Difference Between Duodenum and Jejunum

Duodenum vs Jejunum

Small intestine extends from the pylorus of the stomach to the junction between the cecum and ileum, which makes the longest part of the alimentary canal. It can be divided into three sections, including; duodenum the first part, ileum the last part, and jejunum the middle part. Although there are no clearly defined boundaries between these three parts, there are characteristic features, which reflect their differences in function. The primary digestion and absorption mainly occurs in the duodenum and jejunum.

Jejunum

Jejunum is the second part of the small intestine. It is about 8 feet long and lies between the duodenum and ileum. Jejunum begins at the duodenojejunal flexure. The coils of jejunum are freely mobile and are attached to the posterior abdominal wall by the mesentery of the small intestine. Jejunum has wider bore, thicker walls and more numerous microvilli on the mucus membrane. These microvilli increase the surface area of absorption and increase the efficiency of digestion. This part is specialized to absorb most of monosaccharides and amino acids. The mesentery of jejunum is made up of circular and longitudinal muscles, which helps to move food along the elementary canal, thus gives great mobility within the abdomen.

Duodenum

This is the first part of the small intestine that lies in between the pylorus and jejunum. It is ‘C’ shaped and about 10 inches long. The first part of this tube is very much similar to stomach in structure. The first two inches of duodenum runs upward and backward on the right side of the first lumbar vertebra while the next 3 inches of it runs vertically downward on the right side of second and third lumbar vertebrae. The next 3 inches of duodenum runs horizontally to the left on the subcostal plane and follows the lower margin of the head of pancreas. The rest of 2 inches of it runs upward and to the left to the duodenojejunal flexure. Duodenum basically receives the acidic chyme from the stomach, bile from the liver and gallbladder, and digestive enzymes from the bicarbonate from the pancreas. These digestive enzymes digest larger food particles into smaller fragments in this section.

What is the differences between Jejunum and Duodenum?

• Duodenum is C shaped and makes first portion of the small intestine, while jejunum is a coiled tube and makes the middle portion of the small intestine.

• Jejunum is more longer than doedenum.

•Plicae circularis缺席the first part of the duodenum, while jejunum has larger and more closely set plicae circularis.

•空肠上皮具有简单的圆柱，带有更多的杯状细胞，而十二指肠的圆柱体具有相同的细胞，几乎没有杯状细胞。

• Muscularis mucosa of the duodenum is continuous while that of jejuna is interrupted.

• Duodenum has leaf shaped, numerous villi, whereas jejunum has tall, tongue shaped, numerous villi.

• Unlike the jejunum, duodenum receives the opening of bile and pancreatic ducts.

• The digestion of carbohydrates and protein take place in the duodenum, whereas the absorption of digested products takes place in the jejunum.

• Submucosal Brunner’s glands are present in the duodenum, whereas they’re absent in jejunum.