Dissector Answers - Anterior & Medial Thigh

Learning Objectives:

Upon completion of this session, the student will be able to:

  1. Describe the subcutaneous venous drainage of the lower limb, its relation to the deep veins and the significance of perforating veins.
  2. Describe the lymphatic drainage of the lower limb and areas draining into the superficial and deep inguinal lymph nodes.
  3. Identify the major cutaneous nerves of the lower limb, their source and the areas they innervate.
  4. Define the regional deep fascias of the lower limb and their regional specialization such as iliotibial tract, etc.
  5. Define the femoral triangle and adductor canal, their contents and the spatial relationships of the structures passing through them.
  6. Identify the femoral and obturator arteries and veins and their branches. Give their areas of distribution.
  7. Identify the muscles of the anterior and medial thigh, including their nerve and vascular supply. Describe their role in locomotion.
  8. Predict what nerve or nerves are involved and the probable level of the injury, given a loss of function and/or cutaneous sensation involving the anterior and medial thigh regions.

Learning Objectives and Explanations:

1. Describe the subcutaneous venous drainage of the lower limb, its relation to the deep veins, and the significance of perforating veins. (W&B 577-579, N 544,545, TG 3-02,3-03)
The superficial veins of the lower limb begin as the dorsal venous arch of the foot. This dumps into two primary veins:

greater saphenous vein: on the medial side. It receives blood from the dorsal venous arch. The greater saphenous vein then heads north, traveling anterior to the medial malleolus, up the leg, through the knee region on the posterior aspect of the medial condyle of the femur, then turns anteriorly and laterally as it travels up the thigh. The greater saphenous vein travels through the saphenous opening, a passageway in the fascia of the femoral triangle, to drain into the femoral vein. Along its course the greater saphenous vein receives tributaries from the dorsum of the foot, the heel, the front of the leg, and anterior, medial, and lateral portions of the thigh. Also important, right before emptying into the femoral vein, the greater saphenous vein receives the superficial epigastric, superficial circumflex iliac, and superficial external pudendal veins.

lesser saphenous vein: on the lateral side. It runs posterior to the lateral malleolus and up the middle of the back of the leg. It usually pierces the crural fascia about halfway up the leg, running the rest of the way deep to the fascia. In most cases, the lesser saphenous vein terminates in the popliteal vein.

Images from "Anatomy of the Human Body" by Henry Gray are provided by:

2. Describe the lymphatic drainage of the lower limb and areas draining into the superficial and deep inguinal lymph nodes. (W&B 578-580, N 546, TG 3-70)
The superficial lymph vessels of the lower limb accompany the superficial veins. They end in the superficial inguinal lymph nodes. From there, most lymph passes directly to the external iliac lymph nodes, but some flows to the deep inguinal lymph nodes. The deep lymphatic vessels accompany the deep veins, and drain directly into the deep inguinal lymph nodes.
3. Identify the major cutaneous nerves of the lower limb, their source, and the areas they innervate. (W&B 580-583, N 540, 541, 542, 544, TG 3-68,3-44,3-48,3-69A,3-69B)
The figures on W&B 581 and N543 or TG3-69A and TG3-69B are handy views of dermatomes of the lower limb, though they don't technically show how the fibers get there, i.e., via which nerve. But, if you check out W&B 582, and N540, N542, N544, TG3-63, N542, TG3-64, TG3-65A,TG3-65B,TG3-66,TG3-67, or check out the images below, you'll get the idea.

