Medical Terminology Study Guide: Gastrointestinal System

Gastroenterology: Medical Terminology and Overview

Definition and Scope

Gastroenterology is the medical specialty focused on the anatomy, physiology, diseases, and treatments of the gastrointestinal (GI) system. Gastroenterologists use diagnostic tests, medical and surgical procedures, and drugs to treat GI diseases.

• Gastroenterology: Study of the stomach and intestines.

• Key word parts: gastr/o- (stomach), enter/o- (intestine), -logy (study of).

Anatomy of the Gastrointestinal System

Overview of GI System Structure

The GI system consists of organs and glands connected in a pathway. Food enters the body, is digested, nutrients are absorbed into the blood, and undigested waste is eliminated.

Upper Gastrointestinal System

Oral Cavity and Pharynx

The mouth is the first part of the GI tract and contains several important structures:

• Teeth: Responsible for mastication (chewing).

• Gums: Support the teeth.

• Tongue: Fills the oral cavity; contains taste receptors that send information to the gustatory cortex.

• Hard palate: Forms the anterior roof of the mouth.

• Soft palate: Forms the posterior roof; works with the uvula to sense food and saliva.

Salivary Glands

Three pairs of salivary glands release saliva in response to the sight, smell, and taste of food:

• Parotid glands: Located in front of the ear.

• Sublingual glands: Located below the tongue.

• Submandibular glands: Located below the mandible (lower jawbone).

Pharynx and Larynx

The pharynx is a common passageway for air and food, divided into nasopharynx, oropharynx, and laryngopharynx. The larynx remains open during breathing and speaking, but closes during swallowing to prevent food from entering the trachea. The epiglottis seals the opening and diverts food to the esophagus.

Esophagus

The esophagus is a muscular tube connecting the pharynx to the stomach. Peristalsis (coordinated muscular contractions) moves food toward the stomach.

Stomach

The stomach is an elongated sac with four regions:

• Cardia: Where the stomach joins the esophagus.

• Fundus: Rounded, upper portion.

• Body: Large, curved region.

• Pylorus: Narrow last part joining the duodenum.

Gastric mucosa forms rugae (folds) that expand. Chyme is the mixture of food, saliva, and digestive enzymes leaving the stomach. Two sphincters (lower esophageal and pyloric) keep chyme in the stomach.

Lower Gastrointestinal System

Small Intestine

The small intestine is a long, narrow tube receiving chyme from the stomach. It contains thousands of villi to maximize absorption and consists of three segments:

• Duodenum: First segment (~10 inches).

• Jejunum: Middle segment (~8 feet).

• Ileum: Third segment (~12 feet).

Large Intestine

The large intestine runs from the small intestine to the outside of the body. It consists of:

• Cecum: Short sac with the appendix attached.

• Ileocecal valve: Prevents backflow into the ileum.

• Colon: Ascending, transverse, descending, and sigmoid parts; contains haustra (pouches).

• Rectum: Straight segment connecting to the anus.

• Anus: External opening; anal sphincter is a voluntary muscular ring.

Abdominopelvic Cavity

The intestines lie in the abdominopelvic cavity, lined with peritoneum. The peritoneum secretes fluid and forms the omentum (supports stomach) and mesentery (supports jejunum and ileum).

Accessory Organs

Liver

The liver is the largest solid organ, containing hepatocytes that produce bile. Bile flows through the biliary tree (series of ducts) to the gallbladder and duodenum.

Gallbladder

The gallbladder is a teardrop-shaped sac posterior to the liver. It concentrates and stores bile, releasing it into the duodenum in response to fatty chyme.

Pancreas

The pancreas is a yellow, triangular organ posterior to the stomach. It secretes digestive enzymes into the duodenum and insulin as part of the endocrine system.

Physiology of Digestion

Mechanical Digestion

Mechanical digestion involves physical force and movement:

• Mastication: Chewing by the teeth.

• Deglutition: Swallowing food.

• Peristalsis: Muscular contractions moving food.

Chemical Digestion

Chemical digestion uses enzymes and acids:

• Amylase: In saliva, breaks down carbohydrates.

• Hydrochloric acid: Breaks down food fibers and activates pepsinogen.

• Pepsin: Breaks down proteins.

• Gastrin: Stimulates release of hydrochloric acid and pepsinogen.

• Intrinsic factor: Helps absorb vitamin B12.

• Bile: Produced by liver, stored in gallbladder, breaks down fats (emulsification).

• Lactase: Produced in jejunum, breaks down milk sugars.

