Excretory System.pptx

The Excretory System /
Urinary System /
Renal System
Presented By:
Mr. Nandish . S
Associate Professor
Mandya Institute of Nursing Sciences

The Excretory system consists of
- Two Kidneys
- Two Ureters
- The Urinary Bladder
- The Urethra

Kidneys:
• They 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 12th Thoracic vertebra to the 3rd
Lumbar vertebra.
• The right kidney is slightly lower than the left because of space
occupied by Liver.
• Kidneys are bean shaped organs, about 11 cm long, 6cm wide, 3cm
thick and weigh around 150 gram.
• A sheath of Fibrous connective tissue (Renal Fascia) encloses the
Kidney.

Relationship / Organs Associated:
Right Kidney:
Superiorly – Right Adrenal Gland.
Anteriorly – right lobe of Liver, Duodenum, & Hepatic flexure of
colon.
Posteriorly – the Diaphragm.
Left Kidney:
Superiorly – Left Adrenal Gland.
Anteriorly – Spleen, Stomach, Pancreas, Jejunum & Splenic flexure of
colon.
Posteriorly – the Diaphragm & Muscles of posterior abdominal wall.

Gross Structure of Kidney
There are three Layers of Tissues while viewing Kidney in
Longitudinal Section.
- An outer Fibrous Capsule.
- The Cortex, a reddish brown layer of tissue below capsule, that
surrounds pyramid.
- The Medulla, inner most layer consisting of pale conical shaped
striated structure called Pyramids. Each pyramid has pointed end
called Papilla.

- Hilum is the concave medial border of kidney, where the renal
blood and Lymph vessels , ureter and Nerves enter.
- Urine formed in Kidney passes through Renal papilla into the
drainage system that begins at Minor Calyx.
- Several Minor calyses merge into Major Calyx.
- Two or three Major calyses combine to form Renal Pelvis, A
hollow funnel shaped structure that narrows when it leaves Kidney
as Ureter.
- Peristalsis and Intrinsic contraction of renal pelvis propels urine to
bladder.

Microscopic Structure
- The kidney contains 1- 2 millions of structural and functional units
called Nephrons.
- It also contains Collecting Ducts transport urine through Pyramid
to the calyses, giving pyramids their striped appearance.
- The collecting ducts are supported by Connective tissue, blood
vessels, Nerves and Lymph vessels.

The Nephron
- It is essentially a Tubule that is closed at One end and opens into
collecting duct at another end.
- The closed or blind end forms cup shaped structure called Glomerular or
Bowman’s Capsule.
- The capsule completely encloses with coiled tuft of capillaries called The
Glomerulus.
- The capsule further continues around 3 cm long and is classified into three
parts.
a) Proximal Convoluted Tubule
b) Medullary Loop (Loop of Henle)
c) Distal Convoluted Tubule, leading into Collecting Duct.

- The Kidneys receive about 20% of cardiac output.
- At Hilum, renal artery divides into smaller arteries and arterioles.
- In cortex, afferent arteriole and arteriole enters each Capsule and
subdivides into cluster of tiny arterial capillaries forming Glomerulus.
- The blood vessels leading away from glomerulus is Efferent arteriole.
- The afferent arteriole has larger diameter than Efferent arteriole, which
increases pressure inside the glomerulus and drives filtration.
- The walls of glomerulus and glomerular capsule consists of single layer
of flattened Epithelial cells.
- The glomerular walls are very permeable to facilitate filtration.
- The walls of remainder of Nephron and collecting duct are formed by
single layer of Simple Squamous Epithelium.

Blood Supply:
Arterial – Renal Artery
Venous Drainage – Renal Vein
Nerve Supply:
Renal Blood vessels are supplied by both Sympathetic and
parasympathetic nerves. The presence of both divisions controls renal
blood flow and renal blood vessel diameter.

Functions:
- Formation of Urine, maintaining water and electrolyte balance.
- Maintaining Acid – Base balance.
- Excretion of waste products.
- Production and secretion of Erythropoietin, the hormone that
stimulates formation of Red Blood Cells.
- Production and secretion of Renin, an enzyme in the long term
control of Blood Pressure.

