this ppt can easily be used for projects

1. Human excretory system
Kidneys, nephrons

2. What is human excretory system…
• The excretory system is a passive biological
system that removes excess, unnecessary
materials from the body fluids of an organism,
so as to help maintain internal
chemical homeostasis and prevent damage to
the body. The dual function of excretory
systems is the elimination of the waste
products of metabolism and to drain the body
of used up and broken down components in a
liquid and gaseous state. In humans and
other amniotes(mammals, birds and reptiles)
most of these substances leave the body
as urine and to some degree exhalation,
mammals also expel them through sweating.
• Only the organs specifically used for the
excretion are considered a part of the excretory
system. In the narrow sense, the term refer to
the urinary system. However, at excretion
involves several functions that are only
superficially related, it is not usually used in
more formal classifications of anatomy or
function.

3. Kidneys
• The kidneys are bean-shaped organs that
serve several essential regulatory roles
in vertebrates. They remove excess organic
molecules from the blood, and it is by this
action that their best-known function is
performed: the removal of waste products
of metabolism. Kidneys are essential to
the urinary system and also
serve homeostatic functions such as the
regulation of electrolytes, maintenance
of acid–base balance, and regulation
of blood pressure (via maintaining the salt
and water balance). They serve the body as
a natural filter of the blood, and remove
water-soluble wastes which are diverted to
the bladder. In producing urine, the kidneys
excrete wastes such
as urea and ammonium. They are also
responsible for the reabsorption
of water, glucose, and amino acids. The
kidneys also

4. • Homeostasis is the process of
maintaining the ideal internal
conditions (i.e. correct temperature,
right amount of water and glucose &
other solutes) for the body to work at
it’s optimum.
• Excretion is the process of removing
metabolic waste products and other
toxins.
• Osmoregulation is maintaining the
correct balance between water and
solutes.
• Excretion, which includes
osmoregulation, is thus extremely
important in maintaining homeostasis.
• Secretion is the release of useful
substances, e.g. hormones, from the
body. Thus, it is not excretion.
Egestion, i.e. defecation, is also not
excretion.

5. • Certain waste products would become highly
toxic if they were to accumulate. This could
damage tissues.
• An excess of water could also lead to a number
of complications.
• Thus, the waste products must be removed –
they continually move into the bloodstream,
which carries them to the excretory organs.

7. • There are four main excretory
organs:
▫ Lungs
▫ Colon
▫ Skin
▫ Kidneys
• The liver is not an excretory
organ, but produces many
products which are excreted
elsewhere. Toxins and drugs as
well as alcohol, is broken down
in the liver. Hence, an excess of
smoking, medication and
alcohol is extremely harmful to
the liver.

8. • The carbon dioxide
released from cellular
respiration is carried to
the lungs in the blood.
It then diffuses across
the respiratory
membrane and is
exhaled.
• A small amount of heat
and water is excreted
this way.

9. • Bile pigments, from the break down of
haemoglobin, and cholesterol are synthesised in
the liver.
• They pass into the small intestine as bile and are
finally excreted in the faeces as bile salts, from
the colon.
• Mucus and bacteria are too excreted through the
colon.

10. • Sweat, which is excreted
through the skin, contains
water, salts and some
urea.
• As the water in the sweat
is excreted, heat is lost
and the body is cooled.
• Sweat is a form of
excretion as it rids the
body of waste, as well as a
form of secretion as it
maintains the body
temperature.

11. • When amino acids and nucleic acids
are broken down, nitrogenous wastes
are released as ammonia, urea, uric
acid and creatinine. Ammonia is
toxic if it accumulates and is
therefore converted to less toxic urea
in the liver.
• The following substances are made
in the liver and excreted by the
kidneys:
▫ Urea, the main nitrogenous waste
compound secreted. It is formed by the
breakdown of excess amino acids in the
process of deamination.
▫ Uric acid, the nitrogenous end product
of nucleic acid metabolism.
▫ Creatinine is formed from creatinine
phosphate, found in the muscle cells.
▫ Non-nitrogenous waste, e.g. CO2, excess
water, ions, hormones, poisons and
drugs.

12. • The main function of the urinary system is to maintain
homeostasis by regulating the volume and concentration
of body fluids. It filters and reabsorbs certain materials
from the blood.
• The urinary system is made up of the following parts:
A) Two kidneys
B) Urinary bladder
C) urethra

13. • Stores urine
• Is stimulated by impulses
from a motor nerve, to
contract to expel the urine.
• Has sphincter muscles at the
base to control the flow of
urine
• Carries urine from the
bladder to outside the
body

14. • Found in abdominal cavity below the diaphragm, near the
posterior, on either side of the vertebral column.
• Kept in position with connective tissue, the peritoneum, as
well as renal blood vessels. They are wedged in with other
organs.
• Externally they are bean-shaped, dark red and the size of a
large bar of soap.
• The inner, concave border is called the hilum.
• Surrounded by three layers of protective tissue:
▫ A tough, fibrous renal capsule on the surface protects them from
disease.
▫ A middle layer of adipose tissue cushions them against blows.
▫ An outer layer of fibrous connective tissue, the renal fascia, anchors
the kidneys to surrounding structures.

