PHGY 210 Study Guide - Glutamine, Proteinuria, Hyperkalemia

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Published on 14 May 2012
School
McGill University
Department
Physiology
Course
PHGY 210
Professor
SUMMARY: RENAL PHYSIOLOGY
Kidney: General concepts:
-Functions:
oRegulation of water and inorganic ion balance
most important function
oRemoval of metabolic waste products from the blood and their excretion in
the urine
More relevant in terms of pathology
oRemoval of foreign chemicals from the blood.
oProduction of hormones/enzymes:
Erythropoietin: controls erythrocyte production
Renin: controls the formation of angiotensin and influences blood
pressure and sodium balance.
1,25-dihydroxyvitamin D: active vitamin that influences calcium
balance
-Anatomy:
oPaired organs
o150 grams each
oBehind the peritoneum on either side of the vertebral column against the
posterior abdominal wall.
oUrine goes from kidney to ureter to bladder to urethra for excretion.
oThe renal medulla is the interior part of the kidney. It is formed of triangles
called the renal pyramids
oThe renal cortex is on the exterior part of the kidney. It surrounds the
medulla.
oBlood supply:
Renal artery branches to:
Interlobar artery, which turns at 90 to become:
Arcuate artery, which turns at 90 to become:
Interlobular artery
oNote that the venous structure is parallel to the arterial structure and that
nephrons receive bood by the afferent arterioles
o Nephron (1 million/kidney):
Renal corpuscle:
Glomerulus (capillary loops)
Note that the terms corpuscle and glomerulus can be
used interchangeably.
Bowman’s capsule
Tubule
oNotes about the anatomy of the nephron:
The tubule is surrounded by a monolayer of epithelial cells
All the convoluted parts of the nephrons are in the cortex, while the
parts in the medulla are straight.
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oThe renal corpuscle:
The glomerulus is surrounded by a kind of balloon with a monolayer
of epithelial cells called Bowman’s capsule.
The exterior part of Bowman’s capsule is made of the parietal layer,
and the interior part is made of the visceral layer.
oGlomerular capillary wall:
Capillary loops are surrounded by podocytes (foot processes)
The foot processes are interdigitating in adjacent capillaries, with
narrow spaces in between called the filtration slits.
The fenestrae and filtration slits in the glomerular basement
membrane (GBM) allow the passage of the filtrate from the
capillary lumen to the capsular space.
The capillary wall is composed of:
Fenestrated endothelial cells
GBM
Visceral epithelial cells with podocytes.
oVascular supply of the nephron:
The efferent arteriole branches into peritubular capillaries, which
provide blood to the tubules, but also receive material from the
tubules.
Sections of the nephron and their functions:
-Glomerulus:
oLocation: always in the cortex
-Proximal tubule:
oLocation:
convoluted: cortex
Straight: half cortex, half medulla
oFunctions:
Reabsorbs most of the filtered water and solutes (2/3 of all filtered
water and sodium)
It is also a major site of secretion for various solutes, except K+
Reabsorbs all amino acids and glucose
Water reabsorption:
Not regulated
Water reabsorption in the proximal tubule depends on Na+
reabsorption
1. Na+ is reabsorbed from the tubular lumen to the
interstitial fluid across the epithelial cells
2. The local osmolarity in the lumen decreases, while
the local osmolarity in the interstitium increases.
3. The difference in osmolarity causes net diffusion of
water from the lumen into the interstitial fluid
a. Via tubular cells’ plasma membrane
b. Via tight junctions
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4. From the interstitium, water, sodium and everything
else dissolved in the ISF move together by bulk flow
into peritubular capillaries
oTransport mechanisms:
Diffusion (ex: urea)
Sodium reabsorbed by Na+/H+ antiporter or Na+-glucose
contransporter
-Descending thin limb of Henle’s loop:
oLocation: medulla
oFunctions:
Reabsorbs water
oParticularities:
No sodium reabsorption!
Highly permeable to water
-Ascending thin limb of Henle’s loop:
oLocation: medulla
oFunction:
Not really important physiologically
We will ignore it and consider the ascending part of the loop of
Henle as being composed of the thick limb only.
-Ascending thick limb of Henle’s loop:
oLocation: half medulla, half cortex
oFunctions:
Reabsorbs sodium to create the countercurrent multiplier system.
oProperties:
Reabsorbs NaCl
Impermeable to water
-The juxtaglomerular apparatus:
oJuxtaglomerular cells:
Location:
Function: secrete renin
Regulation: receives information from tubular fluid via macula
densa cells and afferent arterioles.
oMacula Densa:
Location: cortex, at the end of the thick ascending limb of Henle’s
loop, between the afferent and efferent arterioles.
-Distal convoluted tubule:
oLocation: cortex
oFunctions:
Fine tuning
Homeostatic control
Adjusts rates of reabsorption and secretion according to
physiological needs.
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Document Summary

Anatomy: regulation of water and inorganic ion balance, removal of metabolic waste products from the blood and their excretion in. More relevant in terms of pathology: removal of foreign chemicals from the blood, production of hormones/enzymes: Renin: controls the formation of angiotensin and influences blood pressure and sodium balance. It is formed of triangles: the renal cortex is on the exterior part of the kidney. It surrounds the: blood supply: posterior abdominal wall. called the renal pyramids medulla. Interlobar artery, which turns at 90 to become: Arcuate artery, which turns at 90 to become: Interlobular artery: note that the venous structure is parallel to the arterial structure and that, nephron (1 million/kidney): nephrons receive bood by the afferent arterioles. Tubule: notes about the anatomy of the nephron: Note that the terms corpuscle and glomerulus can be. The tubule is surrounded by a monolayer of epithelial cells.

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