Renal physiology Flashcards
What is the function of the kidney ? (8)
- makes urine
- excretes waste
- electrolyte balance
- extracellular fluid vol
- BP (renin)
- gluconeogenesis
- RBC numbers (EPO)
- plasma Ca2+ (PTH target organ)
kidneys:
- where are the located ?
- what is the blood supply ?
- what is the functional unit ?
- retroperitoneal organ
- blood supply from the renal artery (direct form aorta)
- nephron is the functional unit
what % of the CO do the kidneys receive ?
20%
what is auto regulation in regards to the kidney ?
pressure changes (auto regulation) controlled by afferent + efferent arteriolar resistance - prevents glomerular pressure increase when arterial pressure increases
- over varying MAP, GFR remains quite steady (important because large volumes)
how much urine is produced per day
1-1.5 L
what are the ureters ?
located where ?
parked muscle tubes
- retroperitoneal
- curve down obliquely towards bladder (makes sphincter)
- urine moves along ureter by peristalsis
describe the vague anatomy of the bladder ? what is the capacity ?
muscular bag, reggae stretch out as bladder fills
- 99% time storage
- Capacity: 400-500ml (should be 0ml post-void)
why are women more prone to incontinence ?
muscle at bladder neck is v weak so rely on pelvic floor = external urethral sphincter (both voluntary)
what happens as bladder fills ? describe detrosrs and sphincter changes
- PSNS or SNS ?
as bladder fills => detrusor relax (sym T11-L2), external urethral sphincter close (prudential S2-S4)
- bladder stretch => inhibit para, Sam stimulated, somatic => external contraction
what is receptive relaxation in terms of the bladder
detrusor relax
- allow increase in vol without increase in pressure
what happens when bladder at max stretch and time to void ? describe detrusor and sphincters
increased signals from detrusor indicate time to void
- detrusor contract (para) + external sphincter relax (pudendal inhibition)
describe the PSNS involvement in micturition ? what nerve roots
para (cholinergic) S3-5: depressor contraction, smooth muscle sphincter relaxation
describe the SNS involvement in micturition ? what nerve roots
sympathetic (NAd) T10-12: inhibit detrusor contraction (allows receptive relaxation), smooth muscle sphincter contraction
describe the somatic involvement in micturition ?
striated external sphincter contraction/relaxation
what happens when the macular dense cells detect low NaCl ?
increased NaCl absorption at PCT => low NaCl detected at macula dense => dilation of afferent arteriole => increase hydrostatic pressure => restore GFR
increased NaCl reabsorption at PCT. How is GFR restored ?
- dilation of afferent arteriole
- renin release (efferent arteriole vasoconstriction)
where is renin released from ? in response to what ? what does this cause ?
macula dense cells detect decrease in sodium delivery to distal convoluted tubule => renin please from juxtaglomerular cells => angiotensin II => efferent vasoconstriction => increase hydrostatic pressure = restore GFR
- released in response to low Na, reduced renal perfusion, SNS
what is creatinine ? what is the clearance ratio ?
creatine is a waste product of metabolism => usually all excreted (1:1 between production + excretion) so an increase suggests renal impairment
what factors can lead to a reduction in GFR ?
- damage to filtration membrane (HTN, diabetes)
- increase BCP (kidney stone)
what is the glomerulus ? function ?
it is a loop of capillaries in ball shape surrounded by Bowmans capsule
- site of ultrafiltration
what 3 layers does the filtration barrier of the glomerulus have ? describe a bit ?
- endothelial cells:have many fenestrations (prevent filtration of RBC)
- glomerular basement membrane: limit filtration of intermediate-large sized solutes
- podocytes (Bowmans capsule epithelial cells)
where is ACE predominantly produced ?
produced by vascular endothelial cells in the lungs
what does angiotensin II act on ? to cause release of what form where ?
acts on the adrenal cortex => stimulates release of aldosterone (mineralocorticoid - steroid hormone released from zona glomerulosa)
what electrolyte changes does aldosterone cause ?
- increase serum Na2+
- decrease serum K+