Images from "Anatomy of the Human Body" by Henry Gray are provided by:
Images from "Anatomy of the Human Body" by Henry Gray are provided by:

knee and above:

  • subcostal nerve: from T12. Supplies the skin of the thigh over greater trochanter of femur.
  • iliohypogastric nerve: from L1 (lumbar plexus). The lateral cutaneous branch supplies the skin of the superolateral buttock, while the anterior cutaneous branch supplies the skin superior to pubis.
  • ilioinguinal nerve: from L1 (lumbar plexus). Branches supply the skin of the proximal, medial thigh, near the external genitalia.
  • genitofemoral nerve: from L1 and L2 (lumbar plexus). Femoral branches supply the skin of the proximal, anterior thigh, just inferior to inguinal ligament.
  • lateral femoral cutaneous nerve: from L2 and L3 (direct branch of the lumbar plexus). Anterior branches supply the skin of the lateral and anterior thigh. The posterior branch supplies the skin of the thigh from the greater trochanter to just proximal to the knee.
  • anterior femoral cutaneous nerves: from the femoral nerve (L2 through L4, lumbar plexus). Supply to the skin of the medial and anterior thigh.
  • obturator nerve: (L2 through L4, lumbar plexus). A branch (variable) sometimes supplies the skin of the medial aspect of the proximal thigh.
  • posterior femoral cutaneous nerve: from S1 through S3 (sacral plexus). Supplies the skin of the lower buttock, posterior thigh, and the skin of the posterior knee.

below the knee:

  • saphenous nerve: from the femoral nerve (L2 through L4, lumbar plexus). Supply to the skin of the anterior and medial side of the leg and the medial side of the foot.
  • sural nerve: from both tibial and common fibular nerves (which come from the sciatic nerve, L4 through S3): Supplies the skin on the posterior and lateral aspects of the leg and lateral side of the foot.
  • lateral sural cutaneous nerve: from the common fibular nerve (which comes from the sciatic nerve, L4 through S3): Supplies the skin of the posterolateral leg.
  • superficial fibular nerve: from the common fibular nerve (which comes from the sciatic nerve, L4 through S3): Supplies the skin of the inferior third of the anterior leg and the dorsal part of the foot.
4. Define the regional deep fascias of the lower limb and their regional specializations. (W&B 584-588, 608-610, N 509,522,530, TG 3-02,3-03,3-45)
The deep fascia of the lower limb is called the fascia lata in the thigh and the crural fascia in the leg. These have the following specializations:

fascia lata:
  • iliotibial tract: a thickening of the fascia lata that stretches from the tubercle of the crest of the ilium to attach to the lateral condyle of the tibia. Serves as insertion point for the tensor fascia lata and part of the insertion for the gluteus maximus.
  • lateral intermuscular septum: from the iliotibial tract to the lateral epicondylar line and the lateral lip of the linea aspera, both on the femur. It separates the vastus lateralis muscle from the biceps femoris muscles, therefore separating the quadriceps group from the hamstrings.
  • medial intermuscular septum: attaches to the medial lip of the linea aspera of the femur. It separates the vastus medialis muscle (quadriceps) from the adductor group (medial) of muscles.
  • saphenous opening (hiatus): a passageway through the fascia lata for the great saphenous vein.
crural fascia:
  • retinacula of the patella: formed by the attachments of the crural fascia to the medial and lateral condyles of the tibia and the head of the fibula. This also includes tendinous fibers from the vastus muscles. (Latin, retinacula = halter, cable)
  • anterior intermuscular septum: from the crural fascia to the anterior aspect of the fibula. It separates the anterior (extensor) muscles from the lateral (fibular) muscles. Also, one could say that it is the boundary between the anterior and lateral compartments.
  • posterior intermuscular septum: from the crural fascia to the posterior aspect of the fibula. It separates the posterior (flexor) muscles from the lateral (fibular) muscles. Also, one could say that it is the boundary between the posterior and lateral compartments.
  • transverse intermuscular septum: from the posterior intermuscular septum, around to the anteromedial aspect of the tibia. It separates the deep posterior muscles from the superficial posterior muscles.
  • popliteal fascia: two layers, superficial and deep, that cover the popliteal fossa. This fascia stretches with the movement of the knee joint, providing protection for the neurovascular structures traveling through the area.
In the ankle region, the crural fascia thickens to form retinacula that hold tendons close to the bone, creating a sort of pulley sytem. They are listed here:
  • superior extensor retinaculum: superior to the ankle, on the anterior aspect of the leg
  • inferior extensor retinaculum: on the anterior aspect of the ankle. It is Y-shaped, extending onto the dorsum of the foot.
  • flexor retinaculum: on the posteromedial aspect of the ankle
  • superior and inferior fibular retinacula: on the posterolateral aspect of the ankle
5. Define the femoral triangle and adductor canal, their contents and the spatial relationships of the structures passing through them. (W&B 585-586, TG3-18)