15. Renal pyramid
Interlobular artery
Renal artery
Renal vein
Renal hilum
Renal pelvis
Ureter
Minor calyx
Renal capsule
Inferior renal
capsule
Superior renal
capsule
Inter lobular
vein
Nephron
Minor calyx
Major calyx
Renal papilla
Renal column

16. The damage of the kidneys
• Pyelonephritis (infection of kidney pelvis): Bacteria may infect the kidney, usually
causing back pain and fever. A spread of bacteria from an untreated bladder infection
is the most common cause of pyelonephritis.
• Glomerulonephritis: An overactive immune system may attack the kidney, causing
inflammation and some damage. Blood and protein in the urine are common
problems that occur with glomerulonephritis. It can also result in kidney failure.
• Kidney stones (nephrolithiasis): Minerals in urine form crystals (stones), which may
grow large enough to block urine flow. It's considered one of the most painful
conditions. Most kidney stones pass on their own but some are too large and need to
be treated.
• Nephrotic syndrome: Damage to the kidneys causes them to spill large amounts of
protein into the urine. Leg swelling (edema) may be a symptom.
• Polycystic kidney disease: A genetic condition resulting in large cysts in both kidneys
that impair their function.
• Acute renal failure (kidney failure): A sudden worsening in kidney function.
Dehydration, a blockage in the urinary tract, or kidney damage can cause acute renal
failure, which may be reversible.

17. …….
• Chronic renal failure: A permanent partial loss of kidney function. Diabetes
and high blood pressure are the most common causes.
• End stage renal disease (ESRD): Complete loss of kidney function, usually
due to progressive chronic kidney disease. People with ESRD require
regular dialysis for survival.
• Papillary necrosis: Severe damage to the kidneys can cause chunks of
kidney tissue to break off internally and clog the kidneys. If untreated, the
resulting damage can lead to total kidney failure.
• Diabetic nephropathy: High blood sugar from diabetes progressively
damages the kidneys, eventually causing chronic kidney disease. Protein in
the urine (nephrotic syndrome) may also result.
• Hypertensive nephropathy: Kidney damage caused by high blood pressure.
Chronic renal failure may eventually result.

18. ……..
• Kidney cancer: Renal cell carcinoma is the most common cancer affecting
the kidney. Smoking is the most common cause of kidney cancer.
• Interstitial nephritis: Inflammation of the connective tissue inside the
kidney, often causing acute renal failure. Allergic reactions and drug side
effects are the usual causes.
• Minimal change disease: A form of nephrotic syndrome in which kidney
cells look almost normal under the microscope. The disease can cause
significant leg swelling (edema). Steroids are used to treat minimal change
disease.
• Nephrogenic diabetes insipidus: The kidneys lose the ability to concentrate
the urine, usually due to a drug reaction. Although it's rarely dangerous,
diabetes insipidus causes constant thirst and frequent urination.
• Renal cyst: A benign hollowed-out space in the kidney. Isolated kidney cysts
occur in many normal people and almost never impair kidney function.

19. The kidney needs to have a constant supply of
blood in order to control the composition of body
fluids.
• The renal artery, a branch from the aorta, enters
the kidney at the hilum. It supplies blood rich in
nitrogenous waste, oxygen and nutrients.
• The renal vein carries purified, deoxygenated
blood to the inferior vena cava, and then to the
heart.

20. Glomerulus
Efferent arteriole Bowman’s capsule
Proximal convoluted
tubule
Cortical collecting
duct
Distal convoluted
tubule
Henle’s loop
Papillary duct
Peritubular
capillaries
Arcuate vein
Arcuate artery
Afferent
arteriole
Juxtaglomerular
apparatus

21. Functioning of nephrons
• The nephron carries out nearly all of the kidney's functions. Most of these
functions concern the reabsorption and secretion of various solutes such
as ions (e.g., sodium),carbohydrates (e.g., glucose), and amino
acids (e.g., glutamate). Properties of the cells that line the nephron change
dramatically along its length; consequently, each segment of the nephron
has highly specialized functions.
• The loop of Henle, is a U-shaped tube that extends from the proximal
tubule. It consists of a descending limb and an ascending limb. It begins in
the cortex, receiving filtrate from the proximal convoluted tubule, extends
into the medulla as the descending limb, and then returns to the cortex as
the ascending limb to empty into the distal convoluted tubule. The primary
role of the loop of Henle is to concentrate the salt in the interstitium, the
tissue surrounding the loop.

22. Bowman’s capsule
• Bowman's capsule is a cup-like sac
at the beginning of the tubular
component of a nephron in the
mammalian kidney that performs
the first step in the filtration of
blood to form urine.
A glomerulus is enclosed in the
sac. Fluids from blood in the
glomerulus are collected in the
Bowman's capsule (i.e., glomerular
filtrate) and further processed
along the nephron to form urine.
This process is known
as ultrafiltration. The Bowman's
capsule is named after Sir William
Bowman, who identified it in 1842.