Understanding the Human Digestive System

Digestive systems

Organs and glands involved in food digestion.

Digestion

Breaking down food into nutrients for absorption.

Absorption

Uptake of nutrients by small intestine cells.

Mouth

Initial site for mechanical digestion and taste.

Salivary amylase

Enzyme initiating carbohydrate digestion in mouth.

Lingual lipase

Enzyme starting lipid digestion in the mouth.

Taste sensations

Five basic tastes: Sweet, Sour, Bitter, Salty, Umami.

Bolus

Chewed food mixed with saliva before swallowing.

Chyme

Liquid state of food in the stomach.

Peristalsis

Muscle contractions moving food down digestive tract.

Segmentation

Mixing chyme with digestive juices in small intestine.

Sphincter

Muscle controlling passage between digestive organs.

Pyloric sphincter

Regulates chyme entry into the small intestine.

Gastric juices

Acidic mixture aiding digestion in the stomach.

Hydrochloric acid

Component of gastric juices with pH <2.

Sodium bicarbonate

Neutralizes acidic chyme in small intestine.

Bile

Emulsifier produced in liver, stored in gallbladder.

Gallbladder

Stores bile until released into small intestine.

Duodenum

First segment of the small intestine.

Jejunum

Middle segment of the small intestine.

Ileum

Final segment of the small intestine.

Hiatal hernia

Stomach portion above diaphragm causing acid reflux.

Acid reflux

Backflow of stomach contents into esophagus.

Small intestine

Majority of nutrient absorption occurs here.

Villi

Finger-like projections increasing surface area for absorption.

Crypts

Spaces between villi secreting intestinal juices.

Goblet cells

Secrete mucus to protect the small intestine.

Microvilli

Enzymes and pumps acting on nutrients.

Fiber

Retains water; cannot be broken down except by bacteria.

Diverticula

Small pockets in the large intestine that can trap food.

Diverticulosis

Condition from trapped food in diverticula.

High fiber diet

Prevents formation of diverticula.

Low fiber diet

Recommended after diverticula formation.

Colon

Absorbs water and recycles dissolved salts.

Ileocecal valve

Controls flow from small intestine to large intestine.

Peristalsis

Muscle contractions moving contents through intestines.

Absorption techniques

Methods include simple diffusion, facilitated diffusion, active transport.

Simple diffusion

Particles move to lower concentration areas.

Facilitated diffusion

Requires a carrier for nutrient transport.

Active transport

Nutrients moved against concentration gradient using energy.

Bloodstream

Carries water-soluble nutrients and smaller digestion products.

Lymphatic system

Transports larger fats and fat-soluble vitamins.

Chylomicrons

Transport larger fats through the lymphatic system.

Hepatic portal vein

Conducts absorbed materials to the liver.

Gastric juice

Acidic digestive fluid with pH between 1 and 2.

Bile

Basic digestive fluid with pH between 8 and 9.

Pancreatic juice

Basic digestive fluid with pH around 8.

Hepatic artery

Supplies oxygenated blood to liver cells.

Capillary network

Distributes nutrients and oxygen throughout liver.

Hepatic vein

Returns blood from liver to heart.

Lymphatic system

One-way route for nutrient circulation.

Subclavian vein

Entry point for lymph into bloodstream.

Chylomicron

Packages fats for transport through lymphatic system.

Gastrointestinal microbes

Bacteria influencing digestion and health.

Dietary factors

Probiotics and prebiotics affect microbial presence.

Stomach acid

Destroys harmful bacteria before illness occurs.

Microbiome diversity

Linked to obesity and various disorders.

Homeostasis

Stability of internal body conditions.

Gastrin

GI hormone that stimulates gastric acid secretion.

Secretin

GI hormone regulating water homeostasis.

Cholecystokinin (CCK)

Stimulates digestion of fats and proteins.

Choking

Food blockage in trachea, common in young and elderly.

Abdominal thrusts

Technique to relieve choking.

Vomiting

Mechanism to expel toxins from the body.

Diarrhea

Frequent loose stools, can be life-threatening.

IBS

Irritable bowel syndrome with unknown causes.

Colitis

Inflammation of the large intestine.

Celiac disease

Autoimmune reaction to gluten causing intestinal inflammation.

Gluten

Protein found in wheat, rye, and barley.

Diagnosis of celiac

Blood test and endoscopy of small intestine.

Anemia

Condition characterized by low red blood cells.

Dermatitis

Inflammation of the skin, often itchy.

Blood test

Laboratory analysis of blood samples.

Endoscopy

Procedure to visualize the gastrointestinal tract.

Gluten challenge

Test to assess gluten sensitivity effects.

Gluten-free diet

Diet excluding gluten-containing foods.

Nonceliac Gluten Sensitivity

Symptoms improve on gluten-free diet, no positive tests.

Self diagnosis

Identifying a condition without professional help.

Constipation

Infrequent bowel movements, less than 3x a week.

Bowel movements (BM)

The act of passing stool.

Belching

Release of air from the stomach through the mouth.

Intestinal gas

Normal digestive byproduct; excessive may indicate disease.

Gastroesophageal Reflux (GERD)

Condition where stomach contents back up into esophagus.

Heartburn

Painful sensation caused by acid reflux.

Lower esophageal sphincter

Muscle preventing stomach contents from entering esophagus.

Peptic ulcer

Sore on the stomach or intestinal lining.

H. Pylori

Bacterial infection causing peptic ulcers.

Gastric Juice

Digestive fluid containing water, enzymes, and acid.

Chyme

Partially digested food mixed with digestive juices.

Peristalsis

Rhythmic contractions moving food through the GI tract.

Segmentation

Churning of chyme to enhance digestion and absorption.

Pyloric sphincter

Muscle controlling chyme passage into the small intestine.

Enzyme hydrolysis

Breakdown of molecules using water in chemical reactions.

Salivary glands

Glands producing saliva to aid in digestion.

Salivary digestion

Carbohydrate digestion stops when acid erodes bolus.

Salivary enzymes

Proteins digested once they enter the stomach.

Energy nutrient digestion

Begins after food leaves the stomach.

Pancreatic juice

Contains enzymes for breaking down carbs, fats, proteins.

Intestinal wall enzymes

Digestive enzymes located on intestinal surface.

Sodium bicarbonate

Neutralizes stomach acids in pancreatic juice.