Posterior Region of the Thigh

How to Discuss the Posterior Region of the Thigh in an Anatomy Oral Exam

When discussing the posterior thigh, structure your explanation similarly to the anterior thigh by covering boundaries, muscles, nerves, arteries, and veins.

1. Boundaries of the Posterior Thigh Region

• Superior: Gluteal fold.

• Inferior: Popliteal fossa (posterior knee region).

• Lateral: Lateral intermuscular septum of the thigh.

• Medial: Medial intermuscular septum of the thigh.

• Anterior: Adductor magnus and femur (separating posterior from anterior compartments).

2. Muscles of the Posterior Thigh

The posterior compartment contains the hamstring muscles, which primarily extend the hip and flex the knee.

Key Muscles:

1. Biceps Femoris:

   • Origin:

     • Long head: Ischial tuberosity.

     • Short head: Linea aspera and lateral supracondylar line of femur.

   • Insertion: Head of the fibula.

   • Action: Flexes the knee and laterally rotates the leg when the knee is flexed. The long head also extends the hip.

   • Innervation:

     • Long head: Tibial division of the sciatic nerve (L5-S2).

     • Short head: Common fibular division of the sciatic nerve (L5-S2).

2. Semitendinosus:

   • Origin: Ischial tuberosity.

   • Insertion: Medial surface of the proximal tibia (pes anserinus).

   • Action: Extends the hip, flexes the knee, and medially rotates the leg when the knee is flexed.

   • Innervation: Tibial division of the sciatic nerve (L5-S2).

3. Semimembranosus:

   • Origin: Ischial tuberosity.

   • Insertion: Posterior part of the medial tibial condyle.

   • Action: Extends the hip, flexes the knee, and medially rotates the leg when the knee is flexed.

   • Innervation: Tibial division of the sciatic nerve (L5-S2).

4. Adductor Magnus (Hamstring Part):

   • Origin: Ischial tuberosity.

   • Insertion: Adductor tubercle of the femur.

   • Action: Extends the hip.

   • Innervation: Tibial division of the sciatic nerve (L4).

3. Nerves of the Posterior Thigh

The sciatic nerve (L4-S3) is the primary nerve of the posterior thigh:

• Travels deep to the long head of the biceps femoris.

• Divides into:

  • Tibial nerve: Innervates the semitendinosus, semimembranosus, long head of the biceps femoris, and the hamstring part of the adductor magnus.

  • Common fibular nerve: Innervates the short head of the biceps femoris.

Sensory innervation of the skin in the posterior thigh is provided by:

• Posterior femoral cutaneous nerve (S1-S3): Supplies the skin of the posterior thigh and popliteal fossa.

4. Arteries of the Posterior Thigh

The posterior thigh lacks a major artery running through it but is supplied by branches of the deep femoral artery:

• Perforating branches: Pass through the adductor magnus to supply the hamstring muscles.

• Additional blood supply comes from the inferior gluteal artery, a branch of the internal iliac artery.

5. Veins of the Posterior Thigh

• Deep veins:

  • Perforating veins that drain into the deep femoral vein.

• Superficial veins:

  • Small saphenous vein: Runs along the posterior leg, draining into the popliteal vein.

6. Clinical Relevance

• Sciatic Nerve Compression: May occur due to piriformis syndrome or injury, causing posterior thigh pain.

• Hamstring Injuries: Common in athletes due to overstretching or tearing.

Key Points to Emphasize

1. Start with the boundaries to provide anatomical context.

2. Explain the hamstring muscles with their dual functions (hip extension, knee flexion) and respective innervations.

3. Discuss the sciatic nerve, its divisions, and clinical significance.

4. Highlight the vascular supply, particularly the perforating branches.

Feel free to ask for a diagram to complement your oral presentation!