Kidney 2 Flashcards
What is a nephron
what happens there?
Nephron = functional unit
Filtration under pressure
renal blod flow
Valuable substances begin to be reabsorbed in PCT
What determine which solutes pass through into nephron
filtration barrier restricts solute movement based on size and change
WHat is GRF=?
What detemines Glomerular filtration rate?
125ml/min= RF
Renal blood flow , which = 1.25 litre/min, there a mechansisms in place to maintain renal blood flow
What happens in the proximal tubule?
70% of water is reabsorbed and solutes
What structure is present on the PCtubule?
2) What is reabsorbed and in what form?
3) what else does it do?
microvilli
2) bulk of filtered NaCL as isotonic NaCl solition
3) blood secretes organic molecules into tubules like penincillin, bile salts, noradrenaline and and involved in pH homeostasis
NcCl uptake is closely linked to:
uptake o essential solutes e.g. glucose, aa
regulation of body fluid pH
Apical Na+ transport couple to:
- co-transport of glucose or aa
2. counter-exchange of H+
In loop of Henle what happens in descending limb
- H2O moves out
- NaCl stays
In loop of Henle what happens in thick ascending limb
Thick Ascending Limb NaCl moves out
H2O stays
Na+-K+ ATPase
K+ channels, Na+-H+ exchanger (Na+ in , H+ out),
What happens in distal convoluted tubule?
-NaCl moves out -H2O stays
What happens in Collecting duct?
Collecting duct
- NaCl moves out
- H2O reabsorption depends on ADH (next lecture)
- H+ and HCO3- movement
WHat are the 2 cell types in the Collecting duct?
prinicipal cells- have Na+ transporters
Intercalated cells- H+ transport involved in pH
How is hypertension treated, how does it work?
what else effects this cahnnels
- amiloride, inhibites ENaCC, a Na+ reabsorbed in the collecting duct
aldosterone
What is the osmolarity o plasma?
What percentage must its concentration be kept in?
3) How is it controlled?
Plasma kept within 1% of of 290 mosm/l
3) Brought about by alterations in WATER content of urine
Glomerular filtrate can have the same osmolarity as the plasma BUT sometimes excretion of an isosmotic urine is not desirable.
Excretion of dilute or concentrated urine is achieved by the____________.
Countercurrent Mechanism
Describe urine compared to plasma afer
1) H2O load
2) H2O restriction
After H2O load: H2O must be excreted in excess of solute in a dilute urine that is hyposomotic to plasma
After H2O restriction: H2O must be retained and a hyperosmotic or concentrated urine must be excreted
1) The function of the loop of Henle is:
2) How is the countercurrent multiplier achieved?
to remove NaCl more than H2O from the lumen and deposit in interstitium
2) 2 parallel limbs with fluid flowing inopposite directions- countercurrent flow,
Active NaCl transport from ascending limb into interstitium, therefore osmality of intersticium increases, descending limb is permeable to water but not NaCl, therefore water exits descending limb, this then repeats,
Compare osmarity in the descending limb compared to end of ascenidng limb:
ascending limb has a lower osmolarity, as NaCl has left, descending limb has a higher osmalrity as water has left
What is the NaCl pumped into from the ascenidng limb?
Blood is supplied by vasa recta without washing gradient away
What is the role of the vasa recta in the countercurrent mechanism?
creates a hypertonic soltution around the descendng limb
What is the role of the urine in the countercurrent mechanism?
- urea enters filtrate through glomerular filtration.
- the urea is trapped in the descending limb until the collecting duct, thus raising its osmolarity. This assist is increasing the amount of NaCl that moves out of the ascending limb into the interstitium.
3) Urea enters the interstitium in the collecting duct contributing to its hypertonicity meaning more water will be reabsorbed at the descending limb.
4) Some urea will enter the ascending limb and be recycled to the collecting duct.
Describe how renal adjustment deals with acidosis and alkalosis?
acidosis: excrete H+ in urine, reabsorb HCO3-
alkalosis, vice versa
What are alpha intercalated cells involved in?
What enzyme is present inside?
What transporters are present and which membrane?
excretion of H+,
carbonic anhydrase,
H+ transported on apical membrane, basolateral membrane cabonate transporter
What are alpha intercalated cells involved in?
What enzyme is present inside?
absorbtion of H+,
carbonic anhydrase,
H+ transported on basolateralmembrane, apical membrane cabonate transporter
