Understanding Normal and Clinical Nutrition Chapter 3: Digestion, Absorption, and Transport

VOCABULARY flashcards covering key terms related to digestion, absorption, GI secretions, hormones, anatomy, microbiome, and common GI conditions.

Digestion

The breakdown of food into smaller nutrient units that can be absorbed and used by the body.

Absorption

The uptake of nutrients from the GI tract into blood or lymph, primarily in the small intestine.

Peristalsis

Coordinated, rhythmic contractions that move digested contents along the GI tract.

Segmentation

Cyclic contractions of circular smooth muscle in the small intestine that mix chyme and expose it to digestive juices.

Mouth

The entry point for digestion where chewing and mixing with saliva begin mechanical and chemical digestion.

Saliva

Digestive fluid from salivary glands that moistens food, begins carbohydrate digestion, and protects the mouth.

Pharynx

The region that directs food from mouth to esophagus during swallowing.

Esophagus

Tube carrying swallowed food to the stomach via peristalsis; contains upper and lower esophageal sphincters.

Upper esophageal sphincter

Ring of muscle at the top of the esophagus that prevents air entry and relaxes to let swallowed food pass.

Lower esophageal sphincter

Ring of muscle at the junction of esophagus and stomach that prevents backflow of stomach contents; relaxes to allow bolus entry.

Pyloric sphincter

Sphincter at the stomach’s exit controlling chyme release into the small intestine and preventing backflow.

Stomach

Organ where food is churned; gastric juice acids and enzymes begin protein digestion; mucus protects lining.

Gastric juice

Hydrochloric acid, enzymes, and mucus in the stomach that digest proteins and protect the stomach lining.

Pancreas

Gland producing digestive enzymes and bicarbonate, released into the small intestine via the pancreatic duct.

Pancreatic juice

Bicarbonate-rich fluid plus enzymes that digest carbohydrates, fats, and proteins in the small intestine.

Bile

Digestive fluid produced by the liver, stored in the gallbladder, that emulsifies fats to aid digestion.

Bile duct

Tube that transports bile from liver/gallbladder to the small intestine.

Gallbladder

Stores bile until it is needed for fat digestion.

Liver

Organ that produces bile and other digestive secretions.

Small intestine

Major site of digestion and absorption; consists of duodenum, jejunum, and ileum; lined with villi and microvilli to aid absorption.

Duodenum

First section of the small intestine where chyme mixes with bile and pancreatic juice; primary site of chemical digestion.

Jejunum

Midsection of the small intestine where most nutrient absorption occurs.

Ileum

Final section of the small intestine where absorption continues; bile acids and some vitamins are absorbed.

Villi

Finger-like projections on the small intestinal lining that increase surface area for absorption.

Microvilli

Even smaller projections on villi forming the brush border with enzymes and pumps to aid absorption.

Goblet cells

Mucus-secreting cells in the intestinal lining that lubricate and protect.

Crypts

Glands in the intestinal lining that secrete intestinal juices.

Enterocytes

Absorptive cells lining the villi responsible for nutrient uptake.

Lacteal

Lymphatic vessel in a villus that transports absorbed fats via the lymphatic system.

Chylomicrons

Lipoprotein particles formed in enterocytes to transport long-chain fats via lymph.

Hepatic portal vein

Blood vessel that carries water-soluble nutrients from the GI tract to the liver for processing.

Lymphatic system

Network including lacteals that transport absorbed fats; fats bypass the liver initially.

Emulsification

Process by which bile breaks fats into small droplets to increase fat digestion by enzymes.

Pancreatic enzymes

Digestive enzymes produced by the pancreas that digest carbohydrates, fats, and proteins.

Hydrolysis

Chemical reaction in which water is used to break down complex molecules during digestion.

Gastrin

GI hormone released by stomach glands in response to food; stimulates hydrochloric acid secretion.

Secretin

GI hormone released by the small intestine in response to acidic chyme; stimulates bicarbonate-rich pancreatic juice.

Cholecystokinin (CCK)

GI hormone released in response to fat and protein in the small intestine; stimulates bile and pancreatic enzyme release and slows gastric emptying.

Negative feedback loop

Regulatory mechanism where a change in a condition triggers responses to restore homeostasis; example: gastrin-stimulated acid production is inhibited when pH drops.

Gastrointestinal microbiome

Community of microbes in the GI tract; influenced by diet, probiotics, and prebiotics; affects digestion and health.

Probiotics

Live microorganisms that confer health benefits by supporting a healthy gut flora.

Prebiotics

Non-digestible fibers that feed beneficial gut bacteria and support a healthy microbiome.

Gastroesophageal reflux (GERD)

Condition where stomach acid frequently flows back into the esophagus due to a weak lower esophageal sphincter, causing heartburn.

Peptic ulcers

Ulcers in the stomach or duodenum caused by bacterial infection (e.g., H. pylori), NSAIDs, or excessive acid.

Choking

Obstruction of the airway by food in the trachea; requires immediate aid such as abdominal thrusts.

Vomiting

Protective reflex that expels stomach contents; can lead to dehydration.

Diarrhea

Frequent watery stools due to rapid intestinal transit or insufficient water absorption.

Constipation

Infrequent or hard stools; not a disease but a preventable condition with fiber, fluids, and activity.

Belching

Expulsion of swallowed air from the stomach through the mouth.

Hemorrhoids

Swollen veins in the rectum or anus that can cause pain or bleeding.

Diverticulosis

Presence of diverticula (pouches) in the colon, which can become inflamed.

Lumen

The inner hollow space of a tubular organ, such as the intestine.

Bolus

Mass of swallowed food formed in the mouth before it moves to the stomach.

Chyme

Semi-liquid, partially digested food that leaves the stomach and enters the small intestine.