Comprehensive Digestive and Urinary System Review for Independent Learners

Digestive System

System responsible for ingestion, digestion, and absorption of food.

GI System vs. Accessory Organs

GI System includes the alimentary canal; accessory organs aid in digestion.

Major Functions of the Digestive System

Ingestion of vitamins and minerals, fluid and electrolyte homeostasis, acid-base homeostasis.

Alimentary Canal

Mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus.

Stomach

Muscular organ involved in storing food and churning it with gastric juices.

Hard & Soft Palate

Functions in separating oral cavity from the nasal cavity.

Gallbladder

Located on the posterior side of the liver, removal affects bile storage.

Colon

Also known as large intestine, absorbs water and salts from waste.

Cecum

First portion of the large intestine.

Duodenum

Receives chyme from the stomach.

Ileum

Final section of the small intestine.

Esophagus

Muscular tube that transports food and liquids from pharynx to the stomach.

Teeth

Involved in mechanical digestion as they are major organs of mastication.

Oral Cavity

Involved in ingestion, chemical digestion, and propulsion.

Large Intestine

Absorbs water, electrolytes, and vitamins.

Small Intestine Surface Area Increased by

Microvilli, circular folds, and villi.

Microvilli

Created brush border appearance.

Circular Folds

Deep ridges in mucosa and submucosa.

Villi

Small finger-like projections on the inner mucosa.

Cardia

Where food first enters after its passage through the relaxed gastroesophageal sphincter.

Mucousa

Innermost epithelium of the stomach facing the lumen.

Mesentery

Fold of the peritoneum attaching organs to the posterior wall of the abdomen.

Filiform

Type of tongue papillae that lacks taste buds.

Falciform ligament

Separates the right and left lobes of the liver.

Taeniae Coli

Longitudinal layer of muscularis externa.

Pyloric Sphincter

Controls the passage of chyme from the stomach to the duodenum.

Ileocecal valve

Prevents backflow from the large intestine into the small intestine.

External anal sphincter

Operated voluntarily and controlled by the cerebral cortex.

Upper esophageal Sphincter

First sphincter encountered in the alimentary canal.

Chief cells

Release pepsinogen.

Parietal cells

Release hydrochloric acid into the stomach.

Gastrin

Hormone that increases acid secretion by the stomach.

Gastric-Inhibitory Peptide (GIP)

Inhibits acid secretion from parietal cells.

Pancreatic juices

Destined for the duodenum.

Acinar cells

Found in the pancreas and release pancreatic juice.

CCK Cholecystokinin (CCK)

Hormone that stimulates acinar cells.

Physical Digestion

Mechanical Digestion

Motility

Damage to the enteric nervous system that innervates the digestive organs could affect this.

Emulsification

Requires bile salts.

Facilitated diffusion

Passive physical process and how fructose is absorbed.

Chemical Digestion

Involves breaking bonds as a form of chemical reaction.

Absorption

Movement of food particles through the wall of the alimentary canal (not a main function of the stomach).

Salivary Amylase

Catalyzes carbohydrates in the mouth.

Enzymatic hydrolysis

Nutrient breakdown.

Lactase

Breaks lactose into glucose and galactose.

Enteric Nervous System

Controls the migrating motor complex.

Gastric Pacemaker

Regulated churning and peristalsis.

Diffuse neuroendocrine System (DNES) cells

Release gastrin.

Enterogastric Reflex

Decreases vagal activity and acid secretion.

Ingestion

First process to occur in the digestive system.

Defecation

Last process to occur in the digestive system, stretch of the rectum triggers this reflex.

Deglutition

Ability to swallow, specialized type of propulsion.

Segmentation

Involves intestinal churning.

Mass movements

Peristaltic contractions that propel contents of the colon.

Propulsion

Main job of the pharynx.

Vagus Nerve

Regulates peristalsis and segmentation in the small intestine.

Digestion of proteins

Requires enough stomach acid.

Important stimulus for bile release

Bile salt re-entry into the liver.

Salivation

Primarily controlled by the parasympathetic nervous system.

Mumps

Glands that secrete saliva.

Splanchnic Circulation

Blood supply that feeds and drains the abdominal digestive organs.

Bile

Liver secretion that emulsifies lipids.

Hepatocytes

Cells that compose liver lobules, if damaged will affect bile production.

Gallstones

Can block bile when they get stuck in the cystic duct.

Transportation of Bile

Occurs in the cystic duct, common hepatic duct, and common bile duct.

Helicobacter Pylori (H. pylori)

Spiral-shaped bacterium, lives in the stomach lining (mucosa), and one of the few bacteria that can survive in acidic environments.

Ammonia

Neutralizes stomach acid which helps H. pylori survive and damage tissue.

Conversion of pepsinogen

Into the active form pepsin requires an acidic pH.

Stomach removal

Affects digestion of proteins and risk for pernicious anemia.

Functions of normal flora in Large Intestine

Metabolize undigested wastes, produce vitamins, and deter the growth of harmful bacteria.

Nephron

Functional units of the kidney.

Glomerulus

Capillaries that are located within the renal corpuscle, fed by the afferent arteriole and drained by the efferent arteriole.

Fenestrations

Increases permeability of glomerulus, 'leaky' capillaries.

Podocytes

Prevent the filtration of large molecules such as albumin.

Tubular Reabsorption

Reclaims items from filtrate and returns them to the blood.

Loop of Henle

Thick segment is impermeable to water but permeable to sodium and chloride ions.

Ureter

Transports urine from kidney to the urinary bladder.

Erythropoietin

Role is to regulate RBC production.

Micturition Reflex

Triggered by stretch receptors in urinary bladder wall that signal sacral region of spinal cord.

Countercurrent Mechanism

Low blood pressure triggers renin-angiotensin-aldosterone system (RAAS).

Urine

Typically about 1.8 liters of urine is produced each day.

GI tract

The tube food passes through including mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus.

Accessory organs

Help digestion but food does not pass through them, including teeth, tongue, salivary glands, liver, gallbladder, and pancreas.

Mucosa

Innermost layer of the GI tract that lines the lumen, site of secretion and absorption.

Submucosa

Connective tissue layer containing blood vessels, lymphatics, and nerves that supports the mucosa.

Muscularis externa

Smooth muscle layer that produces peristalsis and segmentation.

Serosa or adventitia

Outer covering of the GI tract; serosa is a serous membrane in organs inside body cavities, adventitia is connective tissue that anchors organs.

Surface area increase

More surface area means more absorption; achieved through circular folds, villi, and microvilli.

Mechanical digestion

Physical breakdown of food, examples include chewing, mixing, churning, and segmentation.

Amylase

Enzyme that digests carbohydrates.

Proteases

Enzymes that digest proteins.

Lipases

Enzymes that digest fats.

Nucleases

Enzymes that digest nucleic acids.

Pacemaker cells

Cells that generate rhythmic contractions in the GI tract.

Secretin

A GI hormone that stimulates the pancreas to secrete bicarbonate.

Cholecystokinin

A GI hormone that stimulates the gallbladder to release bile.

Renal corpuscle

Part of the nephron that includes glomerulus and Bowman's capsule.

Juxtaglomerular apparatus

Helps control GFR and blood pressure.

RAAS

Renin-Angiotensin-Aldosterone System, triggered by low blood pressure or low GFR.

ADH

Hormone that adds aquaporins to collecting ducts to increase water reabsorption.