Digestive System Lecture Notes

Comprehensive vocabulary flashcards covering the components, functions, and terminology of the human digestive system based on lecture notes.

Digestive System

An organ system that breaks down food to extract energy and nutrients and then evacuates the remaining waste.

Gastrointestinal (GI) Tract

A continuous hollow pathway of organs stretching out from the mouth to the anus, responsible for digesting food, absorbing nutrients, and eliminating wastes.

Mouth/throat

The initial intake and breakdown of food.

Pharynx

A muscular tube in your throat that acts as a shared pathway for both air and food; connects the mouth to the esophagus.

Esophagus

A muscular tube that uses involuntary contractions to push the bolus towards the stomach.

Bolus

A ball of food shaped by the tongue and pushed into the pharynx.

Stomach

An organ that mixes and breaks down food using acids and enzymes; features thick muscular walls lined with rugae.

Chyme

The thick, soupy substance in the stomach consisting of acid and food mixed together.

Small intestine

The longest digestive organ, which primarily absorbs nutrients and water; contains the duodenum, jejunum, and ileum.

Large intestine (colon)

Organ that processes wastes and absorbs remaining water and minerals; includes the cecum, ascending colon, transverse colon, descending colon, and sigmoid colon.

Rectum

An organ that stores feces until they are eliminated.

Anus

The opening that eliminates waste from the body.

Accessory organs

Organs that are not part of the GI tube but help with the process, including teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

Digestion

The process of making food absorbable by mechanically and enzymatically breaking it down into simple chemical compounds in the alimentary canal.

Mechanical digestion

The physical breakdown of food by the teeth and muscle movements of the digestive system.

Chemical digestion

The chemical breakdown of food by digestive enzymes and acids.

Ingestion

The process of taking food, drink, or medicine into your body by swallowing it.

Duodenum

The first section of the small intestine.

Jejunum

The middle section of the small intestine.

Ileum

The lowest section of the small intestine.

Cecum

A pouch at the beginning of the large intestine that connects to the small intestine and receives undigested food via the ileocecal valve.

Salivary glands

Glands that release saliva containing enzymes as you chew to begin the chemical breakdown of food.

Uvula

A small tear-shaped piece of fleshy tissue that prevents food from going up into your nasal cavity.

Liver

An accessory organ that releases bile into the duodenum.

Bile

A substance that emulsifies lipids, breaking large fat globules into tiny droplets to increase surface area.

Pancreas

An organ that releases enzymes (like lipase, protease, and amylase) and hormones (like insulin and glucagon) into the duodenum.

Appendix

A "safe house" for good bacteria, storing them until they are released after illnesses like diarrhea.

Sphincter

A ring of muscle surrounding a passage in the body that constricts or relaxes to regulate the flow of substances.

Upper esophageal sphincter

Located at the top end of the esophagus; allows food to travel when swallowing and plays a role in burping.

Lower esophageal sphincter

Allows food to pass from the esophagus into the stomach and prevents stomach acid from moving up into the esophagus.

Pyloric sphincter

Connects the stomach to the small intestine, allowing partially digested food to pass through.

Pepsin

An enzyme most active in the stomach that breaks down proteins.

Amylase

An enzyme that breaks down starch into smaller disaccharides.

Gut microbiome

The community of microorganisms, mainly in the large intestine, that aids digestion, trains the immune system, and influences metabolism.

Serotonin

A neurotransmitter produced in the gut ($90-95\%$ of the body's total) that affects mood and sleep.

Peristalsis

The involuntary propulsion of food accomplished by circular muscle fibers that squeeze along the alimentary canal.

Alimentary canal

Another name for the gastrointestinal (GI) tube.

Mesentery

A contiguous set of tissues that attaches the intestines to the posterior abdominal wall, stores fat, and allows blood vessels and nerves to supply the intestines.

Villi

Tiny fingerlike projections in the small intestine.

Epiglottis

The flap of skin that covers the trachea to prevent food from entering the airway.

Gallbladder

A small pouch that stores bile.

Endocrine glands

Glands that produce hormones without using ducts, releasing them directly into the bloodstream.

Exocrine glands

Glands that use ducts to produce fluids like enzymes, sweat, and saliva; these fluids do not enter the bloodstream.

G-tube

A tube inserted directly into the stomach through the abdominal wall for long-term feeding or venting.

J-tube

A tube inserted directly into the jejunum for patients who cannot tolerate food entering their stomach.

Ostomy Bag

A lightweight, odor-resistant collection pouch worn over a stoma to collect digestive waste or urine.

Stoma

A surgically created opening in the abdominal wall where a piece of the intestine is brought through the skin.

Rugae

Folds in the stomach lining that allow it to expand and contract.