Development of the gastrointestinal tract

The different parts of the digestive system are :

1. Pharynx

2. Esophagus

3. Stomach

4. Small intestine

5. Large intestine http://totalphysiology.com/2021/04/large-intestine

The accessory glands/associated organs -Liver, Biliary System, and Pancreas.

         The digestive system develops from

1. Foregut

2. Midgut and

3. Hindgut 

Foregut : 

 The pharynx, the esophagus, the stomach, parts of the duodenum proximal to the opening of the bile duct, the liver, the pancreas, and the biliary system arise from the foregut. In addition to that foregut forms trachea and lungs. The trunk of the celiac artery supplies organs developed from the foregut except for the pharynx and lower part of the respiratory system.

Midgut 

The midgut forms the remaining part of the duodenum distal to the opening of the bile duct, the jejunum, the ileum, the cecum, the appendix, the ascending colon, and the proximal 2/3rd of the transverse colon. These organs get their blood supply from the superior mesenteric artery,

From the midgut, the primary intestinal loop develops, from which above mentioned organs develop. The primary intestinal loop overgrows during 5-6 th weeks of intrauterine development and protrudes into the umbilical cord as the development of the abdominal cavity is slow (Physiological hernia). And in the 10th week, it returns to the abdominal cavity. During this period, the midgut rotates at first to 90, then 180 degrees, a total of 270 degrees counterclockwise.

Hindgut : 

The hindgut forms the distal 1/3rd of the transverse colon, the descending colon, the sigmoid colon, the rectum, and the upper 2/3rd of the anal canal. The inferior mesenteric artery supplies the hindgut.

The lower 1/3rd of the anal canal develops from the surface ectoderm of the cloaca. The ectoderm present on the surface part of the cloaca forms the anal pit. Degeneration of the cloacal membrane connects the upper and lower parts of the anal canal, marked by an irregular folding of the mucosa – the Pectinate line.

Importance of the Pectinate line  

1. At this line epithelial layer changes from columnar epithelium to the stratified squamous epithelial lining. 

2. Above this line, blood supply is from the superior rectal arteries, branches of the inferior mesenteric artery. While below this line, blood supply is from the inferior rectal arteries, branches of the internal pudendal arteries.

Sources  

‘learn and fly.co.in ‘does not provide medical advice. Instead, the article is based on information from academic literature and many books.