PHGY 210 Lecture Notes - Abdominal Wall, Furosemide, Proximal Tubule

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Published on 11 Sep 2014
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KIDNEY is behind peritoneum, on both sides of vertebral column, against posterior abdominal wall. 150 g each.
-regulation of water, inorganic ions and acid-bas balance
-remove of metabolic wastes (urea) from blood and their exertion in the urine
-removal of foreign chemicals from blood and eliminate it with urine ( drugs)
-production of hormones/enzymes:
a) erythropoietin- hormone controls erythrocyte production
b) renin – enzyme controls the formation of angiotensin and influences blood pressure and sodium balance
c) 1,25-dihydroxyvitamin D- active vitamin that influences Ca balance.
Renal arteryinterlobar arteryarcuate arteryinterlobular arteryafferent arterioleglomerulusefferent
Each kidney has 1 million nephrons, each consists of: renal corpuscle (Glomerulus + Bowman’s capsule) + tubule.
GlomerulusBowmans Capsule proximal convoluted tubule proximal straight tubule descending thin limb of Henles
loopascending thin limb of Henle’s loop thick ascending limb of Henle’s loop  macula densa here distal convoluted
tubulecortical collecting duct medullary collecting duct.
Bowman’s capsule consists of parietal layer-outside one and visceral layer -inside one, made of podocytes.
In glomerulus arterioles are very tight to each other, plus they are surrounded by those podocytes and their cell processes.
Filtration barrier consists of visceral glomerular epithelial cells (podocytes), GBM, endothelial cells.
From capillary  endothelial fenestrabasement membrane filtration slits of podocytesBowmans capsule.
Urine formation:
1) Glomerular filtration. Urine formation begins with filtration of plasma from glomerular capillaries into Bowman’s
space (glomerular filtration).
2) Tubular reabsorption – from tubules peritubular capillaries. Para- and Transcellular ( more regulatable).
Diffusion: is Paracellular( in b/w tubular epithelial cells), often across tight junctions connecting the tubular
epithelial cells. Depends on concentration gradient. e.g. Urea is freely filtered at glomerulus, in proximal tubule
water reabsorption occurs, urea concentration becomes higher, urea diffuses into interstitial fluid and reabsorbed by
peritubular capillaries.
Mediated transport: exclusively by transcellular (thru tubular epithelial cells), requires assistance of
transport proteins, often coupled to sodium reabsorption. Na is actively pumped to peritubular cap. by Na/K
ATPase so Na, AA, glucose. freely diffuses from tubular lumen into cell using symports.
Transport maximum –amount of substance that can be transported at any one time. When all the
transporters are saturated (occupied) then no more solute can pass through and transport maximum has been
reached.. e.g. glucose transport in diabetics.
3) Tubular secretion – from peritubular capillaries tubules. Also by diffusion and transcellular mediated transport.
Most important substances secreted: H+ and K+. Usually coupled to reabsorption of Na+.
Amount excreted= Filtered-reabsorbed+secreted.
PAH – all will be excreted, Na and H20 – filtered and a lot reabsorbed 99%, Glucose – all 100% reabsorbed.
Urea – 44% reabsorbed. K+ - 86% reabsorbed, but also secreted.
Cells, Proteins (albumin, globulins), Protein bound substances (50% of Ca+ ion usually bind to albumin, fatty acids)
DOESN’T Filtrate to Bowman’s capsule.
There are three 3 physical forces that establish filtration rate:
PGC –glomerular capillary blood pressure, pushing plasma into Bowman’s space.
PBS – fluid pressure in Bowmans capsule, pulls filtrate back to capillary.
GπC – osmotic force due to protein in plasma, pulls filtrate back to capillary
Net glomerular filtration pressure = PGC-PBS- Gπ C
GFR – volume of fluid filtered from the glomerulus into Bowman’s space per unit time.
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