the renal system juxtaglomerulous apparatus &bladder (1)
TRANSCRIPT
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The Renal System Juxtaglomerulousapparatus &bladder
By Associate Professor Dr /Sohair AlyHassan
College of medicine,[RCMP] Perak
&National Research Center/Cairo, Egypt
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Chapter 14: The Kidneys and Regulation of
Water and Inorganic Ions
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L objectives
At the end of this lecture, the students shouldbe able to:
discuss the functional unit of the kideny
Nephron discuss the blood flow to the kidney
c) explain the basic mechanisms of Glomerular
filtration, tubular reabsorption and secretiondiscuss the different cell types in thejuxtaglomerular apparatus
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Section A:
Basic Principles of Renal Physiology:
1- Glomerular filtration
2- Tubular reabsorption
3- Tubular secretion
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The paired kidneys form a filtrate of the blood that is modified by
reabsorption and secretion; urine designated for excretion moves along
the ureters to the bladder.
Figure 14-1
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Fluid filtered from the blood in the glomerular
capillaries is altered by reabsorption and secretion
along the length of the 1,000,000 nephrons/kidney.
Figure 14-2
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Nephrone
Create osmotic gradient assisting in
water reasorption
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Due to the hydrostatic
pressure of the cardiac
pump, fluid is filtered from
the blood through fenestra inthe glomerular capillaries
into slit pores in the capsule.
Figure 14-3
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The outer layer
of the kidney is
the renal cortex;
it is the site of
glomerular filtration
and the convoluted
tubules.
The inner part of
the kidney is the
renal medulla; this is
the location of the
longer loops of Henle,and the drainage of the
collecting ducts into
the renal pelvis and ureter.
Figure 14-4
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The intersection of the macula densa in the distal tubule
with the afferent and efferent arterioles forms the
juxtaglomerular apparatus, which secretes the endocrine
signal known as renin into blood in the afferent arteriole.
Figure 14-5
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juxtaglomerular cells(JG cells, or granular cells) are
cells in the kidney that synthesize, store, and secrete the enzyme renin. They are
specialized smooth muscle cells in the wall of the afferent arteriole that delivers blood to
the glomerulus. In synthesizing renin, they play a critical role in the renin-angiotensin
system and thus in renal autoregulation, the self-governance of the kidney
http://en.wikipedia.org/wiki/Cell_(biology)http://en.wikipedia.org/wiki/Kidneyhttp://en.wikipedia.org/wiki/Reninhttp://en.wikipedia.org/wiki/Smooth_muscle_cellhttp://en.wikipedia.org/wiki/Nephronhttp://en.wikipedia.org/wiki/Glomerulus_(kidney)http://en.wikipedia.org/wiki/Renin-angiotensin_systemhttp://en.wikipedia.org/wiki/Renin-angiotensin_systemhttp://en.wikipedia.org/wiki/Renal_autoregulationhttp://en.wikipedia.org/wiki/Renal_autoregulationhttp://en.wikipedia.org/wiki/Renal_autoregulationhttp://en.wikipedia.org/wiki/Renin-angiotensin_systemhttp://en.wikipedia.org/wiki/Renin-angiotensin_systemhttp://en.wikipedia.org/wiki/Renin-angiotensin_systemhttp://en.wikipedia.org/wiki/Renin-angiotensin_systemhttp://en.wikipedia.org/wiki/Renin-angiotensin_systemhttp://en.wikipedia.org/wiki/Glomerulus_(kidney)http://en.wikipedia.org/wiki/Nephronhttp://en.wikipedia.org/wiki/Smooth_muscle_cellhttp://en.wikipedia.org/wiki/Reninhttp://en.wikipedia.org/wiki/Kidneyhttp://en.wikipedia.org/wiki/Cell_(biology) -
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1. Glomerular filtration
refers to the
movement of fluid
and solutes from the
glomerular capillaries
into Bowmans space.
Figure 14-6
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2. Tubular secretionrefers to the
secretion of solutes
from the peritubular
capillaries into the
tubules.
1. Glomerular filtration
refers to the
movement of fluid
and solutes from the
glomerular capillaries
into Bowmans space.
Figure 14-6
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3. Tubular reabsorption refers to the movement of materials from the
filtrate in the tubules into the peritubular capillaries.
2. Tubular secretionrefers to the
secretion of solutes
from the peritubular
capillaries into the
tubules.
1. Glomerular filtration
refers to the
movement of fluid
and solutes from the
glomerular capillaries
into Bowmans space.
Figure 14-6
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Substance X is filtered and secreted but not reabsorbed.
Substance Y is filtered and some of it is reabsorbed.
Substance Z is filtered and completely reabsorbed. Glucose
Figure 14-7
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Formation of the glomerular filtrate in Bowmans capsule
is the outcome of opposing pressures:
hydrostatic pressure from the heart favors filtration, osmotic and
hydrostatic pressure of the filtrate oppose it.
Figure 14-8
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GLOMERULAR FILTRATION
Depends upon the interaction of a number of forces:
1. Glomerular blood hydrostatic pressure (GBHP) - This is the chief force. It is the
pressure of blood in the glomerular capillaries, i.e., 75mm.
