Structural basis of kidney function Flashcards
what is the standard amount of fluid we should have
2 Litres for a 70 kg Man
How can ADH kill you?
- ADH makes you thirsty
- once you have too much ADH, thirst stops so they become overly dehydrated which kills the person
What are the functions of the kidneys?
Production of urine:
- Filtration of blood plasma
- Selective re-absorption of contents to be retained
- Tubular secretion of some components
- Concentration of urine as necessary
-Sensitive to body needs via hormones, nerves
Endocrine function - signals to rest of body (hormones include renin, erythropoietin, 1,25-OH vitamin D):
State some endocrine functions of the kidneys.
Production of erythropoietin
Hydroxylation of 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol by 1 alpha hydroxylase (in other words: production of calcitriol)
Activation of the renin-angiotension system by secreting renin
Describe the filtration of the blood plasma
- Lots of tubules
- outer cortex is very granulated
- medulla is striated structure
- filteration takes place and end up in the major calyces
- comes out of the ureter.
What part of the kidney dies first if someone is going through kidney failure?
- The kidneys are clinically important because it receives a lot of blood supply.
- When someone is going through kidney failure, the amount of blood is reduced to the kidneys and the bowel.
- The part to die first of the kidney is the pyramid as it receives the most minimum amount of blood and the cortex receives the most.
- This can be seen in people’s urine
What causes the granular structure and the striated structure?
- Granular because it is not a regular structure
- in the medulla: have very straight tubules so the medulla looks very different.
What is the renal corpuscle?
Bowman’s capsule
glomerulus consists of capillaries
podocytes associated with glomerulus
Describe filtration and the components filtered?
-Blood passing through glomerulus is filtered,
-Filtrate consists of all components
-at urinary pole of corpuscle
drains to proximal convoluted tubule
Describe what happens to people with uncontrolled hypertension?
- Renal artery comes off the aorta
- very short distance
- high pressure structure
- these arterioles have a lot of pressure
- hypertension: capillaries get damaged
- proteins in the urine
- because filter is damaged
Describe some features of the glomerulus.
The capillaries are fenestrated. There is a specialised basal lamina that filters the blood.
What are the 3 components of the filter?
- High SA, lots of capillaries
- Inner surface of capillaries is fenestrated endothelium, so acts like a sieve.
- Modified basement membrane allows blood to filter.
How many layers of filtaration on the glomerulus. Describe another feature which is used for filtration?
There are 3 layers of filtration on the glomerulus.
Outside of the capillaries, there are podocytes which provide filtration.
Describe some features of the glomerulus.
The capillaries are fenestrated. There is a specialised basal lamina that filters the blood.
what type of fluid leaves after filtaration
ISOTONIC.
State the five stages of urine production.
Ultrafiltration Selective Reabsorption Creation of hyper-osmotic ECF Adjustment of ion concentration in urine Final adjustments of urine concentration
Where does most reabsorption take place?
Proximal convoluted tubule (70% reabsorbed)
State some features of the proximal convoluted tubule and what happens at this structure
Larger diameter than the distal convoluted tubule
Brush border
Abundant mitochondria
CUBOIDAL epithelium sealed with tight junctions
Aquaporins
Sealed with (fairly water-permeable) tight junctions
Membrane area increased to maximise rate of resorption
brush border at apical surface
interdigitations of lateral membrane
Functions
Reabsorption of 70% of glomerular filtrate
Na+ uptake by basolateral Na+ pump
Water and anions follow Na+
Glucose uptake by Na+/glucose co-transporter
Amino acids by Na+/amino acid co-transporter
Protein uptake by endocytosis
What mechanism creates the hyperosmotic extracellular fluid?
Countercurrent mechanism
Describe features of the descending and ascending limbs of the loop of Henle.
Descending Thin, squamous epithelium Permeable to water Ascending Thick, cuboidal epithelium Few microvilli Prominent mitochondria (for active transport of ions) Na+ and Cl- are pumped out into the ECF Water impermeable
State some features of the distal convoluted tubule. Which features are different from the proximal convoluted tubule?
Smaller diameter than the proximal convoluted tubule
Few microvilli
Numerous mitochondria
Complex lateral membrane interdigitations
Adjusts Na+, K+, H+ and NH4+ under the influence of aldosterone
Macula densa cells
What is the role of the collecting duct?
Final adjustment of urine concentration
Which transporters are involved in the movement of water into the cell via the apical membrane and out of the cell via the basolateral membrane?
Aquaporin 2 - apical membrane
Aquaporin 3 - basolateral membrane (not affected by vasopressin)
What type of epithelium do the calyces and the renal pelvis have and what are its properties?
Urothelium - resistant to urine, ability to stretch, low permeability
