Chapter 13 - Urinary System -dcsd Copy.pdf

CHAPTER – 13
URINARY SYSTEM
BIJI JOSE

Urinary system is the main
excretory system of the
body. It consists of
1. Two kidneys
2. Two ureters
3. Urinary blader
4. Urethra
The nitrogenous wastes are
removed from the body by
the excretory system.

ANOTOMY AND PHYSIOLOGY OF URINARY SYSTEM
1. KIDNEYS
➢ Kidneys are been shaped structures present in the
abdominal cavity
➢ It is reddish brown in colour.
➢ The right kidney is placed lower than the left kidney.
PISITION OF THE KIDNEYS
➢ The kidneys extended from the level of last thoracic
vertebra to the 3rd lumbar vertebra.
➢ The right kidney is smaller than the left kidney.
➢ Each kidney measure 11 cm in length ,5 cm in width and
weight about 150 gm.

STRUCTURE OF KIDNEYS
➢ The outer layer of the kidney is covered by 3 layers of
supportive tissues namely
➢ Renal fascia.
➢ Perirenal fat capsule.
➢ Fibrous capsule.
➢ The longitudinal section of kidney reveals
➢ An outer cortex
➢ Inner medulla
➢ Pelvis

➢The medulla is divided in to a few conical tissue masses
called medullary pyramids or renal pyramids.
➢The part of cortex that extends in between the medullary
pyramids is the renal columns of Bertini.
➢The centre of the inner concave surface of the kidney has a
notch called the renal Hilum.
➢The inner hilum is a funnel shaped space called the renal
pelvis with projection called Calyces.
➢The walls of the calyces, pelvis and ureter have smooth
muscles.
➢The calyces collect the urine, which is stored in the urinary
blader, which is opens in to the urethra through which urine
is expelled out.

2. URETERS
➢ It is the duct which carries urine from the kidney to blader.
➢ It is a tube like structure, the length is 26 cm.
➢ It is a thin muscular tubes emerging out from the hilum.
➢ Urine enters the ureter from the renal pelvis and is conducted
along the ureter by peristaltic movements of its walls.
➢ The ureters carry urine from kidney to urinary blader.
➢ The ureter is made of
➢ 1. Outer fibres layer.
➢ 2. Middle muscular layer.
➢ 3. Inner mucus layer.

3. URINARY BLADDER
➢ It is appear shaped muscular sac which act as a reservoir
of urine.
➢ It lies in the pelvic activity.
➢ The lowest part of bladder is called as base and the upper
part is called Fundus.
➢ Blader has 3 openings.
2 for ureters
1 for urethra
➢ The triangle are between these openings is the trigone of
the blader.

➢ Bladder is made of 4 layer
1. Outer serous coat
2. Muscular coat
3. Sub- mucous coat
4. Mucous lining made of transitional epithelium.
➢ The bladder is controlled by pelvic nerves and sympathetic
fibres from hypogastric plexus.
➢ It stores urine temporarily.

4. URETHRA
➢ It is a membranous tube, which urine passes from the
blader to the out side.
➢ The urethral spincters keep the urethra closed and opens
only at the time of micturition (urination).
BLOOD SUPPLY TO KIDNEY
➢ Kidneys are supplied by renal arteries which are branches
of abdominal aorta.
➢ Venous blood of kidney is drained by renal veins which
open into inferior vena cava.

STRUCTURE
➢ Microscopically the kidneys are made up of a number of
structural and functional units called nephrons.
➢ There are about one million nephrons in each kidney.
➢ A nephron consists of 2 parts
1. Malphigianbodies
2. Renal tubules.

1. MALPHIGIAN BODIES
It is made of
1. An upper expanded end of the renal tubule called
Bowman’s capsule.
2. A bunch of capillaries called glomerulus which are
packed in Bowman’s capsule.
➢ The malphigian bodies are present in the cortex.

2.RENAL TUBULES
They consists of 4 parts
1. Proximal convoluted tubule situated in the cortex.
2. Loop of henle presented in the medulla
3. Distal convoluted tubule present in the cortex.
4. Collecting tubules (duct) present in the medulla and open in
to the pelvis of kidney.