Images from "Anatomy of the Human Body" by Henry Gray are provided by:

The borders of the femoral triangle are the inguinal ligament (superior), the sartorious muscle (lateral) and the adductor longus muscle (medial). It contains, from lateral to medial, the femoral nerve and branches, the femoral artery and branches, and the femoral vein and tributaries. (The image above shows the left femoral triangle, in case the "Orientation Penis" didn't make that clear.)

The following specializations of abdominal fascia in this region are also important:

  • femoral sheath: a diverticulum of the transversalis fascia. It wraps the femoral vessels for the first 2 or 3 centimeters of their trip through the femoral triangle. The femoral sheath does not wrap around the femoral nerve. It has three compartments. The lateral compartment contains the femoral artery, the middle compartment has the femoral vein, and the medial compartment is designated as the femoral canal.
  • femoral canal: the medial compartment of the femoral sheath. It usually contains fat, a few lymph vessels, and maybe a deep inguinal lymph node (node of Cloquet).
  • femoral ring: the opening at the superior end of the femoral canal.

The adductor canal allows passage of the femoral vessels and the saphenous nerve through the middle one-third of the thigh. The quadriceps femoris muscles are separated from the adductor muscles by a deep groove. Put a roof on that baby, let's say the sartorious muscle, and you have the adductor canal. The canal ends at the adductor hiatus, which is a split in the adductor magnus muscle.

6. Identify the femoral and obturator arteries and veins and their branches. Give their areas of distribution. (W&B 600-605, TG3-22, TG3-23)

The femoral artery supplies a major portion of the thigh. (Analogously, the femoral vein drains a good deal of the thigh.) The femoral artery gives off the superficial epigastric artery, the superficial circumflex iliac artery, the superficial external pudendal artery (all three just distal to the inguinal ligament), the deep external pudendal artery, the deep femoral artery, and the descending genicular artery. The largest and most important of these is the deep femoral artery.

The deep femoral artery supplies the hip joint, proximal thigh, and posterior thigh, including the neck of the femur. It gives off two important branches. The medial femoral circumflex artery supplies the iliopsoas muscle, pectineus muscle, and the hip joint via ascending and descending branches. The lateral femoral circumflex artery supplies the lateral hip, thigh, and knee via ascending, transverse, and descending branches. The descending branch anastomoses with both the descending genicular branch of the femoral artery as well as the lateral superior genicular branch of the popliteal artery, to provide collateral circulation to the knee. (Latin, poples = ham of the knee, genu = knee)

The obturator artery supplies the medial thigh and hip, including the head of the femur (to a limited degree). It accomplishes this via anterior and posterior branches.

7. Identify the muscles of the anterior and medial thigh, including their nerve and vascular supply. Describe their role in locomotion. (W&B 590-595, TG3-16, TG3-17, TG3-19, TG3-20, TG3-21, TG3-22, TG3-23)
MUSCLE INNERVATION BLOOD SUPPLY ACTION
iliopsoas VPR L2-4, femoral n. Iliolumbar a. Flexor - aids in raising thigh for initial raising during locomotion
pectineus Femoral n. Medial femoral circumflex a. Flexor - see above
rectus femoris Femoral n. Lateral circumflex femoral a. Flexor of hip; Extensor of leg - provides forward extension of leg to meet ground and provide support for body weight.
vastus medialis Femoral n. Lateral circumflex femoral a. Extensor of leg - see above
vastus intermedius Femoral n. Lateral circumflex femoral a. Extensor of leg - see above
vastus lateralis Femoral n. Lateral circumflex femoral a., perforating branches of deep femoral a. Extensor of leg - see above
gracilis Obturator n. - anterior div. Obturator a. Adduction; also provides medial rotation of thigh to counteract the lateral rotation given by the extensor of the thigh, gluteus maximus m.
adductor longus Obturator n. - anterior div. Obturator a., deep femoral a. Adduction; also provides medial rotation - see above
adductor brevis Obturator n. - anterior div. Obturator a., deep femoral a. Adduction; also provides medial rotation - see above
adductor magnus Obturator n. - posterior div., tibial n. Obturator a., deep femoral a., medial circumflex femoral a. Adduction; also provides medial rotation - see above

