Urinary System Flashcards
What is the function of the urinary system?
- Removes metabolic wastes
- Kidneys filter blood, removing toxins, metabolic wastes, excess ions
- Returns nutrients back to blood
Describe the stages of filtration
1) Excretion
- removal of metabolic wastes
2) Elimination
- Discharge of wastes from body
3) Homeostatic regulation
- controls volume and solute concentration
What are homeostatic function of the urinary system?
1) Regulating blood volume and blood pressure
2) Regulating plasma ion concentration
3) Helps to stabilise blood PH
4) Conserves valuable nutrients
5) Assists liver
Describe the structure and location of the kidneys
- Bean shaped, lies at back of abdominal lining
- Has renal fascia (dense connective tissue surrounding kidneys), fatty mass protecting kidney from trauma & fibrous capsule protecting from infection
What is the function of the adrenal gland?
Triangle shaped endocrine glands that produce adrenaline/noradrenaline (stress response), cortisol (influences metabolism) and aldosterone (controls BP)
What is the renal cortex?
Outer granular region that contains the nephron
What is the renal medulla?
- Middle region with renal pyramids
- Empty urine from minor –> major calyx
- Transports urine to renal pelvis
What is the renal pelvis?
-Inner region
-Drains into ureters
Each kidney receives blood through renal artery to arterioles
What is the nephron
Structural and functional unit of the kidneys
Describe the renal corpuscles
- Consists of 2 parts:
1) Bowman’s Capsule - surrounds glomerulus capillaries
2) Glomerulus - Afferent arterioles brings blood into nest of capillaries
- Filtered blood returned to circulation via efferent arteriole: blood cells, large proteins
- Renal corpuscle produce filtrate: enters renal tubule
Describe the renal tubule
- Tubular fluid gradually changes in composition: substances reabsorbed or secreted
1) Proximal convoluted tubule
2) Loop of henle
3) Distal convoluted tubule - Reabsorb useful organic nutrients that enter filtrate
- Reabsorb water
- Secrete waste products
Describe glomerular filtration
Blood hydrostatic pressure forces fluid and solutes through filtration membrane
What is the glomerular filtration rate (GFR) ?
- Amount of filtrate kidneys produces
- Dependent on net filtration pressure, total filtration surface area and filtration membrane permeability
Describe intrinsic regulation of GFR
- Locally acting at kidney
- Renal regulation of GFR
- Changing diameter of afferent arteriole, efferent arterioles and glomerular capillaries
- Reduced blood flow triggers:
- Dilation of afferent arteriole
- Constriction of efferent arteriole
Describe neural extrinsic regulation of GFR
Sympathetic NS:
- Adrenaline/Noradrenaline released, causes constriction of afferent arterioles
- Decreased efferent renal sympathetic nerve activity
Describe hormonal extrinsic regulation of GFR
- RAAS system in response to low BP/low GFR to restore homeostasis
- Constricts efferent arterioles, decreases blood flow out of glomerulus, increases GFR
What is the process of the RAAS system
Homeostasis normal (normal GFR) Homeostasis disturbed (decrease GFR) Renin Angiotensin activation Elevation of BP and BV Homeostasis restored (increased GFR)
Describe at reabsorption at PCT
Substances for reabsorption diffuses out of tubular into blood capillaries
- Reabsorption of nutrients
- Active transport of ions
- Reabsorption of water
- Passive reabsorption of ions
- Secretion
Describe at reabsorption at nephron loop
Reabsorption of water and sodium/chloride ions, sets up concentration gradient
Describe at reabsorption in DCT
- Hormonally regulated
- Selective reabsorption alters solute composition and volume of tubular fluid
Describe tubular secretion in PCT
- Remove selected substances from blood back into tube
- Eliminates undesirable substances controls PH by altering H+ and HCO3- in urine
What is aldosterone?
- Promotes sodium reabsorption in collecting ducts
- Increase BV & BP, decrease potassium levels
What is atrial natriuretic peptide?
- Increases renal Na+ salt excretion in collecting ducts
- Reduces blood Na+, decrease blood volume and pressure
What is parathyroid hormone?
Acts on PCT to increase calcium ion reabsorption
