Urinary system Flashcards
→ general structure and function → anatomy of the organs of the urinary system - species and sex differences → physiology of the urinary system
What are the main functions of the urinary system?
Maintains body fluid composition.
Excretes waste products (e.g., urea).
Regulates blood pressure.
Regulates pH balance.
Produces and excretes urine of appropriate volume and concentration.
Why is the urinary system closely related to the reproductive system?
Both systems develop from the urogenital ridge during embryogenesis.
In males, the urethra serves both urinary and reproductive functions.
Shared structures (e.g., prostate gland, urethra) lead to functional overlap.
How do hormones influence the urinary system?
Testosterone and estrogen affect the urinary tract’s function and structure
Where are the kidneys located?
Dorsal part of the abdominal cavity, near the lumbar region.
Right kidney is more cranial than the left.
How do kidney shapes differ among species?
Most domestic animals: Bean-shaped.
Horses: Right kidney is heart-shaped.
Pigs: Flattened kidneys.
Cattle: Lobated kidneys.
What are the two types of kidney structures?
Multilobar: Pigs and cattle (can have smooth or lobated surfaces).
Unilobar: Horses, sheep, cats, and dogs (smooth surface).
What is the renal pelvis, and which species lacks it?
It is the origin of the ureter.
Cattle lack a renal pelvis.
What are the main parts of the kidney’s internal structure?
Renal cortex: Reddish-brown, fine granular appearance.
Renal medulla: Darker outer and pale inner, striated appearance.
Renal pelvis: Origin of the ureter (except in cattle).
What percentage of arterial blood is directed to the kidneys?
> 20% of blood from the left ventricle is filtered by the kidneys
How much blood is processed by the kidneys daily?
1000-2000 L of blood perfuses the kidneys per day.
200-300 L is filtered.
1-2 L is excreted as urine.
What are the key components of the nephron?
Glomerular capsule (Bowman’s capsule): Collects filtrate.
Glomerulus: A network of capillaries where blood is filtered.
Proximal convoluted tubule (PCT): Reabsorbs water, ions, and nutrients.
Loop of Henle: Regulates water and salt balance.
Distal convoluted tubule (DCT): Fine-tunes ion reabsorption and secretion.
Collecting tubule: Collects urine and regulates water concentration.
What is the function of the nephron?
Maintains fluid and electrolyte balance.
Regulates blood pressure via the renin-angiotensin system.
Controls pH balance
What are the three main processes of urine formation?
Glomerular filtration.
Selective tubular reabsorption.
Selective tubular secretion.
What are the three layers of the glomerular filtration barrier?
Endothelial layer (fenestrated).
Basement membrane (stops large molecules).
Podocytes (filtration slits for selective passage).
What is glomerular filtration?
Plasma filtration through the glomerulus into Bowman’s capsule, forming ultrafiltrate.
What substances are reabsorbed in the proximal tubule?
Sodium chloride (NaCl).
Water (H₂O).
Glucose, amino acids.
Bicarbonate (HCO₃⁻)
What substances are secreted in the proximal tubule?
Hydrogen ions (H⁺).
Ammonia (NH₃).
What happens in the Loop of Henle?
Descending limb: Water exits, concentrating the filtrate.
Ascending limb: NaCl is actively transported out, diluting the filtrate.
How does the countercurrent mechanism in the nephron work?
Maintains an osmotic gradient for water reabsorption.
The vasa recta slows blood flow to support gradient maintenance.
What is the final step of urine formation?
Final reabsorption of NaCl and water in the distal tubule & collecting duct.
Regulated by antidiuretic hormone (ADH).
What is the function of the ureter?
To transport urine from the kidney to the bladder via peristaltic waves
What are the three layers of the ureter?
Fibrous external layer.
Smooth muscle layer.
Mucous membrane (transitional epithelium).
What is the function of the bladder?
To store urine until excretion.
What are the structural features of the bladder?
Three muscle layers.
Mucosa is folded when empty.
Lined with transitional epithelium for expansion.
