Digestion, Absorption, and Metabolism Practice Flashcards
Overview of the Gastrointestinal System
Structures Involved in the Digestive System:
Mouth: The entry point for food.
Teeth: Used for mechanical breakdown.
Tongue: Facilitates movement of food.
Pharynx: Connects the oral cavity to the esophagus.
Esophagus: The passage to the stomach.
Stomach: Site of chemical and mechanical digestion.
Small Intestine: Divided into the duodenum, jejunum, and ileum.
Large Intestine: Divided into the cecum, ascending colon, transverse colon, descending colon, sigmoid colon, rectum, and anus.
Anus: Terminal end for waste elimination.
Accessory Organs:
Salivary Glands: Secrete saliva to begin digestion.
Liver: Produces bile.
Gallbladder: Concentrates and stores bile.
Pancreas: Secretes digestive juices and produces insulin.
Eating and Swallowing Processes
Pathway:
Starts in the Mouth.
Moves through the Pharynx.
Enters the Esophagus.
Esophageal Sphincters:
Pharyngoesophageal Sphincter: Located where swallowing begins.
Gastroesophageal or Lower Esophageal Sphincter (LES): Prevents gastric reflux from the stomach back into the esophagus.
Functions of the Oral Cavity and Salivary Glands
Mouth:
Recognized as the first part of the digestive tract.
Contains the tongue and teeth; receives secretions from salivary glands.
Tongue: Composed mostly of skeletal muscle; it is the most movable organ in the mouth.
Teeth: Adults have a total of permanent teeth, categorized into:
Cuspids
Incisors
Bicuspids
Molars
General Function: Receives food and breaks it down into smaller pieces; mixes food with saliva to initiate the digestive process.
Parotid Glands:
These are the largest salivary glands.
There is one on each side, located anterior and inferior to the ear.
They secrete saliva into the mouth to begin the chemical digestion of starches.
The Pharynx and Esophagus
Pharynx:
Connects the nasal and oral cavities specifically to the esophagus.
Food is forced into the pharynx by the action of the tongue.
Esophagus:
A muscular tube approximately long.
Propels food from the pharynx into the stomach via muscular contractions.
The lining of the esophagus secretes mucus to facilitate passage.
The Stomach: Structure and Gastric Function
Location and Capacity:
Located in the upper-left quadrant of the abdomen.
Has a capacity of approximately .
Structural Features:
Equipped with two sphincters.
Acts as a temporary storage place for food.
Primary Functions:
Regulates the rate of gastric emptying.
Secretes gastric juice, which includes hydrochloric acid ().
Secretes gastric hormones and intrinsic factor.
Mixes food with digestive juices, changing it into a semiliquid state.
Begins the digestion of proteins.
Absorbs vitamin and other limited substances.
Digests a limited amount of food.
The Small Intestine
Anatomical Parts:
Duodenum: The first segment.
Jejunum: The middle segment.
Ileum: The final segment.
Primary Functions:
Digestion and Absorption: Finishes digestion and absorbs nutrients.
Mixing: Mixes food with secretions from the liver and pancreas.
Hormone and Enzyme Secretion: Secretes hormones and digestive enzymes, including Secretin and Cholecystokinin.
Absorption Microstructure (Duodenum):
Contains Villi and Microvilli: These folds significantly increase the surface area available for absorption.
The interior of these structures is composed of capillaries and lacteals.
Absorbed end products of digestion are delivered to the hepatic portal system and lymphatics.
The Large Intestine and Accessory Organs
Large Intestine Anatomy:
Cecum.
Vermiform Appendix.
Colon: Includes the Ascending, Transverse, Descending, and Sigmoid segments.
Rectum and Anus.
Large Intestine Functions:
Absorption of water and electrolytes.
Synthesis of vitamins by intestinal bacteria.
Temporary storage of waste products.
Elimination of waste (feces) and gas (flatus).
