Digestive and Urinary Systems Lecture Notes

Flashcards covering the anatomy, physiology, and clinical disorders of the human digestive and renal systems as presented in the lecture transcript.

Ingestion

The process of taking food into the system through the mouth, including eating, deglutition (swallowing), and the initial entry of food content.

Propulsion

Mechanical movements involving peristalsis that progress food in a caudal direction.

Peristalsis

A series of involuntary contractions and relaxations of smooth muscles that move the food or chyme forward.

Mechanical Digestion

The physical breaking of food, such as chewing or stomach churning, into smaller segments.

Chemical Digestion

The use of enzymes and acids to reduce complex molecules into smaller units that can be absorbed.

Absorption

The movement of small molecules across the epithelium of the GI tract, primarily the small intestine, into the blood or lymph systems.

Excretion

The removal of indigestible or metabolically useless material from the body as feces.

Enzymes

Specialized proteins that catalyze the breakdown of specific bonds in large food molecules.

Carbohydrases

Enzymes that break down carbohydrates into disaccharides or smaller sugars.

Amylase

The first enzyme to appear in the GI tract, found in saliva, which cleaves amylose (starch).

Proteases

Enzymes that function to break proteins down into amino acids.

Pepsin

The primary protease enzyme located in the stomach.

Lipases

Enzymes produced in the pancreas and by brush border cells that cleave fats into fatty acids and monoglycerides.

Pepsinogen

The inactive precursor form of pepsin that becomes active in the low pH environment of the stomach lumen.

Hydrochloric Acid (HCl)

Stomach acid that optimizes enzyme function, breaks down food products, and kills ingested microorganisms.

Mucosa

The innermost layer of the GI tract consisting of the epithelium, lamina propria, and muscularis mucosae.

Stratified Squamous Epithelium

The specific epithelial type found in the esophagus used for protection.

Simple Columnar Epithelium

The epithelial type found in the stomach and intestines specialized for secretion and absorption.

Lamina Propria

The connective tissue layer that supports the epithelium within the mucosa.

Muscularis mucosae

A thin layer of smooth muscle that aids in dislodging food particles and moving lymph and blood in the mucosal space.

Submucosa

A GI tract layer containing blood vessels, lymph vessels, and nerves for signal transmission and nutrient transport.

Muscularis externa

The layer responsible for motility, typically consisting of an internal circular layer and an external longitudinal layer.

Internal circular layer

The part of the muscularis externa that constricts the GI tube.

External longitudinal layer

The part of the muscularis externa that shortens the GI tube to push content forward.

Segmentation

The process of breaking chyme into smaller fractions through coordinated muscle layers.

Serosa

The outer protective layer of the GI organ that connects to the mesentery.

Mesentery

Fibrous connective tissue that holds organs in place and provides a pathway for major vessels and nerves.

Parotid glands

Salivary glands located near the back of the ear that are commonly infected by the mumps virus.

Sublingual glands

Salivary glands located specifically under the tongue.

Submandibular glands

Salivary glands located below the mandible.

Mucin

A glycoprotein found in saliva utilized for lubrication.

Lysozyme

An immunity-related component found in saliva along with IgA and defensins.

Epiglottis

A valve that closes the passage to the trachea (larynx) during swallowing to prevent choking.

Esophagus

A tube roughly $25\,\text{cm}$ long that moves food through the diaphragm to the stomach via peristalsis.

Gastroesophageal Sphincter

A muscular valve between the esophagus and stomach that, if dysfunctional, leads to GERD.

GERD (Gastroesophageal Reflux Disease)

A condition where stomach acid erodes esophageal epithelium because it lacks protective mucus.

Cardia

The anatomical region of the stomach located near the heart and esophageal entrance.

Fundus

The upper, rounded part of the stomach.

Pyloric Sphincter

A strong muscle managing the passage of chyme from the stomach into the duodenum.

Rugae

Large longitudinal folds in the stomach that allow it to expand significantly to accommodate meals.

Gastric Pits

Deep crypts in the stomach mucosa containing specialized secretory cells.

Parietal Cells

Specialized cells that produce Hydrochloric Acid ($HCl$) and Intrinsic Factor.

Intrinsic Factor

A substance produced by parietal cells that is vital for Vitamin $B_{12}$ absorption.

Chief Cells

Cells in the gastric pits that produce the enzyme precursor pepsinogen.

G Cells

Enteroendocrine cells responsible for producing the hormone gastrin.

Mucous (Goblet) Cells

Cells that produce a thick bicarbonate-rich mucus barrier to protect the stomach from acid.

Helicobacter pylori

Bacteria that survives stomach acid and destroys the mucus barrier, leading to ulcers.

Pernicious Anemia

An autoimmune condition attacking parietal cells, causing a lack of Vitamin $B_{12}$ and hindering red blood cell formation.

Emesis (Vomiting)

A protective reflex involving the contraction of abdominal muscles and the diaphragm to force stomach contents upward.

