This document provides information about the excretory system and its organs. It focuses on the structure and function of the kidneys. The kidneys filter waste from the blood to produce urine through processes of filtration, reabsorption, and secretion. Urine is transported from the kidneys to the urinary bladder via ureters. The bladder stores urine until urination. The kidneys play key roles in regulating water balance, electrolyte levels, blood pressure, and producing hormones.

1. By
Meghsham Gholap
PIMS,CON

2. Introduction
 As a normal consequence of being alive, every cell in the
body produces metabolic wastes includes excess water and
salts, carbon dioxide and urea. Urea is a toxic compound that
is produce when acids are used for energy. The process by
which these metabolic waste are removed from the body is
called excretion.
 The job of the excretory system is to remove various
produced by the body. The removal is known as excretion. It
is important for the body to remove these various waste, also
known as toxic, because toxic build up can lead to severe
death.

3.  About sixty percent of body contains water. A portion of the
water is in the tissues and cells. The water contains salt. the
salt needs to be kept at the right concentrations. If there is
little salt the body feeds it more, if there is too much salt the
body gets rid of the salt not needed. This is the task of the
two Kidneys.

4. Organs of excretory system
1. Kidney -2
2. Ureters- 2
3. Urinary bladder – 1
4. Urethra -1

5. Kidney
 The paired kidneys are Bean- shaped, reddish brown organ
 They are located just above the waist between peritoneum and the
posterior wall of abdomen one on either sides of the vertebral
column
 It is 10-12 cm long, 5-7 cm wide and 3 cm thick weighs about 125-
170 g
 Blood enters each kidney through renal artery and leaves it through
renal vein
It is surrounded by three layer of tissue
i. The deep layer is renal capsule
ii. The middle layer is adipose capsule
iii. The superficial layer is renal fascia

9. Beneath the coat are:
1. Renal cortex: outer reddish brown coloured region
containing more than a million of tubes called nephrons
(functional units of the kidney, tiny biological filters)
2. Renal medulla: middle layer consisting several
triangular renal pyramids and renal columns in between.
It contains ducts that transport urine from nephron to the
renal pelvis
3. Renal pelvis: inner central chamber or cavity receiving
urine from nephrons

10. Blood supply
 Normal renal blood flow is 1100 to 1200 ml/min
 Blood supply is from renal artery
Arterial Supply:
 Renal arteries which are the direct branches of abdominal aorta
& are large in size.
Venous Drainage:
 Renal veins, ends in inferior vena cava. The left renal vein is
longer than the right.
Nerve Supply:
 Sympathetic fibers derived and parasympathetic fibers from
vagus nerve.
Lymphatic drainage:
 into lateral aortic nodes.

11. functions
The kidneys do major work of the urinary system
1. Regulation of blood ionic composition- helps in the blood
level of several ions, sodium (Na+), potassium (K+),
calcium (Ca+), Chloride (CI¯)
2. Regulation of Blood pH- the kidney excrete a variable
amount hydrogen ions into blood and conserve bicarbonate
ions
3. Regulation of blood volume- the kidney adjust blood
volume by conversing or eliminating water in the urine
4. Enzymatic regulation of blood pressure- it secrets
enzyme rennin which indirectly cause increase in blood
pressure

12. 5. Maintenance of blood osmolarity–by separately
regulating loss of water and loss of solutes in the urine it
maintain constant blood osmolarity
6. Production of hormone-produces calcitriol helps
regulates calcium homeostasis, and erythropoietin
stimulates the production of blood cells
7. Regulation of blood glucose level-by glycogenesis
8. Excretion of wastes and foreign substances-by forming
urine, the kidney helps to excrete wastes

13. Functions
1. Formation of urine
2. Excretion of metabolic waste products
3. Maintains water balance
4. Regulates acide base balance
5. Secretes renin and erythropoietin
6. It forms active form of vitamin D
7. It secrets prostaglandin

14. URETERS
• The ureters are two tubes 10-12 inches in length and one
half inch in diameter.
• They are composed of smooth muscle tissue, and they
extend from the renal pelvis of each kidney to the
posterior portion of the urinary bladder.
• Their function is to conduct urine from the kidneys to the
urinary bladder.
• At the junction where the ureters join the bladder, a
valve-like structure prevents the urine from flowing back
to the ureters.

