BIPN 102 DIGESTIVE SYSTEM — 20 FLASHCARDS Final

What are the major anatomical organs of the digestive system and accessory organs?

Main tract:

• Oral cavity

• Esophagus

• Stomach

• Small intestine

• Large intestine

• Rectum

Accessory organs:

• Salivary glands

• Liver

• Gallbladder

• Pancreas

Image suggestion:
Lecture 18 — Slide/Page 4 (full digestive system anatomy diagram)

What are the key sphincters that regulate movement through the GI tract?

• Upper esophageal sphincter

• Lower esophageal sphincter

• Pyloric sphincter

• Ileocecal sphincter

• Sphincter of Oddi

These regulate movement of food and digestive secretions between compartments.

Image suggestion:
Lecture 18 — Slide/Page 6 (sphincters and organ list)

What are the four fundamental processes of the digestive system?

1. Motility – movement of food via muscle contraction

2. Digestion – chemical + mechanical breakdown of food

3. Secretion – movement of substances from cells into lumen or ECF

4. Absorption – movement of nutrients from lumen into blood/ECF

Image suggestion:
Lecture 18 — Slide/Page 3 (Functions diagram)

Layers of the GI tract wall (lumen → outside) and their function?

• Mucosa — interact with food
  (epithelium, lamina propria, muscularis mucosae)

  Submucosa — support & control
  (blood vessels, glands, Meissner plexus)

  Muscularis externa — move food
  (circular + longitudinal muscle, peristalsis)

  Serosa — protect & reduce friction

  Logic:
  Interact → Control → Move → Protect

• Image suggestion:
  Lecture 18 — Slide/Page 8 (GI wall layers diagram)

What are the main functions of motility in the digestive system?

Motility:

• Moves food through GI tract

• Mechanically mixes food to break it into smaller particles

Image suggestion:
Lecture 19 — Slide/Page 2 (motility diagram)

What are the two major types of GI smooth muscle contractions?

Tonic contractions

• Sustained minutes to hours

• Found in sphincters

• Prevent backward movement

Phasic contractions

• Last seconds

• Responsible for peristalsis and segmentation

Image suggestion:
Lecture 19 — Slide/Page 4 (types of contraction graphs)

What are the major patterns of GI contraction?

• Peristalsis → propels food forward

• Segmentation → mixes contents

• Migrating Motor Complex (MMC) → fasting “housekeeping” motility pattern

Image suggestion:
Lecture 19 — Slide/Page 5 (patterns list)

What is the Migrating Motor Complex (MMC) and when does it occur?

• Cyclic motility pattern during fasting

• Clears residual food and bacteria from stomach and intestine

• Absence associated with:

  • gastroparesis

  • intestinal pseudo-obstruction

  • bacterial overgrowth

Image suggestion:
Lecture 19 — Slide/Page 6 (MMC diagram)

What do Interstitial Cells of Cajal (ICC) do in the GI tract?

• Autorhythmic pacemaker cells

• Generate slow-wave potentials

• Trigger action potentials when threshold is reached

• Control rhythmic smooth muscle contractions

Image suggestion:
Lecture 19 — Slide/Page 3 (slow wave graph)

What are the two major plexuses of the Enteric Nervous System (ENS)?

Myenteric plexus

• Controls motility

Submucosal plexus

• Controls secretion

!!ENS can function independently of the CNS!!

Image suggestion:
Lecture 19 — Slide/Page 10 (ENS diagram)

What are short vs long digestive reflexes?

Short reflex

• Integrated entirely in ENS (enteric nervous system)

Long reflex

• Integrated in CNS

• Example: cephalic reflex

Image suggestion:
Lecture 19 — Slide/Page 10 (ENS reflex diagram)

What are the three phases of digestion?

1. Cephalic phase

2. Gastric phase

3. Intestinal phase

Each phase regulates digestion through neural and hormonal signals.

Image suggestion:
Lecture 19 — Slide/Page 12 (phase overview)

What occurs during the cephalic phase of digestion?

Triggered by:

• sight

• smell

• thought of food

Mechanism:

• Long reflex begins in brain/medulla

• Activates vagus nerve

• Stimulates gastric secretion and motility

Image suggestion:
Lecture 19 — Slide/Page 13 (cephalic reflex diagram)

What occurs during the gastric phase?

!WHEN FOOD ENTERS THE STOMACH!

Stimulates:

• HCl secretion

• Pepsinogen secretion → pepsin

• Protein digestion

Also includes protective mucus secretion.

Image suggestion:
Lecture 19 — Slide/Page 15 (gastric phase diagram)

What are the six gastric cell types and their functions?

Mucous cells
• secrete protective mucus
• function: protects stomach lining from acid

Parietal cells
• secrete HCl
• secrete intrinsic factor
• function: acid for digestion; intrinsic factor for B12 absorption

Chief cells
• secrete pepsinogen
• function: precursor → pepsin for protein digestion

Enterochromaffin-like (ECL) cells
• release histamine
• function: stimulates parietal cells → ↑ HCl

D cells
• secrete somatostatin
• function: inhibits gastric secretion

G cells (“gassy”)
• secrete gastrin
• function: stimulates acid secretion

Image suggestion:
Lecture 19 — Slide/Page 16 (gastric gland cell diagram)

What hormones regulate the intestinal phase?

CCK (Cholecystokinin)

• stimulates pancreatic enzyme secretion

• gallbladder contraction

Secretin

• stimulates pancreatic bicarbonate secretion

GIP (Glucose Inhibitory Peptide)

• stimulates insulin secretion, lowers gastric emptying

GLP-1

• stimulates insulin release and promotes satiety, lowering glucagon/gastric function

Image suggestion:
Lecture 20 — Slide/Page 11 (intestinal hormone table)

What is the function of bile and the liver in digestion?

Liver

• produces bile

Bile salts

• emulsify lipids → increase fat digestion

Gallbladder

• stores and concentrates bile

Image suggestion:
Lecture 20 — Slide/Page 12 (bile system diagram)

What are the pancreatic exocrine secretions and cells?

Acinar cells

• secrete digestive enzyme zymogens

Duct cells

• secrete bicarbonate (HCO₃⁻)

Bicarbonate neutralizes stomach acid in the duodenum.

Image suggestion:
Lecture 20 — Slide/Page 7 (pancreas cell diagram)

How are carbohydrates absorbed in the small intestine?

Glucose + galactose

• secondary active transport via SGLT

Fructose

• facilitated diffusion via GLUT5

All exit enterocytes via GLUT2.

Image suggestion:
Lecture 20b — Slide/Page 3 (carbohydrate absorption diagram)

How are peptides and amino acids absorbed in the intestine?

Amino acids

• Na⁺ cotransport

Di- and tripeptides

• H⁺ cotransport via PepT1

Inside cell → broken into amino acids → enter blood.

Image suggestion:
Lecture 20b — Slide/Page 6 (peptide absorption diagram)