1. Proximal convoluted tubule - situated in the cortex.
▪ From glomerulus blood passed in to PCT.
▪ The maximum reabsorption takes place in the PCT.
▪ The reabsorption in the PCT is facilitated by the lining of simple
cuboidal epithelium
▪ PCT maintains the electrolyte and acid base balance of the body
fluids.
2. Loop of henle - presented in the medulla
▪ It has 2 ,Descending and an Ascending limb, both show different
permeability.
▪ The descending limb of loop of henle is permeable to electrolyte
but impermeable to water.

▪ While ascending limb of loop of henle is permeable to water but
impermeable to electrolyte
3. Distal convoluted tubule - present in the cortex
▪ It is the last part of the nephrone, connects and empties its
content in to collecting duct
▪ It maintain the Ph and sodium ,potassium level in the blood.
4. Collecting tubules (duct)- present in the medulla and open in
to the pelvis of kidney.
▪ it is the long strait tube h+ and k+ ions are secreted and maintain
the electrolyte balance of the blood
▪ This is the region the maximum reabsorption of water takes
place to produce concentrated urine.

FUNCTIONS OF KIDNEYS
❑Excretion of water and waste products of protein
metabolism.
❑Excretion of excess salt.
❑Excretion of harm full substances, drugs and toxins.
❑Regulation of PH of blood.
❑Maintains fluid and electrolytes balance in our body.
❑Maintains the osmotic pressure in blood and tissue.
❑Helps to retain the plasma constituents like glucose and
amino acids.
❑The nitrogenous wastes are removed from the body.

PHYSIOLOGY OF URINE FORMATION
Urine formation involves 3 main processes.
1. Glomerular filtration
2. Tubular secretion
3. Tubular reabsorption
1. GLOMERULAR FILTRATION
✓ The 1st step in the urine formation is the filtration of blood,
that takes place in the glomerulus.
✓ Blood is composed of large quantities of water ,colloidal
proteins, sugar, salt and nitrogenous products.

✓ The filtration of blood takes place in the glomerulus called
glomerular filtration.
✓ It is a passive process.
✓ The fluid leaves from glomerular capillaries are called
glomerular filtrate.
✓ It enters in the Bowman’s capsule.
✓ From their fluid is entered in to the proximal convoluted
tubule (PCT).

2. TUBULAR SECRETION
It is an active process which occurs in the convoluted tubules.
Substances such as H+, K+ NH4
+, creatinine and organic acids
are eliminated by this process.
Some drugs like penicillin are excreted by tubular secretion.

3. TUBULAR REABSORPTION
✓ The rate of glomerular filtration is about 100ml/ minute.
✓ About 6 litres of glomerular filtrate can be formed in one
hour.
✓ The volume of urine eliminated per day is only about 1.5
litres.
✓ 99% of glomerular filtrate is reabsorbed.
✓ Reabsorption of water occurs in the convoluted tubules
and collecting tubules after 3 process fluid is converted in
to urinary blader through ureter.

REABSORPTION
PROXIMAL CONVOLUTED TUBULE (PCT)
In the PCT----- glucose, lactate, amino acids, Na+ and water
is reabsorbed.
Sodium is reabsorbed by active transport.
Urea and uric acid are also reabsorbed.
DESCENDING LIMB
Water , Na+, Cl-
are reabsorbed.

ASCENDING LIMB OF LOOP OF HENLE’S
Na+, Cl-, K+ are reabsorbed.
DISTAL CONVOLUTED TUBULE
Potassium, sodium, chlorine, water, bicarbonate, and
hormone are reabsorbed.
COLLECTING DUCT
Water, potassium, sodium are reabsorbed.

RENIN- ANGIOTENSIN SYSTEM
▪ The granular cells secret an enzyme called renin.
▪ Glomerular blood flow and glomerular filtration rate can
activate JG (Juxta glomerular) cells to release renin.
▪ Which convert Angiotensinogen (plasma protein) to
Angiotensin- I.
▪ Angiotensin converting enzyme (ACE) convert Angiotensin- I to
Angiotensin- II.
▪ Angiotensin –II stimulate Na+ reabsorption in the proximal
convoluted tubule.

▪ Angiotensin –II stimulates adrenal cortex to secret aldosterone.
▪ In the adrenal gland Angiotensin –II is converted in to
Angiotensin –III.
▪ Aldosterone causes reabsorption of Na+and K+.
▪ Inhibition of aldosterone increases urine out put.
▪ This mechanism is know as Renin- Angiotensin system.

