Juxtaglomerular Apparatus

It consists of: • Specialized macula densa cells • Specialized granular juxtaglomerular (JG) cells

Macula Densa Cells:

The ascending limb of LOH make contact with afferent arteriole, here the columnar tubule cells become crowded which are known as macula densa.

Juxtaglomerular cells

Along side the macula densa the wall of afferent arteriole contains modified smooth muscle fibers called juxtaglomerular cells.

* The Juxtaglomerular Apparatus

Afferent Arteriole

Efferent Arteriole

Ascending limb of LOH

Macula Densa Cells

Granular Juxtaglomerular (JG) Cells

PCT

Bowman’s Capsule

Functions of Juxtaglomerular Apparatus

The JGA helps regulate blood pressure

https://www.wisc-online.com/learn/natural-science/life-science/ap2204/the-juxtaglomerular-apparatus

* The Juxtaglomerular Apparatus

Afferent Arteriole

Efferent Arteriole

Ascending limb of LOH

Macula Densa Cells

Granular Juxtaglomerular (JG) Cells

PCT

Bowman’s Capsule

Function of NephronTo produce urine the nephron and CD performs three major functions: Glomerular Filtration Tubular Reabsorption Tubular Secretion

Blood flow through Glomerulus

Glomerular FiltrationThe 1st step in urine production

In this process the water and most solutes in blood plasma move across the wall of glomerular capillaries into glomerular capsule and then into renal tubule

Directions of tubular reabsorption and secretion

Tubular ReabsorptionAs filtered fluid flows along the renal tubules and through the collecting ducts, tubule cells reabsorb about 99% of filtered water and many useful solutes.

The term reabsorption refer to return of substance into the blood stream.

The term absorption mean entry of new substance into the body, as occur in Gastrointestinal tract

Tubular Secretion:

As the fluid flow along the renal tubule and through the collecting duct, the tubule and duct cells secrete other material such as wastes, drugs and excess ion into the fluid.

Passage of glomerular filtrate

Glomerular capsule PCT nephron loop DCT collecting duct papillary duct minor calyx major calyx renal pelvis ureter urinary bladder urethra

FILTRATION

Filtration through Glomerulus

Glomerular filtrate:The fluid that enter the capsular space is called the glomerular filtrate

Filtration membrane:The endothelial cells of the glomerular capillaries along with basal lamina, and the podocytes which completely encircle the capillaries form a leaky barrier called filtration membrane.

VISCERAL LAYER

PARIETAL LAYER

Basal lamina

Characteristics of Filtration membraneGlomerular endothelial cells are quite leaky, they have large fenestration (pores) that measure 70-100nm. This permit all solutes in blood plasma to exit glomerular capillaries except blood cells.

Foot like processes extend from podocytes called pedicels surround the capillaries. The space between pedicel are called filtration slit. It permit the passage of molecule having a diameter smaller then 6-7 nm. Therefore, water, glucose, vitamin amino acids, ammonia and ion passes through filtration slits.

Physical Pressures involve in Glomerular filtration

Glomerular blood hydrostatic pressure GBHP

It is the blood pressure in glomerular capillaries it is 55mmHg. It promote filtration.

Capsular hydrostatic pressure CHP

Hydrostatic pressure exerted by fluid which are already present in the capsular space. It is 15 mmHg

It oppose filtration

Blood osmotic pressure BCOP

The plasma protein present in blood exert a pressure which is known as BCOP. It is 30mmHg. It oppose filtration

Net filtration pressure =

GBHP – (CHP +BCOP)

7.3-(4+2) = 1.3kPa,

or

55-(30+15) =10mmHg.

• Define Glomerular filtration rate. • Discuss the different mechanisms which regulate

GFR• Describe reabsorption of water and solute in renal

tubule.• Outline the structure and function of ureter• Describe the structure of urinary bladder• Compare and contrast the process of micturition in

babies.

Glomerular Filtration Rate (GFR)

It is the amount of filtrate formed in all the renal corpuscles of both kidney per minute .Adult GFR averages 125ml/min in male and 105/min in female

Three mechanism control GFR Renal auto regulation Neural regulation Hormonal regulation

Renal Auto-regulation

The kidney themselves help to maintain constant renal blood flow and GFR despite normal, everyday changes in the blood pressure. This capability of the kidney is called renal auto regulation.

Renal auto regulation consists of two mechanism the Myogenic Mechanism Tubuloglomerular feed back.

Myogenic mechanism

Myo=muscle

Genic= producing

Tubuloglomerular feedback

Nitric oxide (NO) causes vasodilation

when not release then the vessels

constrict