ANTERIOR AND MEDIAL COMPARTMENTS OF THE (Grant's Dissector [16th Ed.] pp. 183-196)

TODAY’S GOALS: 1. Identify the , cutaneous nerves, and superficial in the superficial of the anterior thigh. 2. Identify the boundaries and contents of the . 3. Identify the muscles and nerves in the anterior compartment of the thigh. 4. Identify the muscles and nerves in the medial compartment of the thigh. 5. Trace the course of the in the thigh and identify its major branches and their distribution.

DISSECTION NOTES: I. Anterior Compartment of the Thigh

A. Superficial Fascia of the Anterior Thigh See Dissector p. 185, Fig. 6.3 for incisions for removing the skin. For this lab session, follow the incision line indicated by letters D,F, and E and the midline incision to just below the . Consider removing the skin of the entire lower limb if time allows. Pay attention to important superficial veins (great saphenous and small saphenous veins) and cutaneous nerves contained within the superficial fascia.

Identify and follow the course of the great saphenous vein (Dissector p. 186, Fig. 6.4). Note that it arises from the medial side of the venous arch on the dorsum of the and ascends anterior to the medial malleolus to continue its ascent along the medial aspect of the leg. It takes a posteromedial course at the knee before entering the medial side of the thigh. It terminates by passing through the (fossa ovalis) in the just below the and emptying into the . The small or lesser saphenous vein arises from the lateral side of the dorsal venous arch and passes posterior to the lateral malleolus before ascending on the posterior surface of the leg toward the . At various locations, perforating veins connect these superficial veins to deep veins. Valves within these superficial veins prevent reflux of blood and muscular contractions promote venous flow toward the heart. What happens if these venous valves become incompetent? (See Clinical Correlation Great Saphenous Vein in Dissector p. 187).

Be aware of the numerous cutaneous nerves distributed on the anterior thigh. (Dissector p. 186, Fig. 6.4). The provides several cutaneous branches to most of the skin on the anterior thigh. Skin of the lateral aspect of the thigh is supplied by the lateral femoral cutaneous nerve. A limited area of skin on the medial thigh is supplied by branches of the obturator nerve.

Superficial Inguinal Lymph Nodes – a group of lymph nodes located in the proximal thigh and organized into two groups (Dissector p. 188, Fig. 6.5): • Horizontal group – arranged parallel to and inferior to the inguinal ligament • Vertical group – arranged parallel to the terminal end of the great saphenous vein These nodes drain lymph from the lower abdominal wall, the external genitalia, the gluteal region, and the lower limb. Lymph from these nodes drain into deep inguinal lymph nodes.

B. and the Anterior Compartment of the Thigh Deep to the superficial fascia is the deep fascia of the thigh called the fascia lata. It is thickened along the lateral side of thigh where it is known as the or band. Internally, medial and lateral intermuscular septa connect the fascia lata to the femur and divide the thigh into compartments: anterior (extensor), medial (adductor), and posterior (flexor).

Proceed to reflect and remove the fascia lata in the proximal thigh according to the incisions indicated in the Dissector p. 189, Fig. 6.7. This will bring into view the boundaries of the femoral triangle and its contents (Dissector p. 190, Fig. 6.8; Clinical Correlation Femoral Triangle p. 189).

1. Boundaries of the femoral triangle: • Superior border/Base of the triangle – inguinal ligament • Lateral border – • Medial border – • Floor – pectineus and muscles

2. Contents of the femoral triangle: Contains the femoral nerve (N) and the (Dissector p. 190, Fig. 6.8). The femoral sheath is a conical extension of transversalis fascia that contains 3 compartments. From lateral to medial these compartments contain the femoral artery (A), femoral vein (V), and the , which contains lymph vessels and deep inguinal lymph nodes (L). The acronym, NAVL, may help you remember the relationship of these structures within the triangle. The proximal portion of the femoral canal is open to the and is called the . This is the site of femoral hernias (see Clinical Correlation Femoral Hernia p. 191). Open these compartments to reveal these structures.

The apex of the femoral triangle is the point of intersection of the sartorius and adductor longus muscles. This marks the beginning of the subsartorial or (Hunter's canal). Here, the femoral vessels and two branches of the femoral nerve (nerve to the and ) enter the canal. The canal ends distally at the , which opens behind the knee (popliteal fossa). Only the femoral vessels emerge through the hiatus. The nerve to the vastus medialis is a motor nerve; the saphenous is a sensory nerve that descends below the knee to supply skin on the medial side of the leg, ankle, and foot. The sartorius muscle forms the roof of the adductor canal. Mobilize or transect this muscle in order to view these structures.

