2 24 Biology Notes Q Just by looking at the cow s digestive system what can you assume A Its long length suggests that cows eat food that is difficult to digest Structure and function of the human digestive system Ingestion mouth teeth Mechanical breakdown teeth Chemical breakdown Absorption small intestine Elimination rectum mouth salvia stomach Human Digestion Fig 34 4 mouth ingestion and breakdown Chewing mechanical breakdown Enzymes amylase chemical breakdown enzyme in salvia breaks down carbohydrates stomach breakdown Mixing mechanical breakdown Enzymes pepsin proteins chemical breakdown Secreted as pepsinogen Fig 34 14 small intestine chemical breakdown Enzymes in pancreas chemical breakdown Other secretions in gall bladder chemical breakdown bile needed for lipid digestion emulsifier Fig 34 15 small intestine absorption Villi and Microvilli a connection to circulatory system Fig 34 16 large Intestine absorption Reabsorption of water and vitamins Fermentation by bacteria Q Why is there so much folding in the intestines A increased surface area How is digestion controlled Digestion is controlled by the nervous system and hormones Food triggers nervous system responses Salivary glands and other parts of the digestive system preparing it to digest and absorb food Hormonal Regulation Amino acids and peptides in chyme stimulate cells in the stomach lining to release gastrin into the bloodstream Gastrin stimulates further acid secretion in the stomach which promotes protein digestion Fig 34 17 Table 34 5 Urinary System Homeostasis What is it something staying the same when the environment around it changes
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