Anatomy overview I

Question 1

What makes up the rectus sheath?

Answer 1

The rectus sheath is formed by the aponeuroses of the transverse abdominus and the external and internal oblique muscles. It contains the rectus abdominis and pyramidalis muscles.

Question 2

What 3 layers are found below the rectus sheath?

Answer 2

o Transversalis fascia
o Extraperitoneal fat
o Parietal peritoneum

Question 3

What are the differences between the rectus sheath above and below the arcuate line?

Answer 3

Above the arcuate line:
o At the lateral margin of the rectus, the aponeurosis of the internal oblique divides into two lamellae:
o One of which passes in front of the rectus, blending with the aponeurosis of the external oblique as well as the aponeurosis of the anterior half of the internal oblique.
o The other, behind it, blending with the aponeurosis of the transversus as well as the posterior half of the internal oblique, and these, joining again at the medial border of the rectus, are inserted into the linea alba.
Below the arcuate line:
o Below this level, the aponeuroses of all three muscles (including the transversus) pass in front of the rectus.

Question 4

What is the arcuate line?

Answer 4

The arcuate line of the abdomen is a horizontal line that demarcates the lower limit of the posterior layer of the rectus sheath. It is also where the inferior epigastric vessels perforate the rectus abdominis

Question 5

Describe a mesentery

Answer 5

The mesentery is a double layer of visceral peritoneum that attaches the posterior back wall to the gastrointestinal tract. There are often blood vessels, nerves, and other structures between these layers

Question 6

Describe an omentum

Answer 6

The omentum are double folds passing from the stomach and duodenum to other organs or the body wall

Question 7

Describe the greater omentum

Answer 7

The greater omentum (or gastrocolic) hangs from the greater curve of the stomach and loops down in front of the intestines before curving back upwards to attach to the transverse colon

Question 8

Describe the lesser omentum

Answer 8

The lesser omentum (or gastrohepatic) is attached to the lesser curvature of the stomach and the liver.

Question 9

What connects the two sacs (omenta) in the body?

Answer 9

The two sacs are connected by the epiploic foramen

Question 10

How is the greater momentum formed?

Answer 10

• The greater omentum develops from the dorsal mesentery that connects the stomach to the posterior abdominal wall.
• During its development, the stomach undergoes its first 90° rotation along the axis of the embryo, so that posterior structures are moved to the left and structures anterior to the stomach are shifted to the right. As a result, the dorsal mesentery folds over on itself, forming a pouch with its blind end on the left side of the embryo.
• A second approximately 90° rotation of the stomach, this time in the frontal plane, moves structures inferior if they were originally to the left of the stomach, and superior if they were originally to the stomach’s right.
• Consequently, the blind-ended sac (also called the lesser sac) formed by the dorsal mesentery is brought inferiorly, where it assumes its final position as the greater omentum

Question 11

What are the names of the two flexures of the large intestine?

Answer 11

• The hepatic flexure lies in the right upper quadrant of the human abdomen. It receives blood supply from the superior mesenteric artery.
• The left colic flexure or splenic flexure (as it is close to the spleen) is the sharp bend between the transverse colon and the descending colon