Chapter 25: The Digestive System

These flashcards cover key terms and concepts related to the digestive system, including definitions and processes essential for understanding digestion and nutrient absorption.

Digestive System

The organ system that processes food, extracts nutrients, and eliminates waste.

Alimentary Canal

The continuous muscular tube (GI tract) extending from the mouth to the anus, including the esophagus, stomach, and intestines.

Accessory Digestive Organs

Organs that assist in digestion but are not part of the GI tract, including the teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

Ingestion

The process of taking food and liquids into the body through the mouth.

Propulsion

The movement of food through the alimentary canal via swallowing and peristalsis.

Mechanical Digestion

Physical processes like chewing (mastication), churning in the stomach, and segmentation that break food into smaller pieces.

Chemical Digestion

The series of hydrolysis reactions managed by enzymes that break macromolecules into their chemical monomers.

Absorption

The passage of digested end products (plus vitamins, minerals, and water) from the GI tract lumen into the blood or lymph.

Defecation

The elimination of indigestible substances and waste from the body in the form of feces.

Oral Cavity (Mouth)

The site of ingestion where mechanical digestion (chewing) and chemical digestion of carbohydrates begin.

Salivary Amylase

An enzyme in saliva that begins the breakdown of starch into smaller sugars.

Bolus

A soft, rounded mass of chewed food mixed with saliva prepared for swallowing.

Pharynx

The throat region that serves as a common passageway for food, fluids, and air.

Esophagus

A muscular tube that conducts food from the pharynx to the stomach through peristalsis.

Peristalsis

Successive waves of involuntary muscle contractions and relaxations that move food along the GI tract.

Stomach

AJ-shaped organ that acts as a temporary storage tank where chemical protein digestion begins and food is converted to chyme.

Rugae

Large, longitudinal folds in the stomach mucosa that allow the organ to expand when full.

Chyme

The creamy, acidic, soupy mixture of partially digested food and gastric juice.

Gastric Juice

A mixture of HCl, pepsinogen, and intrinsic factor produced by the stomach glands.

Hydrochloric Acid (HCl)

Produced by parietal cells; it activates pepsin, denatures proteins, and kills many ingested bacteria.

Pepsin

An enzyme secreted in an inactive form (pepsinogen) that digests proteins in the highly acidic environment of the stomach.

Intrinsic Factor

A glycoprotein required for the absorption of vitamin B_{12} in the small intestine.

Pyloric Sphincter

The valve that controls the release of chyme from the stomach into the small intestine.

Small Intestine

The body's major digestive organ where virtually all absorption occurs and chemical digestion is completed.

Duodenum

The first and shortest part of the small intestine where chyme mixes with bile and pancreatic juice.

Jejunum

The middle portion of the small intestine, primarily responsible for nutrient absorption.

Ileum

The final section of the small intestine that joins the large intestine at the ileocecal valve.

Villi

Fingerlike projections of the intestinal mucosa that vastly increase surface area for nutrient absorption.

Microvilli

Tiny projections on the plasma membrane of absorptive cells (forming the brush border) that contain digestive enzymes.

Segmentation

Non-adjacent segments of the intestine contract and relax to mix food with digestive juices and increase absorption efficiency.

Liver

The largest gland in the body, which produces bile and processes nutrient-rich blood from the digestive tract.

Bile

A yellow-green alkaline solution containing bile salts that emulsify fats (break them into smaller droplets).

Gallbladder

A small sac beneath the liver that stores and concentrates bile until it is needed in the duodenum.

Pancreas

An organ that produces pancreatic juice rich in bicarbonate and a wide array of digestive enzymes.

Pancreatic Juice

An alkaline fluid containing enzymes for digesting proteins, fats, carbohydrates, and nucleic acids.

Cholecystokinin (CCK)

A duodenal hormone that triggers the gallbladder to contract and the pancreas to secrete enzyme-rich juice.

Secretin

A duodenal hormone that stimulates the pancreas to release bicarbonate-rich juice to neutralize acidic chyme.

Large Intestine (Colon)

The organ responsible for absorbing remaining water, synthesizing certain vitamins, and forming/propelling feces.

Cecum

The pouch-like start of the large intestine, located below the junction with the ileum.

Haustra

Pocket-like sacs of the large intestine caused by the muscle tone of the teniae coli.

Colonic Flora

The trillions of bacteria inhabiting the large intestine that ferment indigestible carbohydrates and synthesize B complex vitamins and Vitamin K.

Hepatic Portal System

The venous system that carries nutrient-rich blood from the digestive viscera to the liver for metabolic processing.

Flatus

Gas produced in the large intestine through the fermentation of und