RENAL SYSTEM
1. Kidneys
2. Ureters
3. Urinary bladder
4. Urethra
1= Basic Functional Unit
2,3,4= Conducting & Storage System
1
2
3
4
• Divided into 2
• Outer Cortex
• Inner Medulla
• The Functional Unit
of kidney is Nephron
– Nephron is located
both in Cortex and
Medulla
STRUCTURE OF NEPHRON
Nephron has 3
components
1. Vascular
Component
2. Tubular
Component
3. Tubovascular
Component
STRUCTURE OF NEPHRON
Vascular components
• Afferent & Efferent arterioles
• Glomerulus
• Peritubular capillaries
Tubular components
•
•
•
•
Proximal convoluted tubule
Distal convoluted tubule
Loop of Henle
Collecting duct
Tubo-vascular component
• Juxtaglomerular appartus
STRUCTURE OF NEPHRON AND ITS
RELATED BLOOD VESSELS
FUNCTIONS OF NEPHRON
• Filtration
• Reabsorption
• Secretion
• Excretion
Reabsorption
Filtration
Secretion
Excretion
FUNCTIONS OF KIDNEY
• Filtration
• Reabsorption
• Secretion
• Excretion
Filtration
• First step in urine formation
• Transport of fluid from blood to kidney nephron
like urea, glucose, myoglobin, hemoglobin, Serum
albumin.
Re-absorption
• Returning of filtered material to blood vessels like
glucose & proteins.
Secretion
• Some hormones like Erythropoietin & Renin ,
Toxins, Medicines and Foreign substances.
Excretion
• Loss of fluid from the body in the form of urine
Excretion = Total Filtration +Total Secretion – Reabsorption
of urine
OTHER FUNCTIONS OF KIDNEY
• Urine production
• Regulate the volume and composition of the extracellular
fluid.
– Control pH of blood.
– Control blood volume & blood pressure.
– Controls osmolarity.
– Controls ion balance.
• Production of hormones which have important functions
– Renin Maintains Extracellular volume of blood
plasma, interstitial fluid, lymph by renin-angiotensin
system
– Erythropoietin  Maintains RBC production
URINE FILTRATION
• Happens in Glomerulus on filtration membrane.
• The urine gets filtered by 3 forces due to change in
pressure, these are
1. Capillary hydrostatic pressure = 55 mm Hg
(OUTWARD PRESSURE MEANS FROM BLOOD
VESSELS TO NEPHRON BOWMANS CAPSULE)
2. Colloid osmotic pressure = 30 mm Hg
3. Capsular hydrostatic pressure = 15 mm Hg
• Net Filtration Pressure
• 55  (30+15) = 45
• 55 - 45 = 10mmHg
GLOMERULAR FILTERATION RATE
Across the Filtration Membrane which has vast
surface area due to many capillaries and blood
vessels, this 10 mmHg of Filtration Pressure
creates a Glomerular Filtration Rate (GFR) of
125ml/min which equates to a fluid volume of
180L/day entering the glomerular capsule. So most
of the filtrate is re-absorbed.
So tubular reabsorption occurs.
Tubular Reabsorption
• Tubular reabsorption occurs in Proximal
Convoluted Tubule surrounded by peritubular
capillaries.
• Plasma is Filtered and Cleared from unwanted
materials, toxins, ions by tubular reabsorption
process and the remaining filtrate is passed as
urine.
Peritubular capillaries
• The reabsorbed molecules of ions, plasma
products, glucose go back to blood through
peritubular capillaries.
• Peritubular capillaries have
- Low hydrostatic pressure &
- High colloid osmotic pressure
• Which helps in reabsorption process.
Tubular secretion
• Movement of unwanted material from the
peritubular capillaries and interstitial space into
the nephron tubules.
• So further removal of unwanted substances occurs
here.
EXCRETION
Excretion = Total Filtration +Total Secretion – Reabsorption
of urine
Urination or Micturition
After excretion urine passes through two ureters
and goes to the urinary bladder where it gets
collected continuously.
And as the micturition reflex starts, a person urinates