QS Study

Rectus sheath is an aponeurotic sheath covering the rectus abdominis muscle. The rectus sheath is made up of two parts, known as the posterior sheath and the anterior sheath. These sheaths are made of fibers of the transversus abdominis, internal abdominal oblique (IAO), and external abdominal oblique (EAO), which are muscles of the abdomen. The anterior rectus sheath is incised along a line connecting the perforators.

Formation

Fig: Rectus sheath in anterior view

(A) Above the coastal margin:

Anterior wall – External oblique aponeurosis.

Posterior wall – Deficient, rectus muscle rests directly on the costal cartilages.

(B) Between the coastal margin and the arcuate line:

(1) Anterior wall –

  1. External oblique aponeurosis.
  2. Anterior lamina of the internal oblique aponeurosis.

(2) Posterior wall –

  1. Posterior lamina of the internal oblique aponeurosis.
  2. Aponeurosis of transversus abdominis.

(C) Below the arcuate line:

(1) Anterior wall – Aponeurosis of all the three flat muscles of the abdomen.

(2) Posterior wall – Deficient, rectus muscle rests on the fascia transversals.

Contents

(A) Muscles –

  • The rectus abdominis,
  • The pyramidalis.

(B) Arteries –

  • The superior epigastric artery,
  • The inferior epigastric artery.

(C) Veins –

  • The superior epigastric vein,
  • The inferior epigastric vein.

(D) Nerves –

  • Terminal parts of lower five intercostal nerves,
  • Terminal parts of subcostal nerves.

Functions

(1) It checks bowing of the rectus muscle during its contraction and thus increases the efficiency of the muscle.

(2) It maintains the strength of the anterior abdominal wall.