Ureters:
- They are hollow muscular tubes about 25 – 30 cm long with
diameter of 3mm.
- It is continuous with funnel shaped renal pelvis.
- It travels downwards through the abdominal cavity, behind
peritoneum, passes obliquely through the posterior wall of bladder.
- when the urine accumulates and the pressure in bladder rises, the
ureters are compressed and the openings into bladder are occluded.

Structure :
- Ureter consists of three layers of tissue.
- An outer covering of fibrous connective tissue.
- A Middle muscular layer consisting of interlacing smooth muscle
fibres that form functional unit.
- An inner layer (Mucosa) composed of transitional epithelium.
Function:
They carry urine from kidney to the urinary bladder. Peristaltic
property of muscular layer propels urine along with ureter increase its
frequency with volume of urine produced.

Urinary Bladder
It is a reservoir for urine. It lies in the pelvic cavity. Its size and position vary
depending on the volume of urine it contains.
Structure :
- It is pear shaped and becomes balloon shaped as it fills with urine.
- The posterior surface is the base & bladder opens into urethra at its lowest point
Neck.
- The peritoneum covers only the superior surface, posteriorly it surrounds the
uterus in females and rectum in males.
- Bladder wall is composed of Three layers.
a) The outer layer of loose connective tissue containing blood & lymphatic vessels
and Nerves.

b) The middle layer consisting of interlacing smooth muscle fibres and elastic tissue
arranged in three layers. This is called Detrusor Muscle.
c) The inner mucosa composed of transitional epithelium which permits distension
of bladder.
- When the bladder is empty the inner lining is arranged in folds, called Rugae and
it disappears as bladder fills.
- The bladder is distensible, total capacity is upto 600 ml.
- Three orifices in the bladder wall form triangle or trigone. Upper two orifice on
the posterior wall are openings of ureters and the lower orifice is the opening into
urethra.
- The internal urethral sphincter controls outflow of urine from the bladder.

Urethra
- It is the canal extending from neck of the bladder to the exterior at external urethral
orifice.
- It is longer in males than females.
- Male urethra is associated with both reproductive and urinary system.
- Female urethra is approximately 4 cm long and 6cm in diameter.
- The external urethral orifice is guarded by external urethral sphincter, which is
under voluntary control.
- The wall of female urethra has two main layers : an outer muscle layer and inner
lining of mucosa.
- Outer muscle layer has smooth muscle(involuntary) and outer striated muscle
(Voluntary).
- Inner mucosa is supported by fibro elastic connective tissue containing blood
vessels and nerves.

Structure of Skin
- It is the largest organ in our body and has a surface area about 1.5 to 2 Sq.
Mtr in adults.
- It contains accessory structures like Glands, Hair and Nails.
- It varies in thickness being thickest on the palms of the hand and soles of
the feet.
- There are mainly 2 layers:
a) Superficial layer is Epidermis
b) Below that Dermis.
c) Between the dermis and underlying structures there is subcutaneous layer
composed of Areolar tissue and Adipose tissue.

Epidermis
- It is composed of stratified keratinised squamous epithelium.
- There are no blood vessels or nerve endings in the epidermis.
- There are several layers of cells in the epidermis which extend from deepest
basal layer to superficial stratum corneum.
- The cells of epidermis originate in basal layer, which is made up of
cuboidal, nucleated, highly active epithelial cells that are constantly
dividing.
- As they progress towards surface, their shape and structure gradually
change. By the time they reach skin surface, they are flat, thin, non
nucleated or dead cells.
- Complete replacement of the epidermis takes about a month.

- Hairs, secretions from sebaceous glands and ducts of sweat glands pass
through the epidermis to reach skin surface.
- Upward projections of dermal layer (Papillae) help epidermis to pass and
exchange of nutrients and wastes to the lower part of the epidermis. This
arrangement stabilises the two layers.
- Skin is subject to greater wear and tear.
Ex : palms of hands and soles of feet ( Epidermis is thicker and hairs are
absent)
- Patterns of ridges on the fingertips is unique to every individual and the
impression made by them is “Fingerprint”.

