Digestion and Absorption

Pepsin (in gastric juice) digests proteins to peptides, 6-12 amino acids long. Pepsin is an endopeptidase, which means it hydrolyses peptide bonds in the middle of a polypeptide chain. It is unusual in that it has an optimum pH of about 2 and stops working at neutral pH.

The muscularis externa consists of an inner circular layer and a longitudinal outer muscular layer. The circular muscle layer prevents food from traveling backward and the longitudinal layer shortens the tract.

Lining mucosa, is made up of nonkeratinised stratified squamous epithelium. It is found almost everywhere else in the oral cavity.

The simplest receptor found in the mouth is the salt (NaCl) receptor. An ion channel in the taste cell wall allows Na⁺ ions to enter the cell. This on its own depolarises the cell, and opens voltage-regulated Ca²⁺ gates, flooding the cell with ions and leading to neurotransmitter release.

Pancreatic lipase enzymes digest triglycerides to fatty acids and glycerol in the duodenum.

Von Ebner glands are found in a trough circling the circumvallate papillae on the dorsal surface of the tongue near the sulcus terminalis. They secrete a purely serous fluid that begins lipid hydrolysis.

Fructose is absorbed by facilitated diffusion.

Yes, it is correct. The transverse colon is the part of the colon from the hepatic flexure to the splenic flexure. The transverse colon hangs off the stomach, attached to it by a wide band of tissue called the greater omentum.

Pancreatic amylase digests all the remaining starch in the duodenum. Amylase digests starch molecules from the ends of the chains in two-glucose units, forming the disaccharide maltose. Glycogen is also digested here.

The pancreas is also the main source of enzymes for digesting fats (lipids) and proteins. The enzymes that digest polysaccharides, by contrast, are primarily produced by the walls of the intestines.

The striated duct is well developed in the submandibular gland. The epithelium of the striated duct participates in ion and water transport and secretes kallikrein. A segment of this duct is lined by cuboidal-to-columnar epithelial cells with basal infoldings containing numerous mitochondria.

Unlike most of the other facial muscles, which are innervated by the facial nerve (or CN VII), the muscles of mastication are all innervated by the trigeminal nerve (or CN V). More specifically, they are innervated by the mandibular branch.

Segmentation occurs only in the small intestine as short segments of intestine contract. Segmentation helps to increase the absorption of nutrients by mixing food and increasing its contact with the walls of the intestine.

Crohn's disease is a common chronic inflammatory bowel disease (IBD), which can affect any part of the GI tract, but it mostly starts in the terminal ileum.

After passing through the small intestine, food passes into the large intestine. In the large intestine, some of the water and electrolytes (chemicals like sodium) are removed from the food. Many microbes (bacteria like Bacteroides, Lactobacillus acidophilus, Escherichia coli, and Klebsiella) in the large intestine help in the digestion process.
After being in the stomach, food enters the duodenum. In the small intestine, bile (produced in the liver and stored in the gall bladder), pancreatic enzymes, and other digestive enzymes produced by the inner wall of the small intestine help in the breakdown of food.