Question: Why do adductors medially rotate the femur?

Most of the adductor group of muscles attach on the posterior surface of the femur, so it is always a mystery how they medially rotate the thigh. If you look at an articulated skeleton while you read this, it will all become clear.

If the femur was a perfectly straight and round cylinder and you attached something to the back of it, like the adductors attach, the cylinder would rotate laterally when you pulled medially on the back of it. However, the catch is - the femur is not a perfectly straight cylindrical shape. It bows anteriorly, quite a bit. Think of it as a bucket handle. If you grab a bucket handle, either from the back or the front, the bucket handle will move toward you when you pull. If you are an adductor and you grab the anteriorly bowed femur, it moves toward you, pivoting on both ends like a bucket handle (which connects to the bucket at both ends). Now, imagine you flex the hip, lifting the leg to take a step forward. The flexion of the hip makes the femur act even more like a bucket handle, so that the pull of the adductors lies in front of the pivot point of the head of the femur. Adductors pull the femur toward the pubic ramus, medially rotating the femur and counterbalancing the lateral rotational force of the big extensor of the hip - gluteus maximus.

8. Predict what nerve or nerves are involved and the probable level of the injury, given a loss of function and/or cutaneous sensation involving the posterior and medial thigh regions. (TG3-17, TG3-21)
Cultural enrichment: Check out these sections from the 1918 version of Gray's Anatomy of the Human Body! Some of the terms are (of course) out-of-date, but the illustrations are timeless.

The Femur - The Muscles and Fascia of the Thigh - The Veins of the Lower Extremity, Abdomen, and Pelvis - The Arteries of the Lower Extremity - Surface Anatomy of the Lower Extremity - Surface Markings of the Lower Extremity - The Muscles and Fascia of the Thigh - The Veins of the Lower Extremity, Abdomen, and Pelvis - The Arteries of the Lower Extremity - Surface Anatomy of the Lower Extremity - Surface Markings of the Lower Extremity

Questions and Answers:

9. Do you see accessory tributaries or varicosities of the superficial veins?
There is usually a fairly large accessory saphenous vein draining the medial thigh, in addition to numerous smaller accessory tributaries. The superficial veins communicate with the deep veins of the lower limb via perforating veins through the deep fascia of the lower limb. These perforating veins have valves that direct the blood superficial to deep as the result of limb motions and muscle contractions. However, the valves may become incompetent, resulting in retrograde blood flow from deep to superficial. The superficial veins may become dilated and torturous, especially in the leg.
10. To what vein does the greater saphenous vein drain?
The greater saphenous vein drains to the femoral vein, through the saphenous hiatus. N544,TG3-02
11. From what regions do the superficial inguinal lymph nodes receive lymph?
The superficial inguinal lymph nodes receive lymph from the superficial tissues of lower abdominal wall, the external genitalia, the perineum, the buttocks, and the lower limb. N546,TG3-70
12. Where do the superficial inguinal lymph nodes drain?
They drain primarily to external iliac lymph nodes, but some drain to the deep inguinal lymph nodes.
13. Where would you find the deep inguinal lymph nodes?
The deep inguinal lymph nodes, approximately three in number, lie within the femoral canal, within the femoral sheath, medial to the femoral vein. N546,TG3-70
14. What is the distribution of the femoral branch of genitofemoral nerve?
This small branch of the genitofemoral nerve within the abdomen passes beneath the inguinal ligament on the external iliac artery. It innervates a small area of skin on the upper medial thigh. N544,TG3-02
15. From what are the cutaneous nerves of the anterior thigh derived?
The lateral femoral cutaneous nerve is from the lumbar plexus, specifically L2 and L3. The anterior femoral cutaneous nerves are branches of femoral nerve. The femoral branch of genitofemoral nerve is from the lumbar plexus, specifically L1 & L2. N544TG3-14
16. What is the source of the saphenous nerve?
The femoral nerve is the source of the saphenous nerve. N545,TG3-24
17. The sartorius muscle inserts via the pes anserinus along with which other two muscles?
Pes anserinus is the common insertion of the gracilis, sartorius, and semitendinosus muscles. (TG3-57A)
18. Do you see deep inguinal lymph nodes in the femoral canal?