Duodenum

The first $25\,\text{cm}$ of the small intestine where chyme, bile, and pancreatic secretions meet.

Jejunum

The middle region of the small intestine, measuring approximately $2.5\,\text{m}$ in length.

Ileum

The final region of the small intestine, measuring approximately $3.6\,\text{m}$ in length.

Plicae circulares

Permanent circular folds within the small intestine that help increase surface area for absorption.

Villi

Finger-like protrusions of the small intestine mucosa that expand internal surface area.

Microvilli

Projections on the surface of brush border cells that contain membrane-bound enzymes.

Lacteals

Specialized lymph vessels in the villi used for the absorption of fat contents.

Liver

The body's second largest organ, which produces bile and processes nutrients via the portal system.

Gallbladder

A muscular sac that stores and concentrates bile, releasing it in response to cholecystokinin.

Cholecystokinin

The hormone triggered by the presence of fat that causes the gallbladder to contract.

Bile Salts

Components of bile that act as a detergent to emulsify large fat droplets for lipase action.

Bilirubin

A byproduct of heme degradation from old red blood cells found in bile.

Jaundice

A yellowing of the skin or eyes caused by bile accumulation in the blood due to liver disease or obstruction.

Cholelithiasis

A clinical condition characterized by the formation of gallstones from crystallized bile.

Cirrhosis

Advanced liver damage where hepatocytes are replaced by fat and fibrous tissue.

Acinar cells

Exocrine cells of the pancreas that produce digestive enzymes and bicarbonate.

Alpha cells

Endocrine cells in the Islets of Langerhans that produce glucagon to increase blood glucose.

Beta cells

Endocrine cells in the Islets of Langerhans that produce insulin to decrease blood glucose.

Delta cells

Pancreatic cells that produce somatostatin to inhibit insulin and glucagon.

Gamma cells

Pancreatic cells that produce pancreatic polypeptide to reduce appetite.

Tenia coli

Muscle ribbons found along the large intestine.

Haustra

Pockets formed in the large intestine by muscle contractions.

Internal anal sphincter

An involuntary smooth muscle sphincter located at the anal canal.

External anal sphincter

A voluntary striated muscle sphincter that allows for the control of defecation.

Hemorrhoids

Varicose veins in the rectum or anal canal often caused by pressure and bacterial gas.

Cardiac Output (Kidney Flow)

Approximately $25\%$ of total output, equating to a flow rate of about $1.2\,L/min$ to the kidneys.

Sodium ($Na^+$)

The primary ion reclaimed by the kidneys, essential for secondary active transport.

Erythropoietin (EPO)

A hormone produced by the kidneys to stimulate red blood cell production.

Vitamin $D_3$ Activation

A hormonal function of the kidneys that helps direct calcium to the bones.

Gluconeogenesis (Kidney)

The production of glucose in the kidneys, which can contribute up to $40\%$ of the body's glucose during starvation.

Renal Hilum

The "doorway" of the kidney where the renal artery, vein, lymphatics, and nerves enter or exit.

Ureters

Tubes that transport urine from the kidneys to the urinary bladder.

Adrenal Glands

Glands located on the superior pole of each kidney producing adrenaline, cortisol, sex hormones, and aldosterone.

Aldosterone

A hormone critical for the RAAS that acts on the kidney to reclaim sodium.

Renal Cortex

The outer layer of kidney parenchyma and the primary site for filtration.

Renal Medulla

The inner portion of the kidney containing pyramids, responsible for urine concentration.

Renal Pyramid

Triangle-shaped structures in the medulla where the concentration of urine occurs.

Papilla

The apex or tip of the renal pyramid where urine drips into the minor calyx.

Renal Pelvis

The central collecting region of the kidney that funnels urine into the ureter.

Cortical Nephrons

The $85\%$ of nephrons located mostly in the cortex with small Loops of Henle specialized for reabsorption.

Juxtamedullary Nephrons

The $15\%$ of nephrons with long Loops of Henle responsible for concentrating urine.

Filtrate

The fluid being processed within the nephron before it enters the minor calyx.

Glomerulus

The site in the renal corpuscle where plasma moves through fenestrations to begin filtration.

Transcellular Reabsorption

The movement of substances from filtrate back into the blood by passing through the cell.

Paracellular Reabsorption

The movement of substances from filtrate back into the blood by passing between cells.

Apical Surface

The cell surface that faces the lumen of the nephron tube.

Basolateral Surface

The cell surface that faces the interstitium or blood vessels.

Proximal Convoluted Tubule (PCT)

The primary site of mass reabsorption, reclaiming $100\%$ of glucose and most salts.

Descending Limb (Loop of Henle)

A segment permeable to water via Aquaporin-1 but impermeable to salt, making filtrate hyper-concentrated.

Ascending Limb (Loop of Henle)

A segment impermeable to water that uses pumps to blast salt into the medullary interstitium.

Macula Densa cells

Cells in the early DCT that monitor sodium levels and signal for Renin release if levels are low.