By:M. Thiru murugan Unit – 8: Structure and functions of the kidney, ureters, urinary bladder and urethra Formation and composition of urine. Fluid and electrolyte balance Structure and functions of the skin. Regulation of the body temperature. Excretory system: The excretory system is performs the function of excretion It is the process of removing the wastes There are several parts of the body that are involved in this process such as sweat glands, the liver, the lungs and the kidney system Kidney: The kidneys are a bean-shaped organs - found abdominal cavity, just below the rib cage. The right kidney is slightly lower than the left because of the position of the liver. Every human has two kidneys. Diagram of Renal System Structure of kidney: Kidney consist of 3 basic parts Renal cortex (outer layer ) Renal medulla (inner layer ) Renal pelvis. Renal cortex: The renal cortex is the outer layer of the kidney, it is covered with capsule Erythropoietin a hormone is produced in the renal cortex (Erythropoiesis) Renal medulla: Renal medulla is the inner layer of the kidney. The medulla consists of multiple pyramidal tissue masses, called the renal pyramids, which are triangle structures that contain a network of nephrons Renal pelvis: The renal pelvis contains the hilum. The hilum is the concave part of the bean-shape where blood vessels and nerves enter and exit the kidney It is also the point of exit for the ureters carry urine away from the kidney Both of the ureters supply the urine into urinary bladder, From there, urine is expelled through the urethra and out of the body. The blood arrives at the kidney via the renal artery, renal veins collect deoxygenated blood Nephron: The nephron is the structural and functional unit of the kidney. It is composed of renal corpuscle and a renal tubule. Parts of Nephron: Renal corpuscle (glomerulus within bowman's capsule) Proximal convoluted tubule Intermediate tubule (loop of Henle) Distal convoluted tubule Collecting ducts 1. The Glomerulus: The glomerulus is receives blood supply from an afferent arteriole of the renal circulation. Here, fluid and solutes are filtered out of the blood and into the space made by Bowman’s capsule. A group of specialized cells known as juxtaglomerular apparatus (JGA) are located around the afferent arteriole where it enters the renal corpuscle. The JGA secretes an enzyme called renin, it is involved in the process of blood volume homeostasis (Bp). 2. Proximal Convoluted Tubule: The proximal tubule is the first site of water reabsorption into the bloodstream, and the site where the majority of water and salt reabsorption takes place. 3. The Loop of Henle: The loop of Henle is a U-shaped tube that consists of a descending limb and ascending limb. It transfers fluid from the proximal to the distal tubule 4. Distal Convoluted Tubule: The distal convoluted tubule is the final site of reabsorption in the nephron. 5. Collecting Duct: The collecting duct

1. By:
M. Thiru murugan
The Excretory system

2. Unit – 8:
a) Structure and functions of the kidney, ureters,
urinary bladder and urethra
b) Formation and composition of urine.
c) Fluid and electrolyte balance
d) Structure and functions of the skin.
e) Regulation of the body temperature.

3. Excretory system:
• The excretory system is performs the function of excretion
• It is the process of removing the wastes
• There are several parts of the body that are involved in this process
such as sweat glands, the liver, the lungs and the kidney system
Kidney:
• The kidneys are a bean-shaped organs - found abdominal cavity,
just below the rib cage.
• The right kidney is slightly lower than the left because of the
position of the liver.
• Every human has two kidneys.

4. Diagram of Renal System

5. Structure of kidney:
• Kidney consist of 3 basic parts
1. Renal cortex (outer layer )
2. Renal medulla (inner layer )
3. Renal pelvis.
Renal cortex:
• The renal cortex is the outer layer of the kidney, it is covered with capsule
• Erythropoietin a hormone is produced in the renal cortex (Erythropoiesis)
Renal medulla:
• Renal medulla is the inner layer of the kidney. The medulla consists of multiple
pyramidal tissue masses, called the renal pyramids, which are triangle
structures that contain a network of nephrons

6. Renal pelvis:
• The renal pelvis contains the hilum.
• The hilum is the concave part of the bean-shape where blood vessels and
nerves enter and exit the kidney
• It is also the point of exit for the ureters carry urine away from the kidney
• Both of the ureters supply the urine into urinary bladder,
• From there, urine is expelled through the urethra and out of the body.
• The blood arrives at the kidney via the renal artery, renal veins collect
deoxygenated blood

7. Functions of kidney;
1.Formation of urine
2.Controlling acid-base balance.
3.Controlling water balance.
4.Maintaining electrolyte
balance.
5.Removing toxins
6.Removing waste products
7.Controlling Bp.
8.Producing the hormone
erythropoietin.
9.Red blood cell production,
10.Activating vitamin D.
Renal pyramids
Capsule
Diagram :

8. Nephron:
• The nephron is the structural and functional unit of the kidney.
• It is composed of renal corpuscle and a renal tubule.
Parts of Nephron:
1. Renal corpuscle (glomerulus within bowman's capsule)
2. Proximal convoluted tubule
3. Intermediate tubule (loop of Henle)
4. Distal convoluted tubule
5. Collecting ducts

