy photo:35:08-0100 at the SUNY Downstate Medical Center - "Anterior Abdominal Wall: The Inguinal Ligament" Anatomy image:7179 at the SUNY Downstate Medical Center Anatomy image:7431 at the SUNY Downstate Medical Center Diagram at gensurg.co.uk
The saphenous nerve is the largest cutaneous branch of the femoral nerve. It is a sensory nerve, has no motor function, it approaches the femoral artery where this vessel passes beneath the sartorius, lies in front of the artery, behind the aponeurotic covering of the adductor canal, as far as the opening in the lower part of the Adductor magnus. Here it diverges from the artery, emerges from behind the lower edge of the aponeurotic covering of the canal; the nerve passes along the tibial side of the leg, accompanied by the great saphenous vein, descends behind the medial border of the tibia, and, at the lower third of the leg, divides into two branches: one continues its course along the margin of the tibia, ends at the ankle. The other passes in front of the ankle, is distributed to the skin on the medial side of the foot, as far as the ball of the great toe, communicating with the medial branch of the superficial peroneal nerve; the saphenous nerve, about the middle of the thigh, gives off a branch which joins the subsartorial plexus.
At the medial side of the knee it gives off a large infrapatellar branch, which pierces the sartorius and fascia lata, is distributed to the skin in front of the patella. Below the knee, the branches of the saphenous nerve are distributed to the skin of the front and medial side of the leg, communicating with the cutaneous branches of the femoral, or with filaments from the obturator nerve. Procedures such as saphenous vein cutdown or orthopedic surgery that includes incisions or dissection over the distal tibia or medial malleolus can result in damage to the saphenous nerve, resulting in loss of cutaneous sensation in the medial leg; this is due to the intimate path that the great saphenous vein travel. The saphenous nerve is often damaged during vein harvest for bypass surgery and during trocar placement during knee arthroscopy. There appears to be occasional meaningful individual variation in the pathway of this nerve, such that the illustration of it done for Gray's Anatomy, for example represents an unusual rather than usual course.
The saphenous nerve can experience entrapment syndrome from exercises involving the quadriceps or from prolonged walking or standing. It is characterized by a burning sensation in most patients. Pain occurs at night, long after the physical exercise which induced it has stopped, may be aggravated by climbing stairs. In this case, motor function of the lower leg will not be impaired; this is a key distinction between lower back radiculopathy. Saphenous nerve neuropathy only demonstrates sensory alterations, while lumbar radiculopathy will affect the motor and deep tendon reflexes of the lower leg; this article incorporates text in the public domain from page 956 of the 20th edition of Gray's Anatomy Anatomy photo:12:08-0102 at the SUNY Downstate Medical Center - "Structures of the Adductor Canal"