2. Capsular hydrostatic pressure (CHP) - CHP is a back pressure due to the presence of
fluid already in the renal tubule and the resistance of the tubule walls.
3. Blood Colloid osmotic pressure (BCOP) - The presence of non-filtrating proteins inthe blood of the glomerular capillaries creates an osmotic pull on water in the
relatively protein-free filtrate.
Pressure #1 is opposed by Pressures #2 and #3, This produces an effective filtration
pressure (Peff) of 25mm Hg
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As vasodilation and vasoconstriction of the afferent and
efferent arterioles alter the blood flow through the
glomerular capillaries, there are corresponding alterations
in the glomerular filtration rate (GFR).
Figure 14-9
http://www.wisc-
online.com/objects/Vie
wObject.aspx?ID=ap22
04
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Glomerular Filtration
[GFR ]is the volume of fluid filtered from the
glomeruli into Bowmans space per unite time
Determined by
permeability of the corpuscular membranes
Surface area available for filtration
GFR for normal person is 125ml/min or 180L /day /
the renal plasma flow is about 625 ml/min in a
'normal' kidney
clearance values/ml/min
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The luminal
section of the
plasma
membrane of
the tubule cells
faces the
filtrate,
whereas the
basolateral
section is in
close proximity
to the peritubularcapillary.
Figure 14-10
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Reabsorpition
Tubular reapsorpition
Diffusion
Mediated have a limited amounts of material they cantransport/unit time [transport maximum Tm] this is
because the binding site on the membrane transport
proteins become saturated when the concentration ofthe transported substance increases to a certain level.
Eg glucose[normal is 150 mg/100ml Fig 14-11 Glucouria when start to appear in urine[in hyperglycemia] or
Drop in the nephron efficiency to reabsorb the excess of filtered load of glucose[nephropathy] active
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Tubular Secretion move substances from
peritubular capillaries into the tubular lumen
Occure by diffusion
Mediated transport
Substances secreted are H,K, choline ,
creatinine
penicillin
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Kidney Concept of Clearance
Is the vol of plasma from which the substance
is completely removed [cleared] by kidney
per unit time.
Cs= Mass of S excreted/unit time/plasma
concentration of S
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Inulin, a biologically inert polysaccharide, can be used
to estimate the glomerular filtration rate since it is
filtered, but not reaborbed or secreted.
Figure 14-11 CONCEPT OF RENAL CLEARANCE
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Release of urine from the bladder, called
micturition, is coordinated by a combination of
smooth and skeletal muscle relaxation and
contraction.
Figure 14-12
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MICTURITION
Micturition is the process by which urine is
expelled from the bladder.
The neural mechanism causing micturition is
called Micturition reflex.
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Micturition cycle occurs two phases .
it consist of a filling phase and emptying phase.
Each phase requires a coordination interactionbetween the bladder and the nervous system.
Urine formed by the nephrone is ultimately carried
to the urinary bladder.
Where it is stored till a voluntary signal is given by
the central nervous system [CNS].
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The signal is initiated by the stretching of the
urinary bladder as it gets filled with urine.
In response ,the stretch receptors on the walls of
the bladder send signals to the CNS.
The CNS passes on motor messages to initiate the
contraction of smooth muscles of the bladder .
The simultaneous relaxation of the urethralsphincter causing the release of urine.
This type urine releasing process are called
MICTURITION
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Bladder control problems
For the urinary system to do its job, muscles and
nerves must work together to hold urine in the
bladder and then release it at the right time. Nerves carry messages from the bladder to the
brain to let it know when the bladder is full.
They also carry messages from the brain to thebladder, telling muscles either to tighten or release
. A nerve problem might affect your bladder control
if the nerves that are supposed to carry messages
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in case nerve damage?
Nerves that work poorly can lead to three different
kinds ofbladder control problems.
1-Overactive bladder. Damaged nerves may sendsignals to the bladder at the wrong time, causing its
muscles to squeeze without warning. The
symptoms of overactive bladder includeurinary frequency-defined as urination eight or more times a day or two or more
times at night
urinary urgency-the sudden, strong need to urinate immediately
urge incontinence-leakage of urine that follows a sudden, strong urge to urinate
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2-Poor control of sphincter muscles.
Sphincter muscles surround the urethra and keep it closed to hold urine in the bladder. If the
nerves to the sphincter muscles are damaged, the muscles may become loose and allow leakage
or stay tight when you are trying to release urine.
Urine retention.
For some people, nerve damage means their bladder muscles do not get the message that it istime to release urine or are too weak to completely empty the bladder. If the bladder becomes
too full, urine may back up and the increasing pressure may damage the kidneys. Or urine that
stays too long may lead to an infection in the kidneys or bladder. Urine retention may also lead
to overflow incontinence.
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What causes nerve damage?
Many events or conditions can damage nerves and nerve pathways. Some of the
most common causes are
vaginal childbirth
infections of the brain or spinal cord
diabetesstroke
accidents that injure the brain or spinal cord
multiple sclerosis
heavy metal poisoning
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