Digestive, Respiratory & Metabolism – Unit 4 Review

Vocabulary flashcards covering major structures, enzymes, physiological processes and clinical concepts from the digestive, respiratory and metabolic systems discussed in the Unit 4 exam review.

Greater omentum

A large fold of peritoneum that contains adipose tissue and cushions the anterior and lateral abdominal wall.

Functions of the oral cavity

Includes analysis, mechanical processing, carbohydrate digestion and lubrication—but NOT absorption of monosaccharides.

Myenteric plexus

Enteric nerve network between circular & longitudinal muscle layers that coordinates intestinal motility.

Pylorus

Distal region of the stomach that empties into the duodenum through the pyloric sphincter.

Common bile duct obstruction

Blocks bile delivery to intestine, causing undigested fat (steatorrhea) to appear in feces.

Amylase

Digestive enzyme that hydrolyzes polysaccharides (starch) to smaller sugars.

Jejunum

Middle segment of the small intestine, specialized for most nutrient absorption.

Parotid glands

Salivary glands most often infected by the mumps virus; secrete serous, enzyme-rich saliva.

Parietal cells

Gastric cells that secrete hydrochloric acid (HCl) and intrinsic factor.

Pancreas (digestive role)

Accessory organ that produces enzymes and bicarbonate-rich juice for all food classes.

Metabolism

Sum of all chemical reactions occurring in body cells; contrasts with digestion, which is food breakdown in the GI tract.

Bile

Liver secretion that emulsifies fats and carries bilirubin; contains no digestive enzymes.

Stomach functions (exceptions)

Stores food, mechanically churns, denatures proteins and starts protein digestion—does NOT absorb triglycerides.

Post-cholecystectomy diet

Patients without a gallbladder are advised to eat meals low in fat because bile release is less regulated.

Mesenteries

Double layers of peritoneum that suspend visceral organs and convey blood vessels, nerves and lymphatics.

Villi

Finger-like mucosal projections that greatly increase absorptive surface area in the small intestine.

Cephalic phase of gastric secretion

Reflex phase in which vagus nerve stimulation increases gastric juice before food reaches stomach.

Phases of deglutition

Buccal, pharyngeal and esophageal phases; there is no ‘gastric’ phase of swallowing.

Peristalsis

Waves of coordinated muscular contractions that propel material through the GI tract.

Pancreatic sodium bicarbonate

Alkaline secretion that neutralizes acidic chyme entering the duodenum from the stomach.

Enterocytes

Columnar absorptive cells lining intestinal villi; possess microvilli (brush border).

Goblet cells

Mucus-secreting epithelial cells that lubricate the intestinal lumen.

Plicae circulares

Permanent circular folds of the small intestine that increase mucosal surface area.

Lacteals

Lymphatic capillaries in intestinal villi that absorb chylomicrons (complex fats).

Duodenal (Brunner’s) glands

Submucosal glands in the duodenum that secrete alkaline mucus to protect against gastric acid.

Muscularis externa

Smooth-muscle layer (usually circular + longitudinal) responsible for peristalsis; stomach uniquely adds a third oblique layer.

Serosa

Outermost visceral peritoneum covering intraperitoneal digestive organs.

Lamina propria

Areolar connective tissue layer of mucosa containing blood vessels, lymphatics and immune cells.

Gas-flow equation

Gas flow = Pressure gradient / Resistance; resistance = pressure gradient / flow.

Pulmonary surfactant

Phospholipid secretion from type II alveolar cells that lowers surface tension and prevents alveolar collapse.

Diffusion (gas exchange)

Passive movement by which O₂ and CO₂ cross alveolar and cellular membranes.

Terminal bronchiole

Smallest conducting-zone airway; lacks alveoli and performs no gas exchange.

High-altitude erythrocytosis

Lower atmospheric O₂ pressure stimulates EPO release and increases RBC count.

Dissolved oxygen in plasma

Accounts for only ~1.5 % of total blood O₂; the rest is bound to hemoglobin.

Carbonic anhydrase

RBC enzyme that catalyzes CO₂ + H₂O ↔ H₂CO₃, affecting plasma bicarbonate levels.

Pulmonary ventilation

Mechanical process of moving air into and out of the lungs (breathing).

Pleural adhesion forces

Surface tension of pleural fluid plus negative intrapleural pressure keep the lungs attached to thoracic walls.

Hypercapnia

Elevated arterial CO₂ (Pco₂), often stimulating increased ventilation.

Chloride shift

Exchange of Cl⁻ for HCO₃⁻ across RBC membranes that balances charge during CO₂ transport.

Pontine respiratory group (PRG)

Pons center that smooths transition between inspiration and expiration.

Respiratory membrane

Thin barrier of alveolar epithelium + fused basement membranes + capillary endothelium for gas exchange.

Obstructive pulmonary disease

Condition (e.g., COPD, asthma) characterized by low FEV₁ (≈40 %), indicating airflow obstruction.

Bohr effect

Decrease in blood pH (increased H⁺/CO₂) weakens hemoglobin-O₂ bond, enhancing O₂ release to tissues.

Lung cancer

Leading cause of cancer death in North America for both sexes.

Hepatic portal system

Vascular network delivering nutrient-rich blood from GI tract to the liver for processing.

Liver (digestive role)

Organ that synthesizes bile, processes absorbed nutrients, detoxifies blood and stores glycogen.

Gastric muscular layers

Stomach possesses longitudinal, circular and unique inner oblique muscle layers for strong churning.

Large-intestine microbiota

Colonic bacteria ferment undigested chyme, producing vitamins (K, B₅) and gases.

Salivary glands

Parotid, submandibular and sublingual glands produce saliva to moisten food and begin starch digestion.