- Colour of Skin is affected by various factors.
a) Melanin a dark pigment derived from amino acid tyrosine and secreted
by melanocytes in the deep germinative layer. Amount of secretion is
genetically determined and the difference in colour is depends on
melanin secretion.
b) Normal saturation of Haemoglobin and amount of blood circulating
gives pink colour to skin. When the oxygen saturation is low, it appears
blue.
c) Excessive levels of bile pigment in blood and carotenes in subcutaneous
fat give the skin a yellowish colour.

Dermis
- It is tough and elastic.
- It is formed by connective tissue and matrix contains collagen fibres.
- Rupture of elastic fibres occurs when the skin is overstretched, resulting in
permanent stretch marks. (Pregnancy)
- Fibroblasts, Macrophages and Mast cells are the main cells found in
Dermis.
- Structures found in the dermis are:
• Small blood and lymph vessels.
• Sensory nerve endings.
• Sweat glands and their ducts.
• Hairs, Arrector pili muscles and sebaceous glands

Blood and Lymph vessels:
Here arterioles supply sweat glands, sebaceous glands, hair follicles and
dermis. Lymph vessels also form a network through out the dermis.
Sensory Nerve Endings:
Sensory receptors are specialised nerve cells sensitive to Touch,
Temperature, Pressure and Pain. They are widely distributed in dermis and receive
information about their environment. This will reach sensory area of cerebrum,
where the sensations are perceived.

Sweat Glands:
These are widely distributed through out the skin. They are most numerous
in Palms of the hands and Soles of the feet, Axillae and Groins.
There are two types of Sweat glands.
- Eccrine Glands : open on to the skin surface through tiny pores. The
sweat produced here is clear, watery fluid.
- Apocrine Glands : open into the hair follicles and become active at
puberty. Bacterial decomposition of their secretions causes unpleasant
odour.
* Their main function is to regulate body temperature.

Hairs:
- These grow outward from hair follicles.
- The hair is formed by multiplication of cells of the bulb (Hair papilla) and
hairs are pushed upwards.
- The part of hair above skin is shaft and remainder is Root.
- Hair colour is genetically determined and depends on amount and type of
melanin present. Hairs turn white, when melanin production by the
follicle stops.

Arrector pili:
- These are the little bundles of smooth muscle fibres attached to the hair
follicle.
- Contraction of Muscle fibres make the hair stand erect and rises the
skin around the hair (Gooseflesh / Goosebumps). It is stimulated by
sympathetic nerve fibres in response to fear and cold.

Sebaceous Glands:
- They consists of Secretory Epithelial cells derived from Hair follicles.
- They secrete an oily antimicrobial substance called Sebum into the hair
follicles. They are most numerous in scalp, face, axillae and groins.
- They are present all over the skin except palms of hand and soles of feet.
- Sebum keeps hair soft, pliable and gives it a shiny appearance.
- It waterproofs the skin, acts as bactericidal and fungicidal agent
preventing infection.
- It also prevents cracking and drying of skin.

Nails
- Human Nails are equivalent to the claws, horns and hooves of animals.
- They are hard, horny keratin plates that protect the tips of fingers and
toes.
- The root of the nail is embedded in the skin and covered by the cuticle,
which forms the hemispherical pale area called Lunula.
- Nail plate is the exposed part that has grown out from the nail bed.
- Finger nails grow more quickly than toe nails.

Functions :
- Protection : deeper and more delicate structures.
- Regulation of body temperature.
- Formation of Vitamin – D.
- Sensation.
- Absorption (Transdermal patches)
- Excretion (Sodium Chloride in sweat)

Composition of Urine
- Urine is clear liquid.
- It is Amber yellow in colour due to the presence of pigment called
Urobilin.
- The specific Gravity may range from 1.002 to 1.037.
- Normal Ph is around 6.2. with a range of 5.5 to 7.0.
- A healthy adult pass urine from 1000 ml to 1500 ml per day.
- The volume of urine produced and specific gravity vary according to
fluid intake and the amount of solute excreted.