CLEARANCE TEST AND MICTURITION
MICTURITION
The process of release of urine from the blader is called
micturition or urination.
Urine formed by nephrons and it is accumulate in the
bladder.
The stretch receptors are present in the urinary bladder.

When urine filled in the bladder this receptors stimulated
and stretching of its wall.
The micturition occurs due to contraction of the spincter.
The external spincters are open and the urine is expelled
out.
The capacity of blader is 170-230 ml of urine.

COMPOSITION OF URINE
The volume of urine 1-2 lit. daily.
The colour is pale amber .
The PH is 6.
Specific gravity is 1010 to 1025.
Urine consists of
1. water – 96%
2. urea -- 2%
3. uric acid and salt – 2%

CLEARANCE TEST
There are 3 types of renal clearance test
1. Blood creatinine level
2. Creatinine clearance
3. Blood urea nitrogen levels

1. BLOOD CREATININE LEVEL
✓ Creatinine blood test is the measures of the level of
creatinine in the blood.
✓ This test is done to see how well your kidneys are
working.
✓ Creatinine is a chemical waste product of creatine.
✓ If kidney function is not normal the creatinine level in
blood will increase.
NORMAL VALUE
0.7 to 1.3 mg/dl for men
0.6 to 1.1 mg/dl for women
Women have lower creatinine level than men.

2. CREATININE CLEARANCE
Creatinine is a nitrogenous waste product formed from the
metabolism of creatine in skeletal muscle.
This test is used as a kidney function test .
Creatinine clearance mg of creatinine excreted/minute UV
mg of creatinine per ml of blood P
U – mg of creatinine /100 ml of urine
P --- mg of creatinine / 100 ml of blood
V --- ml of urine excreted / minute.
Normal Urinary creatinine in male -14 to 26 mg / kg / day
Normal urinary creatinine in female – 11 to 20 mg/ kg / day

▪ Plasma creatinine increases in exercise ,high protein, renal
artery stenosis and decreased renal function.
▪ Plasma creatinine decreases in pregnancy starvation and
patients taking corticosteroids.
▪ Urinary creatinine increases in exercise, acromegaly,
gigantism, infections and hypothyroidism.
▪ Urinary creatinine decreases in hyperthyroidism, anaemia,
paralysis, inflammatory diseases of muscles and leukaemia.
3. BLOOD UREA NITROGEN (BUN)
➢ Urea is the main waste product of protein breakdown , is
eliminated by the kidneys.
➢ This test is used to measure the presence of urea in blood
used to assess the renal function.

The normal blood urea =15 to 45 mg/dl.
The bun is lower in pregnancy, liver disease and protein
malnutrition is occur.
The bun is high some pathological conditions such as
ulcerative colitis, severe burns, cardiac failure, diabetic
coma, acute glomerulonephritis, chronic pyelonephritis,
renal tuberculosis, stones in urinary tract, tumours of
bladder and enlargement of prostate.

DISORDERS
1. RENAL FAILURE
➢ It is failure of the kidneys to excrete wastes.
➢ As a result to accumulation of urea with marked
reduction in the urine output.
Renal failure is of 2 types.
1. Acute renal failure --- In this case the kidney stops its
function, chances for recovery.
2. Chronic renal failure ----- In this case is a progressive loss
of function of nephrons which gradually decreases the
function of kidneys.

2. URINARY TRACT INFECTION
a. URETHRITIS ---- Inflammation of urethra.
b. CYSTITIS ----- Inflammation of urinary bladder.
c. PYELITIS ----- Inflammation in pelvis of kidney due to
infection.
3. UREMIA
➢ It is a condition of abnormally high levels of waste
products in the blood.
➢ It is characterised by increase in urea, non-protein
nitrogenous substances like uric acid and creatinine in
blood.

4. RENAL CALCULI
➢ It is due to the accumulation of crystals of salts of sodium
oxalates and certain phosphates.
➢ It is also called renal stone or kidney stone or
nephrolithiasis.
➢ It is the formation of hard stone like masses in the renal
tubule of renal pelvis.
5. GLOMERULONEPHRITIS
It is also called Bright’s disease and it is an inflammation
of the glomeruli of both kidneys.

6. POLYUREA
➢ Secretion of large quantities of urine.
5. ANUREA
Failure of the kidneys to produce urine.

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