Wikinotes

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regulation of water, inorganic ion balance, acid-base blance
removing foreign particles or metabolic waste products from the blood and excreting them into urine
- (kidney makes pee)
produce hormones and enzymes:
- erythropoietin: hormone that controls erythrocyte production
- renin: enzyme that control formation of antgiotensin (which influences blood pressure and sodium balance... will see later)
- 1,25-dihydorxyvitamine D : vitamind that influences calcium balance

paired organs, 150g each.
located behind peritoneum on either side of the vertebral column against the posterior abdominal wall
has ureter which send urine to bladder.

outer to inner: renal cortex, renal medulla (like pyramid), renal pelvis.
has ureter, renal artery, and renal vein
afferent arteriole : blood supply to nephron (functional unit of kidney).
- arcuate artery : line the boundary between renal cortex and medulla
- interlobar artery: between pyramid (renal medulla)
- interlobular artery: in renal cortex. perpendicular to arcuate artery.

each kidney has ~1 million nephrons (smallest functional unit)
nephron consists of :
- renal corpuscle
  - glomerulus (capillary loops) : always entirely in cortex.
  - bowman's capsule
- tubule
vascular supply:
- after blood enters into glomerulus via afferent arteriole, it leaves via efferent arteriole.
- efferent arteriole then supplies the tubule.

glomerulus -> bowman's space in bowman capsule ->
proximal convoluted tubule (which starts in cortex) ->
proximal straight tubule (partially in medulla)
Loop of henle -->
- descending thin limb
- ascending thin limb (we don't talk about its function)
- ascending thick limb
distal convoluted tubule (starts where glumerolus touches tubule. ends where tubule of other nephrons are merging).
collecting duct
renal pelvis
ureter
bladder.

where distal convoluted tubule touches afferent arteriole originating from the glomerulus, there are a bunch of cells (juxtaglomeruluar cells) that regulate secretion.
glomeruluar capillary wall is covered by foot processes of potocyte.
capillary is also fenetrated.
- it's a filtration barrier:
  - plasma can diffuse through fenetrations, glomerulus BM (basement membrane), filtration slits between foot processes of potocytes (visceral endothelial cells), and go into capsular space.
  - glomerulus filter blood to make urine.

cortex:
- renal corpuscle (always always in cortex)
- proximal tubule (convoluted and straight)
medulla:
- Henle's loop (has 3 parts)
  - descending thin limb
  - ascending thin limb
  - thick ascending limb (has macula densa at the end)
cortex again:
- distal convoluted tubule
back to medulla:
- collecting duct (where nephrons merge together.)

glomerular filtration (in glomerulus)
- filtrate is cell-free (you don't excrete cells)
- filtrate contains all substances (except proteins) as those present in plasma. (more details later)
tubular secretion and reabsorption (in tubule)
- as filtrate passes through tubule, its composition is altered by movement of substances
  - reabsorption : substances move from tubule to peritubular capillaries
  - secretion : bllod to tubules
- types of secretion/reabsorption: (examples)
  - PAH (para-amino-hippurate): some is filtered into glomerus and the rest is dumped in the urine by 100% secretion inot the tubule after glomerulus) -- > 100% excretion
  - sodium, water : some is filtered at glomerulus (i.e. going into the tubule) and then reaborption occurs in the tubule, taking some of that back into the blood --> high reabsorption)
  - glocose: amount filtered in the glomerous is totally reabsorpted in tubule. --> 100% reabsorption
rate of filtration, reabsorption, or secretion is subject to physiological control.

Friday, March 30, 2012
Renal: Anatomy of kidney