PHIS 206 1st EditionLecture 25Outline of Last Lecture I. Review TermsOutline of Current Lecture I. GI Tract and HomeostasisII. AnatomyIII. Function of the Digestive SystemIV. Wall of the GI TubeV. Differences in the Gut WallVI. Hepatic Portal SystemVII. MotilityVIII. SecretionIX. DigestionX. AbsorptionXI. Regulation StimuliXII. Stimuli + ReceptorsCurrent LectureI. GI Tract and Homeostasis-help transfer sources of energy (nutrients, water, electrolytes) into the body nutrients used to create energy for the body to useThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-body does not change its absorptive capacity if you increase intake, no effect on what gets absorbed body will take the nutrients it need despite how much you put in-GI tract is mainly smooth muscle Interstitial Cells of Cajal: cells that generate slow-waves II. Anatomy-Tract mouth pharynx esophagus-Accessory Organs stomach small intestine large intestine: colon, cecum, rectum anus-Accessory Glands sublingual (under tongue) + submandibular (under jaw) salivary glands parotid salivary gland liver/gallbladder pancreasIII. Function of the Digestive System-Four Processes to Digest food and Absorb Nutrients into the Blood1. Motility2. Secretion3. Digestion4. AbsorptionIV. Wall of the GI Tube-mucosa: absorption and secretion of fluids-villa: increases surface area of mucosa; finger-like structure-submucosa: small blood vessels; connective tissue; houses vessels-muscularis externa outer longitudinal muscle: shorten length of whole tube inner circular muscle: gets food inside body to outside body-myenteric plexus: control of muscular system; nerve network-submucosal plexus: in submucosa; nerve network -serosa: pushing on other parts; lubricationV. Differences in the Gut Wall-Different tubes specialize in different tasks-stomach has extra muscle layer-colon: flat; not much reabsorptionVI. Hepatic Portal Systemhelps withmotility-liver: processes, stores, and detoxifies; modifies ingested drugsTylenol scenario: not good because stuff is stored in liverVII. Motility-Regulated process: movement and mixing off contents through muscular contractions-2 types propulsive (peristaltic)o moves food through GI tract (different parts have different rates) mixing (segmentation)o food mixed with digestive juice and helps absorptionVIII. Secretion-release of water, electrolytes, , enzymes, and mucus into the gut-Endocrine: internal (in the wall of lumen, goblet cells)-Exocrine: external glands/organs (pancreas, liver, salivary)IX. Digestion-the chemical and mechanical breakdown of ingested material into absorbable molecules (glucose)-enzymes usually do this (but gastric acids help)-digestion is NOT regulated, but secretion IS regulatedX. Absorption-movement of products (gut lumen mucosa of the gut wall into the BLOOD-NOT directly regulatedXI. Regulation Stimuli-Luminal stimuli distention of gut wall chyme osmolarity (solute concentration) chyme acidity specific digestive products in the chyme-Brain/CNS sight, thought, smell of food (Ex: t.v. commercials) may affect emotional stateXII. Stimuli + Receptors-Chemical/molecules Chemoreceptors -Pressure/stretch/brush Mechanoreceptors-Osmolarity/concentration
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