Digestive System

What is the overall digestion pathway?

Mouth -> pharynx -> esophagus -> stomach -> small intestine -> large intestine -> rectum -> anus.

What are the four main functions of the digestive system?

Chemical digestion, mechanical digestion, propulsion, and absorption.

What digestive enzyme is found in saliva in the mouth?

Salivary amylase (breaks down starch).

What is a bolus?

A rounded mass of food created by chewing in the mouth.

What is the function of the upper esophageal sphincter?

Prevents air from entering the digestive tract and blocks acid reflux.

What is peristalsis?

Wave-like smooth muscle contractions that propel a bolus forward through the digestive tract.

What are the primary functions of the stomach?

Storage, mixing food with gastric juice to form chyme, physical breakdown, and chemical breakdown of proteins by pepsin.

What are gastric pits?

Indentations in the stomach wall containing cells that secrete substances via ducts (exocrine glands).

What do mucous cells secrete in the stomach?

Mucus, which lubricates and protects the epithelial lining from acid.

What do chief cells secrete in the stomach?

Pepsinogen, which is converted by low pH into active pepsin.

What do parietal cells secrete in the stomach?

Hydrochloric acid (HCl) and intrinsic factor (IF).

What is the function of intrinsic factor?

Aids in vitamin B-12 absorption in the ileum.

What do G cells secrete in the stomach?

Gastrin, which stimulates acid release.

What do enterochromaffin-like (ECL) cells release?

Histamine in response to gastrin, which stimulates parietal cells to produce HCl.

What causes peptic ulcers?

Wounds in the stomach lining caused by excess stomach acid and Helicobacter pylori.

What regulates the entry of chyme into the small intestine?

Pyloric valve/sphincter.

What are the three segments of the small intestine?

Duodenum, jejunum, and ileum.

Where does most nutrient absorption occur?

Small intestine.

What is the function of the duodenum?

Receives chyme and mixes it with bile and pancreatic juice for most digestion; secretes secretin.

What is the function of the jejunum and ileum?

Absorb nutrients into the bloodstream; the ileum contains Peyer's patches.

What are villi and microvilli?

Finger-like projections on intestinal walls that increase surface area for absorption.

What is secreted by the pancreas into the duodenum?

Bicarbonate (to neutralize chyme) and digestive enzymes (trypsin, chymotrypsin, pancreatic lipase, pancreatic amylase, nucleases).

Where does bile come from, and where is it stored?

Produced by the liver and stored in the gallbladder.

What is the function of bile?

Emulsifies fats into smaller pieces to increase surface area for lipase; contains bicarbonate but no digestive enzymes.

What are the major functions of the liver?

Bile production, detoxification and filtration of blood (via Kupffer cells), vitamin and mineral storage, erythrocyte destruction, carbohydrate metabolism (gluconeogenesis and glycogenesis), fat metabolism, and protein metabolism (deamination of amino acids into urea).

Through what opening do bile and pancreatic juice enter the duodenum?

Ampulla of Vater via the Sphincter of Oddi.

What are the four parts of the large intestine (colon)?

Ascending, transverse, descending, and sigmoid colon.

What is the function of the large intestine?

Reabsorbs water and electrolytes to form feces.

What are the functions of the gut microbiome?

Assist in digestion, provide immune protection, and synthesize vitamins K and B-12.

What are excitatory digestive hormones?

Gastrin, secretin, and cholecystokinin (CCK).

What are inhibitory digestive hormones?

Gastric Inhibitory Peptide (GIP) and somatostatin.

Which hormone initiates hunger?

Ghrelin.

Which hormones suppress hunger?

Leptin, Peptide YY (PYY), insulin, and epinephrine.