LSS2 Science- Circulatory System

Question 1

Transport of materials in unicellular orgaisms

Answer 1

• Do NOT need a transport system for exchange or distribution of materials
• No part of the cell is far from the environment outside
• Exchange of materials occur easily by DIFFUSION

Question 2

Need for transport system in multicellular organisms

Answer 2

Diffusion is inadequate for transport; due to,

• Larger body (Reduced surface area to volume ratio)
• Cells are located deeper in the body, further away from the external environment

Question 3

What does blood contain?

Answer 3

• Plasma
• White blood cells
• Platelets
• Red blood cells

Question 4

White blood cells OR leucocytes

Answer 4

• Larger than red blood cells
• Fewer in numbers compared to red blood cells
• Production: Bone marrow
• Destroyed: Spleen
• Limited lifespan of a few days
• Colourless (No haemoglobin)
• Irregular in shape (Nucleus present)
• Mobile

Question 5

White blood cells or leucocytes > Types

Answer 5

• Lymphocytes

- Phagocytes

Question 6

White blood cells or leucocytes > Types > Lympocytes

Answer 6

• Large rounded nucleus
• Small amount of non-granular cytoplasm
• Produce antibodies against microorganisms

Question 7

White blood cells or leucocytes > Types > Phagocytes

Answer 7

• Lobed nucleus
• Granular cytoplasm
• Able to ingest foreign particles

Question 8

Blood platelets OR thrombocytes

Answer 8

• Not true cells
• Fragments of cytoplasm which are membrane bound
• Important for the clotting of blood
• Life span: 6 days

Question 9

Plasma

Answer 9

About 90% water in which the following are dissolved and transported;

• Proteins: Fibrogen, Prothrombin & antibodies
• Mineral salts: chlorides and sulfates of calcium and sodium
• Food substances: Glucose, Amino acids and fats
• Waste products: Urea, uric acid and creatine
• Hormones

Question 10

Red blood cells OR erythrocytes

Answer 10

• Constitute 99% cells in the blood
• Production: Bone marrow
• Destroyed: Spleen
• Limited lifespan of 120 days

Question 11

Features of red blood cells

Answer 11

• Filled with red pigment haemoglobin
  (Essential for binding oxygen)
• Absence of nucleus
  (Allows more haemoglobin to be packed into cell)
• Biconcave shape
  (increases surface area to volume ratio for efficient uptake of oxygen)
• Elastic (Enable cells to squeeze through tiny blood capillaries)

Question 12

Functions of blood

Answer 12

• Transport function
  • to carry various substances from one part of the body to another
• Protective function
  • To protect the body against disease-causing organisms
  • Blood clotting or coagulation prevents entry of bacteria into the bloodstream and excessive blood loss

Question 13

Functions of blood > Transport function

Answer 13

Blood acts as a transport medium carrying various substances

• Digested food substances
• Excretory products
• Hormones
• Heat
• Oxygen

Question 14

Functions of blood > Transport function > Transport of oxygen to body cells

Answer 14

1. Blood passes through lungs, oxygen diffuses from the air sacs into the blood
2. Haemoglobin combines with oxygen to form oxyhaemoglobin
3. Blood transports oxygen to all the tissues of the body
4. At the tissue cells, oxyhaemoglobin releases the oxygen

Question 15

Functions of blood > Protective function of blood

Answer 15

• Blood clotting
• Phagocytosis
• Production of antibodies

Question 16

Functions of blood > Protective function of blood > The clotting process

Answer 16

• Blood clots when exposed to air

- This seals the wound, prevents the entry of bacteria and further loss of blood

Question 17

Functions of blood > Protective function of blood > Phagocytosis

Answer 17

‘Phagocytes’ is the process of engulfing and ingesting foreign particles by phagocytes

Question 18

Transport systems in humans

Answer 18

Made up of ;

• Heart
• Veins
• Arteries
• Venules
• Capillaries

Question 19

[S] Transport systems in humans > Heart

Answer 19

A muscular pump which pumps blood out of the heart into the circulation

Question 20

[S] Transport systems in humans > Veins

Answer 20

Many Venules unite to form bigger veins which carry blood towards the heart

Question 21

[S] Transport systems in humans > Venules

Answer 21

Capillaries are linked to small veins called venules

Question 22

[S] Transport systems in humans > Arteries

Answer 22

Blood vessels that carry blood away from the heart

Aorta > Arteries > Arterioles

Question 23

[S] Transport systems in humans > Capillaries

Answer 23

Microscopic blood vessels that arise from branches of the arterioles

Question 24

At the capillary bed

Answer 24

Arterial blood:

• Oxygen
• Glucose

Venous blood:

• Carbon dioxide
• Metabolic waste products

Question 25

Production of antibodies

Answer 25

• Production: Lymphocytes
• Bind to bacteria and cause their surface membranes to rapture
• Bacteria cells clump together in the presence of antibodies
• Toxins produced are neutralised
• Prevents viruses from binding to host cells

Question 26

Organ transplant and tissue rejection

Answer 26

Tissue or organ transplant involves replacing damaged or diseased tissue organ with a healthy tissue or organ from the same person or a donor

• The body may produce antibodies to destroy the transplant
  (Introduction to foreign substances)

Ways to reduce tissue rejection;
• Tissue match
• Immunosuppressive drugs

Question 27

Blood vessels (In depth)

Answer 27

Artery- Carries blood away from the heart
Capillary- Allows exchange of materials between blood and tissue
Vein- Carries blood towards the heart

Question 28

Arteries

Answer 28

• Transport oxygenated blood from the heart to other organs in the body
• Thick, muscular walls: Support blood from the heart [Higher in pressure]
• Muscles contract and relax to cause constriction and dilation of the artery respectively

Question 29

Veins

Answer 29

• Transport deoxygenated blood back to the heart
• Thin walls with less elastic tissue: Slower blood flow [Lower pressure]
• Valves: Prevent blood from flowing backwards
  [Folding of inner walls of the veins]

Question 30

Capillaries

Answer 30

• Endothelium consists of a single layer of flattened cells and the walls are partially permeable, allowing dissolved substances to diffuse quickly through it
• Capillary network increases surface area and total cross sectional area: More efficient enchange

Question 31

Double circulation

Answer 31

Blood passes through the heart twice as it moves from the pulmonary circulation into the systemic circulation

Question 32

Advantages of a double circulation

Answer 32

• Blood enters the pulmonary circulation at a low pressure, ensuring sufficient time for the blood to be fully oxygenated before returning it to the heart
• Blood is pumped into the systemic circulation at a high pressure, ensuring oxygenated blood is quickly distributed to all tissues of the body

Question 33

Coronary heart disease

Answer 33

• The tissues of the heart need oxygen for respiration
• The tissues of the heart are supplied by the coronary arterieds
• Excess cholesterol can build up in deposits in the artery walls, causing blockage and disruption and flow of blood

Question 34

Coronary heart disease > Process

Answer 34

Buildup of fatty substances on inner surfaces of coronary arteries (atherosclerosis)