Constituents of Urine
Water – 96%
Urea – 2%
Uric acid
Creatinine
Ammonia
Sodium
Potassium 2%
Chlorides
Phosphates
Sulphates
Oxalates

Formation of Urine
- The Kidneys form Urine, which passes to the bladder for storage prior to
excretion.
- The composition of urine reflects the exchange of substances between
nephron and renal capillaries.
- Waste products of protein Metabolism are excreted, water & Electrolyte
levels are controlled & Ph is maintained by excretion of Hydrogen ions.
- Three processes involved in the formation of urine are :
a) Filtration
b) Selective reabsorption
c) Tubular Secretion.

Filtration :
• It takes place through glomerulus and glomerular capsule.
• Water and other small molecules readily pass through and reabsorbed later.
• The fluid filtered from bloodstream into the glomerular capsule is called
Filtrate.
• Blood cells, plasma proteins and other large molecules are too big to filter,
hence they remain in the capillaries.
• Filtration takes place because there is a difference between the blood
pressure in glomerulus and the pressure of filtrate in the glomerular
capsule.

• The volume of filtrate formed by both kidneys in each minute is called
Glomerular Filtration Rate (GFR).
• In a Healthy adult the GFR is about 125 ml / min.
• 180 litres of filtrate formed each day by both the kidneys , with less than
1% excreted as urine (1 to 1.5 litres).
• Renal blood flow and GF is protected by mechanism called
Autoregulation, where renal blood flow is maintained at constant pressure.
• GF is completely depends on blood pressure which fluctuates significantly
depends on Activity, Emotional state, etc.
• Autoregulation operates independently of Nervous system.

Selective Reabsorption
• Most of reabsorption from filtrate back into blood takes place in Proximal
Convoluted Tubule.
• Substances reabsorbed here are water, electrolytes, organic substances like glucose
and amino acids. Some of the reabsorption is passive, but some are actively
transported.
• Only 60 – 70 % of filtrate reaches Loop of Henle. Here Maximum amount of
water, sodium and chloride are reabsorbed.
• Only 15 – 20% of original filtrate reaches Distal Convoluted Tubule.
• More electrolytes are reabsorbed here (Sodium), hence Filtrate entering collecting
Ducts are quite Dilute. Main function of collecting Ducts is to reabsorb water as
much as body needs.
• Reabsorption of Nitrogenous waste products such as Urea, Uric acid and creatinine
is very limited.

Hormones influence Selective Reabsorption
Several hormones play such role, each being regulated negative feedback
mechansim.
- Parathyroid Hormone : It is secreted by Parathyroid gland.it regulates
reabsorption of calcium and phosphate from Distal convoluted Tubule along
with calcitonin.
- Antidiuretic Hormone (ADH): it is secreted by Posterior Pituitory. It
increases water reabsorption from DCT & collecting ducts.
- Aldosterone : it is secreted by adrenal cortex. It increases reabsorption of
sodium and water and excretion of Potassium.
- Atrial Natriuretic Peptide (ANP): It is secreted by Atria of Heart in
response to stretching of Atrial wall. It decreases reabsorption of sodium &
water from PCT and Collecting Ducts.

Tubular secretion
• Some substances like drugs including penicillin, aspirin may not be
entirely filtered out of blood because the molecules are too large to pass
through the filtration pores.
• Such substances are cleared by secretion from peritubular capillaries into
the filtrate within convoluted tubules.
• Tubular secretion of Hydrogen ions is very important in maintaining
normal Blood ph.

Water Balance:
• Source of body water is ingested food and fluid & small amount is
formed by cellular metabolism.
• Water is excreted through urine, expired air, faeces and sweat.
• Amount lost in faeces & expired air is constant. The amount lost in sweat
is adjusted according to environmental and body temperatures.
• The balance between fluid intake and output is controlled by Kidneys.
• The hormones that play major role in water balance are Anti Diuretic
Hormone and Atrial Natriuretic Peptide.

