STRUCTURE AND FUNCTIONS OF
NEPHRON
Dr.Mohammed Sharique Ahmed Quadri
Assistant prof. Physiology
Al Maarefa College
• Indeed, in the creation of the heavens and earth, and the
alternation of the night and the day, and the [great] ships
which sail through the sea with that which benefits people,
and what Allah has sent down from the heavens of rain, giving
life thereby to the earth after its lifelessness and dispersing
therein every [kind of] moving creature, and [His] directing of
the winds and the clouds controlled between the heaven and
the earth are signs for a people who use reason.
• "Behold! In the creation of the heavens and the earth;
in the alternation of the night and the day;
in the sailing of ships through the ocean, for the profit of mankind;
in the rain which Allah sends down from the skies,
and the life which He gives therewith to an earth that is dead;
in the beasts of all kinds that He scatters through the earth;
in the change of the winds,
and the clouds which they trail like their slaves between the sky and
the earth;
here indeed are Signs for a people that are wise"
(Qur'an 2:164)
Objectives
• list the general functions of the kidney
• Identify the different parts of nephron
• Describe in sequence the tubular segments through which
ultrafiltration flows after it is formed at Bowman’s capsule
• Identify each structure as being located in the renal cortex
or renal medulla.
• Compare Cortical with Juxtamedullary nephron
• Correlate the structure of nephron with functions
• Describe in sequence the blood vessels through which
blood flows when passing from the renal artery to the renal
vein
• Describe the three layers comprising the glomerular
filtration barrier
• Describe juxtamedullary apparatus and its function
• list the general functions of the kidney
Urinary System
• Consists of
– Urine forming organs
• kidneys
– Structures that carry urine from the kidneys to the
outside for elimination from the body
• Ureters
• Urinary bladder
• Urethra
Urinary System
Kidneys
• The kidneys are a pair of bean-shaped organs
that lie in back of abdominal cavity
• Each kidney is supplied with a renal artery and a
renal vein
• Acts on plasma flowing through it to produce
urine
• Formed urine drains into the renal pelvis
– Located at medial inner core of each kidney
– Urine is drained into channels called ureters, and
stored temporarily in the bladder before it’s emptied
through the urethra to outside the body.
Ureters
• Smooth muscle-walled duct
• Exits each kidney at the medial border in close
proximity to renal artery and vein
• Carry urine to the urinary bladder
Urinary Bladder
• Temporarily stores urine
• Hollow, distensible, smooth muscle-walled sac
• Periodically empties to the outside of the
body through the urethra
Urethra
• Conveys urine to the outside of the body
• Urethra is straight and short in females
• In males
– Much longer and follows curving course from
bladder to outside
– Dual function
• Provides route for eliminating urine from bladder
• Passageway for semen from reproductive organs
Nephron
• Functional unit of the kidney
• Approximately 1 million nephrons/kidney
• Each nephron has two components
• Vascular component
• Tubular component
• Arrangement of nephrons within kidney gives rise to
two distinct regions
• Outer cortex
– Renal cortex (granular in appearance)
• Inner medulla
– Renal medulla
– Made up of striated triangles called renal pyramids
The Nephron
You should know
• The kidney cannot regenerate new nephrons.
• Aging causes a gradual decrease in nephron
number.
• Adaptive changes in the remaining nephrons
allow them to perform the function.
Nephron (Vascular component)
– Dominant part is the glomerulus
• Glomerulus is a tuft of glomerular capillaries.
• large amounts of fluid & solutesare filtered from the
blood.
Juxtaglomerular apparatus
Nephron (Tubular component)
– Hollow, fluid-filled tube
• single layer of epithelial cells
– Components
• Bowman’s capsule
• Proximal convoluted tubule
• Loop of Henle
– Descending limb
– Ascending limb
• Juxtaglomerular apparatus
• Distal convoluted tubule
• Collecting duct or tubule
Nephron
• Two types of nephrons
• Distinguished by location and length of their
structures
– Juxtamedullary nephrons
– Cortical
nephrons
Regional differences in nephron structure
 Cortical nephrons
-have glomeruli located in
the outer cortex.
