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)
INTRODUCTION
3.
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
LOCATION
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. 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
11.
12.
13.
14. CORTEX
• A reddish brown layer of tissue, immediately
below the capsule and outside the renal pyramids
15.
16. MEDULLA
• The innermost layer, consisting of pale conical
shaped striations, the renal pyramids
17. HILUM
• Is the concave medial border of the kidney
where the renal blood and lymph vessels,
the ureter and nerves enter
18. • 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
19. • 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
20.
21. 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
22.
23. • The collecting ducts are supported by
connective tissue, blood vessels,
nerves and lymph vessels
24. 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
25.
26.
27. • 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
28.
29.
30. • The collecting ducts unite, forming larger
ducts that empty into the minor calyces
• The kidneys receive about 20% of the
cardiac output.
31.
32.
33. • 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
34. • Between these capillary loops are connective
tissue phagocytic mesangial cells.
• The blood vessel leading away from the
glomerulus is the efferent arteriole.
35. • 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.
37. • 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.
39. • 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
40. • 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 capillariess
41. • 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
42. • The presence of both divisions of the autonomic
nervous system controls the renal blood vessel
diameter and renal blood flow independently of
autoregulation