Electrolyte Balance:
Changes in the concentration of electrolytes in body fluids due to
- Body water content
- Electrolyte level.
Sodium & Potassium Balance:
• Sodium is the most common Cat ion in Extra cellular fluid & Potassium is
most common in intracellular cat ion.
• Intake of sodium usually in excess than body needs.
• The amount of sodium excreted in sweat is insignificant unless sweating
is excessive.
• It occurs during Fever, High Environmental Temperature, during sustained
Physical exercises.
• The Renin – Angiotensisn – Aldosterone mechanism maintains the
concentration of sodium and potassium within physiological limits.

pH Balance:
• In order to maintain normal blood Ph, proximal convoluted tubules
secrete hydrogen ions into filtrate, where they combine with buffers.
• bicarbonate forms carbonic acid
(H + HCO3 H2CO3)
Ammonia forms Ammonium
(H + NH3 NH4 )
Hydrogen phosphate forming Dihydrogen phosphate
(H + HPO4 H2PO4 )

• Carbonic acid is converted to carbon dioxide and water where CO2 is
reaborbed and maintains the buffering capacity of blood.
• Hydrogen ions are excreted in the urine as ammonium salts & hydrogen
phosphate.
• Normal Ph of urine depends on diet, time of the day and other factors.

Micturition
 It is the process of discharging urine from the body. The purpose of
micturition is to remove metabolic products and toxic wastes filtered
from kidneys.
 Micturition is a complex mechanism that involves coordination by the
sympathetic, parasympathetic & somatic nervous system.
 Normal muscle tone, absence of physical obstruction, psychological
inhibition and other factors play a role in this process.

Mechanism :
 It is a complex and highly distributed process involving pathways at
multiple levels of brain, spinal cord and peripheral nervous system along
with multiple Neurotransmitters.
 At basic level, the micturition reflex is triggered when the bladder fills
with urine.
 The Detrusor muscle remains relaxed until the bladder fills to about 250
ml of urine.
 As the bladder fills, the Detrusor muscle contracts, which increases
pressure inside bladder and stimulating stretch receptors in Detrusor
muscle exciting parasympathetic fibres to relay information to sacral
nerves of Spine.

 Parasympathetic fibres help convey the bladder’s degree of fullness.
 Within Spine, this information is integrated and relayed to the brain
through two different sets of neurons.
 Then the brain determine the urgency & responds by sending command
signals back to the bladder to either hold on or to void.
 If the response is to void, Parasympathetic Motor neurons, cause
contraction of Detrusor muscle, which causes intra – bladder pressure to
increase.
 It results in opening of internal sphincter, that allow urine to enter the
bladder neck and flow into the urethra.

 Simultaneously somatic motor neurons inhibits Pudendal Nerve which
causes external sphincter to relax, allowing urine to expelled from body.
 Typically around 50 ml of urine remains in the bladder after a voluntary
void in the normal healthy Adult.

Glomerular Filtration Rate:
- Volume of plasma filtered in unit time.
- It is approximately 180 litres / day.
- About 99% of the filtrate is reabsorbed.
Influencing Factors:
- Blood pressure & Blood flow.
- Obstruction to urine flow.
- Hormonal regulation
a) Renin – Angiotensin c) Aldosterone
b) Anti Diuretic Hormone d) ANP

JuxtaGlomerular Apparatus
- Juxtaglomerular cells are present in the walls of afferent arteriole.
- Macula Densa in final portion of Loop of Henle monitor Sodium,
Chloride concentration and water level.
- It control blood flow into the Glomerulus.
- Control Glomerular Filtration.

Regulation of Body Temperature:
• Core body temperature remains constant around 36.8 to 37 degree C.
• In normal health, variations limited to 0.5 to 0.75 degree C.
• Temperature raises slightly in the evening, during exercise and in
women just after ovulation are considered normal.
• To maintain this constant temperature, A negative feedback system
regulates balance between heat produced and heat lost.

Heat Production:
• When metabolic rate increases, body temperature rises and when it
decreases, body temperature falls.
• Most active organs produce mmost heat. The principal organs involved
are ;
- Skeletal Muscle contraction, which produce large amount of heat.
- Liver is metabolically very active. It generates heat as by-product of
metabolism.
- The digestive organs generate heat during peristalsis and chemical
reaction.

Heat Loss:
- Most heat loss from body occurs through skin.
- Small amount of heat lost in expired air, urine and faeces.
- Heat lost through the skin can be regulated and heat lost through
other routes cannot be controlled.
- Heat loss through skin is affected by difference between body and
environment temperature, body surface area and type of clothes
worn.

