Digestive System

Functions of structures of digestive tract A. Mouth – Chemical and mechanical digestion B. Esophagus – move food to stomach 1. Peristalsis – smooth muscle contractions C. Stomach – Chemical and mechanical digestion (Produces chyme) D. Small Intestine – Chemical digestion and nutrient absorption into the blood E. Large Intestine – Water reabsorption (maintains water balance – diarrhea, constipation), contains E. coli which produce vitamin K

Accessory Organs and their functions A. Liver – produces bile (helps digest fats), detoxifies blood, creates glycogen for carbohydrate storage B. Gall bladder – stores and concentrates bile C. Pancreas 1. Produces digestive enzymes 2. Produces enzymes that regulate blood sugar (insulin and glucagon) 3. Produces sodium bicarbonate to neutralize stomach acid in the small intestine *** All three feed into the same duct into the duodenum***

Chemical digestion by enzymes A. Mouth – salivary amylase breaks down carbohydrates B. Stomach – pepsin and other proteases break down proteins (requires HCl as a cofactor for enzyme activity) C. Small intestine 1. Does not produce its own enzymes – provided by pancreas 2. Pancreatic amylase – carbs 3. Pancreatic lipase – lipids 4. Trypsin - proteins

***Reminder Macromolecule Polymer Monomer Carbohydrates Polysaccharides Monosaccharides Lipids Triglycerides Glycerol and fatty acids Proteins Polypeptides Amino acids Nucleic acids DNA, RNA Nucleotides

Nutrient Absorption Mostly in the jejunum and ileum of small intestine Villi – finger-like projections on interior of small intestine Increase surface area Each has a capillary bed (absorbs amino acids and monosaccharides into blood) and a lacteal (absorb fatty acids into lymph)

V. Diseases of the Liver A. Cirrhosis –scaring due to disease, toxins B. Jaundice – build up of bilirubin (from breakdown of old red blood cells) because bile is not properly produced causes yellowing of skin C. Hepatitis – viral infection of the liver 1. A – fecal-oral transmission, acute 2. B & C – blood-bourne, chronic 3. Often contributes to liver cancer later