The digestive system is made up of the gastrointestinal tract—also called the GI tract or digestive tract—and the liver, pancreas, and gallbladder. The GI tract is a series of hollow organs joined in a long, twisting tube from the mouth to the anus. The hollow organs that make up the GI tract are the mouth, esophagus, stomach, small intestine, large intestine, and anus. The liver, pancreas, and gallbladder are the solid organs of the digestive system.

The small intestine has three parts. The first part is called the duodenum. The jejunum is in the middle and the ileum is at the end. The large intestine includes the appendix, cecum, colon, and rectum. The appendix is a finger-shaped pouch attached to the cecum. The cecum is the first part of the large intestine. The colon is next. The rectum is the end of the large intestine.

The duodenum is the first of the three parts of the small intestine that receives partially digested food from the stomach and begins with the absorption of nutrients. It is directly attached to the pylorus of the stomach. It has a C-shape, it is closely related to the head of the pancreas and consists of four sections: superior, descending, horizontal, and ascending parts.

Histologically speaking, the duodenum consists of the typical three layers common to all hollow organs of the gastrointestinal tract, but it has Brunner’s glands, which is the characteristic feature of the duodenum.

The liver is the largest internal organ of the human body, weighing approximately 1.5 kg. Embryologically it develops from the foregut and it spans the upper right and part of left abdominal quadrants. Anatomically the liver consists of four lobes: two larger ones (right and left) and two smaller ones (quadrate and caudate).

Histologically speaking, it has a complex microscopic structure, that can be viewed from several different angles. Physiologically speaking, the liver also performs many essential functions and it is your best friend when you are enjoying some beers with your friends. This article will examine every histological component of the liver, its macroscopic and microscopic vascular supply, and the biliary system.

The small intestine is composed of three distinct parts, the last one being the ileum. At the distal end, the ileum is separated from the large intestine, into which it opens, by the ileocecal valve. The ileum itself is very rich in lymphoid follicles and is attached to the abdominal wall by the mesentery. Its vascular supply is provided by the ileal arteries and its innervation via the coeliac and superior mesenteric plexi.

In terms of histology, the mucosa of the ileum consists of simple columnar epithelium comprising of enterocytes and goblet cells. A characteristic histological feature of the ileum are Peyer’s patches.