EXCRETORY SYSTEM ENOTE

WEEK FIVE

CLASS: GRADE 8

SUBJECT: BASIC SCIENCE

TERM: SECOND

TOPIC: EXCRETORY SYSTEM

MEANING OF EXCRETORY SYSTEM AND EXCRETION: Excretion is defined as the removal of waste products or by products of metabolism accumulated as a result of chemical activities of the body cells.  

NEED FOR EXCRETION:

1. To maintain water balance

2. To remove poisonous or unwanted substances.

3. It helps in controlling body temperature.

4. To maintain salt-balance (i.e homeostasis).

5. It saves protozoa like amoeba from bursting.

VARIOUS EXCRETORY ORGAN AND THE WASTE PRODUCTS THEY EXCRETE:

Organs	Substances Secreted
1. Skin	Sweat containing salt and water, urea
2. Lung	Carbon dioxide and water vapor
3. Kidney	Urine-urea, salts, water
4. Liver	Bile salt

PROBLEMS OF EXCRETION:

1. Uremia. Under this condition, the urea accumulation is comparatively high.

2. Renal Failure.

3. Renal Calculi or Kidney Stones.

4. Nephritis or Bright’s Disease.

5. Hypertension due to rennin secretion.

6. Renal Tabular Acidosis

7. Diabetes Insipidus

8. Oedema

ASSIGNMENT:

OBJECTIVE QUESTIONS:

1. Diabetes means excess – in the body A. blood B. fat C. protein D. sugar   

2. The removal of waste products from the body of an organism is called A. assimilation B. defecation C. excretion D. ingestion

3. Urine is formed in the A. bladder B. kidney C. penis D. ureter

4. The following are excretory organs EXCEPT A. kidneys B. liver C. lungs D. nose

5. The following are waste products of excretion EXCEPT A. carbon dioxide B. salt C. urine D. faeces

6. Which of these organs secrets carbon dioxide? A. Kidney B. Liver C. Lung D. Skin

THEORY QUESTIONS:

1. What is excretion?

2. State five needs for excretion.

3. List four organs and substances excreted by the organs.

4. Mention 8 problems of excretion.