Additional Accessory Functions:
Liver and Gallbladder: Work together to concentrate, store, and secrete bile into the duodenum.
Pancreas: Secretes digestive juices to aid digestion and produces insulin for glucose regulation.
Essential Nutrition and Digestion Terminology
Ingestion: The process of consuming food by the mouth and moving it through the digestive system.
Digestion: A systemic process that includes the breakdown and absorption of nutrients.
Absorption: Occurs as components of nutrients pass through the digestive system into the bloodstream and lymphatic system.
Metabolism: The sum of all chemical processes that occur on a cellular level to maintain homeostasis.
Catabolism: The breaking down of substances with the resultant release of energy.
Anabolism: The use of energy to build or repair substances.
Protein: Roles and Requirements
Importance: A constant supply is essential for rebuilding and replacing body tissues.
Biological Roles: Hormone production, fluid balance, antibody production, and transportation of nutrients.
Energy Content: Supplies approximately .
Composition: Composed of amino acids:
essential amino acids.
nonessential amino acids.
Sources:
Animal Sources: Red meat, eggs, milk and milk products, poultry, fish. These are considered Complete or high-quality proteins.
Plant Sources: Grains, legumes, and most vegetables. These are considered Incomplete or low-quality proteins.
Protein Excess:
Stressful to the liver and kidneys.
Kidneys must work to rid the body of excess waste products.
The liver's function is strained with the excess load metabolizing protein.
Can lead to excess fat in the diet.
Dietary Fiber
Definition: The portion of the carbohydrate that cannot be broken down during digestion. It passes through the intestine undigested.
Functions:
Increases bulk in the stool.
Aids in elimination.
May decrease the absorption of fat.
Recommended Intake: to .
Sources:
Fruits: Apples, bananas, oranges, grapefruits, cantaloupe, strawberries.
Vegetables: Green beans, broccoli, cauliflower, celery, corn, potato (with skin), sweet potato.
Grains and Cereals: Breads, All Bran, oatmeal, Shredded Wheat.
Legumes (cooked): Kidney beans, pinto beans, lima beans, black-eyed peas.
Basal Metabolic Rate (BMR)
Definition: BMR is the number of calories the body needs to stay alive and function at rest (e.g., breathing, heart beating, maintaining body temperature).
Factors Affecting BMR:
Lean body mass.
Hormones.
Body surface area.
Age.
Sex.
Medications.
Disease.
Pregnancy.
Malnutrition.
Aging and the Digestive System
Oral/Upper GI Changes:
Dental Caries and Tooth Loss: Decrease a person’s ability to chew food.
Decreased Gag Reflex: Increases the risk of aspiration.
Decreased Sense of Taste: May lead to a loss of appetite.
Decreased Muscle Tone at Sphincters: Increases the risk of esophageal (acid) reflux.
Lower GI/Systemic Changes:
Decreased Gastric Secretions: May interfere with the overall digestion of food.
Decreased Peristalsis: Increases the risk of constipation.
Metabolism and Energy Management
Biological Process:
Large molecules are broken down into smaller molecules to make energy available to the organism.
Enables absorbed nutrients to enter the bloodstream after digestion.
Digestion converts food into chemical substances like proteins and simple sugars to be used for energy production and cellular metabolism.
Consequences of Slow Metabolism:
Weight gain (if calorie intake stays the same).
Fatigue or low energy.
Cold sensitivity.
Slow digestion.
Difficulty losing weight.
Strategies to Increase Metabolism:
Building Muscle: Muscle burns more calories than fat, even at rest.
Staying Active: Regular exercise, especially strength training and cardio.
Eating Enough: Skipping meals or eating too little can slow metabolism.
Eating Protein-rich Foods: Protein takes more energy to digest and supports muscle growth.
Drinking Water: Hydration helps the body burn calories efficiently.
Getting Enough Sleep: Poor sleep can lower metabolism and increase weight gain.", "title": "Comprehensive Study Notes on Digestion, Absorption, and Metabolism"}