Digestive System

Epithelial tissue

A tissue that covers exposed surfaces, lines internal passageways, and produces glandular secretions in the GI tract

Pyloric sphincter

A muscular valve that regulates the passage of chyme from the stomach to the duodenum.

Peristalsis.

Peristalsis is the coordinated contraction and relaxation of muscles that moves food through the digestive tract.

Greater omentum

A large, fatty fold of peritoneum that drapes over abdominal organs, providing insulation, protection, and immune function.

Mucosa, Submucosa, Muscularis Externa, and Serosa/Adventitia.

What are the four layers of the GI tract?

Brunner’s glands

Glands that secrete alkaline mucus to neutralize stomach acid in the duodenum.

Peyer’s patches

In the ileum, they help protect against pathogens in the digestive system.

Reabsorption of water, vitamins, and electrolytes; propulsion of feces; and synthesis of vitamins by gut flora

What are the main functions of the large intestine?

Internal hemorrhoids occur inside the anal canal, while external hemorrhoids protrude outside the anus.

What is the difference between internal and external hemorrhoids?

The esophagus- stratified squamous epithelium

stomach - simple columnar epithelium with gastric glands.

How does the histology of the esophagus differ from the stomach?

• Duodenum

• Jejunum

• Ileum

What are the three parts of the small intestine

rectum

Organ that temporarily stores feces and triggers the urge to defecate.

• Parietal cells

• Chief cells

• Mucous cells

histology of the stomach that allow for digestion

Microvilli

Small intestine cells that increase surface area for nutrient absorption.

Plicae circulares, villi, and microvilli.

What are the three structural modifications of the small intestine that increase absorption?

• Intraperitoneal: Almost entirely covered by peritoneum (e.g., stomach, small intestine).

• Retroperitoneal: Partially covered, located behind the peritoneum (e.g., kidneys, pancreas).

What is the difference between intraperitoneal and retroperitoneal organs?

gastroesophageal reflux disease (GERD)?

A disease caused by improper closing of the lower esophageal sphincter, allowing stomach acid to enter the esophagus.

• Taenia coli: Longitudinal bands of smooth muscle.

• Haustra: Pouch-like structures that slow fecal movement.

What are taenia coli and haustra in the large intestine?

Ingestion, mechanical digestion, propulsion, chemical digestion, absorption, and defecation.

What are the six essential digestive processes?

• Mechanical digestion: Physical breakdown of food (e.g., chewing, churning).

• Chemical digestion: Enzymatic breakdown into smaller molecules.

What is the difference between mechanical and chemical digestion?

Saliva

IA sort of fluid that contains amylase for carbohydrate digestion and lubricates food for easier swallowing.

Mesentery

A fold that connects the intestines to the abdominal wall, providing blood supply and structural support.

Serous membrane

A membrane in the digestive tract that reduces friction between organs and allows smooth movement within the abdomen.

Tongue

A muscle that moves food, aids in chewing and swallowing, and contains taste buds.

Lingual frenulum

A small fold of mucous membrane that secures the tongue to the floor of the mouth.

The orbicularis oris muscle.

What muscle helps keep food within the mouth?

Uvula

A fleshy extension in the mouth that closes off the nasal passages to prevent food from entering the nasal cavity.

Pharyngeal constrictor muscles

Muscles that propel food from the oropharynx into the esophagus during swallowing.

Stratified squamous non-keratinized epithelium (protection against abrasion).

What type of epithelium lines the esophagus?

Gastroesophageal sphincter

A sphincter that prevents acid reflux by controlling the passage of food from the esophagus into the stomach.

Rugae

A fold in the stomach that allow the stomach to expand when food enters.

• Outer longitudinal layer

• Middle circular layer

• Inner oblique layer

What are the three layers of stomach muscles?

Cardia, fundus, body, and pylorus.

What are the four main regions of the stomach?

Digestion and absorption of nutrients.

What is the primary function of the small intestine?

Segmentation in digestion

A process that moves food back and forth to enhance mixing and absorption.

They increase surface area for maximum nutrient absorption.

How do villi and microvilli aid in absorption?

It absorbs dietary fats (lipids) into the lymphatic system.

What is the function of the lacteal in each villus?

Gut microbiota

bacteria in the large intestine that help in digestion, produce vitamins (B-complex & K), and aid in immune function.

ileocecal valve

A valve that prevents backflow from the large intestine into the small intestine.

• Internal sphincter: Involuntary (smooth muscle).

• External sphincter: Voluntary (skeletal muscle).

What is the difference between the internal and external anal sphincter?

pectinate line

A boundary that separates visceral (autonomic) and somatic (conscious) nerve innervation in the anal canal.

Hemorrhoids

Swollen veins in the anal canal that can be internal (inside the rectum) or external (outside the anus).

Bacterial infection and blockage of the appendix leading to inflammation.

What causes appendicitis?

Duodenum.

Chemical digestion & enzyme secretion.

Parietal cells

A cell that secrete HCl for protein digestion.

Jejunum

Major site of nutrient absorption.

Ileum

Absorption of vitamin B12 and bile salts.

Chief cells

A cell that release pepsinogen, which becomes pepsin.

Mucous cells

a cell that produce mucus for protection.