Kidney Flashcards
(41 cards)
Controls extracellular fluid volume (Na+ and water are reabsorbed)
Aldosterone
Controls plasma osmolarity (water is reabsorbed, but Na+ is not)
ADH (vasopression)
What are the hormones produced in the kidney?
- erythropoietin
- calcitrol
- prostaglandins
What causes the kidney to release erythropoietin?
- inadequate O2 delivery to the kidney (anemia, reduced intravascular volume, hypoxia)
- severe kidney dz reduces EPO production and leads to chronic anemia
How is Calcitrol synthesized in the kidneys?
- calciferol is synthesized by injested vit D or light exposure
- in the liver calciferol is converted to 25 [OH] Vit D3 (inactive Vit D3)
- in the kidney (under control of the parathyroid hormone) 25 [OH] Vit D3 is converted to calcitrol (1, 25 [OH]2 Vit D3 (active form)
What are the 2 functions of calcitrol?
- stimulate intestine to absorb Ca+2 from food
- stimulate bone to store Ca+2
stimulate kidney to reabsorb Ca+2 and phosphate
What are the renal prostaglandin hormones and what do they do?
- PGE2 and PGI2 vasodilate renal arteries
- thromboxane A2 constricts the renal arteries
What is urine output related to?
- linearly r/t MAP > 50mmHg
- NOT autoregulated
What are the two most important processes that carry out autoregulation?
- myogenic mechanism
- tubuloglomerular
What are conditions that increase renin release?
- Dec. renal perfusion pressure (hemorrhage, PEEP,CHF, liver failure w/ascites, sepsis, diuresis)
- SNS activation - Beta 1 (circulating catecholamines, exogenous catecholamines)
- tubuloglomerular feedback (dec Na+ & Cl in distal tubule)
What is Conn’s disease?
- excess aldosterone production
- Na+ retention and K+ loss
What is the principle determinant of osmolarity?
Na+ concentration
What are the two mechanisms that control ADH release?
- increased osmolarity in the ECF
- decreased blood volume
ADH stimulates which receptor in the collecting ducts and does what to cAMP?
- V2 receptor
- increases cAMP
What receptor does ADH stimulate to cause vasoconstriction in the peripheral vasculature? (inc IP3, DAG, Ca+2)
- V1
- net result is inc SVR
GFR is how many mL/min or L/day?
- 125 mL/min
- 180 L/day
What is the glomerular filtration fraction?
- 20% of RBF is filtered by glomerulus
- 80% is delivered to peritubular capillaries
What determines GFR?
hydrostatic pressure across the glomerulus
What is freely filtered by the glomerulus?
water, electrolytes, and glucose
What are the 3 determinants of hydrostatic pressure across the glomerulus?
- arterial blood pressure
- afferent arteriole resistance
- efferent arteriole resistance
Where is the region of the nephron where the MOST of the filtered Na+ is reabsorbed?
- Proximal tubule 65%
- Loop of Henle (thick ascending) 20%
- Distal tubule 5%
- Collecting duct 5%
- Urine 5%
What is reabsorbed in the proximal tubule?
- potassium
- chloride
- bicarb
- sodium
- water
What is secreted into the proximal tubule?
- organic bases and acids (bile salts, uric acid, catecholamines, toxins)
- H+ ions
What is reabsorbed in the Loop of Henle (descending)?
- water (20%)
