Muscles of the Thigh. 6.1 Identify, describe the attachments of and deduce the actions of the muscles of the thigh: Anterior group

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1 Muscles of the Thigh 6.1 Identify, describe the attachments of and deduce the actions of the muscles of the thigh: Anterior group Sartorius: This is a long strap like muscle with flattened tendons at each end It is the most superficial muscle in the anterior group and runs across all muscles lateral to medial It is the longest muscle in the body The upper attachment is the anterior superior iliac spine The lower insertion is the medial line on the shaft of the tibia Actions are usually associated with sitting cross legged Ie it contributes to flexion of the hip and knee, lateral rotation and abduction of the thigh Summarized by saying that it paces the heel on the medial side of the knee Note: the other anterior muscles (excluding sartorious) make up the quads Rectus femoris: This is a spindle shaped bipennate muscle, it seems to stand out on the front of the thigh It is the at the very middle, front of the thigh, superficial, and just medial of the vastus lateralis Its upper attachment is two heads which are continuous, one to the anterior inferior iliac spine, the other to and area above the acetabulum The lower insertion is at the upper border of the patella The actions are hip flexion and knee extension Vastus lateralis: This is situated on the anterolateral aspect of the thigh, lateral to the rectus femoris (ie the outside of the thigh) The upper attachment is the intertrochanteric line It also attaches to the fascia lata From this origin the fibres run downwards and forwards The lower insertion is the tibial tuberosity The action is the knee extension Vastus medialis: This is situated on the anteromedial aspect of the thigh, medial to the rectus femoris (ie inside of the thigh) Its upper attachment is extensive at the intertrochanteric line

2 It then runs down around the linea aspera and the upper part of the supracondylar line Its upper fibres pass downwards, whilst its lower fibres tend to pass nearly horizontally laterally The lower insertion is the tendon of the rectus femoris The action is the extension of the knee Vastus intermedius: The deepest part of the quadriceps femoris lying between the lateralis and medialis It is deeper than the rectus femoris The upper attachment is the upper two thirds of the anterior and lateral surfaces of the femur In the middle of thigh it is difficult to separate from the lateralis, whilst at the bottom difficult to separate from the medialus The lower insertion is the tibial tuberosity via the tendon of rectus femoris The action is extension of the knee Posterior group (hamstrings) Biceps femoris: Situated on the posterolateral part of the thigh Long head: this has an upper attachment at the ischial tuberosity, with the tendon of semitendinosus With a posterior view it is in the middle, and fairly superficial and large The lower insertion is the head of the fibula Short head: this attaches to the linea aspera The lower insertion is the head of the fibula The actions are the extension and external rotation of hip, and flexion and external rotation of knee Semitendinosus: The upper attachment is the facet of the ischial tuberosity The tendon then combines with the long head of the biceps femoris, and the muscles run together It then forms a fusiform muscle belly, which gives way to a long thin tendon It passes downward and medially behind the medial condyle of the femur This is just lateral of the semimembranosus muscle The lower attachment is the medial surface of the tibial shaft The nerve supply is the tibial division of the sciatic nerve

3 Actions are extension of hip, flexion and medial rotation of knee Semimembranosus: It is situated on the posterior medial side of the thigh, deeper than the semitendinosus The upper attachment is the ischial tuberosity It then passes downward and medially It is muscle at the top and a thick flat sheet of membrane at the bottom At the bottom it spreads in many directions, particularly upward forming the oblique popliteal ligament The lower attachment is the medial tibial condyle The actions are extension of hip, flexion and medial rotation of knee (same as semitendinosus) Medial group Gracilis: From posterior view this is the small, long, thin medial muscle This is the most superficial muscle of the adductor group The upper attachment is the front of the body of the pubis It develops a fusiform shaped belly at its middle It becomes tendinous above the knee and crosses the joint The lower insertion is medial surface of the shaft of the tibia Its actions are mainly flexion of knee, but also adduction of hip and medial rotation of thigh (with knee semi flexed) Pectineus: This is a quadrilateral muscle situated at the upper and medial part of the thigh It appears to consist of two layers, superficial and deep, supplied by different nerves Its upper attachment is the superior ramus of the pubis Its fibres pass downward and laterally between the psoas major and adductor longus Its lower insertion is the pectineal line (line from lesser trochanter to linea aspera) The action is flexion and adduction of the hip Adductor magnus: This is the largest and most posterior of the adductor muscles (lies posterior to brevis and longus) It lies anterior to semimembranosus and semitendinosus (is very deep)

4 Its upper attachment is the ischiopubic ramus, running down toward the ischial tuberosity - The ischiopubic fibres fan out forming a large triangular muscular sheet - These fibres pass laterally and slightly backward toward the linea aspera, and may be fused with the quadratus femoris - The fibres from the ischiopubic ramus run the length of the linea aspera - The posterior ischial fibres pass downwards and attach to the adductor tubercle on the medial condyle of the femur Action is hip adduction Note: be careful as this sometimes may look like part of the hamstrings Adductor longus: This is a long slender, triangular muscle (also very deep) It is situated on the medial aspect of the this, overlying the middle part of the adductor magnus The upper attachment is the obturator crest on the body of the pubis It passes downward and laterally The lower attachment is the middle half of the linea aspera Actions are adduction of the thigh, flexion of extended thigh and extension of flexed thigh Adductor brevis: This is a triangular muscle situated on the medial aspect of the thigh Its upper attachment is the inferior ramus of the pubis Its fibres pass downwards and laterally backwards Its lower insertion is the upper half of the linea aspera (anterior to the adductor magnus, and posterior to the adductor longus) Its action is simply adduction of the thigh 6.2 Using the muscles of the thigh as an example, describe the effect on joint function of muscles, which cross two joints Long muscles act across two joints (ie the hamstrings, rectus femoris) In this case they can only work efficiently across one joint at one time Ie the hamstrings can only extend the hip strongly with the knee in extension 6.3 Describe the functions of the different components of the quadriceps femoris muscle Each of the quadriceps femoris has a particular role in a certain range of movement Rectus femoris: commonly performs the swing phase of walking, when the limb is carried forward and the knee is being extended Vastus medialis: in the final stages of the extension of the knee, helps the locking mechanism of the joint

5 Vastus lateralis and intemedius are used for the extension of the knee 6.4 Observe and palpate on a living subject the bellies and / or tendons of the following muscles of the thigh: Rectus femoris: This can be palpated near the hip on anterior surface of the spine Externally rotate hip and then resist flexion, a v is formed pointing toward the foot The space in between the v is called the rectus femoris Vastus lateralis: Forms a visible bulge on the lateral side on the knee with isometric contraction Vastus medialis: Forms a visible bulge on the medial side of the knee with isometric contraction Semitendinosus: With medial rotation, both the gracilis and semitendinosus are prominent The semitendinosus is the larger of the two and most lateral Semimembranosus: Most prominent tendon in the back of the knee on the medial side Most palpable when the patient is prone or seated and resisting knee flexion Biceps femoris: Palpate from common origin on ischium to insertion on lateral side Most prominent when the patient is prone and resisting knee flexion Sartorius: This is most easily palpated at its proximal end, just below the anterior superior iliac spine Here the strap like shape can be easily palpated particularly when the knee is slightly flexed It is best when the left is raised slightly from the floor when lying in supine