Question

Highlight and name the origin and insertion areas for the; Biceps Femoris, Semimenbranousus, Semitendinousus, Gluteus maximus, and the six Deep lateral rotators. Then, show their primary and secondary (and tertiary if they have three functions) functions/movements they produce. Which of the five muscles has the GREATEST force generating capacity, and which has the LEAST and why?

Answer 1

Biceps femoris

The biceps femoris is a muscle of the thigh located to the posterior, or back. it has two parts, one of which (the long head) forms part of the hamstrings muscle group.
Origin tuberosity of the ischium, linea aspera, femur

It has two heads of origin:

the long head arises from the lower and inner impression on the posterior part of the tuberosity of the ischium. This is a common tendon origin with the semitendinosus muscle, and from the lower part of the sacrotuberous ligament.

the short head, arises from the lateral lip of the linea aspera, between the adductor magnus and vastus lateralis extending up almost as high as the insertion of the gluteus maximus, from the lateral prolongation of the linea aspera to within 5 cm. of the lateral condyle; and from the lateral intermuscular septum.

The two muscle heads joint together distally and unite in an intricate fashion. The fibers of the long head form a fusiform belly, which passes obliquely downward and lateralward across the sciatic nerve to end in an aponeurosis which covers the posterior surface of the muscle and receives the fibers of the short head. Inferiorly, the aponeurosis condenses to form a tendon which predominantly inserts onto the lateral side of the head of the fibula. There is a second small insertional attachment by a small tendon slip into the lateral condyle of the tibia.

At its insertion the tendon divides into two portions, which embrace the fibular collateral ligament of the knee-joint. Together, this joining of tendons is commonly referred to as the conjoined tendon of the knee.

From the posterior border of the tendon a thin expansion is given off to the fascia of the leg. The tendon of insertion of this muscle forms the lateral hamstring; the common fibular (peroneal) nerve descends along its medial border.

Insertion the head of the fibula which articulates with the back of the lateral tibial condyle

Action flexes knee joint, laterally rotates knee joint (when knee is flexed), extends hip joint (long head only)
Both heads of the biceps femoris perform knee flexion.

Since the long head originates in the pelvis it is also involved in hip extension.The long head of the biceps femoris is a weaker knee flexor when the hip is extended (because of active insufficiency). For the same reason the long head is a weaker hip extender when the knee is flexed.

When the knee is semi-flexed, the biceps femoris in consequence of its oblique direction rotates the leg slightly outward.

Semimenbranousus

The semimembranosus is the most medial of the three hamstring muscles. It is so named because it has a flat tendon of origin. It lies posteromedially in the thigh, deep to the semitendinosus.
Origin Ischial tuberosity
The semimembranosus, so called from its membranous tendon of origin, is situated at the back and medial side of the thigh.

Its origin is the superolateral aspect of the ischial tuberosity and it inserts on the medial condyle and nearby margin of tibia; intercondylar fossa of femur and medial condyle of femur; and the ligament of the popliteal region (at the back of the knee). It arises by a thick tendon from the upper and outer impression on the ischial tuberosity, 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.

Insertion Medial condyle of tibia
It is inserted mainly into the horizontal groove on the posterior medial aspect of the medial condyle of the tibia.

The semimembranosus is wider, flatter, and deeper than the semitendinosus (with which it shares very close insertion and attachment points).

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 medial collateral ligament of the joint and the fascia of the leg.

The muscle overlaps the upper part of the popliteal vessels.

ActionsExtension of hip and flexion of knee
The semimembranosus helps to extend (straighten) the hip joint and flex (bend) the knee joint.

It also helps to medially rotate the knee: the tibia medially rotates on the femur when the knee is flexed. It medially rotates the femur when the hip is extended. The muscle can also aid in counteracting the forward bending at the hip joint

Semitendinosus

The semitendinosus is a long superficial muscle in the back of the thigh. It is so named because it has a very long tendon of insertion. It lies posteromedially in the thigh, superficial to the semimembranosus.

Origin Lower Quadrangular part of tuberosity of the ischium
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; it also arises from an aponeurosis which connects the adjacent surfaces of the two muscles to the extent of about 7.5 cm. from their origin.

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; it then curves around the medial condyle of the tibia and passes over the medial collateral ligament of the knee-joint, from which it is separated by a bursa, and is inserted into the upper part of the medial surface of the body of the tibia, nearly as far forward as its anterior crest.

The semitendinosus is more superficial than the semimembranosus (with which it shares very close insertion and attachment points).because the semimembranosus is wider and flatter than the semitendinosus.

