BIOS 256: Case Study 1 Digestive system

Upper digestive tract Mouth- Functions: Ingestion of the food. Deglutition Mechanical digestion (mastication) Production of saliva. Sense the food. Moist the food – make the bolus. Chemical digestion -Enzyme (Components in saliva help keep the pH in your mouth between 6.5 and 7 so that the enzyme salivary amylase can start to break down carbohydrates. The enzymes that help digest food in the stomach, such as pepsin, work best at a pH around 2, while those that function in the intestines, including peptidases and maltase, work best at a pH around 7.5) Saliva also contains a small amount of lipase, which digests lipids. Sometimes called lingual lipase because it is produced by the lingual salivary glands, it functions at a low pH and thus can break down lipids as it moves into the stomach and into the upper duodenum. Lingual lipase-lipids. Pharynx- The act of swallowing, or deglutition, moves a rounded mass of food, called a bolus, from the mouth to the stomach. As the food bolus passes from the mouth, it enters the oropharynx by passing through a constricted, archlike opening called the faucets. Deglutition only Esophagus- The esophagus, a collapsible, muscular, mucosa-lined tube about 25 cm (10 inches) long, extends from the pharynx to the stomach and pierces the diaphragm in its descent from the thoracic cavity to the abdominal cavity. Deglutition and Peristalsis Stomach- Functions of the stomach 1. Reservoir for food until it is partially digested and moved farther along the GI tract 2. Secretes gastric juice to aid in digestion of food 3. Breaks food into small particles and mixes them with gastric juice 4. Secretes intrinsic factor and HCL 5. Performs limited absorption 6. Produces gastrin and ghrelin 7. Helps protect the body from pathogenic bacteria swallowed with food Duodenum- The duodenum is the uppermost division and the part to which the pyloric end of the stomach attaches. It is about 25 cm (10 inches) long and is shaped roughly like the letter C. The name duodenum, meaning “12 fingerbreadths,” refers to the short length of this intestinal division. The duodenum is rich of absorbing enterocytes, mucus producing goblet cells and peptide hormone producing endocrine cells. The main functions of the duodenum are: • Neutralization of acidic gastric juice through production of alkaline secrets. • Mechanical processing and digestion of chyme. • Mixing bile and pancreatic enzymes. • Absorption of water, electrolytes and nutrients (especially water-soluble substances such as monosaccharides). • Produces CCK in the presence of fats. • Produces Secretin. The role of the duodenum is to absorb nutrients such as vitamins, minerals, carbohydrates, fats, proteins, and water. When pH levels in the duodenum become low, secretin is released.