Urinary System Intro & glomerular filtration Flashcards
What makes up the urinary system?
Bladder
Kidneys
Ureter
Urethra
What does the bladder do?
Store urine
What does the urethra do?
Convey urine to the outside world
What do the ureters do?
Transport urine from the kidney to the bladder
Where are the kidneys in the body?
Either side of the spine
Behind the caudal rib
What are the functions of the kidneys?
Regulate fluids and electrolytes
Excrete waste
Produce hormones
Blood enters and leaves the glomerulus via which vessels?
Enters via afferent arterioles
Leaves via efferent arteriole
What is the arterial/venous blood supply to and from the kidneys?
Renal artery Segmental artery Inter-lobar artery Arcuate artery Interlobular artery Interlobular vein Arcuate vein Inter-lobar vein Segmental vein Renal vein
Which blood vessels are found between the interlobular artery and vein?
Afferent arterioles
Glomerulus capillaries
Efferent arterioles
Peritubular capillaries
What is the difference between filtrate and urine?
Filtrate is in the nephron,
Filtrate becomes urine when it’s in the bladder
Why do cells and proteins not usually enter the kidney?
The membrane between the glomerulus and Bowman’s capsule is impermeable to most proteins. Cells are too large to pass through it
What happens in the proximal convoluted tubule?
Bulk reabsorption (unregulated)
What happens in the loop of Henle?
An osmotic gradient is set up
Describe the differences in permeability between the ascending and descending loop of Henle
Descending very permeable to water, little ion channels
Ascending very permeable to ions, not to water
Which ions are transported out of the descending limb? How are they transported?
Active transport
Na, K, Cl
What does the distal convoluted tubule do?
Controls reabsorption/secretion of water
and ions
How long does it take the kidneys to filter out the entire volume of blood in the body?
25 minutes
How much urine does a normal animal excrete?
1ml/kg/hour
How are is the glomerulus adapted to filtration?
50X more permeable than normal capillaries
Does Starling’s Law of capillaries apply to the glomerulus? What happens to the filtration pressure if oncotic pressure increases?
No - constantly filtering.
As oncotic pressure increases, filtration pressure increases
The glomerulus does not have a normal capillary bed. What system does it use? What is different about this system?
Uses the portal system
There are two sets of capillaries before draining into the venule
What 3 factors affect glomerular filtration rate?
Surface area of glomerular capillaries
Flow rate of glomerular capillaries
Hydrostatic pressure of glomerular capillaries
Arterioles are able to control blood flow using what in their structure?
Smooth muscles
How is glomerular filtrate rate maintained short term?
Myogenic response
Causes smooth muscle in afferent arterioles to vasoconstriction/dilate
What effect does afferent arteriole vasoconstriction have on the GFR?
Decreases it
What is the long term way of maintaining glomerular filtrate rate?
Tuboglomerular feedback
How does tuboglomerular feedback work?
Macula densa cells in LOH detect increase in GFR
Causes a paracrine signal
Constricts arterioles and causes decrease in production of renin
What is an autocrine response?
Cell releases a substance which binds on itself
What is a paracrine response?
A hormone which has effect on the gland secreting it
Which cells decrease the production of renin?
Juxtaglomerular cells
What is renin
An enzyme which controls angiotensin levels
What is angiotensin?
A hormone which controls blood pressure
Which cells release renin?
Juxtaglomerular cells
