review for exam 2-digestive system
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Created by:
krystalelizabeth on June 3, 2011
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23 terms
Terms | Definitions |
|---|---|
 heterotrophs | herbivore - plant material carnivore - other animals omnivore - both plant and animal |
| Digestive system (vertebrates) | one way tube with a separate mouth and anus and accessory organs; functions to ingest and digest food, absorb nutrients, and eliminate indigestables |
| GI tract | Mouth with 32 teeth (adults), canines and incisors to cut food, molars and premolars to grind food; 3 pairs of salivary glands; epiglottis prevents food from entering trachea when swallowing; pharynx last area both air and food pass through, esophagus, stomach, small intestines, large intestines, rectum, anus |
| GI tract | Consider: Choking involves food entering trachea instead of esophagus. |
| mechanical digestion | can include cutting and grinding of food with teeth and churning and mixing of food thru peristalsis and within stomach |
| process of swallowing | elevation of the palate to seal off the nasal cavity; folding of the epiglottis over the trachea; pressure against the pharynx to initiate swallowing; the swallowing center stimulates successive waves of contraction. |
| esophagus | muscular tube that passes bolus (moistened mass of chewed food swallowed) to stomach; food moves through rhythmic contractions (peristalsis) of the two layers of smooth muscle; sphincter muscle at entrance of stomach must relax before food can enter stomach; acid reflux results from incomplete closure of the sphincter allowing acid to move into the esophagus |
| What are the layers of the alimentary canal, moving from the inside to outside? | mucosa, submucosa (contain plexuses - nerves that regulate activities of GI tract), muscularis , and serous |
| layers of the alimentary canal | Consider: The muscularis has two layers of smooth muscle oriented in different directions. One is circular and one is longitudinal. These orientations promote peristalsis (movement of material thru tract) and segmentation (mechanical mixing of material). |
| Digestion begins | salivary amylase begins digestion of starch in the mouth, pepsin begins digestion of protein in the stomach, lipids begin digestion in the small intestines (duodenum) |
| digestion begins | Consider: Most digestion of all organic molecules is completed in the duodenum (1st 25 cm.) of the small intestines. |
| acid reflux | when gastric fluid is able to move past Gastroesophageal sphincter (muscle that encircles tubes and acts as a circular valve to control flow) and affect the esophagus (tube used only to transport bolus); referred to as heartburn |
| acid reflux | Consider: Over the counter remedies like Tums or Rolaids lower acidity of stomach fluid. |
| peristalsis | rhythmic contractions in the digestive tract from the pharynx to the anus that mixes and moves the bolus (mouth to stomach) and chyme (stomach to small intestines) thru tract |
| gastric glands within stomach | mucus secreting gland: mucus (protects stomach walls from low pH); parietal cells: secrete HCl (produces low pH which helps to denature proteins, activates pepsinogen into pepsin which then begins to hydrolyze protein, and kills microorganisms) and intrinsic factor (facilitates vitamin B12 absorption necessary for RBC production...lack leads to pernicious anemia; chief cells: produce pepsinogen, precursor (activated by lowering pH) to pepsin which begins digestion of protein |
| gastric glands within stomach | secretions in green |
| gastric glands within stomach | Consider: The sequential processes occurring in the stomach are 1. The arrival of food into the stomach triggers gastric juice secretions. 2. Secretion of HCl lowers pH, activating pepsinogen into pepsin. 3. The acidic chyme moves through the pyloric sphincter to the small intestines. |
| gastric glands within stomach | Consider: While no nutrients are absorbed across the stomach wall, water, alcohol, and aspirin are. |
| gizzards | area where food is ground in some animals, such as birds |
| roles of the liver | first organ to receive the products of digestion; produces bile, removes excess glucose and produces glycogen for storage, stores vitamins, destroys old/damaged red blood cells, removes alcohol, toxins, pesticides, and carcinogens from blood |
| roles of the liver | Consider: The hepatic portal system connects the liver to the small intestines. The hepatic portal vein carries blood with ingested materials to the liver which screens the blood and then it continues on through the hepatic vein. |
| bile | produced by liver hepatocyte cells in dilute form, moves to gallbladder where it is stored and concentrated, released into duodenum where the bile salts act as emulsifier/digester of lipids |
| bile | Consider: After bile emulsifies and lipases hydrolyze fats into triglycerides, the triglycerides are combined with proteins in the small intestine to make them into water soluble particles called chylomicrons which are absorbed into lymphatic capillaries. |
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