Circulatory System

Question 1

How does plasma contribute to homeostasis of the body

Answer 1

Maintaining optimum pH of blood through buffers
Maintaining water potential of blood: Blood solutes affect water potential and is largely due to presence of sodium ions and plasma proteins. Regulates movement of water between blood and tissues.
Maintains temperature of the blood as water in the blood plays a part in distribution of heat

Question 2

What is the function and adaptations of red blood cells

Answer 2

Functions to transport oxygen and carbon dioxide
Adaptations:
Presence of haemoglobin
Circular, flattened biconcave disc shape
No nucleus
Elastic and can turn bell-shaped

Question 3

Why are red blood cells elastic

Answer 3

In order to squeeze through blood vessels smaller than itself in diameter without breaking

Question 4

Function of white blood cells

Answer 4

Function to protect the body against disease-causing organisms

Question 5

Shape and functions of phagocytes

Answer 5

Irregular in shape with lobed nucleus so it can move, changes shape and squeezes through capillary walls
Function: Engulf and ingest foreign particles by phagocytosis
Phagocytosis is process of engulfing and ingesting foreign particles. In process of fighting bacteria, phagocytes are killed with bacteria forming pus.

Question 6

Shape and functions of lymphocytes

Answer 6

Round in shape, large nucleus
Function: When pathogens or disease causing organisms enter bloodstream, they stimulate lymphocytes to produce antibodies to protect body against bacteria by:
Agglutination, causes bacteria to clump together and attract phagocytes to engulf clump bacteria by phagocytosis. Antibodies neutralise toxin produced by bacteria

Question 7

Describe platelets

Answer 7

They function to prevent excessive blood loss from body and entry of pathogens, either by formation of platelet plug or initiating blood clotting. They are small cell fragments without nucleus

Question 8

Importance of blood clotting

Answer 8

Seals the wound to prevent entry of bacteria and further loss of blood

Question 9

Describe blood clotting

Answer 9

When blood vessels are damaged, damaged tissue and platelets produce thrombokinase which converts prothrombin into thrombin(enzyme). Thrombin converts soluble fibrinogen into insoluble fibrin threads that trap red blood cells and whole mass forms a clot or scab

Question 10

How does body prevent excessive blood clotting

Answer 10

Undamaged blood vessels contain anti-clotting substance called heparin. When thrombokinase is released in damaged tissues, it neutralises heparin so clotting can take place

Question 11

Why is blood typing important

Answer 11

If the wrong type of blood is transfused, this would cause agglutination(binding of antibodies in recipients plasma to antigens on donated RBCs) or clumping of red blood cells and could lead to death as clumps may block small blood vessels and prevent flow of blood. Red blood cells become cross-linked to one another and trigger immune system to rupture RBCs and released haemoglobin may cause kidney damage

Question 12

Why is blood group O universal donor

Answer 12

There are no antigens on donor’s red blood cells and thus recipients antibodies would not cause agglutination of donor’s blood

Question 13

How is blood typing done (using anti-A serum)

Answer 13

If blood agglutinates when serum is used, RBCs contain antigen A

Question 14

Why is there a need for transport system

Answer 14

In simple unicellular organism, movement of materials in and out of cell occurs by diffusion as no part of cell is far from external environment
In multicellular organism, transport system is needed to carry materials from one part of the body to another, as cells are located deep in body far from external environment

Question 15

What are advantages of double circulation

Answer 15

Complete separation of oxygenated and deoxygenated blood in double circulation
Blood passes through heart twice in one complete circuit: pulmonary circulation at lower pressure and systemic circulation at higher pressure

Question 16

Describe reason for complete separation of oxygenated and deoxygenated blood in double circulation

Answer 16

Ensures only oxygenated blood reach tissue cells. Efficiency of transport of oxygenated blood

Question 17

Describe reason for blood passing through heart twice in one complete circuit

Answer 17

Blood enters lung at lower pressure compared to blood leaving the heart. This ensures blood flows slowly at lungs, allowing sufficient time for blood to be well oxygenated before it returns to heart.
Systemic circulation has higher pressure so oxygenated blood is distributed to rest of body tissues more quickly. Helps to maintain high metabolic rate in animals

Question 18

Describe following for artery:
Structure
Size of lumen
Blood pressure
Speed of blood flow
Direction of blood flow

Answer 18

Thick, elastic muscular wall. Semi-lunar valves absent except in pulmonary artery and aorta
Small lumen relative to diameter of blood vessel
High blood pressure
Blood flows rapidly, pulses reflecting rhythmic beating action of heart
Flows away from heart to organs

