Lecture 6 Flashcards
Path of Nutrients in the body:
- Digestion and Absorption
- Transport throughout body
- Metabolism in the cells
- Elimination of metabolic wastes
Digestion and Absorption
Digestion: The process of breaking food into component parts small enough to be absorbed into the body
Absoprtion: Process of taking substances into the interior of body
Components of Digestive Tract
Gastrointestinal tract: a long tube components of this tube
Accessory Organ: aid the digestive process
Look at diagram later
Transit Time
Time it takes food to pass length of GI tract
Typically 24-72 hours
Indigestible food: Components will travel full lenght of tract and elimnated in Feces
Digestible Food: Components will enter cells of S.intestine where absorbed
Fibre increases transit time
Unabsorbed dye added to meal and found in feces to measure time
Structure of Gut Wall
Small intestine: Layers of tissues Lumen: Space inside of the tube of GI tract Mucosal Cells (Mucosa): Tissue layer lining the lumen Absorbs nutrients Secrete mucus
GI tract and immune function
Muscus secreted by cells of digestive tract
Barrier against infectious microbes ingested with food
Barrier unsucessful immune system respond
White blood cells: Phagocytes and Lymphocytes
Immune syste vulnerable to nutrient deficiency
Phagocyctes
Respond first to infection
First line of defense
Engulf harmful microbes and present its antigen
Antiben is a protein found on microbe and promotes immune response
Antigens and Antibodies
Antigens stimulate production of antibodes
antibodes bind to microbes with the antigen
Easier for phagocytes to detect microbes
Certain types of lymphocytes will bind to infected body cells
Allergy: Proteins in food causes immune response
Mouth
Digestion begins in mouth
Breakdown food with saliva and teeth
Saliva lysozyme kills bacteria that cause decay
washes away food particles
Salivary amylase breaks down startch
Epiglottis covers lung opening to prevent choking
Esophagus
Connects pharynx to stomach
Persistalsis: Alternating circular and longitudinal contraction
Sphincters: Muscular valves that sperate organs in GI tract
Stomach
Specialized cells produce acid to aid muscular structure in mixing
Bolus is mixed with acidic gastic jucies to form semi liquid mixture called chyme
Muscular structure designed to mx
Cells in the lining of the Stomach
Gastric pits contrain specialized cells that secrete various products
Parietal cells produce HCL and intrinsic factors to absorb vitamen B12
Chief Cells produce pepsinogen Peopsinogen is activated by HCL to pepsin
Pepsin: active enzyme that breakdown short chain polypeptides
Stomach Regulation by nerves and hormones
Sight/smell of food signals the brain
Increased secretion of gastric jucies and increascie muscle activity/gastric motility
Stretching/Distension of stomach muscle signals brain to release gastrin
Gastrin increases gastric secretion and motility
Stomach Regulation by Nerves and Hormones part 2
Chyme takes 2-6 hours to enter S.I through the pyloric valve
Distention of intestine causes nerve and hormone signals to the stomach
Causes slow gastric secretion and motility
Chyme enters S.I at controlled rate
Small Intestine
Most of Digestion and absorption is here
Structure of S.I. maximizes nutrient absorption by increasing the surface area of intestinal wall to food
Surface area is increase by large surface folds
Folds covered with villi projections
Villi
Contain blood and lymphatic vessels (Lacteal)
Nutrients apss from lumen through surface mucosa layer to enter wither vessel for transport
Microvilli, Enterocytes and Brush Border
Microvilli/Brush Border:
Same as vill and on the surface of mucosal cells that faces the lumen
Enterocytes:
Mucosal cells with microvilli
Pancreas
Secretes bicabonate ion to neutralize HCL in chyme Secretes digestive enzyme: Amylase: Starch Digestion Proteases: Typsin and chymotrpsin Lipases: Digestion of triglycerides
Gall Bladder
Stores bile that was produced by the liver
Bile emulsify fat, break into small droplets makign it soluble and transportalble
Small Intestine Enzymes
Intestinal Juice - water, mucous mixture that mixes chyme and digestive juices
Brush border Enzymes: breaksdown small polypeptides into AA
Digests differernt types of sugars - Lactase, sucrase, Maltase and dextrinase