بسم الله الرحمن الرحيم

Development of Intestine Origin: Endoderm of midgut  mucosa & glands. Splanchnic secondary mesoderm  submucosa & musculosa and serosa.

Morphogenesis of The Midgut-hindgut Mitosis and growth elongates the distal foregut and midgut forming the intestinal loop. The loop undergoes rotatation 270o anticlockwise (when viewed from the front) around the superior mesenteric artery. There seems such a lot of repetition in this slide sequence. Far too much on gut. Too little on lungs, liver, pancreas

Figure is from Langman’s Embryology

Stages of development: 1- Preherniation stage: Straight midgut  midgut loop cranial limb  caudal limb Cranial limb  small intestine (jejunum + upper part of ileum. Caudal limb  large intestine ( lower part of ileum + caecum + appendix + ascending colon + right 2/3 transverse colon.

2- Herniation stage: Time: sixth week Causes: 1- Small abdominal cavity. 2- Large liver and kidney. Site: Extraembryonic coelom of umbilical cord. Rotation 900 anticlockwise cranial limb right limb & caudal limb  left limb.

Postherniation stage: Time: tenth week Reduction of small intestine first, large intestine second and caecum last. Rotation 1800 Anticlockwise  right limb (small intestine)  left & left limb (large intestine) right Proliferation  recanalization of the endoderm of the intestine occurs.

Congenital anomalies: 1- Congenital umbilical hernia: due to presence of defect in the anterior abdominal wall (gastroschisis)  herniation of loop of the intestine.

2- Exomphalos (omphalocele): due to failure of a loop of intestine to return back to the abdominal cavity loop of intestine coming from the base of umbilicus covered by amnion.

3- Meckl’s diverticulum: due to persistance of small part of the yolk stalk. *Length : 2 inches * Distance from caecum: 2 feet *Incidence: 2% of people. 4- Congenital umbilical fistula due to persistance of all yolk stalk. The umbilicus will discharge feces.

5- Rotation clockwise transposition 5- Rotation clockwise transposition. 6- Intestinal atresia: due to failure of recanalization of the intestine. 7- Intestinal stenosis: due incomplete recanalization. 8- Duplication of the intestine: duplication of segment of the intestine due to abnormal recanalization.

Thank You Prof.: Dr. Shawky Tayel