Anatomy of Digestion 2025.01.15 PDF

**Learning Objectives:** LO 3.1 Describe the muscle and chemical actions of digestion as foods move through the digestive system LO 3.2 Describe the anatomical features that line the small intestine and facilitate nutrient absorption LO 3.3 Explain how nutrients are routed in the circulatory syst...

**Learning Objectives:** LO 3.1 Describe the muscle and chemical actions of digestion as foods move through the digestive system LO 3.2 Describe the anatomical features that line the small intestine and facilitate nutrient absorption LO 3.3 Explain how nutrients are routed in the circulatory systems from the GI tract into the body and identify which nutrients enter the blood directly and which first enter the lymph LO 3.4 Describe how bacteria, hormones, and nerves influence the health and activities of the GI tract LO H3 Outline strategies to prevent or alleviate common GI problems **3.1 Anatomy of Digestion:** Involuntary movement from the esophagus onwards Digestion - The process of by which food is broken down into absorbable units → Digest = take apart Absorption - The uptake of nutrients by the cells of the small intestine for transport into either the blood or the lymph → Absorb = suck in Gastrointestinal (GI) tract - One flexible and continuous tube (inside is called the lumen) → A digestive tract → Principal organs are the stomach and the intestines → Gastro = stomach and intestines = intestine Sphincter muscle - A ring-shaped muscle that relaxes or tightens to open or close a passage or opening in the body Mouth (the oral cavity containing the tongue and teeth): - - - - - - Esophagus (the food pipe; the muscular conduit from the mouth to the stomach): - - - Stomach (digestive tract that grinds and churns swallowed food, mixing it with acid and enzymes to form chyme): - - - Small Intestine (major site of digestion and absorption of nutrients): - - - - Large Intestine (Colon): - - - **Muscular (Mechanical) Digestion:** Chewing and Swallowing: - - Peristalsis (wavelike muscular contractions of the GI tract that propel its contents along): - - - Stomach Actions: - Segmentation: - - Segmentation - A periodic squeezing of partitioning of the intestine at intervals along its length by its circular muscles Sphincter Contractions: - - - - - - **Chemical Digestion** **The Chemical Action of Digestion:** - - - - - - - Enzyme - A protein that facilitates a chemical reaction → Is a catalyst that remains unchanged itself → Digestive enzymes facilitate hydrolysis Catalyst - A compound that facilitates chemical reactions without itself being changed in the process → The enzyme itself remains unchanged → A substance that speeds up a chemical reaction Hydrolysis - The addition of water to break a molecule into smaller pieces Common Digestive Enzymes: Carbohydrase - An enzyme that hydrolyzes carbohydrates Lipase - An enzyme that hydrolyzes lipids (fats) Protease - An enzyme that hydrolyzes proteins Digestive enzymes - Proteins found in digestive juices that act on food substances causing them to break down into simpler compounds Saliva: - Gastric Juice: Gastric Juice - The digestive secretion of gastric glands in the stomach → Gastric glands secrete gastric juice into the stomach - - - - - Pancreatic Juice and Intestinal Enzymes: - - - - Bile: - - - - - The Final Stage: - - - - - Stool - Waste matter discharged from the colon; also called fece - **3.2 Absorption** Small Intestine (Primary): - - - - - -  - Three different absorption: - - - Preparing nutrients for transport: - - - Vascular (blood circulatory) system: Closed system in which blood flows continuously with the heart as the pump - - Transportation: Circular System: - Why Liver? - - - - - - Transportation: Lymphatic System: - - - - GI Hormones - Negative Feedback Loop: - - - **GI Health:** - - - - - - - Gut Bacteria: - - - - - - - - Gastrointestinal conditions: - - - - - - -