16. URINARY BLADDER
• The bladder is a muscular bag-like organ that is located
in the front center of the pelvic cavity.
• Its purpose is to store and expel urine.
• Normal storage capacity is about 250 ml., although it can
hold up to 1000 ml.
• When the bladder fills, nerves in the muscular wall are
stimulated, thus the urge to urinate.
• Micturition and to void are terms that also mean
urination

18. Nephron
 It is the structural
and functional
unit of kideny
 There are 1
million nephron
in kidney

20. Urine formation
Urine:
 Yellowish fluid contains water, nitrogenous wastes, ions,
and small amount of water and other substances
 It is produced by kidneys 1-3 liters/ day depending on
how much fluid ingested
Urination:
 Urine flow from the body to outside

21. Urine formation (blood filtration) involves 3 processes:
1. Filtration (glomerular filtration)
2. Reabsorption (tubular reabsorption)
3. Secretion (tubular secretion)

22. Glomerular filtration
Beginning of the process.
 A process by which the blood courses through the
glomeruli, much of its fluid, containg both useful
chemicals and dissolve waste materials, soaks out the
blood through membranes where it is filtered and then
flows into Bowman’s capsule.
Glomerular Filtration Rate
 is the amount of fluid filtered from the blood into the
capsule each minute
 It is 125 ml/min and 180 lit/day

23. Tubular Reabsorption
 A movement of substances out of the renal tubules back
into the blood capillaries located around the tubules
(peritubular capillaries).

24. Tubular Secretion
 Disposing of substances not already in the filtrate (drugs)
 Eliminating undesirable substances that have been
reabsorbed by passive processes (urea and uric acid)
 Ridding the body of excess potassium ions
 Controlling pH

25. Skin
 Skin is the largest organ of the body.
 The average thickness of the skin is about 1-2 mm.
The skin is made up of two layers:
1. Outer epidermis
2. Inner dermis

27. Epidermis
 It is the outer layer of skin
 It dose not have blood vessels
 The nutrition is provided to epidermis by the caplillaris of
dermis
 It is formed by stratified epithelium which consist of 5 layers
1. Stratum corneum
2. Stratum lucidum
3. Stratum granulosum
4. Stratum spinosum
5. Stratum germinativum

28. 1. Stratum corneum – it is the outer most layer which consist
of dead cells.
2. Stratum lucidum – it is made up of flattened epithelial
cells.
3. Stratum granulosum – it is a thin layer with 2-5 rows of
flattened cells.
4. Stratum germinativum - it is a thick layer, new cells are
constantly formed by mitotic division. The newly formed
cells move toward Stratum corneum .

29. Dermis
 Dermis is the inner layer of the skin.
 It is much thicker than epidermis
 It is the connective tissue layer made up of dense and
collagen fibers
 The collagen fibers contain enzyme collagenase, which is
responsible for wound healing
 Dermis is made up of two layers
1. Superficial papillary layer
2. Deeper reticular layer

30. Subcutaneous layer
 Which is deep to the dermis
 This connective tissue layer which is not part of skin.
 It function as a loose binding tissue that unites upper layer
of the skin to deeper structures.

31. Accessory structure of skin
1. Hair follicles with hair
2. Nails
3. Sweat gland
4. Sebaceous gland
5. Mammary gland

32. Colure of skin
1. Pigmentation of skin- cells of skin contain brown
pigment called melanin. The skin becomes dark when
melanin content increases
2. Hemoglobin in the blood- when Hb content decreases
the skin becomes pale. During cyanosis the skin
becomes bluish.

33. Functions of Skin
1. Protective function- bacteria, mechanical blow, UV rays
2. Sensory function- touch, pain, pressure, temperature
3. Storage function- fat, water, sugar.
4. Synthetic function- vitamin D
5. Regulation of body temperature- heat loss, sweat
6. Regulation of water and electrolyte balance-sweat
7. Excretory function
8. Absorptive function
9. Secretory function- sebum to keep skin smooth

34. Regulation of body temperature
 The body temperature is regulated by hypothalamus
 Hypothalamus has two centers which regulates body
temperature
1. Heat loss center- This center is situated in preoptic nucleus
of anterior hypothalamus. Neurons in preoptic nucleus are
heat sensitive which are called thermoreceptors.
Stimulation of it result in cutaneus vasodilatation and
sweating
2. Heat gain (production) center – it is situated in posterior
hypothalamic nucleus, stimulation of this shivering.

35. Mechanism of temperature regulation
When body temperature increases
 It brings back to normal by two mechanisms
1. Promotion of heat loss
i. It stimulates sweat gland and increases secretion of sweat.
ii. Cutaneous vasodilatation causes excess sweating.
2. Prevention of heat production – by inhibiting the mechanism
production such as shivering and metabolic reactions

36. When body temperature decreases
 It brought back to normal by two mechanisms
1. Prevention of heat loss- constriction of cutaneous blood
vessels by increasing vasomotor tone. The blood flow to the
skin decreases and so the heat loss is prevented.
2. Promotion of heat production – by shivering and increased
metabolic reactions