Bile and lipase enzymes break up complex lipid molecules into monoglycerides and fatty acids. The release of bile is stimulated when acidic chyme from the stomach enters the duodenum. It mixes with the food and acts first as an emulsifier on the fats in the chyme, breaking them up into small droplets.
Then the lipase enzymes can work more effectively, to completely break it down so it's easily absorbed.
10. Describe the digestive and hormonal function of the pancreas including special
reference to all of its secretions.
The pancreas is made up of two types of glands:
- exocrine
The exocrine gland secretes digestive enzymes. These enzymes are secreted into a network of ducts that join the main pancreatic duct, which runs the length of the pancreas. - endocrine
The endocrine gland, which consists of the islets of Langerhans, secretes hormones into the bloodstream. - The enzymes secreted by the exocrine gland in the pancreas help break down carbohydrates, fats, proteins, and acids in the duodenum. These enzymes travel down the pancreatic duct into the bile duct in an inactive form. When they enter the duodenum, they are activated. The exocrine tissue also secretes a bicarbonate to neutralize stomach acid in the duodenum.
- The hormones secreted by the endocrine gland in the pancreas are insulin and glucagon (which regulate the level of glucose in the blood)
11. Compare and contrast the chemical digestion and absorption of fats, proteins,
nucleic acids and carbohydrates.
Carbohydrate digestion begins immediately with the release of salivary amylase. This digestive enzyme breaks down complex carbohydrates, such as starch. Once the food reaches your stomach, amylase continues to process any undigested carbohydrate. Next, food enters the small intestine where the enzymes pancreatic amylase, dextrinase, glucomylase, maltase, sucrase and lactase complete the carbohydrate digestion process by turning the carbohydrate into a simpler monosaccharides.
Protein digestion begins in your stomach with the enzyme pepsin, responsible for breaking the peptide bonds holding amino acids together, pepsin digests protein into shorter polypeptides. Inside the small intestine, the pancreatic enzymes trypsin and chymotrypsin break down the polypeptides into smaller chains. Protein digestion is complete when the carboxypeptidase, dipeptidase and amino peptidase enzymes transform short polypeptide chains into individual amino acids.
12. Identify all the parts of the digestive system where absorption takes place and list
the specific substances that are absorbed at each location.
13. Compare and contrast the structure and function of the large and small intestines.
Small intestine is longer and absorbs nutrients, while the large intestine is shorter (1.5 m long) and absorbs water, salts and minerals. Faeces are formed and excreted from the large intestine.
14. Describe the rectum and identify its role for the digestive system.
The main function of the rectum is to act as a temporary storage site for fecal matter before it is eliminated from the body through the anal canal. As the food you eat passes through the digestive system, it is broken down and nutrients are absorbed in the stomach, small and large intestines. Fecal matter, which includes digestive juices, bacteria and fiber, continues to move into the lower portion of the large intestine -- the rectum.
15. Describe the hormonal control system that coordinates the activity of the digestive
system.
The hormones controlling digestive function are synthesized within the gastrointestinal tract by cells scattered in the epithelium of the stomach and small intestine. Most if not all of these hormones are synthesised in the brain.
16. Define what ulcers are and identify some of their causes and cures.
A stomach ulcer, or peptic ulcer, is a sore that forms on the lining of the stomach or the area of the small intestine called the duodenum. An ulcer in the stomach lining is called a gastric ulcer, and one in the intestine is called duodenal ulcer.
-The bacteria helicobacter pylori, commonly called H.pylori, are responsible for the majority of stomach ulcers. These bacteria live in the layer that covers the lining of the stomach and small intestine, when they get out of control, they inflame the area, causing an ulcer.
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