3. Muscles of the anterior compartment of the thigh (know principal bony attachments of these muscles; Dissector p. 194, Table 6.1): a. Sartorius – the sartorius is a long slender muscle that crosses both the and the knee joints; it flexes the thigh, laterally rotates the thigh, and flexes the leg b. Iliopsoas – combined iliacus and psoas major muscles. It attaches inferiorly at the lesser trochanter of the femur and is a strong flexor of the thigh. c. Pectineus*- a cross-over muscle with the medial compartment; both adducts and flexes the thigh d. Quadriceps femoris – consists of 4 muscles: vastus medialis, vastus intermedius, vastus lateralis, and rectus femoris. The tendon of these muscles is the patellar tendon, which contains a sesamoid bone, the . The patellar ligament connects the patella to the tibial tuberosity. Collectively, this muscle extends the leg.

4. Nerve of the anterior compartment of the thigh. (Dissector p. 193, Fig. 6.11) The femoral nerve is the nerve of the anterior compartment of the thigh. It contains fibers from L2,3,4 cord levels. As the nerve descends into the thigh posterior to the inguinal ligament is breaks up into several branches; anterior cutaneous branches to skin of the anterior thigh, and motor branches to the muscles of this compartment. The patellar tendon reflex (knee-jerk) test is used clinically to test the function of this nerve (see Clinical Correlation p. 193).

5. Vascular supply of the anterior compartment of the thigh. (Dissector p. 191, Fig. 6.9) The blood supply to the anterior compartment is the femoral artery. The femoral artery is a continuation of the external iliac artery. Within the femoral triangle, it gives rise to the deep femoral artery, which supplies the medial and posterior compartments of the thigh. • Lateral circumflex femoral artery – this branch commonly arises from the deep femoral artery and gives off three branches (ascending, transverse, and descending) that supply musculature in the lateral part of the thigh • Medial circumflex femoral artery – this branch also commonly arises from the deep femoral artery. It takes a posterior course between the iliopsoas and pectineus muscles. It is the principal blood supply to the head and of the femur. Deep veins, having similar names, accompany the arteries and can be removed to clarify the dissection field.

II. Medial Compartment of the Thigh The musculature of the medial thigh collectively adduct the thigh, hence the name, adductor group of muscles. Carefully remove the fascia lata to reveal these muscles. A. Muscles of the Medial Thigh. (know principal bony attachments of these muscles) (Dissector p. 196, Table 6.2) • Gracilis – a long, slender muscle that also crosses two joints, the hip and the knee; it adducts the thigh and helps with flexion of the leg. • Pectineus* - a cross-over muscle with the medial compartment; it both adducts and flexes the thigh • Adductor longus – forms the medial border of the femoral triangle; lies superficial to the adductor brevis and magnus muscles. Divide this muscle in order to observe them. • Adductor brevis – observe the anterior branches of the obturator nerve, artery, and vein coursing superficial to this muscle. The posterior branches of these structures descend on the deep surface of adductor brevis, between the brevis and the adductor magnus. • Adductor magnus – this is the largest of the adductor muscles. It attaches superiorly to the ischiopubic ramus and ischial tuberosity and attaches inferiorly to the gluteal tuberosity, the medial lip of the , and the adductor tubercle on the medial epicondyle of the femur. The portion of the muscle that attaches to the adductor tubercle (ischiocondylar portion) is innervated by the tibial division of the sciatic nerve, while the remainder of the muscle is innervated by the obturator nerve. • Obturator externus – a minor muscle deep to the iliopsoas and pectineus muscles. It attaches from the external margin of the obturator foramen to a depression on the medial surface of the greater trochanter (trochanteric fossa). It is a lateral rotator of the thigh.

B. Blood Supply to the Medial Compartment (Dissector p. 191, Fig. 6.9) Within the femoral triangle, the femoral artery gives rise to the deep femoral artery or profunda femoris, which supplies the medial and posterior compartments of the thigh. A smaller contribution is provided by the obturator artery. • Observe the deep femoral artery descending between the pectineus and adductor brevis and the adductor longus. It gives off several perforating branches that pass through the adductor brevis and magnus muscles to supply muscles of the posterior compartment of the thigh.

C. Nerve Supply to the Medial Compartment (Dissector p. 195, Fig. 6.13) The nerve supply to the medial compartment of the thigh is the obturator nerve. The anterior and posterior divisions of the obturator nerve pass on corresponding sides of the adductor brevis muscle. PEER TEACHING GUIDE: 1. Demonstration of the great and lesser saphenous veins and their course within the superficial fascia. 2. Demonstration of the boundaries and contents of the femoral triangle. 3. Demonstration of the muscles and nerves in the anterior compartment of the thigh. 4. Demonstration of the muscles and nerves in the medial compartment of the thigh. 5. Demonstration of the course and major branches of the femoral artery.