Insertion Pes anserinus (tibia)
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, and below that of the gracilis, to which it is united. These three tendons form what is known as the pes anserinus.

Actions Flexion of knee, extension of the hip joint
The semitendinosus muscle is one of three hamstring muscles that are located at the back of the thigh. The other two are the semimembranosus muscle and the biceps femoris. The semitendinosus muscle lies between the other two. These three muscles work collectively to flex the knee and extend the hip.

The muscle also 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.

Gluteus maximus

The gluteus maximus is the main extensor muscle of the hip. It is the largest and outermost of the three gluteal muscles and makes up a large part of the shape and appearance of each side of the hips. Its thick fleshy mass, in a quadrilateral shape, forms the prominence of the buttocks.
Origin Gluteal surface of ilium, lumbar fascia, sacrum, sacrotuberous ligament.
The gluteus maximus is the outermost muscle of the buttocks. It arises from connections to nearby structures in this area. It arises from the posterior gluteal line of the inner upper ilium, a bone of the pelvis, as well as above it to the iliac crest and slightly below it; from the lower part of the sacrum and the side of the coccyx, the tailbone; from the aponeurosis of the erector spinae (lumbodorsal fascia), the sacrotuberous ligament, and the fascia covering the gluteus medius (gluteal aponeurosis).

The fibers are directed obliquely downward and lateralward;

The gluteus maximus ends in two main areas:

those forming the upper and larger portion of the muscle, together with the superficial fibers of the lower portion, end in a thick tendinous lamina, which passes across the greater trochanter, and inserts into the iliotibial band of the fascia lata.

the deeper fibers of the lower portion of the muscle are inserted into the gluteal tuberosity between the vastus lateralis and adductor magnus.

Bursae

Three bursae are usually found in relation with the deep surface of this muscle:

One of these, of large size, separates it from the greater trochanter;
a second, is situated on the tuberosity of the ischium;
a third is found between the tendon of the muscle and that of the vastus lateralis.

Insertion Gluteal tuberosity of the femur and iliotibial tract

Actions External rotation and extension of the hip joint, supports the extended knee through the iliotibial tract, chief antigravity muscle in sitting and abduction of the hip
The gluteus maximus straightens the leg at the hip; when the leg is flexed at the hip, the gluteus maximus extends it to bring the leg into a straight line with the body.

Taking its fixed point from below, it acts upon the pelvis, supporting it and the trunk upon the head of the femur; this is particularly obvious in standing on one leg.

Its most powerful action is to cause the body to regain the erect position after stooping, by drawing the pelvis backward, being assisted in this action by the biceps femoris (long head), semitendinosus, semimembranosus, and adductor magnus.

The gluteus maximus is a tensor of the fascia lata, and by its connection with the iliotibial band steadies the femur on the articular surfaces of the tibia during standing, when the extensor muscles are relaxed.

The lower part of the muscle also acts as an adductor and external rotator of the limb. The upper fibers act as abductors of the hip joints.

The six Deep lateral rotators

The lateral rotator group is a group of six small muscles of the hip which all externally (laterally) rotate the femur in the hip joint. It consists of the following muscles: Piriformis, gemellus superior, obturator internus, gemellus inferior, quadratus femoris and the obturator externus.

Origin At or below the acetabulum of the ilium
Insertion On or near the greater trochanter of the femur
Actions Lateral rotation of hip

All muscles in the lateral rotator group originate from the hip bone and insert on to the upper extremity of the femur. The muscles are innervated by the sacral plexus (L4-S2), except the obturator externus muscle, which is innervated by the lumbar plexus.

1. Piriformis muscle
origin Anterior surface of sacrum between and laterally to the anterior sacral foramina
Insertion Superior boundary of greater trochanter

2.Gemellus superior muscle
origin Ischial spine
Insertion Upper edge of Obturator internus muscle tendon (indirectly greater trochanter)

3.Obturator internus muscle
Origin Medial surface of obturator membrane and the surrounding bone
Insertion Medial surface of greater trochanter

4.Gemellus inferior muscle
Origin Just above the tuberosity of the ischium
Insertion Lower edge of Obturator internus muscle tendon (indirectly greater trochanter)

5.Quadratus femoris muscle
Origin Lateral edge of the tuberosity of the ischium
Insertion Intertrochanteric crest

6.Obturator externus muscle
Origin Lateral surface of obturator membrane and the ischiopubic ramus
Insertion Trochanteric fossa