The Renal System Juxtaglomerulous Apparatus &Bladder (1)

7/31/2019 The Renal System Juxtaglomerulous Apparatus &Bladder (1)

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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.


refers to the

movement of fluid



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.


refers to the

movement of fluid



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

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online.com/objects/Vie

wObject.aspx?ID=ap22

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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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The Renal System Juxtaglomerulous Apparatus &Bladder (1)