Renal structure and function Flashcards
Negatively charge acellular Glycocalyx is found where?
Basement membrane.
Where are podocytes located?
Inner epithelial layer.
What kind of molecules pass easily through the basement membrane and Glycocalyx?
Micromolecules (urea, glucose, Toxins, salts, amino acids, small hormones)
What is partially absorbed from tubules?
Urea.
Glomerular filtrate is essentially?
A protein free filtrate of plasma.
The proximal tubule is structurally and functionally organised for?
Bulk re absorption. 65-85% reabsorbed here.
what part of the kidney receives most of the renal blood flow?
Cortex 75% medulla 25%.
What lines the PCTs brush border?
Micro villi.
By the end of the proximal tubule what two substances are usually completely reabsorbed?
Glucose (couple to Na+ but these transporters can become saturated) and amino acids.
Megalin and Cubulin are?
Receptors for proteins to remove them by endocytosis.
At the end of the PCT approx. what percentage of urea is reabsorbed?
50-60%
The kidney is the prime site for removal of what type of toxin?
Water soluble.
What is fanconi syndrome?
A nephrotoxin prevents reabsorption in PCT. Blood is like plasma.
A renal condition in which urine contains abnormal amounts of protein is called?
Proteinuria
Extracellular fluid contains mostly?
Na+
Intracellular fluid contains mostly?
K+
What stimulates aldosterone?
Hyponatraemia.
What inhibits aldosterone?
Hyperatraemia.
What is hyponatraemia?
A condition that occurs when the level of sodium in your blood is abnormally low. Sodium is an electrolyte, and it helps regulate the amount of water that’s in and around your cells.
Where does aldosterone act?
Distal tubule (Na, K ATPase) and collecting ducts.
What does aldosterone do?
Acts to reabsorb Na+ and secretion of K+.
ENaC stands for?
Epithelial Sodium channel, apically located. Mainly in collecting ducts. An aldosterone receptor blocker blocks their ability to reabsorb Na+.
What disease is associated with a lack of aldosterone production which results in dangerously high levels of K+?
Addison’s disease.
Antidiuretic Hormone (Vasopressin) is produced where?
Made in hypothalamus and secreted by posterior pituitary gland.
What does ADH do?
ADH conserves water — Via receptors in cortical and distal collecting duct — activates aquaporins in apical membrane of principal cells
What does RAAS stimulate?
Aldosterone.
RAAS: Angiotensin II induces
The rapid response to restore Na content in body and thus blood volume.
What does atrial natriuretic peptide (ANP) do?
It is released by muscle cells in the upper chambers (atria) of the heart (atrial myocytes) in response to high blood volume. ANP acts to reduce the water, sodium and adipose loads on the circulatory system, thereby reducing blood pressure. ANP has exactly the opposite function of the aldosterone secreted by the zona glomerulosa in regard to its effect on sodium in the kidney – that is, aldosterone stimulates sodium retention and ANP generates sodium loss.
How does the body cope with high Na+, hypertension and high ECF volume?
— Renin secretion inhibited (very powerful response)
— Aldosterone-dependant Na reabsorption does not
occur (again, has huge effect)
— Excess Na excreted in urine (quickly balances)
What are some causes of Hyperkalaemia?
• Insulin resistance **Hyperkalaemia if serum K >5.5
• Beta-blockers Cljnjcal effects at >7.5 mmol
- Hyperkalaemia, if t potassium leak (muscle cells)
. Cell destruction
• Acidaemia
- Hyperkalaemia, structural abnormalities in kidney
• Decreased GFR, decreased filtration, reduced ability to compensatefor rapid changes in K load (secretion)
- Hyperkalaemia, functional abnormalities in kidney
. Decreased luminal flow (affects secretion)
. Metabolic acidosis, hypoaldosteronism
What are some causes of Hypokalaemia?
Common, (anorexia, CKD, IV fluids)
- Hypokalaemia, if renal loss increased
e.g. CKD (reduced ability to concentrate urine)
Diuretic therapy (increased tubular flow rate)
Rhabdomyolysis
- Hypokalaemia, if gastric loss increased
Diarrhea and vomiting
-insulin treatment, hyperthyroidism
. Nephrotoxicdrugs
. Laxatives
What accounts for half of the medullarv interstitial osmolality that drives water reabsorption from the descending limb and medullarv collecting duct.
Urea.
How is urea reabsorbed in the proximal tubule?
Passively.
Can the nephron beyond the PCT absorb Urea?
The nephron beyond is impermeable to urea up to the inner
medullary collecting duct.
What stimulates the passive reabsorption of urea by urea transporters in the collecting duct?
Vasopressin
Which limb of the loop of henle is permeable to water?
Descending.
Which limb of the loop of henle is permeable to ions?
Ascending both thick and thin sections.
What is transported out of the thick ascending limb into the medullary interstitium?
Sodium and chloride. This raises the osmolalitv in the interstitium, which
promotes water movement out of the descending limb.
If the medulla had normal blood capillaries what would happen?
the interstitium would equilibrate with plasma
Vasa recta allow?
counter-current exchange
Which limb of the vasa recta allows water to diffuse out and solutes back in?
Descending limb.
Which limb of the vasa recta allows ions to diffuse out and water back in?
Ascending limb.
Where are vasa recta found?
Juxta-medullary nephons.
Where are peritubular capillaries found?
Cortical nephrons.
What does an animal who is dehydrated but peeing lots suggest is wrong with them?
That it is not able to concentrate urine (renal disease)
How is thirst sensed?
Osmoreceptors in anterior hypothalamus in the same region that produces ADH.
What influences osmolality?
Changes in Na+
What does aldosterone do to Na+ in collecting ducts?
Increases its re-absorption.
Natriuretic peptides does what?
Inhibit Na+ re-absorption and increases GFR by dilating afferent arterioles.
VAsopressin (ADH) does what?
Enhances water retention in collecting ducts.
. to preserve blood volume
. to prevent a diuresis
*to prevent a natriuresis
Dopamine does what in the PCT?
Reduces NA+ re-absorption by inhibiting Na+/H+ exchange.
How to aquaporins work?
They insert a hydrophillic core that allow water to pass through hydrophobic membrane.
Where would you find aquaporin 2?
Collecting duct.
Aquaporin 1 is found where?
PCT and descending loop of henle.
