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ANATOMY & PHYSIOLOGY II BIO 212:
Dr. Lawrence G. Altman www.lawrencegaltman.com Some illustrations are courtesy of McGraw-Hill.
CHAPTER 20 Lecture:
URINARY
Part 1 Part 2
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CLINICAL CONDITIONS Today's lecture continues with the A&P of the Urinary
system; these are the clinical conditions you are responsible for looking up! Will not be covered here-‐-‐-‐just the A&P which will
complement your study of these conditions.
-‐renal calculi (kidney stones) -‐urethritis -‐cystitis -‐nephritis -‐glomerulonephritis -‐proteinuria -‐edema -‐BUN (blood urea nitrogen test)
Additionally, a Clinical Terms Summary may be found at the end of the chapter.
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KIDNEY BLOOD SUPPLY RENAL artery
SEGMENTAL arteries *
* not listed in your books
INTERLOBAR arteries ARCUATE arteries
INTERLOBULAR arteries
ARCUATE artery
AFFERENT arterioles GLOMERULUS
EFFERENT arterioles PERITUBULAR capillaries
VENULES INTERLOBULAR veins
ARCUATE veins INTERLOBAR veins SEGMENTAL veins *
RENAL Vein
In some books aka Cortical Radiate arteries
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The Nephron: Introduction -‐1 million+ .....per kidney -‐urine production -‐cortical nephrons (most) -‐juxtamedullary nephrons
Each NEPHRON -‐Glomerulus (knot of capillaries)*
-‐Renal tubule Bowman's (Glomerular) capsule* Proximal convoluted tubule Loop of Henle Distal convoluted tubule
*RENAL CORPUSCLE: Glomerulus + Bowman's Capsule
Approx 25% of cardiac output filtered through kidney each minute!
Cortical nephron
Juxtamedullary nephron
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GLOMERULUS
-‐tuft of capillaries fed by afferent arteriole
-‐thin walls of glomerulus (capillaries) act as a semi -‐ permeable membrane. -‐production of a protein -‐ free filtrate (blood cells and blood proteins too large)
-‐mechanism: basically passive under some pressure. Very Low blood pressure:
Kidneys may shut down (glomerular filtration stops) Note: Approx 1200 ml/minute of blood filtered through kidneys (20% of cardiac output) 125 ml/minute of filtrate produced, this is called the Glomerular Filtration Rate (GFR)
OBVIOUSLY-‐ some of the filtrate MUST be reabsorbed or bladder
would fill every 5 minutes!!! Reabsorption in tubules...
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GLOMERULUS
-‐endothelium: thin layer; porous (squamous epith)
-‐glomerulus surrounded by the closed end of the renal tubule (Bowman’s or glomerular capsule).
Bowman's capsule: 2 layers
Outer: continuous with proximal convoluted part of renal tubule (simple squamous epithelium)
Inner: Podocytes (branching processes) closely associated with the glomerular capillaries; filtration "slits" between processes
GLOMERULUS
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GLOMERULAR CAPILLARY PODOCYTE
PEDICELS
Cytoplasmic extensions
-‐-‐-‐> branch again
to form PEDICELS
Spaces between Pedicels: FILTRATION SLITS
PODOCYTES SEM
MUCH MORE POROUS than
TYPICAL CAPILLARIES !
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GLOMERULUS
GFR= 125 ml/min
Glomerular Filtration Rate
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= Glomerular Hydrostatic Pressure -‐
55
10 Mm Hg
Glomerular Capsule
Fluid Pressure
Osmotic Pressure of Blood
+ ( )
Glomerular Capsule Fluid Pressure OPPOSES outward flow
15 mm Hg
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Osmotic Pressure of Blood OPPOSES outward flow
30 mm Hg
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Glomerular Hydrostatic Pressure
PROMOTES outward flow 55 mm Hg
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OVERVIEW: TYPICAL TEXTBOOK DIAGRAM
(just know notes)
PRESSURE GRAPH: Decreasing from Renal artery to Renal vein
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Minor CALYX
C O R T E X
M E D U L L A
Renal corpuscles
Proximal Convoluted tubule MANY Microvilli
Loop of Henle:
Thin segment (descending portion)
Thick segment (ascending portion)
at level of
afferent arteriole
Distal Convoluted
tubule
COLLECTING DUCT
many in pyramids (from multiple
nephrons)
JUXTAMEDULLARY NEPHRON:
deep into medulla
Distinguish from cortical?
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EFFERENT ARTERIOLE
EFFERENT ARTERIOLE
PERITUBULAR CAPILLARIES
PERITUBULAR CAPILLARIES
adjacent to proximal and distal tubules
VEINS VASA RECTA
Specialized peritubular
capillaries around
Loop of Henle (urine concentration)
VEINS
In Juxtamedullary nephrons:
Vasa Rectae
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NEPHRON FUNCTIONS:
GLOMERULUS produces filtrate of protein -‐ free plasma
MOST (2/3) doesn't get very far....
PCT & Loop
of Henle
Reabsorption: out to the
peritubular capillaries Secretion:
into tubules
Reabsorption of Na+, K+ and glucose by active transport
Reabsorption of Cl-‐ by diffusion
Obligatory water reabsorption by osmosis
Secretion of certain drugs (e.g. penicillin) by active transport
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Reabsorption of sodium by active transport
Secretion of H+, K+
Reabsorption of water by osmosis
ADH also controls the reabsorption of water
Collecting tubules
DCT – Distal Convoluted
tubule
Reabsorption: out to the peritubular capillaries Secretion: into tubules
NEPHRON FUNCTIONS:
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JUXTAGLOMERULAR APPARATUS
A cuff of smooth muscle around afferent arteriole containing RENIN granules
Sensitive to decreased concentration of Na+
(decreased BP)
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Release of RENIN into bloodstream by JUXTAGLOMERULAR APPARATUS
TWO SITUATIONS:
FALL in SYSTEMIC PRESSURE: Sensed by pressure receptors (juxtaglomerular cells)
in wall of afferent arteriole.
DECREASED Na+: Sensed by chemoreceptors (Macula Densa) in DCT
(Distal Convoluted Tubule)
SIMPLIFIED PATHWAY........
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RENIN PATHWAY
RENIN released into Blood VASOCONSTRICTION via: 1.) peripheral blood vessel
constriction 2.) stimulation of
ALDOSTERONE release in adrenal cortex
END
ANGIOTENSINOGEN (plasma protein)
ANGIOTENSIN I (polypeptide)
ANGIOTENSIN II (potent VASOCONSTRICTOR)
Converting Enzyme
ALDOSTERONE: "Sodium -‐ retaining hormone" promotes reabsorption of Na+
(hence water also), expanding blood volume (pressure).
ALSO: overdrinking Without salts
ADH; aka Vasopressin): "Water -‐ retaining hormone" made by hypothalamus; released by pituitary
