Chapter 14 - Gastrointestinal Tract
The digestive system takes in food, digests and absorbs nutrients, and eliminates the remaining waste material. The digestive system can be divided into the digestive tract (oral cavity, esophagus, stomach, small intestine, and large intestine) and associated digestive organs (salivary glands, pancreas, liver, and gallbladder).
The stomach digests food by acidification and the breakdown of proteins. It is divided into three histological regions (cardiac, body/fundus and pyloric) based on their anatomical location and appearance of their glands.
Gastric glands are found in the fundus/body of the stomach and produce stomach acid and secrete proteolytic enzymes.
Pyloric glands are located in the antrum of the pylorus.
The gastroduodenal junction is the point where the distal stomach (pyloric) joins the proximal duodenum of the small intestine. The pyloric sphincter controls the passage of partially digested food (i.e., chyme) from the stomach into the duodenum
The small intestine is involved in the digestion of food and nutrient absorption. It is divided into the duodenum, jejunum and ileum.
Mucosa-Associated Lymphoid Tissue (MALT)
Lymphoid nodules become increasingly numerous in the ileum and form bulges called Peyer’s patches. The epithelium that covers Peyer's patches contain specialized epithelial cells (M cells) that transport antigens to immune cells to initiate an immune response.
The ileocecal junction is the boundary between the small intestine and the large intestine.
The large intestine absorbs water and consolidates the fecal mass. It is divided into the cecum, appendix, colon, rectum and anal canal.