Digestion And Nutrition PDF

Digestion and Nutrition Chapter 36 Mader: Biology 8th Ed.  Outline Dentition Among Mammals Human Digestive Tract – Mouth – Stomach – Small Intestine – Accessory Organs – Large Intestine Nutrition Mader: Biology 8th Ed.  Adap...

Digestion and Nutrition Chapter 36 Mader: Biology 8th Ed.  Outline Dentition Among Mammals Human Digestive Tract – Mouth – Stomach – Small Intestine – Accessory Organs – Large Intestine Nutrition Mader: Biology 8th Ed.  Adaptations to Diet Dentition differs with mode of nutrition. – Omnivores have a variety of specializations to accommodate both vegetation and meat. – Herbivores often have incisors for clipping, premolars and molars for grinding. – Carnivores use pointed incisors and enlarged canines to shear off pieces small enough to swallow. Mader: Biology 8th Ed. Dentition Among Mammals Mader: Biology 8th Ed.  Human Digestive Tract Humans have a tube-within-a- tube body plan. – Digestion is an extracellular process and digestive enzymes are secreted by digestive tract, or by nearby glands. Mader: Biology 8th Ed.  Human Digestive Tract Mouth – Three major pairs of salivary glands. – Saliva contains salivary amylase. Begins starch digestion. – Tongue is composed of striated muscle. Mixes chewed food with saliva. – Forms mixture into bolus. Mader: Biology 8th Ed.  Swallowing Digestive and respiratory passages come together in the pharynx. – Soft palate closes off nasopharynx. – Epiglottis covers opening into trachea. Blocks air passages. Esophagus takes food to stomach. – Peristalsis - Mader: Biology 8th Ed. Peristalsis Mader: Biology 8th Ed.  Stomach Stomach wall has deep folds, which disappear as the stomach fills to an approximate capacity of one liter. – Epithelial lining of the stomach has millions of gastric pits, which lead to gastric glands. Pepsin is a hydrolytic enzyme that acts on protein to produce peptides. Eventually food mixing with gastric juices becomes chyme. – Whenever sphincter between stomach and small intestine relaxes, a small quantity of chyme passes through the opening into the Mader: Biology 8th Ed.  Small Intestine Chyme from stomach enters the duodenum. – Liver and pancreas send secretions to duodenum. Liver produces bile which is stored in gallbladder. – Bile contains bile salts which break up fat into fat droplets via emulsification. Mader: Biology 8th Ed.  Small Intestine – Pancreas produces pancreatic juice and digestive enzymes. Pancreatic amylase digests starch to maltose. Trypsin digests protein to peptides. Lipase digests fat droplets to glycerol and fatty acids. Epithelial cells of the villi produce intestinal enzymes which complete digestion of peptides and sugars. Mader: Biology 8th Ed.  Absorption by Villi Mucous membrane layer of small intestine has ridges and furrows that give it a corrugated surface. – Villi are ridges on the surface, which contain even smaller ridges, microvilli. Greatly increase absorptive area. Each villus contains blood capillaries and a lymphatic capillary (lacteal). Mader: Biology 8th Ed. Anatomy of Intestinal Lining Mader: Biology 8th Ed.  Accessory Organs Pancreas – Exocrine gland when it produces and secretes pancreatic juices into the duodenum. Liver – Helps maintain glucose concentration in blood at about 0.1% by removing excess glucose as storing it as glycogen. Mader: Biology 8th Ed.  Large Intestine Includes cecum, colon, rectum, and anal canal. – Larger in diameter, but shorter in length than small intestine. Absorbs water, salts, and some vitamins. – Cecum has small projection - appendix. – Colon subdivided into ascending, transverse, descending, and sigmoid colon. – Opening to anal canal - Anus. Mader: Biology 8th Ed.  Nutrition Vitamins – Organic compounds the body is unable to produce, but are required for metabolic purposes. Antioxidants – Cellular metabolism generates free radicals that carry extra electron. Vitamins C, E, and A are believed to defend the body against free radicals. Mader: Biology 8th Ed.  Nutrition Vitamin D – Skin cells contain precursor cholesterol molecule that is converted to vitamin D after UV exposure. Activated into calcitriol that regulates calcium uptake and metabolism. Minerals – Calcium Degenerative Bone Disease. – Sodium Hypertension. Mader: Biology 8th Ed. Ideal American Diet Mader: Biology 8th Ed.