This document summarizes the structure and function of the kidney. It describes that the kidney contains approximately 1-2 million functional units called nephrons. Each nephron contains a glomerular capsule with capillaries that filters blood to form urine. The urine passes through different segments of the nephron and collecting ducts before exiting the kidney. In addition to filtering wastes, the kidneys regulate water, electrolyte and acid-base balance and produce hormones like erythropoietin and renin.

1. STRUCTURE OF KIDNEY
DR.MAHESWARI JAIKUMAR
maheswarijaikumar2103@gmail.com

2. • The urinary system is the main excretory
system and consists of the following
structures:
2 kidneys (secrete urine)
2 ureters (convey urine from the kidney to
the urinary bladder)
Urinary bladder(collects and stores urine)
Urethra (Through which urine leaves the
body)

4. • The urinary system plays a vital part
in maintaining homeostasis of water
and electrolytes within the body.
• The kidneys produce urine that
contains metabolic waste products,
including nitrogenous compounds
(urea and uric acid, excess ions and
some drugs)

5. MAIN FUNCTIONS OF KIDNEY
• The main functions of kidney
are:
• Formation of urine, maintaining
water and electrolyte balance
and acid-base balance
• Excretion of waste products

6. • Production and secretion of
ERYTHROPOETIN (hormone that
stimulates formation of RBC)
• Production and secretion of RENIN
(enzyme to control blood pressure)
• Urine is stored in the urinary
bladder and excreted by the process
of MICTURATION

7. • The kidneys lie on the posterior
abdominal wall, one on each
side of the vertebral column,
behind the peritoneum and
below the diaphragm
• They extend from the level of 12
thoracic vertebra to the 3rd
lumbar vertebra

8. • The right side kidney is usually
slightly lower than the left
probably due to considerable
space occupied by the liver
• Kidneys are bean shaped organs,
about 11 cm long, 6 cm wide
thick and weigh 150gm

9. • They are embedded in and held
in position by a mass of fat
• A sheath of fibrous connective
tissue, the renal fascia, encloses
the kidney and the renal fat

10. ORGANS ASSOCIATED WITH
KIDNEYS
• As the kidney lie on either side
of the vertebral column each is
associated with different
structures

11. RIGHT KIDNEY
• SUPERIORLY- The right Adrenal
gland
• ANTERIORLY- Right lobe of liver, the
duodenum, the hepatic flexure or
the colon
• POSTERIORLY-diaphragm and
muscles of the posterior abdominal
wall

12. LEFT KIDNEY
• SUPERIORLY-Left Adrenal gland
• ANTERIORLY-Spleen, stomach,
pancreas, jejenum and splenic
flexure of the colon
• POSTERIORLY- Diaphragm and
muscles of the posterior abdominal
wall

13. GROSS STRUCTURE OF KIDNEY
• Three areas of tissue can be
distinguished when a longitudinal
section of the kidney is viewed with
the naked eye
• An outer fibrous capsule
• The cortex
• The medulla

17. CORTEX
• A reddish brown layer of tissue,
immediately below the capsule
and outside the renal pyramids

19. MEDULLA
• The innermost layer, consisting of
pale conical shaped striations, the
renal pyramids

20. HILUM
• Is the concave medial border of
the kidney where the renal
blood and lymph vessels, the
ureter and nerves enter

22. • Urine formed within the kidney
passes through a renal papilla at the
apex of a pyramid into a major calyx
• Several minor calyx merge into a
major calyx and two or three major
calyces combine forming the renal
pelvis, a funnel shaped structure
that narrows when it leaves the
kidney as the ureter

23. • The walls of the calyces and renal
pelvis are lined with transitional
epithelium and contain smooth
muscle
• Peristalsis, intrinsic contractions of
smooth muscle, propels the urine
through the calyces, renal pelvis and
ureters to the bladder

25. MICROSCOPIC STRUCTURE
• The kidney contains about 1-2
million functional units, the
NEPHRONS and smaller number of
collecting ducts
• The collecting ducts transport urine
the pyramids into the calyces, giving
the pyramid their striped
appearance

26. • The collecting ducts are
supported by connective tissue,
blood vessels, nerves and lymph
vessels

28. NEPHRON
• Is a tubule closed at one end that
joins a collecting duct at the other
end.
• The closed or blind end is indented
to form cup-shaped GLOMERULAR
CAPSULE (BOWMAN’S CAPSULE)
enclosing network of tiny arterial
capillaries the glomerulus

29. • Continuing from the capsule the
remainder of the nephron is about 3
cm long and described in three parts
• 1. The proximal convoluted tubule
• 2.The medullary loop (Henle’s loop)
• 3.The distal convoluted tubule
leading into a collecting duct

30. • The collecting ducts unite,
forming larger ducts that empty
into the minor calyces
• The kidneys receive about 20%
of the cardiac output.

31. NEPHRON

32. • After entering the kidney at hilum,
the renal artery divides into smaller
arteries and arterioles.
• In the cortex an arteriole (afferent
arteriole) enters the glomerular
capsule and then subdivides into a
cluster of tiny arterial capillaries
forming the glomerulus

33. • Between these capillary loops
are connective tissue phagocytic
mesangial cells.
• The blood vessel leading away
from the glomerulus is the
efferent arteriole.

34. • The afferent arteriole has a
larger diameter than the efferent
arteriole, which increases
pressure inside the glomerulus
and drives filtration across the
glomerular capillary walls

36. • The efferent arteriole divides
into second pertubular (around
tubules) capillary network,
which wraps around the
reminder of the tubule, allowing
exchange between the fluid in
the tubule and the blood stream

38. • This maintains the local supply
of oxygen and nutrients and
removes waste products
• Venous blood drained from this
capillary bed eventually leaves
the kidney in the renal vein,
which empties into the inferior
vena cava

39. • The walls of the glomerulus and
the glomerular capsule consist of
a single layer of flattened
epithelial cells
• The glomerular walls are more
permeable than those of other
capillaries

40. • The remainder of the nephron
and the collecting duct are
formed by a single layer of
simple squamous epithelium
• Renal blood vessels are supplied
by both sympathetic and
parasympathetic nerves

41. • The presence of both divisions of
the autonomic nervous system
controls the renal blood vessel
diameter and renal blood flow
independently of autoregulation

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