GI structures and functions

GI Tract Structure: Mouth (Oral Cavity)

The entry point of the digestive tract where mechanical and chemical digestion begins.

GI Tract Structure: Esophagus

A muscular tube connecting the pharynx (throat) to the stomach.

GI Tract Structure: Stomach

A muscular J-shaped sac located between the esophagus and the small intestine.

GI Tract Structure: Small Intestine

A long, coiled tube divided into the duodenum, jejunum, and ileum.

GI Tract Structure: Large Intestine (Colon)

A wide tube comprising the cecum, colon, and rectum, surrounding the small intestine.

GI Tract Structure: Rectum and Anus

The terminal portions of the gastrointestinal tract ending at the anal sphincter.

GI Tract Function: Mouth

Chews food and mixes it with saliva to initiate carbohydrate digestion.

GI Tract Function: Esophagus

Propels the food bolus to the stomach via peristaltic contractions.

GI Tract Function: Stomach

Mixes food with acid and enzymes to form chyme and break down proteins.

GI Tract Function: Small Intestine

Absorbs most nutrients and water into the bloodstream following chemical breakdown.

GI Tract Function: Large Intestine

Absorbs remaining water and electrolytes, forming and storing feces.

GI Tract Function: Rectum and Anus

Stores fecal matter and controls its elimination from the body.

Mouth Substructure: Teeth & Tongue

Mechanically break down food into smaller pieces and form a bolus.

Mouth Substructure: Salivary Glands

Secrete saliva containing amylase to begin chemical breakdown of carbohydrates.

Esophagus Substructure: Lower Esophageal Sphincter

Prevents stomach acid and chyme from refluxing back into the esophagus.

Stomach Substructure: Gastric Glands

Secrete hydrochloric acid and pepsinogen for protein chemical breakdown.

Stomach Substructure: Pyloric Sphincter

Regulates the release of chyme into the duodenum of the small intestine.

Small Intestine Substructure: Duodenum

Receives digestive enzymes from the pancreas and bile from the gallbladder.

Small Intestine Substructure: Villi and Microvilli

Increase surface area dramatically to maximize nutrient absorption into the blood.

Large Intestine Substructure: Colon & Microbiota

Houses beneficial bacteria that ferment dietary fiber and synthesize vitamin K.