BIOL2302 Chapter 7

Digestive system

The system responsible for nutrient supply through ingestion, motility, digestion, absorption, and elimination.

Gastrointestinal tract (GI tract)

A long tube approximately 30 feet that extends from the mouth to the anus.

Ingestion

The process of masticating food in the mouth and swallowing.

Motility

Propulsion through peristalsis and mixing via segmental contractions.

Secretion

Release of digestive enzymes, bile, and hydrochloric acid.

Digestion

Hydrolytic processes breaking down complex molecules.

Absorption

Movement of digested products into the bloodstream or lymphatic vessels.

Elimination

Removal of indigestible substances as waste.

Mucosa

The inner lining of the GI tract containing epithelium, lamina propria, and muscularis mucosa.

Submucosa

Dense connective tissue layer within the GI tract that contains nerves.

Muscularis externa

Layers of smooth muscle in the GI tract responsible for movement.

Submucosal plexus

Nerve network regulating secretions in the GI tract.

Myenteric plexus

Nerve network controlling muscle contractions in the GI tract.

Sphincters

Muscular valves that regulate food passage through the GI tract.

Esophagus

Muscular tube transporting food from the pharynx to the stomach.

Peristalsis

Wave-like muscle contractions that move food through the GI tract.

Lower esophageal sphincter

Muscle that prevents acid reflux from the stomach.

Stomach

A muscular organ that mixes food with gastric secretions to form chyme.

Gastric mucosa

The lining of the stomach that contains gastric pits and glands.

Chyme

A semi-fluid mass of partly digested food formed in the stomach.

Small intestine

Organ where 90% of digestion and absorption occurs, divided into duodenum, jejunum, and ileum.

Duodenum

First part of the small intestine where chyme, bile, and pancreatic enzymes mix.

Jejunum

Middle section of the small intestine where significant absorption occurs.

Ileum

Final section of the small intestine leading to the large intestine.

Large intestine

About 3 to 4 feet long; responsible for water absorption and feces compaction.

Cecum

First part of the large intestine.

Colon

Major part of the large intestine involved in water absorption.

Rectum

Final section of the large intestine that stores feces.

Anus

The opening at the end of the digestive tract for elimination.

Salivary glands

Accessory organs that produce saliva.

Liver

Accessory organ that produces bile for digestion.

Gallbladder

Accessory organ that stores bile.

Pancreas

Accessory organ that secretes digestive enzymes and buffers.

Peritoneum

Membrane lining the abdominal cavity and covering abdominal organs.

Muscularis mucosa

Thin layer of muscle found in the mucosa layer of the GI tract.

Digestive enzymes

Proteins that catalyze the breakdown of food molecules.

Hydrochloric acid

Substance produced in the stomach to aid digestion.

Pepsinogen

Inactive enzyme that converts to pepsin in the stomach to digest proteins.

Feces

Waste matter expelled from the intestines after digestion.

Bile

Liquid produced by the liver that aids in the digestion of fats.

Digestive process

Sequence of actions involving ingestion, digestion, absorption, and elimination.

Accessory digestive organs

Organs that assist in digestion but are not part of the GI tract.

Nutrient supply

The process of delivering essential substances to the body through digestion.

Segmental contractions

Muscle contractions that mix food within the GI tract.

Hydrolysis

Chemical breakdown of a compound due to reaction with water.

Nutrition

The process of providing or obtaining the food necessary for health and growth.

Digestive tract wall

Structure composed of mucosa, submucosa, and muscularis externa.