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EXCRETIONEXCRETION

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Lesson 1

Learning Objective1.Define excretion as the removal of toxic

materials and the waste products of metabolism from organisms.

Outline What is excretion? Excretory products Excretory organs

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What Is Excretion?

Excretion is the removal of toxic materials and the waste products of

metabolism from organisms.

METABOLISM = ANABOLISM + CATABOLISMMETABOLISM = ANABOLISM + CATABOLISM

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Metabolism Produces waste products. When presents in high concentration...

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Excretion is NOT egestion

Excretion is the removal of toxic materials and the waste products of metabolism from organisms.

Egestion is the removal of undigested food matter from the alimentary canal.

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Is defaecation excretion or egestion?

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Excretory Products

1.Carbon dioxide– Produced as a waste product of respiration– It is harmful because it is an acidic gas, that can slow

down enzyme reaction.

2.Excess water– Excess water– Comes from eating, drinking– Produced as a waste product of respiration– It is harmful because it can cause cells to swell and

burst.

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3. Urea– Produced from the breakdown of amino acids

(deamination)– It is harmful because it is a toxic nitrogenous waste

and can prevent enzyme reaction from taking place.

4. Bile pigment (bilirubin)– Produced from the breakdown of haemoglobin– It is harmful because bile pigment is toxic.

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Excretory Organs

Carbon dioxide

Excess water

&

excreted mainly through

excreted mainly through

also through

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Urea

Bile pigment

excreted mainly through

excreted mainly through

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Past Year Question

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Excretion in mammals

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Exercise

1. What is excretion?2. What is the gas produced during respiration?3. Why is this gas harmful?4. Name the process that produce urea in the liver.5. Bile pigment is the breakdown of __________.6. Another name for bile pigment is __________.7. What is the main excretory organ for excess water?8. What are the other excretory organs for excess water?9. What is the excretory organ for carbon dioxide?10. Defaecation is the removal of faeces. Is it excretion/egestion?

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Lesson 2

Learning Objective1.Describe the removal of carbon dioxide from the

lungs2.Identify on diagrams and name the kidneys,

ureters, bladder, urethra and state the function of each.

Outline Removal of CO2 from the lungs Urinary system

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Removal of CO2 from the lungs

Cell Transport system

Alveoli(Lungs)

Cell respire aerobically

to produce CO2. CO2 diffuses into

the blood.

CO2 enters red blood cells. CO2 reacts with water to form carbonic

acid. Carbonic acid breaks down into

hydrogen carbonate ions. Hydrogen carbonate ions

diffuse out into the plasma.

Hydrogen carbonate ions diffuse back into the red blood cells where they

are converted into carbonic acid and

then into water and CO2. CO2 diffuses

out of blood capillaries into the alveoli and out of

the lungs

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Urinary System

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Urinary System

Renal artery brings oxygenated blood containing urea and excess water to the kidneys.

Renal vein brings deoxygenated blood from the kidneys. Urinary sphincter controls the discharge of urine into the urethra

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Past Year Question

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Urinary system

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Lesson 3

Learning Objective1.Identify how a nephron works.

Outline Structure of kidney Structure of nephron Urine formation

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Structure of Kidney

There are two main regions: Cortex Medulla

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Structure of Nephron

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Urine Formation2 Stages

Stage 1: Ultrafiltration

High blood pressure in the glomerulus forces small

dissolved substances in the blood such as water, urea,

glucose, amino acids, mineral salts out of the

blood into the Bowman's capsule.

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Stage 2: Selective Reabsorption

Glucose, amino acids, useful mineral salts and useful water are reabsorbed back into the blood capillary. Glucose and amino acids are reabsorbed by active transport whereas

water is reabsorbed by osmosis.

Proximal convoluted tubule

Blood capillary

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Excess water, excess mineral salts and nitrogenous wastes (e.g. urea) pass out of the collecting duct as urine.