• Pancreatic enzymes: Amylase (carbohydrates), lipase (fats), protein-digesting enzymes (proteins).

Absorption

Absorption is the process by which fluids and nutrients enter the blood:

• Water and fluids absorbed under the tongue.

• Some fluids absorbed in the stomach.

• Most nutrients and water absorbed in the ileum.

• Remaining water absorbed in the large intestine.

Elimination

Elimination removes undigested fibers, waste, and water from the body. Solid waste is called feces, stool, or bowel movement. The process is known as defecation. Flatus is gas that may accompany feces.

Common Gastrointestinal Diseases

Esophagus and Stomach Diseases

• Dyspepsia: Indigestion caused by excess stomach acid, reflux, overeating, spicy foods, or stress.

• Esophageal varices: Dilated, swollen veins in the esophagus mucosa; can bleed if irritated.

• Gastric ulcer: Raw, irritated mucosa with a central ulcer crater; may bleed.

Small and Large Intestine Diseases

• Intussusception: Intestine folds back on itself, stopping peristalsis and blood flow.

• Volvulus: Intestine becomes twisted, stopping peristalsis and blood flow.

• Diverticula: Pouches in the colon wall where feces can become trapped.

• Diverticulitis: Infection of a diverticulum from trapped feces.

• Polyposis: Presence of polyps, which can become cancerous if irritated.

• Crohn disease: Thickening of the intestinal wall, ulcers, and partial obstruction.

Abdominal Wall and Cavity Diseases

• Hernia: Protrusion of intestine through abdominal wall.

• Sliding hernia: Intestine and peritoneum move in and out of hernia sac.

• Strangulated hernia: Intestine trapped, tissues begin to die.

• Omphalocele: Congenital hernia corrected surgically.

• Peritonitis: Inflammation of the peritoneum, often from perforation and spillage of intestinal contents.

Liver Diseases

• Ascites: Fluid accumulation in the abdominopelvic cavity due to liver disease.

• Cirrhosis: Liver enlargement, nodules, and scar tissue decreasing function.

• Jaundice: Yellow discoloration of sclera (scleral icterus) due to bilirubin buildup.

• Liver cancer: Tumors visible on CT scan.

Gallbladder and Bile Duct Diseases

• Gallstones: Stones in the biliary and pancreatic ducts, causing backup of bile and digestive enzymes.

• Cholelithiasis: Presence of gallstones in the gallbladder.

Laboratory, Diagnostic, and Radiologic Procedures

Barium Enema

Barium contrast medium is inserted through the rectum to fill the colon and cecum, making haustra visible on x-ray.

Endoscopic Retrograde Cholangiopancreatography (ERCP)

An endoscope is passed through the mouth, esophagus, stomach, and duodenum. Contrast dye is injected to visualize the common bile duct and pancreatic duct.

CT Scan

CT scans take multiple x-ray images in slices, viewed as if standing at the patient's feet. The liver, ribs, vertebra, stomach, spleen, and kidney are visible.

Upper Gastrointestinal Series

Patient swallows barium contrast medium, which coats the stomach and intestines, making them visible on a moving x-ray image.

Medical and Surgical Procedures

Nasogastric Tube

A nasogastric (NG) tube is inserted through the nose, esophagus, and into the stomach for liquid feedings or drugs.

Laparoscopic Cholecystectomy

Carbon dioxide gas inflates the abdominal cavity. Laparoscopes visualize and remove the gallbladder.

Colostomy and Stoma

A colostomy is performed on the colon, creating a stoma sutured to the abdominal wall. A colostomy bag collects feces.

Colonoscopy

A colonoscope with a camera is passed through the anus to examine the rectum and colon. Images are recorded for the patient's health record.

Percutaneous Endoscopic Gastrostomy (PEG) Tube

A permanent feeding tube is inserted during PEG for long-term nutrition.

Key Medical Terminology

Word Part	Meaning
gastr/o-	Stomach
enter/o-	Intestine
-logy	Study of
bili/o-, chol/e-	Bile
cholecyst/o-	Gallbladder
cholangi/o-	Bile duct
choledoch/o-	Common bile duct

Summary Table: GI System Regions and Functions

Region	Main Function
Oral cavity	Mastication, taste, saliva production
Pharynx	Swallowing, passage for air and food
Esophagus	Peristalsis, transport to stomach
Stomach	Mechanical and chemical digestion
Small intestine	Absorption of nutrients
Large intestine	Absorption of water, elimination
Liver	Bile production, metabolism
Gallbladder	Bile storage and concentration
Pancreas	Digestive enzyme and insulin secretion