There are often several deep inguinal lymph nodes in the vicinity of the femoral canal. The one located within the canal is called the node of Cloquet. One deep inguinal node may sometimes be found below the femoral canal within the femoral triangle. (TG3-70)

19. What is a femoral hernia?

A femoral hernia is a hernia through the femoral ring and canal. They often even continue through the saphenous hiatus.

20. Define the adductor canal.

See #1 above. (TG3-17)

21. Identify the nerve to the vastus medialis. Source?

The vastus medialis muscle is supplied by the femoral nerve. (TG3-17)

22. How does the relation of the femoral vein to the femoral artery change throughout the thigh?

At the inguinal ligament, the femoral artery is lateral to the femoral vein. At the adductor hiatus, the vein is posterior to the artery. (TG3-17)

23. What are the relations of the popliteal vein to the popliteal artery in the popliteal fossa?

The popliteal vein lies posterior to the artery, but anterior (deep) to the tibial nerve. (TG3-31)

24. Trace the deep femoral artery. What is its relation to the insertions of the adductor muscles?

The deep femoral artery passes between the pectineus muscle and the adductor longus muscle. It then travels inferiorly between the adductor longus muscle and the adductor brevis muscle. (TG3-20)

25. Trace the lateral femoral circumflex artery. Note its three branches, and define the position and area supplied by each. Are there variations in origin?

In 14% of cases, this artery branches directly from the femoral artery. The ascending branch supplies the gluteus muscles and possibly the hip joint. The transverse branch supplies the vastus lateralis and possibly the hip joint. The descending branch supplies vastus lateralis and the knee. (TG3-20)

26. What are the relations of the lateral femoral circumflex artery branches to the rectus femoris muscle and to the femoral nerve?

They pass immediately deep to rectus femoris muscle and femoral nerve, with femoral nerve branches accompanying. (TG3-20)

27. How many perforating arteries do you find?

There are usually 4. (TG3-23)

28. How do you distinguish a perforating artery?

They pass posteriorly through adductor brevis and adductor magnus to enter the posterior thigh. (TG3-23)

29. What is the function of the patella?

The patella provides a bony surface that is able to withstand the compression placed on the quadriceps tendon during kneeling. It is also able to resist friction occurring when the knee is flexed and extended during running. The patella also provides additional leverage for the quadriceps, since it places the tendon more anteriorly, further from the joint's axis, causing it to approach the tibia from a position of greater mechanical advantage. (TG3-56)

30. What muscles does the anterior division of the obturator nerve supply?

The anterior division of the obturator nerve supplies the gracilis muscle, the adductor longus muscle, and the adductor brevis muscle. Occasionally, the pectineus muscle is also supplied by the anterior division of the obturator nerve. (TG3-20)

31. What usually supplies the pectineus muscle?

It is usually the femoral nerve innervating the pectineus muscle. Occasionally, the pectineus muscle is supplied by the anterior division of the obturator nerve. (TG3-63)

32. What artery accompanies this nerve?

The medial femoral circumflex artery. (TG3-23)