Notes in slides for Class 11

1. Excretion in humans
Chapter 11

2. Waste Organ to excrete
Ammonia Kidneys
Urea Kidneys
Uric Acid Kidneys
Excess water Kidneys, Skin
Minerals Kidneys, Skin
CO2 Lungs
Bile pigments Liver
Lactic Acid Liver
O2
Metabolic waste products and toxic substances are excretory
products.
Excretion is the process by which metabolic waste
products and toxic substances are removed by the body of
an organism.

3. Excretion is the process by which metabolic
waste products and toxic substances are
removed by the body of an organism.
5 5
5 2
2
What are nitrogenous waste products?

5. Kidneys are bean shaped organs.
Average size of human Kidney is 10 to 13 cm long and 5
to 7 cm wide.
The human urinary system consist of a pair of Kidneys, a
pair of ureters, a urinary bladder and urethra.
5 5
5
5
2
5
5

6. Organ
Hilus Is an elastic muscular bag to collect and
store urine.
Is the depressed portion of concave surface
of kidney, where renal artery, renal vein and
nerves are connected.
Ureter Is located at the bottom of the bladder and
control urination. Signals from brain
activate these muscles to induce urination.
Is a narrow tube that connects kidney to
urinary bladder to transfer urine from
kidney.
Urinary Bladder Is the duct through which urine released
from the bladder to outside of the body.
Is an elastic muscular bag to collect and
store urine.
Urethra Is a narrow tube that connects kidney to
urinary bladder to transfer urine from
kidney.
Is the duct through which urine released
from the bladder to outside of the body.
Sphincter Muscle Is the depressed portion of concave
surface of kidney, where renal artery, renal
vein and nerves are connected.
Is located at the bottom of the bladder and
control urination. Signals from brain activate
these muscles to induce urination.

9. Organ
Bowman’s Capsule Is the portion of tubule connect with
multiple distal convoluted tubules which in
to medulla region and further open in to
renal pelvis.
Is a cup-like structure at the beginning of
nephron.
Proximal convoluted
tubule
Is the U shaped portion of tubule that
extends in pyramid from cortex region to
medulla and back in to cortex.
Is coiled tubule after capsule.
Loop of Henlé Is a cup-like structure at the beginning of
nephron.
Is the U shaped portion of tubule that
extends in pyramid from cortex region to
medulla and back in to cortex.
Distal convoluted
tubule
Is coiled tubule after capsule. Is the portion tubule that coiled again in
cortex
Collecting duct Is the portion tubule that coiled again in
cortex .
Is the portion of tubule connect with
multiple distal convoluted tubules which in
to medulla region and further open in to
renal pelvis.

11. Blood enters the kidney by the
renal artery, which branches out in
to arterioles.
Each arteriole further branches
into a mass of blood capillaries in
the bowman’s capsule.
Blood leaving the glomerulus
enters blood capillaries
surrounding nephron.
These blood capillaries then unit
for form venules, which in turn join
to form a branch of the renal vein.
Blood enters the kidney by the
renal artery, which branches out in
to arterioles.
Each arteriole further branches
into a mass of blood capillaries in
the bowman’s capsule.
Blood leaving the glomerulus
enters blood capillaries
surrounding nephron.
These blood capillaries then unit
for form venules, which in turn join
to form a branch of the renal vein.
Blood enters the kidney by the
renal artery, which branches out in
to arterioles.
Each arteriole further branches
into a mass of blood capillaries in
the bowman’s capsule.
Blood leaving the glomerulus
enters blood capillaries
surrounding nephron.
These blood capillaries then unit
for form venules, which in turn join
to form a branch of the renal vein.

12. Two main processes in each nephron
1. Ultrafiltration of small molecules from the blood
2. Selective reabsorption of useful substances

13. Ultrafiltration of small molecules from the blood
Hydrostatic blood pressure (or high blood pressure)
provides the main force required for the filtration.
Basement membrane is partial (Semi)
permeable membrane of glomerular
blood capillaries.
Acts like a very fine filter allows only
water and very small molecules to pass
through.
• Filtered: Glucose, Aminoacids, mineral
salts and waste products
• Retained: Blood cells, platelets, proteins,
fat and other large molecules.
Filtrate
(120cm3 per
minute)
• Useful molecules are needed for the body
• Large amount of water loss will dehydrate body

14. Selective reabsorption

15. Water 96.0g/100g
Mineral salts (Mainly NaCl) 1.8g /100g
Urea 2.0 g /100g
Other Nitrogenous Substances 0.2g /100g
Normal Healthy Person
Protein rich diet will increase Urea in urine
Excess water or liquid consumption will increase water
potential of blood, thus will increase the water content
of urine.
High intake of salty food will result in excess salt in
urine
Certain metabolic disorder (diseases) may also cause
abnormal composition of urine.
Example: excess amount of Glucose in urine of a
person with diabetes mellitus.
Composition of urine

16. 1. Urine formation involves ultrafiltration and selective reabsorption
useful substances.
2. Ultrafiltration occurs through the basement membrane in the renal
corpuscles because of the high hydrostatic pressure in the
glomeruli.
3. Useful substances in the filtrate in the nephron are taken back in
the bloodstream by selective reabsorption.
4. In a healthy person, urine normally consists of water, mineral salts,
urea and other nitrogenous waste products. This composition may
change depending on a persons diet and health.
Guess the missing words

17. Osmoregulation
Water potential of the blood depends on the amount of water and mineral salts in
the plasma.
Water potential of the blood has to be kept relatively constant.
• Water will enter in to cells if blood plasma is too diluted (too much of water): Cells will burst.
• Less water in plasma makes blood concentrated and water from cells move out in to plasma. Cells can not
do their normal metabolic function and eventually make permanent damage of organs.
The amount of water in the blood is controlled by
antidiuretic hormone (ADH).
ADH is produced by pituitary gland situated in
hypothalamus of brain

18. Osmoregulation

19. Common causes of kidney failure
• High blood pressure
• Diabetes
• Alcohol abuse
• Physical dame due to severe accidents
• Complications as a result of major surgery.
When one kidney fails, the person still can lead a normal life with the other
kidney.
But when both kidney fail, person could die without medical intervention.
• Kidney transplant
• Dialysis using dialysis machine
Kidney failure

21. The dialysis fluid contains the same
concentration of essential substances as
healthy blood.
• This ensures that essential substances (such as glucose, amino
acids and mineral salts) do not diffuse out of the blood and into
the dialysis fluid. Furthermore, if the patient's blood lacks
these essential substances, these substances will diffuse from
the dialysis fluid into the blood.
The dialysis fluid does not contain
metabolic waste products
• This sets up a concentration gradient that allows waste
products such as urea, uric acid, creatinine, and excess water
and mineral salts, to diffuse out of the tubing into the dialysis
fluid. The waste products are removed from the blood. This
maintains the correct solute composition and water potential of
the blood.
The tubing in the machine is narrow, long and
coiled
• This increases the surface area to volume ratio which helps to speed
up the rate of exchange of substances between the patient's blood
and the dialysis fluid.
The direction of the blood flow is opposite to
the flow of the dialysis fluid.
• This maintains the concentration gradient for the removal of waste
products.