Lec29
Download as PPTX, PDF3 likes772 views
The document provides an introduction to gastrointestinal physiology, outlining the functions of the GI tract which include digestion, the breakdown of food, and absorption, the movement of nutrients into blood or lymph. It describes the layers of the GI tract wall and the roles of motility, secretion, digestion, absorption, storage and elimination in the GI system. Motility is achieved through rhythmic contractions that move food through the tract, aided by secretions from exocrine and endocrine organs and the breakdown of food during digestion and uptake of nutrients during absorption.
Lec29
- 1. Introduction to Gastrointestinal PhysiologyThe function of gastrointestinal (GI) system is to digest food and absorb nutrients, salts and waterDigestion is the process of breaking down food into components that can be absorbedAbsorption is the movement of nutrients, salts and water across the GI epithelium into blood or lymph
- 2. Introduction to Gastrointestinal PhysiologyDigestion requires the secretions of the GI system and motility, the activity of the muscle of the GI tract that mix and propel its contentChemical factors and hormones some from the GI tract act on the hypothalamus, the CNS, regulate the caloric intake by stimulation or suppressing appetite
- 3. Functions of the GI TractMotility:Movement of food through the GI tract.Ingestion:Taking food into the mouth.Mastication:Chewing the food and mixing it with saliva.Deglutition:Swallowing the food.Peristalsis:Rhythmic wave-like contractions that move food through GI tract.
- 4. Functions of the GI TractSecretion:Includes both exocrine and endocrine secretions.Exocrine:HCl, HC03-, bile, lipase, pepsin, amylase, and trypsin are secreted into the lumen of the GI tract.Endocrine:Stomach and small intestine secrete hormones to help regulate the GI system.Gastrin, secretin, and somatostatin.
- 5. Functions of the GI TractDigestion:Breakdown of food particles into subunits (chemical structure change).Absorption:Process of the passage of digestion (chemical subunits) into the blood or lymph.Storage and elimination:Temporary storage and elimination of indigestible food.
- 6. Digestive System (GI)GI tract divided into:Alimentary canal.Accessory digestive organs.GI tract is 30 ft long and extends from mouth to anus.Insert fig. 18.2
- 7. The wall of GI Tract has four layersComposed of 4 parts:Mucosa.Submucosa.Muscularis.
- 8. Serosa.
- 9. MucosaLines the lumen of GI tract.Consists of simple columnar epithelium. Forms the inner or luminal boundaryLamina propria: Thin layer of connective tissue carries blood and lymph vesselsMuscularis mucosae: Thin layer of smooth muscle responsible moving the mucosal surfaceGoblet cells:Secrete mucus.
- 11. SubmucosaThick, highly vascular layer of connective tissue.Absorbed molecules enter the blood and lymphatic vessels.Submucosal plexus Provide autonomic nerve supply to the muscularis mucosae.
- 12. MuscularisResponsible for segmental contractions and peristaltic movement through the GI tract.Inner circular layer of smooth muscle.Outer longitudinal layer of smooth muscle.Contractions of these layers move food through the tract; Myenteric plexus located between the 2 muscle layers.Major nerve supply to GI tract. Fibers and ganglia from both sympathetic and parasympathetic nervous systems.
- 13. SerosaBinding and protective outer layer.Consists of connective tissue
- 14. Describe the features of red muscle fiberDescribe in steps the contraction and relaxation mechanism of smooth muscle cells