Veterinary Gross Anatomy-II

Medial muscles of the hip and thigh

MEDIAL MUSCLES OF THE THIGH (CRURAL REGION)

• This region has eight muscles arranged in superimposed layers. They are
  • First layer
    • Sartorius
    • Gracilis
  • Second layer
    • Pectineus,
    • Adductor and
    • Semimembranosus
  • Third layer
    • Quadratus femoris,
    • Obturator internus,
    • Obturator externus and
    • Gemellus
• Of these the obturator internus is placed within the pelvic cavity.

FIRST LAYER

Sartorius

• This is a long, thin and flat muscle and is the anterior of the two muscles in the first layer. It is narrow at its distal extremity. Its proximal extremity is situated in the abdominal cavity at the pelvic brim and the remainder of its muscular belly is on the medial aspect of the thigh. It extends in an oblique direction downwards and backwards from the posterior part of the sub lumbar region to the medial aspect of the thigh.
• Origin: By two heads. (1) From iliac fascia and (2) From the tendon of psoas minor. The femoral vessels pass between the parts.
• Insertion: Medial straight ligament of patella and the fascia latae and the tuberosity of tibia.
• Action: To flex the hind limb and adduct the limb.
• Blood supply: Femoral artery.
• Nerve supply: Saphenous nerve.

Gracilis

• This muscle is extensively united to its fellow at the origin and is the larger and wider of the two muscles of this layer.
• Origin: Pelvic symphysis and prepubic tendon.
• Insertion: Medial patellar ligament, medial surface of the tibia and fascia latae.
• Action: To abduct the limb and tense the fascia of the leg.
• Blood supply: Deep femoral artery.
• Nerve supply: Obturator nerve.
• (Note: At the proximal part of the medial face of the thigh, the gracilis and the sartorius are separated by a triangular space, the femoral triangle, which lodges the femoral vessels)

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SECOND LAYER

Pectineus

• It is a large, thick, conical muscle situated under the sartorius and gracilis. It extends in an oblique direction downwards, slightly forwards and outwards from the anterior border of the pubis to the proximal extremity of the tibia.
• Origin: Ventral surface of the pubis and the prepubic tendon.
• Insertion: The middle of the medial border of the posterior surface of the femur and in common with sartorius and gracilis to the medial tuberosity of the tibia.
• Action: To abduct the limb, flex the hip and rotate the femur inwards.
• Blood supply: Deep femoral artery.
• Nerve Supply: Obturator nerve.

Femoral canal

• It is a muscular canal bounded in front by the sartorius, behind by the pectineus, medially by the gracilis and iliopsoas and vastus medialis laterally.
• Its lower opening is at the insertion of the fibres of the pectineus. The upper opening of this canal is the femoral ring, which opens into the abdomen.
• It is bounded in front by the Poupart’s ligament or inguinal ligament, behind by the anterior border of the pubis and laterally by the tendon of psoas minor.
• It lodges the femoral vessels, saphenous artery, vein and nerve. The canal terminates below at the lower part of the insertion of the pectineus.

Adductor

• This muscle lies behind the vastus internus and pectineus. It extends from the ventral surface of the pubis and ischium, in an oblique direction, downwards, forwards and outwards to the distal part of the posterior surface of the femur.
• Origin: Ventral surface of the pubis and ischium.
• Insertion: The lateral part of the posterior surface of the femur.
• Action: To adduct the limb, extend the hip and rotate the femur inwards.
• Blood supply: Deep femoral artery.
• Nerve supply: Obturator nerve.

Semimembranosus

• This is very large quadrilateral muscle lies behind the adductor and a large extent of medial face of this muscle comes to view on removal of the muscles of the first layer. It forms the posterior most muscle of the second layer.
• Origin: Ventral face of the ischium and the tuber ischii.
• Insertion: Medial epicondyle of the femur and the medial condyle of the tibia.
• Action: To extend the hip and adduct the limb.
• Blood supply: Deep femoral artery.
• Nerve supply: Sciatic nerve.

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THIRD LAYER

Note: The following muscles are more on the posterior aspect of hip joint.

Quadratus femoris

• It is a narrow short muscle lying under the cover of the origin of the adductor and semimembranosus. .
• Origin: Ventral face of the ischium.
• Insertion: Trochanter minor of the femur.
• Action: To extend the hip and adduct the thigh.
• Blood supply: Deep femoral artery.
• Nerve supply: Sciatic nerve.

Obturator externus

• This muscle is made up of coarse muscular bundles situated around the obturator foramen on the ventral surface of the ischium.
• Origin: Ventral surface of ischium and pubis around the obturator foramen.
• Insertion: In common with the obturator internus to the trochanteric fossa.
• Action: To adduct the thigh and rotate it outwards.
• Blood supply: Deep femoral artery.
• Nerve supply: Obturator nerve.

Obturator internus

• This muscle is extensive and is situated on the floor of the pelvic cavity above and mostly behind the obturator foramen.
• Origin: Pelvic surface of the ischium and pubis around the obturator foramen.
• Insertion: The tendon passes through the obturator foramen and is inserted in common with preceding muscle to the trochanteric fossa.
• Action: To rotate the femur outwards.
• Blood supply: Deep femoral artery.
• Nerve supply: Obturator nerve.

Gemellus

• This is a small, thin muscle extending from the ventral surface of the ischium to the trochanteric fossa.
• Origin: Lateral border of the ischium at the lesser sacro-sciatic foramen and from the lateral face of the posterior part of the sacro-sciatic ligament.
• Insertion: Trochanteric fossa.
• Action: To rotate the femur outwards.
• Blood supply: Deep femoral artery.
• Nerve supply: Sciatic nerve.

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