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Lecture 6

BIOL 1020 Lecture 6: Chapter 24 Digestive System

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University of Memphis
BIOL 1020
Forest Brem

Chapter 24: The Digestive System Functions of Digestive system • Ingestion- taking food into mouth • Secretion – release of water, acid, buffers and enzymes into lumen of GI Tract • Mixing and propulsion- churning and movement of food through GI Tract • Digestion- mechanical and chemical breakdown of food • Absorption- passage of digested products from GI Tract into blood and lymph • Defecation- elimination of feces from GI Tract Layers of GI Tract • Mucosa ( epithelium, lamina propria, muscularis mucosae)< submucosa < muscularis (circular muscle, longitudinal muscle) > serosa (areolar connective tissue, epithelium) Neutral Innervation of the Gut • Enteric Nervous System o Myenteric plexus o Submucosal plexus • Autonomic Nervous System o Sympathetic o Parasympathetic • GI Reflex Pathways o Pathways regulate GI secretion and motility in response to stimuli within the GI Tract o Components of the pathways are sensory receptors that are associated with the sensory neurons of the ENS. o Triggers by stretch of the stomach ▪ Types of reflexes: gastric reflex, ileocecal reflex (clears chyme from the stomach), and defecation reflex Peritoneum (one giant serous membrane) • Wraps around GI organs, but not all • Five major parts: lesser omentum, mesocolon, mesentery (contains adipose tissue), greater omentum (triglycerides storage results in beer belly; adipose tissue) , parietal peritoneum, visceral peritoneal, and peritoneal cavity Mouth • Formed by the cheeks, hard and soft palates, and tongue • Teeth: 32 as adults, 20 as children o Incisors (front teeth/ cuts food/ 8), canines (tear food/4), premolars (crush and grind food/8) , molars (grind food/12) o Enamel (protects from wear and tear) hardest surface in the body; dentin (makes up majority of tooth) is the second hardest substance in the body • Salivary glands: release saliva into oral cavity o Made of 99.5% water and 0.5% solutes • Tongue: pushed food back towards the throat; helps to talk o Composed of skeletal muscle covered with mucous membrane and papillae Pharynx • Nasopharynx respon
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