The current presentation includes the anatomy of nephron with neat labelled diagrams. The slide also includes the details of functions of each part of nephron.

1. Urinary System
Anusha Shaji, B.Pharm, M.Pharm
Assistant Professor
Department of Pharmacology
Nirmala College of Pharmacy,
Muvattupuzha, Ernakulam

2. Nephrons
Nephrons are the structural and functional units of the kidneys.
Each kidney contains over 1 million of these tiny blood-processing
units
↓
Which carry out the processes that form urine
In addition, there are thousands of collecting ducts
↓
Each of which collects fluid from several nephrons
↓
And conveys it to the renal pelvis.

3. Location of Nephron

4. The structure of nephron consists of 2 parts
1. Renal corpuscle
It filters blood plasma
The renal corpuscle consists of 2 parts
(a) Glomerulus- Capillary network
(b) Glomerular (Bowman’s) capsule- Double walled cup
surrounding glomerulus
Collectively, the glomerular capsule and the enclosed glomerulus
are called the renal corpuscle.
Both of these lie within the renal cortex

5. 2. Renal tubule
These are the tubular structures to which the filtered fluid
passes into.
It consists of 3 parts;
(a) Proximal convoluted tubule (PCT)
(b) Descending and ascending Loop of Henle
(c) Distal convoluted tubule (DCT)

6. Structure of Nephron

7. Glomerular capsule/ Bowman's Capsule
It is an epithelial bilayer made up of visceral and parietal layers
The visceral layer consists of modified simple squamous epithelial
cells called podocytes
↓
That wrap foot like projections called pedicels around endothelial
cells of glomerular capillaries and form inner wall of capsule
The parietal layer consists of simple squamous epithelium forms
outer wall of capsule
The fluid filtered from glomerular capillaries enters capsular
(Bowman’s) space (the space between the two layers of bowman’s
capsule)

8. Glomerulus
Glomerulus is basically a network of arterial capillaries which form
a tuft-like structure.
It is situated in the Bowman's capsule.
Afferent arterioles form the glomerulus i.e., a capillary network.
These glomerular capillaries then reunite to form the efferent
arteriole.
Afferent arteriole is wide and short whereas efferent arteriole is
long and narrow.

9. Due to such difference, the glomerular capillary blood pressure is
high
↓
Because considerable force is required to push the blood through
the narrow efferent arteriole → such high pressure facilitates in
filtration.
Endothelium of the glomerular capillaries bears numerous pores
(fenestrae) which are about 50-100 nm in diameter.
Afferent arterioles also contain a group of epithelioid cells called
juxtaglomerular cells in their endothelial lining.
These cells contain granules and are involved in the secretion of
renin, a renal hormone that helps to regulate the blood pressure.

10. Functions of Glomerulus
Glomerulus functions as ultrafilter
↓
Which allows water and small molecular weight solutes to
pass through
↓
But retains high molecular weight solutes like proteins,
blood cells etc.

12. Renal Tubules
The remainder of the renal tubule is about 3 cm (1.2 inches) long
and has three major parts.
It leaves the glomerular capsule as the elaborately coiled proximal
convoluted tubule (PCT)
↓
Makes a hairpin loop called the loop of Henle (also called the
nephron loop or Henle’s loop)
↓
And then winds and twists again as the distal convoluted tubule
(DCT) before emptying into a collecting duct.

13. The terms proximal and distal indicate relationship of the
convoluted tubules to the renal corpuscle
↓
Filtrate from the renal corpuscle passes through the PCT first and
then the DCT
↓
Which is thus “further away” from the renal corpuscle.
Proximal convoluted tubule cells have simple cuboidal epithelial
cell with prominent microvilli with brush border on apical surface
The microvilli increases surface area for reabsorption and
secretion

14. The term convoluted implies that these are highly coiled
Both the convoluted tubules are found in the adrenal cortex
While the loop of Henle initially enters the renal medulla → takes
a turn and finally returns to the adrenal cortex.
Nephron Types
Due to difference in size and length of loop of Henle along with
variations in other aspects, nephrons can be divided into two:
1. Cortical nephrons
2. Juxtamedullary nephrons

