T3 L4: Formation of urine 2 Flashcards
What happens in the descending limb of the loop of Henle?
Extraction of water
What happens in the ascending limb of the loop of Henle?
Extraction of Na+ and Cl-
Describe the cells in the thin descending limb of the loop of Henle
Flat cells because there’s no active transport of salts. Freely permeable to water via AQP1
Describe the cells in the thick ascending limb of the loop of Henle
Tubular cells, impermeable to water. Have specialised Na+/K+/2Cl- (NKCC2) co-transporters
What is osmolality?
The measure of concentrations based on dissolved solutes measured as osmoles per litre
What is countercurrant multiplication in the kidneys?
Salts from the thicker ascending loH leave and attract water to go outside the thin descending loH which allows the reabsorption of water from the descending loH. Its facilitated by NKCC2
What role does urea have in the countercurract multiplication of the kidneys?
It diffuses out of the collecting duct and goes into the medulla down its concentration gradient and adds to the osmolality of the medullary interstitium
Where is urea reabsorbed?
In the proximal tubule
What are the structures in order that tubular fluid goes through in a nephron?
- glomerulous
- proximal tubule
- loop of Henle
- distal tubule
- collecting duct
What happens in the distal tubule?
Active absorption and secretion of solutes. Na+ and Cl- are actively reabsorbed in exchange for K+ and H+ which are secreted into the tubular fluid
What are principal cells, what do they do and what controls them?
Aldosterone makes them reabsorb Na+ and push K+ out in the distal tubule
What do macula densa cells do?
They sense Na+
Where is aldosterone released from?
Adrenal glands
How does aldosterone affect blood pressure?
Aldosterone causes principle cells to reabsorb Na+ so more water moves into the plasma and BP increases
What do intercalated cells do?
They exchange Na+ for H+ in the distal tubule and early collecting duct
What is the difference between alpha-intercalated cells and beta-intercalated cells?
alpha reabsorb bicarbonate and secrete acid via exchangers or ATPase’s, beta reabsorb acid and secrete bicarbonate via pendrin
What can increase permeability of the collecting duct?
ADH/ Vasopressin
Where is ADH released from?
Posterior pituitary as a result of hypothalamic inputs
How does ADH act?
It acts of vasopressin (V2) receptors on the basal membrane of principle cells in the DT and collecting ducts leading to activation of AQP2 channels. There is no net movement of salts, only water
What is diabetes insipidus and what causes it?
Its water diabetes caused by lack of ADH
What causes nephrogenic diabetes insipidus and how is it treated?
Due to inability of the kidney to respond to ADH. Treatment is Chlortalidone (diuretic) and Indometacin (anti-inflammatory)
What causes neurogenic diabetes insipidus and how is it treated?
Due to a lack of ADH production. Treated using Desmopressin (ADH analogue), Vasopressin, and Carbamezapine (anti-convulsive)
What is dipsogenic diabetes?
Psychological thirst
What is Syndrome of inappropriate ADH (SIADH) and how is it treated?
Excessive ADH production caused by head injurt or drugs. Treated using V2 receptor blockers (ADH inhibitors) like demeclocycline and Tolvaptan
What are some compounds we can put into the body that will increase ADH release?
Nicotine, Ether, Morphine, and Barbiturates (cause urine to decrease)
What can inhibit ADH release?
Alcohol because it increases urination
What happens to the water and solutes reabsorped from the tubules?
They are all taken back into the peritubular vessels and vasa recta surrounding the tubules