-have short loops of Henle
that penetrate only a short
distance into the medulla,
-their entire tubular system
is surrounded by
peritubular capillaries.
-Involved in solute
reabsorption.
Regional differences in nephron structure (cont.)
 Juxtamedullary nephrons.
- About 20 to 30 per cent
of the nephrons
- have glomeruli that lie
deep in the renal cortex
near the medulla
- have long loops of Henle
that dip deeply into the
medulla.
- have specialized
peritubular capillaries
called vasa recta
Basic Renal Processes
• Glomerular filtration
• Tubular reabsorption
• Tubular secretion
Urine results from these three
processes.
Excretion = Filtration – Reabsorption + Secretion
Overview of kidney functions
– Maintain H2O balance in the body
– Maintain proper osmolarity of body fluids, primarily
through regulating H2O balance
– Regulate the quantity and concentration of most ECF
ions
– Maintain proper plasma volume
– Help maintain proper acid-base balance in the body
– Excreting (eliminating) the end products (wastes) of
bodily metabolism
– Excreting many foreign compounds
– Producing erythropoietin
– Producing renin
– Converting vitamin D into its active form
Excretion of Metabolic Waste
Products
Eliminating waste products of metabolism that are not
longer needed by the body
• Urea (from protein metabolism)
• Uric acid (from nucleic acid metabolism)
• Creatinine (from muscle metabolism)
• Bilirubin (from hemoglobin metabolism)
• Metabolites of various hormones
Excretion of Foreign Chemicals
•
•
•
•
Pesticides
Food additives
Toxins
Drugs
Regulation of Water and Electrolyte
Balances
•
•
•
•
•
Water
Sodium
Potassium
Hydrogen Ions
Calcium, Phosphate, Magnesium, etc..
Regulation of Water and Electrolyte
Balances
• Regulate the VOLUME of the body fluids
• Regulate the COMPOSITION of the body fluids
• CLEARING (purifying) the body fluids of certain
electrolytes, and CONSERVING some electrolytes
• according to supply and demand
Regulation of Acid-Base Balance
• Lungs
• Body fluid buffers
• Kidneys
– Excrete acids (kidneys are the only means of
excreting non-volatile acids, such as sulfuric acid
and phosphoric acid.
– Regulate body fluid buffers ( e.g. Bicarbonate)
Regulation and production of
hormones and enzymes
• The kidney produces:
• Erythropoietin
• 1,25 dihydroxycholecalciferol (Vitamin D3,
calcitriol)
• Renin
• Vasoactive Agents
Regulation of Erythrocyte Production
Kidneys produce Erythropoietin: a hormone that
stimulates bone marrow to produce red cells.
Hypoxia
O2 Delivery
Kidney
Erythropoietin
Erythrocyte Production
in Bone Marrow
Regulation of Vitamin D Activity
• Kidney produces 1,25- dihydroxycholecalciferol
– The active form of vitamin D that important in
calcium and phosphate metabolism.
Renin production
• It is an enzyme secreted by the kidneys from
granular cells of the juxtaglomerular
apparatus.
• It activates the renin-angiotensin system by
converting angiotensinogen to angiotensin I.
Vasoactive Agents
• Regulate the capacity of the vasculature
– Endothelin
– Thromboxanes
– Prostaglandins
– Nitric oxide
– Natriuretic peptides
Metabolism of Hormones
Most peptide hormones are metabolized and
excreted by the kidney (e.g., insulin, angiotensin II,
etc.)
Regulation of Arterial Pressure
• Control of Extracellular Fluid Volume by
excreting variable amounts of sodium and
water.
• Endocrine Organ secreting vasoactive factors
or substances
– Angiotensin II
– Prostaglandins
References
• Human physiology by Lauralee Sherwood,
seventh edition
• Text book physiology by Guyton &Hall,11th
edition
• Text book of physiology by Linda .s
contanzo,third edition