Organs of Urinary system
Kidney function
• Filter 200 liters of blood daily, allowing toxins,
metabolic wastes, and excess ions to leave the body in
urine
• Regulate volume and chemical makeup of the blood
• Maintain the proper balance between water and salts,
and acids and bases
• Gluconeogenesis during prolonged fasting
• Production of rennin to help regulate blood pressure
and erythropoietin to stimulate RBC production
• Activation of vitamin D
Other Urinary system organs function
• Urinary bladder – Hollow Muscular Organ provides a
temporary storage reservoir for urine
• Paired ureters – transport urine from the kidneys to the
bladder
• Urethra – transports urine from the bladder out of the
body
Location & External Anatomy of kidney
Lumbar vertebrae and
rib cage partially
protect
Kidney location and External Anatomy
• The bean-shaped kidneys
• The right kidney is lower than the left because it is
crowded by the liver
• The lateral surface is convex and the medial surface is
concave, with a vertical cleft called the renal hilus
leading to the renal sinus
• Ureters, renal blood vessels, lymphatics, and nerves
enter and exit at the hilus
External Anatomy of the Kidney
The covering of kidney consists of three layers.
The inner layer, the renal capsule,
The middle layer, the adipose capsule, and the
outer, renal fascia.
• CT coverings
• renal fascia: anchors kidneys to abdominal wall
• adipose capsule: cushions kidney
• renal capsule: encloses kidney like cellophane wrap
Kidney location and External Anatomy
Internal Anatomy
• A frontal section shows three distinct
regions
• Cortex – the light colored, granular superficial
region
• Medulla – exhibits cone-shaped medullary
(renal) pyramids
Internal Anatomy
In a typical adult kidney,
the renal medulla is
subdivided into 8 to 15
distinct conical or
triangular structures
known as renal pyramids.
Blood vessels, nerves, and
the ureter connect to the
kidney at a prominent
medial indentation known
as the hilum
Internal Anatomy
Internal Anatomy
Internal Anatomy
• Renal pelvis – flat, funnel-shaped tube lateral to the
hilus within the renal sinus
• The renal pelvis:
• Collect urine draining from papillae
• Empty urine into the pelvis
• Urine flows through the pelvis and ureters to the
bladder
Internal Anatomy
Internal Anatomy
Internal Anatomy
Blood Supply
Blood Supply
• Approximately one-fourth (1200 ml) of systemic cardiac
output flows through the kidneys each minute
• Arterial flow into and venous flow out of the kidneys
follow similar paths
• The nerve supply is via the renal plexus
Blood Supply
correct sequence
starting from the
renal artery
The Nephron
• Nephrons are the structural and functional units that
form urine, consisting of:
• Glomerulus – a tuft of capillaries associated with a renal
tubule
• Glomerular (Bowman’s) capsule – blind, cup-shaped end of
a renal tubule that completely surrounds the glomerulus
• Kidney has over 1 million nephrons
The Nephron
Following is the order of
parts of nephron through
which the fluids moves
from filtration membrane.
1. Renal corpuscle (the
initial blood-filtering
component of a
nephron. It consists of
two structures: a
glomerulus and a
Bowman's capsule)
2. Proximal tubule
3. Loop of henle
4. Distal tubule
5. Collecting duct
Capillary Beds of the Nephron
• Blood pressure in the glomerulus is high because:
• Arterioles are high-resistance vessels
• Afferent arterioles have larger diameters than efferent arterioles
• Fluids and solutes (primarily glucose and amino acids) are forced out
of the blood throughout the entire length of the glomerulus
Two Types of Nephron
• 1. Cortical nephrons – 85% of nephrons; located in the
cortex
• 2. Juxtamedullary nephrons:
•
•
•
•
Are located at the cortex-medulla junction
Have loops of Henle that deeply invade the medulla
Have extensive thin segments
Are involved in the production of concentrated urine
Functions of different parts of the Nephron
Proximal convoluted tubule : Active transport of
sodium; water follows passively
Descending limb of the nephron loop: passively
permeable to water
Ascending limb of the nephron loop: Active
transport of sodium; impermeable to water
Collecting duct : passively permeable to water under
ADH stimulation.
Mechanisms of Urine Formation
1. Glomerular filtration
refers to the
movement of fluid
and solutes from the
glomerular
capillaries into
Bowman’s space.
2. Tubular secretion
refers to the
secretion of solutes
from the peritubular
capillaries into the
nephron.
3. Tubular reabsorption refers to the movement of materials from the filtrate
in the nephron into the peritubular capillaries.
Mechanisms of Urine Formation
Hormonal Control of Kidney Function
• ADH
• Renin
• Is an enzyme hormon
• Secreted by posterior
produced by kidneys,
pituitary
causes production of
• Regulates water reabsorption
angiotensin II that raises
blood pressure
at the distal convoluted
tubule Aldosterone
• Atrial natriuretic
• Produced in adrenal cortex
hormone
• Affects Na+ and Cl- transport
• Produced by heart when
blood pressure increases
in nephron and collecting
• Inhibits ADH production
ducts
• Reduces ability of kidney
• promotes sodium retention
to concentrate urine
and potassium loss from the
blood across: the wall of the
wall of the distal convoluted
tubule?