17. Proximal Convoluted Tubule (PCT)
It measures about 1.5 cm in length.
PCT is able to absorb about 2.3 Lt of water, almost all glucose and
some Na+, Cl- and HPO4
2- ions.
Loop of Henle
Loop of Henle is a U- shaped structure whose loop enters into the
adrenal medulla.
The loop of Henle can be further divided as,
(1) Descending limb of loop of Henle
(ii) Ascending limb of loop of Henle

18. As the fluid from the PCT is transferred into the descending limb of
loop of Henle
↓
It gets concentrated
↓
Because the latter is highly permeable to water and Na+ ions
↓
Resulting in their absorption.
However, ascending limb is impermeable to water and therefore
reabsorbs only Na+ ions but not water.

19. Distal Convoluted Tubule (DCT)
DCT lies in the adrenal cortex, and measures about 0.4-0.5 cm in
length and is also highly coiled.
When compared to PCT, DCT has a larger diameter and is
abundant in cells.
Moreover, DCT of a nephron comes in contact with the afferent
arteriole.
The cells lining this region are called macula densa, as they bear
closely packed nuclei.
Juxtaglomerular cells of the afferent arteriole and macula densa
together are called juxtaglomerular apparatus.
This is concerned with the regulation of blood pressure.

20. Distal portions of the DCT are mainly composed of principal cells
which respond to two hormones → Vasopressin (ADH) and
Aldosterone.
DCT acts to reabsorb Na+ ions, however in response to
stimulation by the antidiuretic hormone (ADH) DCT becomes
permeable to water resulting in its reabsorption.
Aldosterone stimulates DCT to increase the reabsorption of
sodium.
Numerous collecting ducts combine and in turn transfer their
contents into the fewer papillary ducts which then go through the
minor calyces.

21. Juxtaglomerular Apparatus (JGA)
Juxtaglomerular apparatus is a composite structure found in a
specialized region of nephron
Wherein the distal convoluted tubule comes in direct contact with
the afferent arterioles.
It is made up of specialized cells of afferent and efferent arterioles,
distal tubule and glomerulus.
The three components of juxtaglomerular apparatus are
Juxtaglomerular cells,
Macula densa cells and
Lacis cells.

22. Juxtaglomerular cells
These cells contain secretory granules → hence they are also
known as granular cells.
They are modified smooth muscle cells of afferent arterioles.
They synthesize and store renin that can sense changes in blood
pressure.
They release renin in response to beta1- adrenergic stimulation
↓
Decrease in reabsorption of sodium chloride in macula densa or
decrease in renal perfusion rate.

23. Macula Densa Cells
These are columnar epithelial thickenings of distal convoluted
tubule.
They detect changes in sodium chloride concentration in the
distal tubule and glomerular filtration rate (GFR)
When they sense an increase in concentration of NaCl, they act
via two mechanisms viz
(a) They release vasopressin which acts on the adjacent arterioles
to reduce GFR
(b) They inhibit nitric oxide synthetase and prevent the secretion of
renin.

24. When they sense a decrease in NaCl concentration, they
stimulate nitric oxide synthetase to enhance renin release.
Lacis Cells
These are also known as extraglomerular mesengial cells or polar
cushion cells.
They are enclosed by extracellular matrix.
They have extensive cell processes that form gap junctions
between them and adjacent juxtaglomerular cells.
Their exact function is unclear.
They are thought to function as supportive cells which transfer
information regarding NaCl tubular load to juxtaglomerular cells.

26. Functions of Renal Tubules
Renal tubules are involved in selective reabsorption → They
reabsorb water and other essential nutrients and deliver them to the
bloodstream.
Renal tubules also help in tubular secretion → they transfer the
substances from the circulation into the tubular lumen.
↓
These substances include H+ K+ NH3+; ions and certain drugs like
penicillin etc.
Epithelial cells of the renal tubules synthesize newer substances
like ammonia, inorganic phosphates etc.