student will learn the basics of kidney and histology of nephrons. it will help them learning and understanding the functions, different parts of nephrons.

1. MICROSCOPIC FEATURES OF NEPHRONS
& COLLECTING DUCT
Presenter name: Dr. Kashif Hussain Alvi Awan

2. KIDNEYS
Kidney is a large bean shaped organ located retroperitoneally in the
posteior abdominal wall. On the medial of the kidney is a
depression ‘Hilum’ through which the renal artery enters and renal
vein and ureter leave the organ.
On naked eye inspection, the kidney shows outer reddish brown
zone ‘CORTEX’ and inner lighter zone ’MEDULLA’.
The Medullary substance of each kidney is arranged as 8 to 18
conical masses called Renal pyramids. Based on each pyramids
lies adjacent to the cortex, whereas apex, known as papilla projects
into a minor Calyx of the renal pelvis.

5. THE URINIFEROUS TUBULE
The Uriniferous tubules forms the structural and functional unit of
kidney. It consist of 2 parts i.e.
Nephrons is the longest part of the uriniferous tubules. It is responsible
for the production of urine.
Collecting Tubules conveys the urine from the nephron to a collecting
duct lying in a medullary ray.

6. NEPHRONS
Each kidney contains approximately 1.5
millions nephrons. A nephron is along,
epithelium-lined tube which begins blindly
and ends by joining a collecting tubule. Each
nephron begins as a double-walled, cup
shaped dilatation known as Bowman’s
capsule. A tuft of capillaries called
glomerulus occupies the concavity of the
capsule.

8. TYPES OF NEPHRONS
 Superficial cortical nephrons situated in the outer part of renal cortex.
 Mid cortical nephrons are situated in the mid region of the cortex and
their Loop of Henle are of intermediate length.
 The Juxta-medullary nephrons have their renal corpuscles located in
the deepest part of the renal cortex in close proximity to the base of
the medullary pyramid.

9. RENAL CORPUSCLES
The renal corpuscles are spherical bodies, ranging from 200 to 250 μm in diameter.
A renal corpuscles consist of a Bowman’s capsule and a glomerulus.
The Bowman’s capsule is in the form of a double- walled cup i.e
• Parietal layer.
• Visceral layer.
The parietal layer is made up of a simple squamous epithelium and its basal lamina
which covers the outer surface of the squamous cell.
The visceral layer covers the glomerulus. It is composed of specialized epithelial
cells called podocytes.

10. PODOCYTES
• The podocytes are large, irregular star shaped cells which share a
common basal lamina with the endothelial cells of the glomerular
capillaries. The tentacles give rise to the numerous processes
Pedicles. Podocytes play an important role in glomerular
function. Together with endothelial cells of the glomerular
capillary loop and the glomerular basement membrane they
form a filtration barrier. Podocytes cooperate with mesangial
cells to support the structure and function of the glomerulus

12. THE GLOMERULUS
The glomerulus is a tuft of fenestrated capillaries connecting an afferent
arterioles with an efferent arteriole. The two arterioles usually lie close
together at the vascular pole of the renal corpuscles.
MESANGIUM
The space between the glomerular capillaries is occupied by a special type of
connective tissue called mesangium. The mesangium function is to:
• Provide structural support for the capillary loops
• Act as a phagocyte.
• Can increase or decrease blood flow through their contractile property

14. PROXIMAL TUBULE
The proximal tubule of the nephron consist of 2 parts:
• Proximal Convoluted Tubule
• Proximal Straight Tubule
Proximal Convoluted Tubule is the longest and most tortuous part of the nephron.
It is about 14mm long and has an outside diameter of about 60μm. It also occupy
the major part of the cortex due to longest part of the nephron. PCT contains
simple cuboidal epithelium. EM reveals that it contains numerous long
mitochondria. The principle function of PCT is to actively absorb sodium from the
Glomerular filtrate and to pump it into the intercellular space.
Proximal Straight Tubule is lined by low cuboidal limb of Loop Of Henle. It forms
the descending limb of Loop Of Henle.

16. LOOP OF HENLE
The Loop Of Henle joins the Proximal straight Tubule to the distal
straight tubule which constitute U shaped structure known as LOOP
OF HENLE.
 FUNCTION OF LOH
•
•
•

17. DISTAL CONVOLUTED TUBULES
LM shows that the distal convoluted tubules are lined by
Simple Cuboidal Epithelium.
Principle function of the DCT is resorption of sodium from the
glomerular filtrate under the influence of hormone
‘Aldosterone’.

18. COLLECTING TUBULES AND COLLECTING DUCT
The collecting tubules have an average diameter of 40μm and are
lined by simple cuboidal epithelium. A collecting tubules receives
many DCT. The collecting tubules joins each other to form larger
straight COLLECTING DUCTS.
The collecting ducts are lined by a simple columnar epithelium. The
epithelium lining the Collecting ducts contains two types of cells:
•
•

20. LIGHT CELLS
•
DARK CELLS are further classified into:
•
•
• Alpha cells secretes H+ Ions into collecting duct lumen.
• BETA cells resorbs H+ ions and secretes HCO3 into the lumen of the
collecting duct.

21.  The principle function of Collecting duct and collecting tubules
and ducts is to conduct urine from the nephrons to the renal
pelvis.
 However, under the influence of the ADH, These tubules resorb
water from the glomerular filtrate.

23. THANK YOU !!!