Question 19

Describe adaptations of artery

Answer 19

Function: Transport blood away from heart
Arterial wall can withstand high pressure generated by contraction of ventricles
Elastic tissue in wall enables it to stretch and recoil under high pressure. Helps to push blood in spurts along artery and give rise to pulse
Muscular tissue in wall allows for constriction and dilation to regulate volume of blood flowing through
When artery constricts/dilates, lumen becomes narrower/wider and less/more blood flows through it per unit time

Question 20

Describe following for arteriole:
Structure
Function
Size of lumen
Blood pressure
Speed of blood flow
Direction of blood flow

Answer 20

Elastic and muscular walls, arteries branch to form arterioles
Transports blood away from heart
Small lumen
Lower blood pressure than artery
Blood flows slower compared to arteries
Flows from heart to organs

Question 21

Describe following for capillary:
Structure
Size of lumen
Blood pressure
Speed of blood flow
Direction of blood flow

Answer 21

Capillary wall is one-cell thick, single layer of endothelial cells and intercellular clefts
Very small lumen
Blood pressure falls along capillaries due to increase in total cross-sectional area
Blood flows slowly to allow more time for exchange of substances to take place
Flows around cells within organs

Question 22

Describe function and adaptation of capillary

Answer 22

Allow for exchange of nutrients and waste between blood and tissue fluid
One-cell thick wall allows oxygen, food and waste products to easily diffuse through walls
Presence of intercellular clefts increase rate of diffusion of materials
Extensive network surrounding cells enable efficient exchange of materials with tissue cells

Question 23

Describe following for venule:
Structure
Function
Size of lumen
Blood pressure
Speed of blood flow
Direction of blood flow

Answer 23

Thin and elastic muscular wall
Delivers blood to vein
Large lumen
Very low blood pressure
Blood flows slowly
Flows from organs towards heart

Question 24

Describe following for vein:
Structure
Size of lumen
Blood pressure
Speed of blood flow
Direction of blood flow

Answer 24

Thinner elastic and muscular wall, semi-lunar valves present except vena cava and pulmonary vein
Large lumen
Very low blood pressure
Blood flows slowly, skeletal muscles next to veins assist flow of blood back to heart by compressing veins when muscle contracts

Question 25

Describe function and adaptations of vein

Answer 25

Transports blood towards the heart
Large lumen offers low resistance to blood flow - blood can flow smoothly back to heart
Semi-lunar valves prevent the backflow of blood under low blood pressure to ensure flow of blood in one direction

Question 26

Describe transfer of materials between capillaries and tissue fluid

Answer 26

Tissues and cells surrounded by fluid that supplies cells with requirements - tissue fluid. Fills intercellular spaces and acts as medium for materials to diffuse between blood and cells of body
For materials to get into cells, must diffuse into tissue fluid before diffusing into cells

Question 27

Where are pulmonary artery, pulmonary vein, aorta and vena cava located

Answer 27

Pulmonary vein -> left ventricle -> aorta
Vena cava ->right ventricle -> pulmonary artery

Question 28

Describe ventricular systole

Answer 28

Ventricles contract, pressure rises and pressure of blood pushes av valves upwards forcing them shut. This produces ‘lub’ sound. Pressure in ventricles higher than aortic/pulmonary artery pressure, semi-lunar valves open, blood in ventricles enter aorta/pulmonary artery
(Addition of atrial diastole)
Atria relaxes and blood from pulmonary vein/vena cava starts filling the atria

Question 29

Describe ventricular diastole

Answer 29

Ventricles relax, pressure within chamber falls, resulting in back flow of blood from aorta/ pulmonary artery towards the ventricles. Blood starts to flow backwards and closes the semi-lunar valves, this produces ‘dub’ sound. As ventricles continue to relax, pressure falls quickly. When ventricular pressure drops below atrial pressure and atria contracts to force remaining blood through open AV valves into ventricles

Question 30

Define blood pressure

Answer 30

Blood pressure is force that blood exerts on the walls of blood vessels.

Question 31

Describe pulse

Answer 31

When ventricles contract, blood is pumped into aorta and into arteries. Sudden increase in pressure causes arteries to dilate. Following dilation, arterial walls recoil, forces the blood to move along in series of waves. This gives rise to pulse.

Question 32

Describe coronary heart disease

Answer 32

Condition of cholesterol and fatty deposits on inner surface of coronary arteries called atherosclerosis. Plaque narrows lumen of arteries, resulting in less oxygen and nutrients supplied to heart muscles. When coronary arteries are completely blocked, myocardial infarction may result. heart tissue does not get oxygen and nutrients, tissue dies, resulting in damage to heart. Infarction may disrupt the conduction system of the heart and cause sudden death to patient. May experience agina (pain/discomfort in region of heart with insufficient blood)

Question 33

Factors increasing risk of heart attack

Answer 33

Family history
Being male
Age
Smoker
High intake of saturated fats/sugar/alcohol
Lack of exercise
High blood pressure