Digestive System: Key Terms and Structures for Biology

Chemical Digestion

Breaks down food into monomers so they can be absorbed into the bloodstream

Mechanical Digestion

The physical breakdown of food into smaller pieces

Mouth Digestion

Capable of both mechanical and chemical digestion

Salivary Amylase

Enzyme in saliva that converts starches into simple sugars

Parotid Glands

The largest salivary glands, located in the cheeks

Submandibular Glands

Salivary glands located under the jaw

Sublingual Glands

Salivary glands located under the tongue

Esophagus

A transport tube for food; no digestion occurs here

UES and LES

Upper and Lower Esophageal Sphincters that regulate food passage

Parietal Cells

Stomach cells that produce Hydrochloric Acid (HCl)

Function of HCl

Denatures proteins and changes the shape of molecules in food

Chief Cells

Stomach cells that produce the inactive enzyme Pepsinogen

Activation of Pepsin

Pepsinogen becomes active pepsin when exposed to HCl

Pepsin

The active stomach enzyme responsible for digesting protein

Stomach Anatomy

Includes the Cardia, Fundus, Body, Antrum, and Pylorus

Pyloric Sphincter

The valve at the bottom of the stomach regulating exit to the duodenum

Duodenum

The first part of the small intestine where the majority of digestion occurs

Jejunum

The middle part of the small intestine where the majority of absorption occurs

Ileum

The final section of the small intestine ending at the ileocecal valve

Bile

Produced by the liver and stored in the gallbladder to help digest fats

Pancreatic Amylase

Enzyme in pancreatic juice that breaks starches into sugars

Trypsin

Enzyme in pancreatic juice that breaks proteins into amino acids

Pancreatic Lipase

Enzyme in pancreatic juice that breaks triglycerides (TGs) into fatty acids

Nuclease

Enzyme in pancreatic juice that breaks DNA into nucleotides

Brush Border Enzymes

Digestive enzymes installed on the surface of cells in the GI tract

Small Intestine Surface Area

Increased by plicae circulares, villi, and microvilli

Large Intestine Absorption

Primarily absorbs water, Vitamin K, and electrolytes (Na, K)

Vitamin K Production

Produced by bacteria within the large intestine

Colon Path

Cecum -> Ascending -> Transverse -> Descending -> Sigmoid

Haustra

The small pouches or segments of the colon

Anal Sphincters

Internal and external sphincters that control the timing of defecation

Gastric Juice Electrolytes

Highest source of Chloride (Cl-) loss (125 mEq/L)

Bile/Pancreatic Electrolytes

Highest sources of Sodium (Na+) loss (140-150 mEq/L)

Diarrheal Stool Electrolytes

Major source of high Potassium (K+) loss (50++)