9. Diagram of nephron:
1
2
3
4
5
Renal corpuscle

10. 1. The Glomerulus:
• The glomerulus is receives blood supply from an afferent arteriole of the
renal circulation.
• Here, fluid and solutes are filtered out of the blood and into the space made
by Bowman’s capsule.
• A group of specialized cells known as juxtaglomerular apparatus (JGA) are
located around the afferent arteriole where it enters the renal corpuscle.
The JGA secretes an enzyme called renin, it is involved in the process of
blood volume homeostasis (Bp).
2. Proximal Convoluted Tubule:
• The proximal tubule is the first site of water reabsorption into the
bloodstream, and the site where the majority of water and salt
reabsorption takes place.

11. 3. The Loop of Henle:
• The loop of Henle is a U-shaped tube that consists of a descending
limb and ascending limb. It transfers fluid from the proximal to
the distal tubule
4. Distal Convoluted Tubule:
• The distal convoluted tubule is the final site of reabsorption in the
nephron.
5. Collecting Duct:
• The collecting duct is similar in function to the distal convoluted
tubule. After passage through the collecting duct, the fluid is
brought into the ureter, where it leaves the kidney as urine

12. Function of nephron:
• The Nephron uses 4 mechanisms to convert blood into urine through
filtration, reabsorption, secretion, and excretion.
• Regulates water and soluble substances in the blood by filtering the
blood
• Reabsorbing what is needed
• Excreting the rest as urine.
• Its function is vital for homeostasis (homeostasis is a healthy
maintenance) of blood volume
• Maintain blood pressure,
• Maintain plasma osmolality (measurement of the different components
in plasma.)

13. Ureters:
• Each ureter is a small tube, about 25 cm long, that carries urine from
the renal pelvis to the urinary bladder
Diagram of ureters:

14. Urinary Bladder:
• The urinary bladder is a temporary storage reservoir for urine. It is located in the
pelvic cavity.
• The size and shape of the urinary bladder varies with the amount of urine it contains
and with the pressure it receives from surrounding organs.
Structure:
• There is a triangular area, called the trigone, formed by 3 openings in the floor of
the urinary bladder.
• Two of the openings are from the ureters
• The third opening of the trigone, is the opening into the urethra.
• A band of the detrusor muscle covers this opening to form
the internal urethral sphincter.
Function:
• the bladder stores urine, allowing urination to be infrequent and controlled

15. Diagram of urinary bladder:

16. Urethra:
• The urethra is a tube that connects the urinary bladder to the urinary
meatus for the removal of urine from the body of both females and males.
• Urethra is anatomically linked with the reproductive structures, its
characteristics in males are quite different from those in females
Diagram of male urethra:
Diagram of female urethra:

17. Formation and composition of urine:
Formation of urine:
• The kidneys filter unwanted substances from the blood and produce
urine to excrete them. There are 3 main steps of urine formation
• These processes ensure that only waste and excess water are
removed from the body.
Steps:
1. Glomerular filtration
2. Selective reabsorption
3. Tubular secretion

18. 1. Glomerular filtration
• This takes place through the semipermeable walls of the
glomerular capillaries and Bowman’s capsule.
• The afferent arterioles supplying blood to glomerular capsule
carries useful as well as harmful substances.
• The useful substances are glucose, amino acids, vitamins,
hormones, electrolytes, etc. and the harmful substances are
metabolic wastes such as urea, uric acids, creatinine, etc.
• The glomerular hydrostatic pressure forces the blood to leaves
the glomerulus resulting in filtration of blood.

19. Selective reabsorption
• As the filtrate passes to the renal tubules, useful substances
including some water, electrolytes and organic nutrients such as
glucose, amino acids, vitamins, hormones etc. are selectively
reabsorbed from the filtrate back into the blood
Tubular secretion
• Tubular secretion takes place from the blood in the peritubular
capillaries to the filtrate in the renal tubules and can ensure that
wastes such as creatinine or excess H+ or excess K+ ions are
actively secreted into the filtrate to be excreted.
• The tubular filtrate is finally known as urine.

20. Composition of urine:
• Urine consist of 90% - 95% water and 5% - 10% of solids includes organic and inorganic
components
• It consist of physical properties and chemical properties
Physical properties:
• Volume - 1000-2000 ml/day,
• Color - Normal urine is pale yellow,
• Odour - Normal odour of urine is aromatic in nature
• PH - Normal PH 5.5 – 6.5.
• Specific gravity - Normal range : 1.012 – 1.024
Chemical properties:
• Inorganic: calcium, chloride, inorganic sulphate, phosphate and ammonia
• Organic: urea, uric acid, creatinine, organic sulphate, urobilinogen

21. Fluid and electrolyte balance:
• Fluid balance:
• Water balance is achieved in the body by the amount of water consumed in
food and drink is equals the amount of water excreted.
• Kidneys play role to excrete the Excess water & Electrolytes
• 1 liter of water per day is lost through the skin, lungs, and feces,
• Body can gain water by Ingestion of liquids and moist foods and
Metabolic synthesis of water during cellular respiration
• Water balance is essential for the body to be properly hydrated, avoiding
both dehydration and over-hydration.
• One way the kidneys can directly control the volume of bodily fluids is by
the amount of water excreted in the urine.

