Semimembranosus muscle
Encyclopedia
The semimembranosus is a muscle
in the back of the thigh
. It is the most medial of the three hamstring
muscles.
.
Its origin is the ischial tuberosity and it inserts on the medial condyle and nearby margin of tibia; intercondylar line and lateral condyle of femur; and the ligament of popliteal region. It arises by a thick tendon from the upper and outer impression on the tuberosity of the ischium, above and medial to the biceps femoris
and semitendinosus
.
The tendon of origin expands into an aponeurosis
, which covers the upper part of the anterior surface of the muscle; from this aponeurosis muscular fibers arise, and converge to another aponeurosis which covers the lower part of the posterior surface of the muscle and contracts into the tendon of insertion.
It is inserted mainly into the horizontal groove on the posterior medial aspect of the medial condyle of the tibia
.
The tendon of insertion gives off certain fibrous expansions: one, of considerable size, passes upward and laterally to be inserted into the posterior lateral condyle of the femur, forming part of the oblique popliteal ligament of the knee-joint
; a second is continued downward to the fascia which covers the Popliteus muscle
; while a few fibers join the tibial collateral ligament of the joint and the fascia of the leg.
The muscle overlaps the upper part of the popliteal vessels.
. The tibial nerve consists of the anterior divisions of ventral nerve roots from L4 through S3. These nerve roots are part of a larger nerve network called the sacral plexus
. The tibial nerve is also responsible for innervating the skin of the posterior leg as well as plantar
skin.
.
It also helps medially rotate
the knee: the tibia
medially rotates on the femur
when the knee is flexed. Medially rotates the femur
when the hip is extended. Can aid in counteracting the forward bending at the hip joint.
and giving a slip to the femur or adductor magnus
.
of the thigh
." - "Muscles that form the superficial boundaries of the popliteal fossa
."
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
in the back of the thigh
Thigh
In humans the thigh is the area between the pelvis and the knee. Anatomically, it is part of the lower limb.The single bone in the thigh is called the femur...
. It is the most medial of the three hamstring
Hamstring
In human anatomy, the hamstring refers to any one of the three posterior thigh muscles, or to the tendons that make up the borders of the space behind the knee. In modern anatomical contexts, however, they usually refer to the posterior thigh muscles, or the tendons of the semitendinosus, the...
muscles.
Structure
The semimembranosus, so called from its membranous tendon of origin, is situated at the back and medial side of the thighThigh
In humans the thigh is the area between the pelvis and the knee. Anatomically, it is part of the lower limb.The single bone in the thigh is called the femur...
.
Its origin is the ischial tuberosity and it inserts on the medial condyle and nearby margin of tibia; intercondylar line and lateral condyle of femur; and the ligament of popliteal region. It arises by a thick tendon from the upper and outer impression on the tuberosity of the ischium, above and medial to the biceps femoris
Biceps femoris muscle
The biceps femoris is a muscle of the posterior thigh. As its name implies, it has two parts, one of which forms part of the hamstrings muscle group.-Origin and insertion:It has two heads of origin;...
and semitendinosus
Semitendinosus muscle
The semitendinosus is a muscle in the back of the thigh; it is one of the hamstrings.-Structure:The semitendinosus, remarkable for the great length of its tendon of insertion, is situated at the posterior and medial aspect of the thigh ....
.
The tendon of origin expands into an aponeurosis
Aponeurosis
Aponeuroses are layers of flat broad tendons. They have a shiny, whitish-silvery color, are histologically similar to tendons, and are very sparingly supplied with blood vessels and nerves. When dissected, aponeuroses are papery, and peel off by sections...
, which covers the upper part of the anterior surface of the muscle; from this aponeurosis muscular fibers arise, and converge to another aponeurosis which covers the lower part of the posterior surface of the muscle and contracts into the tendon of insertion.
It is inserted mainly into the horizontal groove on the posterior medial aspect of the medial condyle of the tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
.
The tendon of insertion gives off certain fibrous expansions: one, of considerable size, passes upward and laterally to be inserted into the posterior lateral condyle of the femur, forming part of the oblique popliteal ligament of the knee-joint
Knee
The knee joint joins the thigh with the leg and consists of two articulations: one between the fibula and tibia, and one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee is a mobile trocho-ginglymus , which permits flexion and extension as...
; a second is continued downward to the fascia which covers the Popliteus muscle
Popliteus muscle
The popliteus muscle in the leg is used to unlock the knee during walking/running by laterally rotating the femur on the tibia during a closed chain movement ....
; while a few fibers join the tibial collateral ligament of the joint and the fascia of the leg.
The muscle overlaps the upper part of the popliteal vessels.
Innervation
The semimembranosus is innervated by the tibial nerve, a branch of the sciatic nerveSciatic nerve
The sciatic nerve is a large nerve fiber in humans and other animals. It begins in the lower back and runs through the buttock and down the lower limb...
. The tibial nerve consists of the anterior divisions of ventral nerve roots from L4 through S3. These nerve roots are part of a larger nerve network called the sacral plexus
Sacral plexus
-External links:*...
. The tibial nerve is also responsible for innervating the skin of the posterior leg as well as plantar
Anatomical terms of location
Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...
skin.
Actions
The semimembranosus helps to extend (straighten) the hip joint and flex (bend) the knee jointKnee
The knee joint joins the thigh with the leg and consists of two articulations: one between the fibula and tibia, and one between the femur and patella. It is the largest joint in the human body and is very complicated. The knee is a mobile trocho-ginglymus , which permits flexion and extension as...
.
It also helps medially rotate
Internal rotation
In anatomy, internal rotation is rotation towards the center of the body.The muscles of internal rotation include:* of arm/humerus at shoulder** Deltoid muscle** Subscapularis** Teres major** Latissimus dorsi...
the knee: the tibia
Tibia
The tibia , shinbone, or shankbone is the larger and stronger of the two bones in the leg below the knee in vertebrates , and connects the knee with the ankle bones....
medially rotates on the femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
when the knee is flexed. Medially rotates the femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
when the hip is extended. Can aid in counteracting the forward bending at the hip joint.
Variations
It may be reduced or absent, or double, arising mainly from the sacrotuberous ligamentSacrotuberous ligament
The sacrotuberous ligament is situated at the lower and back part of the pelvis. It is flat, and triangular in form; narrower in the middle than at the ends....
and giving a slip to the femur or adductor magnus
Adductor magnus muscle
The adductor magnus is a large triangular muscle, situated on the medial side of the thigh.It consists of two parts. The portion which arises from the ischiopubic ramus is called the "adductor portion", and the portion arising from the tuberosity of the ischium is called the "hamstring portion"...
.
External links
- "Muscles (hamstrings) of the posterior compartmentPosterior compartment of leg
The posterior compartment of the leg is supplied by the tibial nerve.It contains the plantar flexors:* deep: popliteus, flexor hallucis longus, flexor digitorum longus, tibialis posterior* superficial/calf: gastrocnemius, soleus, plantaris...
of the thigh
Thigh
In humans the thigh is the area between the pelvis and the knee. Anatomically, it is part of the lower limb.The single bone in the thigh is called the femur...
." - "Muscles that form the superficial boundaries of the popliteal fossa
Popliteal fossa
The popliteal fossa is a shallow depression located at the back of the knee joint. The bones of the popliteal fossa are the femur and the tibia.-Boundaries:The boundaries of the fossa are:-Roof:...
."