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Constituents of urine...can vary depending on diet.

Constituents of urine...

High Salty Diet Higher Salt Concentration in Urine

High Fluid Intake Dilute Urine

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Past Year Question

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Discussion

On a hot day, a person consumed only meat before a day of energetic work. Explain the likely changes in the composition of the person's urine

during the day.

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Essay Assignment

Describe what could happen to an amino acid molecule from the time it enters the liver to the time its component elements leave the body.

(7)

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Lesson 4

Outline Function of kidney

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Function of Kidney

As an excretory organ

To remove excess water

and urea from the blood

As an osmoregulator

To control the water potential

of the blood

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Discussion

• How does kidney control the water potential of the blood?

• Why is it important to control the water potential of the blood?

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Kidney as an Osmoregulator

Red blood cells swell and burst

Red blood cellsshrink and crenate

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Kidney as an Osmoregulator Water potential of the blood is controlled by the

amount of water reabsorbed at the Henle's loop. When water potential of blood is high, less water is

reabsorbed at Henle's loop. When water potential of blood is low, more water is

reabsorbed at Henle's loop. A hormone called anti-diuretic hormone (ADH) is

responsible for controlling the amount of water reabsorbed at the Henle's loop.

More ADH secreted More water reabsorbed. Less ADH secreted Less water reabsorbed.

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Discussion

A person drinks a lot of water. State what happen to urine volume and its concentration. Give

reasons for your answer.

Include secretion of ADH and water reabsorption at Henle's loop in your answer.

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Discussion

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Lesson 5

Learning Objective1.Describe dialysis in kidney machines.

Outline Kidney Failure Kidney Dialysis

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Kidney Failure

Kidney failure happens when one or both kidney stops functioning normally

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Kidney Failure

Several causes: Diabetes Hypertension Inherited kidney disease Kidney stones Infection Abuse of painkilling drugs

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Kidney Failure Kidney failure causes wastes like urea to

remain in the blood system. Accumulation of wastes is toxic to the human

system. If not treated, it could be fatal. The treatments available are either dialysis or

kidney transplant.

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Kidney Dialysis

Dialysis machine mimics the function of

kidney. It removes excess salts and

nitrogenous waste (e.g urea) from the

patient's blood.

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Kidney Dialysis (hemodialysis)

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• The patient’s blood is made to pass through the partially permeable tube, immersed in dialysis fluid (has the same concentration as ordinary plasma)

• Small molecules such as urea and other waste products in the blood diffuse out of the tube into the dialysis fluid.

• Large molecules such as blood cells and proteins remain in the tube.

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• The tube is narrow, long and coiled to increase the surface area to volume ratio for faster diffusion.

• The direction of the blood is opposite to the flow of dialysis fluid. This is to maintain diffusion gradient.

• The filtered blood is then returned to a vein in the patient’s arm.

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Kidney Dialysis (Peritoneal)

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Past Year Question

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Past Year Question

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Discussion

Kidney dialysis removes urea and excess salts from the blood. To be able to carry this function, the composition of the dialysis fluid

has to be regulated. Suggest the concentration of urea and salts in the dialysis

fluid.

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Exercise

1. What is the function of ureter?2. What is the function of urethra?3. Where is urea produced?4. Name the main regions of kidney.5. Name 2 stages in urine production.6. Name 2 substances that formed filtrate.7. Name 2 substances that are reabsorbed into the blood

capillary at the proximal convoluted tubule.8. High intake of protein will increase the concentration of

___________ in the urine.

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9. What are 2 functions of kidney?10. What happen to red blood cell if the water potential of blood

plasma is high?11. Where does osmoregulation takes place in the nephron?12. Name the hormone that controls water absorption in the

nephron.13. Where is this hormone secreted?14. If more ADH is secreted, __________ (more/less) water is

reabsorbed.15. What happen to ADH secretion, if a person drinks a lot of

water? Explain.