22. Electrolytes:
• Electrolytes are minerals in your body that have an electric charge. They are in your blood,
urine, tissues, and other body fluids.
• Types:
• CATION - Positively charged Electrolyte
• ANION - Negatively charged Electrolyte
• Electrolyte Balance:
• Healthy body obeys the law of electrical neutrality.
• Fluid in any body compartment contain, equal number of Cations and Anions.
• Electrolytes need to be maintained in an even balance for your body to function
properly. Otherwise, vital organs can be affected.
• The levels of electrolytes in your body can become too low or too high.
• This can happen when the amount of water in your body changes.

23. 1. Water intake
2. Electrolyte intake
3. Organs and Mechanisms:
4. Amino acids
• Hypothalamus
• Pituitary Gland
• Kidneys
• Liver
• Lung
• Adrenal glands
• Cardiac tissue
• Related Genes
• Cholesterol
Factors influencing on fluid and electrolyte balance:

24. Water Electrolyte Imbalance Conditions:
Water imbalance:
• Dehydration is a condition of little water content in body
• Over hydration - more water content in body
Electrolyte Imbalance:
• Calcium : Hypercalcemia and Hypocalcaemia
• Chloride : Hyperchloremia and Hypochloremia
• Magnesium : Hypermagnesemia and Hypomagnesemia
• Phosphate : Hyperphosphatemia or Hypophosphatemia
• Potassium : Hyperkalemia and Hypokalemia
• Sodium : Hypernatremia and Hyponatremia

25. Structure and functions of the skin
• Skin:
• The skin is the largest organ of the body, The skin protects us
from microbes, helps regulate body temperature, and permits
the sense of touch.
• The skin is composed of 3 major layers of tissue: epidermis,
dermis and subcutaneous layer.
• The epidermis is the top layer of skin
• The dermis is the middle layer of skin
• The subcutaneous or hypo dermis is the innermost layer

26. Structure of skin:

27. Epidermis:
• The epidermis is the thin, outer layer of the skin that is visible to the
eye.
• Contains different types of cells: keratinocytes, melanocytes,
Merkel cells and Langerhans cells.
• Melanocytes create melanin, the substance that gives skin color.
These form a pigment shield against UV radiation.
• It does not contain blood vessels
• The epidermis consists of 4 layers: Stratum germinativum, Stratum
spinosum, Stratum granulosum, Stratum corneum
• Main functions: protection, absorption of nutrients and homeostasis.

28. Dermis:
• The dermis is the middle layer of the skin that offers elasticity.
• It is composed of connective tissues and collagen fibers.
• The dermis provides a site for the hair follicles, sweat glands, sebaceous
glands, blood vessels, lymph vessels, sensory receptors, nerve fibers and
muscle fibers.
Subcutaneous:
• The subcutaneous is the layer of tissue directly underneath the dermis. It
is also called hypodermis.
• This layer of tissue is composed of fat cells and connective tissue.
• Its functions include insulation, the storage of energy
• It is the thickest layer of the integumentary system

29. The Accessory Organs of the Skin:
• Nails are a flat plate of keratin that covers the ends of fingers and toes.
• The sebaceous glands secrete the oil sebum, which lubricates the hair and skin, helping
prevent drying and cracking.
• The sweat glands function is to cool the body.
Functions of the skin:
• Provides a protective barrier against mechanical, thermal and physical injury
• Prevents loss of moisture.
• Reduces harmful effects of UV radiation.
• Acts as a sensory organ (touch, detects temperature).
• Helps regulate temperature.
• An immune organ to detect infections etc.
• Production of vitamin D.

30. Regulation of the body temperature (Thermoregulation):
• The maintenance of a particular temperature in a living body.
• Thermal Balance: balance between heat gain and heat loss.
• Hypothalamus Regulation of Temperature:
• Hypothalamus acts as “thermostat” that makes thermoregulatory
adjustments to deviations from temperature in the brain
• Mechanisms are activated in two ways:
• Thermal receptors in skin provide signal
• Direct stimulation of hypothalamus through changes in blood
temperature

31. Thermoregulation in Cold:
1. Vascular adjustments: constrict peripheral blood vessels.
2. Muscular activity: exercise energy metabolism and shivering.
3. Hormonal output: epinephrine and norepinephrine increase basal heat
production
Thermoregulation in Heat
• Heat Loss by Radiation: emit electromagnetic heat waves
• Heat Loss by Conduction: transfer of heat through a liquid, solid, or gas
• Heat Loss by Convection: air or water adjacent to the body is exchanged.
• Heat Loss by Evaporation: Heat transferred as water is vaporized from
respiratory passages and skin surfaces