GU Anatomy & Physiology Flashcards
(13 cards)
Kidney Function
- Filter blood
- -> excretion of metabolic waste (urea, creatinine, urates, chemicals, drugs, hormones, metabolites) - Regulation
- -> regulate water balance
- -> regulate electrolyte balance
- -> regulate acid-base balance
- -> regulate arterial pressure
Nephron
- Functional unit of the kidney*
- 1 million per kidney
- Composed of 2 units: (1) tuft of glomerular capillaries–the glomerulus, aka. the filter (2) a duct system–the renal tubules, aka. the drain (Bowman’s capsule, proximal tubule, Loop of Henle, macula dense, distal tubule, collecting tubules/ducts)
Renal Blood Flow
renal artery –> afferent arteriole –> glomerular capillaries –> efferent arteriole –> peritubular capillaries –> renal vein
Glomerular Microanatomy
Glomerular capillary wall:
- PODOCYTES–extra cells on top of the capillary wall
- BASEMENT MEMBRANE–collagen meshwork
- Fenestrated endothelium
Glomerular Filtration Rate
Normal = ~180 liters (48 gallons) per day
-Measures nephron function
Nephron Function
- FILTRATION: from systemic blood to teh urine duct
- REABSORPTION: from urine duct back into the systemic blood
- SECRETION: from the kidney blood into the urine duct
- EXCRETION: contents that remain in the urine
Glomerular Filtration
1st step in urine formation
- Glomerulus filters the blood -> some contents move out & into the Bowman’s capsule for excretion
- Solution contains salts & organic molecules
Components Affecting Glomerular Filtration
- Renal blood flow & pressure
- -> pt’s baseline arterial BP + tone of afferent & efferent arterioles- high BP = increased GFR
- high afferent VC = decreased GFR
- high efferent VC = increased, then decreased GFR
- Fluid pressure in renal tubules
- -> obstruction = decreased GFR (e.g. hydronephrosis-distention/dilation of the renal pelvis)
Renal Reabsorption
2nd step in urine formation
-Reabsorption of contents from systemic blood into the kidney
Two processes:
- transport across the tubular epithelium into the renal interstitial (passive, active, osmotic, & diffusion mechanisms)
- transport across capillary membrane into the systemic blood (diffusion)
Renal Secretion
3rd step in urine formation
-Addition of some contents into the urine
Renal Excretion
Last step in urine formation
- Urine is excreted-travel from the collecting ducts –> ureters –> urethra –> out
- Usually via active mechanisms (counter-transport mechanisms)
Control of Renal Blood Flow & Glomerular Filtration
- Sympathetic innervation–afferent arteriole vasoconstrictors (NE, epinephrine) -> decreased blood flow & GFR
- Angiotensin II–vasoconstrictor of efferent arterioles -> decrease blood flow & increase hydrostatic pressure -> increase, then decrease GFR
- Nitric oxide, prostaglandins, & bradykinins–afferent arteriole vasodilators -> increase blood flow & GFR
- Autoregulatory feedback mechanisms in the juxtaglomerular apparatus (JGA)–maintains constant GFR
* macula densa cells in proximal, distal tubule
* JGA cells in arterioles-make & store renin
Urinary Excretion
GLOMERULAR FILTRATION – TUBULAR REABSORPTION + TUBULAR SECRETION
