Chapter 3 Flashcards
Digestion, Absorption, and Transport
Digestive System
Digestive System: Includes all organs and glands involved in ingestion and digestion of food. It works with the circulatory, nervous, and hormonal systems.
Challenges of Digestion
Challenges of Digestion: Involves multiple tasks like mouth functions, passage through the diaphragm, steady movement, lubrication, enzyme function, GI tract cell protection, and waste excretion.
Digestion
Digestion: Breakdown of food into absorbable nutrients, later used for energy.
Absorption
Absorption: Nutrients taken up by cells in the small intestine (SI) for transport into the blood or lymphatic system.
Organs
Digestive Tract Anatomy
Organs: Mouth, esophagus, stomach, small intestine, large intestine, rectum, and anus. Connected by the lumen (inner space from mouth to anus).
Mouth
Function: Digestion begins with chewing and saliva production. Saliva helps in swallowing and begins carbohydrate digestion via salivary amylase. The bolus (mass of food) is swallowed and enters the stomach.
Esophagus
Esophagus & Stomach
Esophagus: Contains two sphincters (upper and lower) that control food movement. The bolus moves into the stomach, which churns food and adds digestive juices to form chyme.
Stomach
Esophagus & Stomach
Stomach: The pyloric sphincter releases chyme into the small intestine.
Small Intestine
Intestines
Small Intestine: About 10 feet long, consisting of the duodenum, jejunum, and ileum. The common bile duct drips fluids from the pancreas and gallbladder.
Large Intestine (colon)
Intestines
Large Intestine: Water is withdrawn to form semi-solid waste, which is passed into the rectum. Defecation occurs when the rectal muscles relax, and the 2 anal sphincters open.
ileocecal valve
Intestines
The ileocecal valve is a sphincter muscle situated at the junction of the ileum (last portion of your small intestine) and the colon (first portion of your large intestine).
GI Motility
Muscular Action of Digestion
GI Motility: Spontaneous movements aiding digestion.
Segmentation: Circular muscles contract to mix chyme with digestive juices. Peristalsis: Longitudinal muscles push the chyme forward. Sphincter Contractions: Control the pace of GI tract contents.
Segmentation
Muscular Action of Digestion
Segmentation: Circular muscles contract to mix chyme with digestive juices.
Peristalsis
Muscular Action of Digestion
Peristalsis: Longitudinal muscles push the chyme forward.
Sphincter Contractions
Muscular Action of Digestion
Sphincter Contractions: Control the pace of GI tract contents.
Saliva
Saliva: Moistens food for swallowing and begins carbohydrate digestion.
Gastric Juice
Gastric Juice: Produced in the stomach, primarily aiding protein digestion with enzymes and hydrochloric acid (HCl).
Pancreatic Juice
Pancreatic Juice: Released into the duodenum, contains enzymes for all energy nutrients and sodium bicarbonate to neutralize acidic chyme.
Bile
Bile: Produced by the liver, stored in the gallbladder, and released into the duodenum to emulsify fats.
Villi & Microvilli
Absorption in the Small Intestine
Villi & Microvilli: Increase the surface area for absorption.
Villi move constantly to absorb nutrients, while microvilli contain enzymes for nutrient breakdown.
Absorption Methods:
Simple Diffusion
Facilitated Diffusion
Active Transport
Vascular System
Vascular System: Nutrients (like water-soluble nutrients and small fats) enter the bloodstream via the hepatic portal vein to the liver.
Lymphatic System
Lymphatic System: Larger fats and fat-soluble vitamins are absorbed into the lymphatic system before entering the bloodstream.
GI Microbes
Healthy GI tract microbes aid in digestion and may influence disease. Prebiotics support microbial growth, and probiotics are live beneficial microbes.
Homeostasis
GI Hormones & Nerve Pathways
Homeostasis: The digestive process is regulated by feedback mechanisms involving hormones:
Gastrin
GI Hormones & Nerve Pathways
Gastrin: Secreted by the stomach to maintain acidic pH.
Secretin
GI Hormones & Nerve Pathways
Secretin: Stimulates the pancreas to release bicarbonate to neutralize acidic chyme.
Cholecystokinin
GI Hormones & Nerve Pathways
Cholecystokinin (CCK): Released in response to fat/protein in the small intestine, stimulating the gallbladder to release bile and slowing GI motility.
Choking
Common Digestive Problems & Solutions
Choking: Caused by food blocking the trachea, prevented by eating slowly and chewing well.
Vomiting & Diarrhea
Common Digestive Problems & Solutions
Vomiting & Diarrhea: Vomiting leads to dehydration; diarrhea can be caused by fast-moving intestinal contents. Both require rehydration.
Constipation
Common Digestive Problems & Solutions
Constipation: Prevented with a high-fiber diet, fluids, and exercise.
Gastroesophageal Reflux
Common Digestive Problems & Solutions
Gastroesophageal Reflux: Heartburn caused by stomach acid entering the esophagus. Prevention includes small meals, proper posture, and avoiding irritant foods.
Ulcers
Common Digestive Problems & Solutions
Ulcers: Caused by bacterial infections, anti-inflammatory drugs, or excess acid, treated with medication and diet changes.
