Rectus Sheath

Question 1

What is the rectus sheath?

Answer 1

An aponeurotic sheath covering the rectus abdominis muscle

Question 2

What are the features of the anterior wall of the rectus sheath?

Answer 2

Covers the whole muscle
Firmly adherent to the tendinous intersections of the rectus muscle

Question 3

What are the features of the posterior wall of the rectus sheath?

Answer 3

Incomplete layer - deficient above costal margin and below arcuate line
Free from the rectus muscle

Question 4

What is the linea alba?

Answer 4

Fusion of the aponeuroses in the midline

Question 5

Lateral extent of the rectus sheath

Answer 5

Anterior and posterior walls extend till linea semilunaris

Question 6

Location of the linea semilunaris?

Answer 6

Extends from tip of 9th costal cartilage to pubic tubercle

Question 7

Describe the formation of the rectus sheath above the costal margin

Answer 7

Anterior wall: External oblique aponeurosis
Posterior wall: It is deficient; the rectus muscle rests directly on the 5th, 6th and 7th costal cartilages

Question 8

Describe the formation of the rectus sheath between the costal margin and the arcuate line

Answer 8

Anterior wall: External oblique aponeurosis and anterior lamina of the aponeurosis of the internal oblique
Posterior wall: Posterior lamina of the aponeurosis of the internal oblique and aponeurosis of the transversus muscle
Midway between the umbilicus and the pubic symphysis, the posterior wall of the rectus sheath ends in the arcuate line or linea semi circularis or fold of Douglas (the line is concave downwards)

Question 9

Describe the formation of the rectus sheath below the arcuate line

Answer 9

Anterior wall: Aponeuroses of all the three flat muscles of the abdomen. The aponeuroses of the transversus and the internal oblique are fused, but the external oblique aponeurosis remains separate
Posterior wall: It is deficient. The rectus muscle rests on the fascia transversalis

Question 10

What are the muscles of the rectus sheath?

Answer 10

Rectus abdominis
Pyramidalis

Question 11

What are the arteries of the rectus sheath?

Answer 11

The superior epigastric artery enters the sheath by passing between the costal and xiphoid origins of the diaphragm
The inferior epigastric artery enters the sheath by passing in front of the arcuate line

Question 12

What are the veins of the rectus sheath?

Answer 12

Superior and inferior epigastric vein

Question 13

What are the nerves of the rectus sheath?

Answer 13

Terminal parts of the lower six thoracic nerves, including the lower five intercostal nerves and the subcostal nerves

Question 14

What are the functions of the rectus sheath?

Answer 14

Supports the rectus muscle during its contraction and thus increases the efficiency of the muscle
Maintains the strength of the anterior abdominal wall