Midgut

Illu small intestine

Midgut is a section of the embryo's gut tube that gives rise to a large part of the digestive system in vertebrates, including humans. The midgut is responsible for absorbing nutrients from food as it is digested, making it a crucial component of the gastrointestinal tract.

Development

During embryogenesis, the midgut develops from the endoderm, one of the three primary germ layers in the early embryo. The process begins with the formation of the primitive gut tube, which then differentiates into the foregut, midgut, and hindgut. The midgut extends from the opening of the bile duct to the mid-transverse colon in adults. During development, the midgut undergoes a process known as physiological herniation, where it temporarily protrudes outside the abdominal cavity of the fetus due to rapid growth. This is followed by a 270° counterclockwise rotation around the axis of the superior mesenteric artery before it retracts back into the abdomen.

Anatomy

The midgut includes several major organs of the digestive system, such as the lower part of the duodenum, the jejunum, ileum, cecum, appendix, ascending colon, and the proximal two-thirds of the transverse colon. The blood supply to the midgut is primarily through the superior mesenteric artery, which branches off the aorta. The venous blood from the midgut drains into the superior mesenteric vein, which then joins the splenic vein to form the portal vein.

Function

The primary function of the midgut is the absorption of nutrients from digested food. The jejunum and ileum, in particular, have a highly folded inner surface, increasing the area available for absorption. These folds are covered in villi, which are further covered in microvilli, significantly amplifying the surface area. This structure allows for efficient absorption of carbohydrates, proteins, fats, and vitamins.

Clinical Significance

Several conditions can affect the midgut, including midgut volvulus, a life-threatening condition that occurs when the intestine becomes twisted around the superior mesenteric artery, cutting off blood supply. Another condition is necrotizing enterocolitis, primarily seen in premature infants, where portions of the bowel undergo necrosis. Midgut carcinoids are a type of neuroendocrine tumor that can also arise in the midgut, leading to various symptoms depending on the hormones they secrete.

See Also

• Gastrointestinal tract
• Foregut
• Hindgut
• Superior mesenteric artery