Mechanisms of Heat Loss:
There are four mechanisms.
1) Radiation : it is the most common and main mechanism of heat loss. It
occurs when exposed parts of body radiate heat away from the body.
2) Evaporation : when body is cooled as body heat converts water in sweat
to water vapour.
3) Conduction : when clothes and other objects in direct contact with the
skini take up heat.
4) Convection : when air passing over exposed parts body is heated and
rises and cool air replaces it, setting up convection currents.

Control of body temperature:
• Temperature regulation centre is in the hypothalamus.
• When temperature decrease, it sends nerve impulse to
- Arterioles in dermis, which constrict, decreasing blood flow to skin.
- Skeletal muscles stimulating shivering.
• When the heat conserved, temperature rises and feedback mechanism will
switch off.
• When the temperature rises, sweat glands secret sweat on skin surface.
Evaporation of sweat cools body.
• Loss of heat from body through evaporation and expired air continuous and
comes under insensible heat loss accompanied by insensible water loss.

Alterations in Diseases:
1) Glomerulonephritis:
It is an inflammatory condition, which causes inflammation and impairment
of glomerular filtration.
Classification :
Based on extent of Damage :
- Diffuse – affecting all glomeruli.
- Focal – affecting some glomeruli.
Based on Appearance :
- Proliferative – increased number of cells in glomeruli.
- Membranous – thickening of basement membrane of glomeruar
epithelium.

Signs / Symptoms :
- Oliguria
- Haematuria
- Asymptomatic proteinuria
- Anuria
- Dysuria
- Glycosuria
- Ketonuria
- Nocturia
- Polyuria
- Incontinence

2) Nephrotic Syndrome:
This is not a disease, but is an important feature in several diseases.
It is characterized by
• Marked proteinuria
• Hypoalbuminaemia
• Hyperlipidaemia
• Generalised oedema.
When glomeruli are damaged, permeability of glomerular epithelium
increases and plasma proteins pass through into the filtrate.

It occurs in number of diseases like
- Most forms of glomerulonephritis
- Diabetic Nephropathy
- Systemic Lupus Erythematosus
- Infections (Hepatitis B)
- Treatment (Penicillamine)

3) Diabetic Nephropathy:
It is a complication of diabetes mellitus, develops in an individual due to
severe, long standing hyperglycaemia.
It is characterised by :
 Progressive damage of glomeruli & proteinuria
 Ascending infection leads to acute pyelonephritis
 Arteriosclerosis of renal arteries
 Chronic kidney disease.

4) Acute Pyelonephritis:
It is an acute bacterial infection of the renal pelvis & calyses, which spreads to
kidney and causes small abscess.
It is caused by :
 Ascending infection – upward spread of bacteria from urinary bladder is the
most common cause.
 Blood borne infection - kidneys are more susceptible for this condition due
to their large blood supply ( 20% of cardiac output).
Both of them leads to suppuration and destruction of Nephrons.

5)Chronic Kidney Disease:
 It is also called as chronic renal failure.
 Chronic kidney disease is confirm when GFR has fallen to around 20 %
of normal.
 Onset is slow, asymptomatic and progress irreversibly.
 The main causes are : diabetes mellitus, glomerulonephritis, hypertension.
The main clinical features are :
- Polyuria
- Acidosis
- Electrolyte imbalance
- Anaemia

6) Renal Calculi:
 Stones form in the kidney & bladder when urinary constituents like
oxalate and phosphate salts are precipitated.
 They are recurrent , common in males after the age of 30 years.
 Most of them originate in collecting tubules or renal papillae and then
pass to renal pelvis.
Predisposing factors are :
• Dehydration
• Raised pH of Urine
• Infection
• Metabolic conditions (Hyperparathyroidism)

7) Tumours of Kidney:
Nephroblastoma (Wilm’s Tumour)
It is most common malignant tumour in children under 10 years, usually
occurs in the first 4 years.
Clinical features include :
o Hematuria
o Hypertension
o Abdominal pain
o Intestinal obstruction

8) Urinary Tract Infections (UTI)
They are Infection of the any part of Urinary tract. They can spread upwards
and cause kidney damage.
 Ureteritis : inflammation of the ureter.
 Urethritis : inflammation of urethra.
 Cystitis : inflammtion of the bladder.

Excretory System.pptx

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