The Circulatory System

Question 1

What is the circulatory system?

Answer 1

The circulatory system is a system of tubes (blood vessels) and a pump (the heart) which carry blood around the body.

All cells within the body need a constant energy supply and a means of removing waste products.

The blood, heart and blood vessels fulfil both of these functions.

The circulatory system, together with the respiratory system form the CARDIOVASCULAR SYSTEM.

Question 2

Name the circulatory circuits

Answer 2

The systemic circuit - around the body
The pulmonary circuit - to & from the lungs
The hepatic circuit - the digestive system / liver

Question 3

Explain the functions of the circulatory system

Answer 3

Distribution of oxygen and nutrients to every cell within the body.
Removal of waste products from every cell within the body (along with the lymphatic system).
Individual components of the circulatory system have individual functions above and beyond the main function of the circulatory system.

Question 4

What is blood?

Answer 4

Blood is a liquid tissue contained in a network of tubes known as vessels - arteries, veins and capillaries.
Blood transports vital substances to all areas of the body.
The heart acts as a pump to move the blood around the body.

Question 5

List the functions of blood

Answer 5

Transport of oxygen / carbon-dioxide / hormones / nutrients / waste products around the body.

Defense against disease (leucocytes).

Temperature regulation / heat distribution.

Clotting.

Question 6

What are the components of blood?

Answer 6

Plasma (straw coloured fluid)
Red blood cells (erythrocytes)
White blood cells (leucocytes)
Platelets (thrombocytes)

Plasma contains:
Water (90% +)
Salts
Food substances
Waste material
Hormones

Question 7

Red blood cells (Erythrocytes)

Answer 7

Minute biconcave discs that obtain their red colour from haemoglobin combining with oxygen to form oxyhaemoglobin.

They are made in the red bone marrow.

They carry oxygen from the lungs to wherever it is needed in the body.

Question 8

White blood cells (Leucocytes)

Answer 8

Are colourless cells, contain a nucleus, and are larger than red blood cells.
There are a lot fewer white cells than red cells.

Their main function is to fight infection and protect the body against viruses, toxins and bacteria

Question 9

Platelets (Thrombocytes)

Answer 9

Platelets are formed in the red bone marrow and are tiny fragments that are even smaller than red blood cells.

Their role is to assist in the blood clotting process by producing a substance (enzyme) called thrombokinase.

Question 10

Blood vessels - Arteries

Describe their structure

Answer 10

Have thick muscular walls and a small lumen to keep the pressure inside high.
Contain no valves
Lie deeper within the body
Have the heart as a pump to push the blood through them.

Question 11

Blood vessels - Arteries

Explain their function

Answer 11

Carry blood away from the heart to the rest of the body at high pressure.
Carry oxygenated blood except the pulmonary artery.

Question 12

Blood vessels - Veins

Describe their structure

Answer 12

Have thinner muscular walls and a large lumen as the pressure inside is lower.
Lie superficially within the body.
Run between major muscles to pump the blood (as the heart only pumps blood through the arteries).
Have valves to prevent back-flow

Question 13

Blood vessels - Veins

Explain their function

Answer 13

Carry blood to the heart from the body at low pressure

Carry deoxygenated blood except the pulmonary vein

Question 14

Blood vessels - Capillaries

Describe their structure

Answer 14

Narrow blood vessels which have very thin walls, just one cell thick
Allows substances to pass through its walls (a semi-permeable membrane)

Question 15

Blood vessels - Capillaries

Explain their function

Answer 15

Forms the link between arteries / arterioles and veins / venules.
Allows exchange oxygen and nutrients for carbon dioxide and wastes within all cells and tissues

Question 16

Key arteries (body)

Answer 16

Carotid artery (neck)
Brachial artery (upper arm - brachialis)
Ulnar Artery & Radial artery (forearm - radius / ulna)
Femoral artery (thigh - femur)
Anterior tibial artery (front of shin - tibia)

Question 17

Key veins - body

Answer 17

Jugular vein (neck)
Cephalic vein (upper arm)
Iliac vein (pevlis - ilium)
Femoral vein (thigh - femur)
Saphenous vein (Inner thigh)

Question 18

Describe the heart

Answer 18

The heart is a muscular organ which is involuntary in action – it cannot be consciously controlled and is under the control of the autonomic nervous system.

The heart is made from a specialised kind of muscle known as cardiac muscle.

This kind of muscle is found only within the heart, is able to contract without nervous stimulation and never tires – this property is called ‘myogenic’.

Question 19

Explain the function of the heart

Answer 19

The heart acts as a pump to pump the blood through the arteries around the body and keep it circulating.

The heart also pumps blood through the lungs where it picks up oxygen.

Question 20

Explain ‘blood pressure’

Answer 20

Blood pressure is always measured as two numbers.

The first is the SYSTOLIC pressure. This is the rate at which the blood is pushed out into the arteries.
The second is the DIASTOLIC rate. The pressure measured as the heart rests.

Normal blood pressure is120/80mmHg.

Question 21

Define ‘pulse rate’

Answer 21

Pulse rate is the number of times the heart beats in a minute.

The average when at rest is 72 beats per minute.

Question 22

List the factors which affect blood pressure

Answer 22

Age
Weight
Fitness
Stress levels
Emotional stability / anxiety
Diet
Smoking
Alcohol intake
Genetics
The condition of the heart and vessels

Question 23

Associated organs - the liver

Answer 23

The liver is the largest gland in the body, located in the abdominal cavity.
It receives much of it’s blood supply via the hepatic portal vein.

It’s functions are:
Stores & filters blood
Destroys bacteria & worn out erythrocytes
Detoxes alcohol, drugs & other chemicals
Stores vitamins A,D,E,K & iron
Stores sugar as glycogen
Converts protein & fat into energy when required by the body.

Question 24

Associated organs - The Spleen

Answer 24

The spleen is the largest lymphatic organ.
It is located within the abdomen, behind and to the left of the stomach.
It contains lymphocytes and macrophages (types of white blood cell).

It’s functions are:
To break down old and abnormal red blood cells
Storage of blood – acts as a reserve in crisis
Immune response to infections