2.2 Circulatory System 🫀

Functions of circulatory system

transport substances and fight against disease

Function of red blood cell

carry and transport oxygen

Structure of red blood cell

• contain haemoglobin to carry oxygen

• biconcave shape to provide large surface area for diffusion of oxygen

• no nucleus to provide more space for haemoglobin

Function of white blood cell

Defend the body against disease

Structure of white blood cell

contain nucleus

lymphocytes to make antibodies

phagocytes to engulf and digest microorganisms

Function of platelets

convert fibrinogen to fibrin, forming a mesh that traps blood components

What are platelets needed for

blood clotting and forming scabs

Structure of platelets

cell fragments (very small)

Function of plasma

transport blood cells, glucose, carbon dioxide, urea and hormones

Structure of plasma

yellow coloured liquid

Role of platelets in blood clotting and scab formation

• Blood vessel is damaged and platelets triggered

• Converts fibrinogen (soluble) to fibrin (insoluble)

• Forms a mesh/ net to trap blood components

• A clot is formed which dries to from a scab

Red blood cell lysis

when placed into dilute solution, water moves into cell by osmosis causing them to swell and burst as the dont have a cell wall

Concentration of blood

salts and other chemicals in plasma keep it close to red blood cell’s to prevent lysis

Atery

• thick wall

• thick layer of muscle and elastic fibres

• small lumen

Vein

• thin wall

• thin layer of muscle and elastic fibres

• large lumen

• have valves

Capillary

• very thin, one cell thick

• no layer of muscle or elastic fibres

• very small lumen

Blood in arteries (except pulmonary)

carry oxygenated blood away from the heart to the body

Pulmonary artery

carries deoxygenated blood from the heart to the lungs

Why do arteries have thick walls/ muscles and elastic fibres

to withstand high blood pressure and allow expansion/ recoil with heart beats

Blood in veins (except pulmonary)

carry deoxygenated blood from the body back to the heart

Pulmonary vein

carry oxygenated blood from the lungs to the heart

Why do veins have valves

they close to prevent the backflow of blood (ensures unidirectional flow)

Why do veins have thing walls/ no muscle and elastic fibres

blood is moving at low pressure

Function of capillaries

allow exchange of substances between blood and cells (diffusion)

Walls of capillaries

permeable and one cell thick to provide short diffusion path

Flow of blood

unidirectional pump

Right side of heart

pumps deoxygenated blood to the lungs

Left side of heart

punps oxygenated blood to the body

Why is left ventricle wall thicker than right/ higher pressure

has to pump blood around the entire body, right only pumps to the lungs

Coronary arteries

supply heart muscle with oxygen and glucose for respiration

Labelling the heart

• Vena Cava

• Right Ventricle

• Pulmonary Artery

• Pulmonary Vein

• Left Atrium

• Left Ventricle

• Aorta

Heartbeat cycle

1. Deoxygenated blood enters the right atrium from the vena cava

2. Blood moves into the right ventricle

3. Deoxygenated blood is pumped into the pulmonary artery to the lungs

4. Blood becomes oxygenated in the lungs

5. Oxygenated blood leaves the lungs via the pulmonary vein

6. Blood enters the left atrium

7. Blood moves into the left ventricle

8. Blood is pumped into the aorta to circulate oxygenated blood around the body

Double circulatory system

blood passes through the heart twice in each full circulation

Vena cava

carries deoxygenated blood from the body back to the heart

Aorta

carries oxygenated blood from the heart around the body

Hepatic artery

carries oxygenated blood to the liver

Hepatic vein

carries deoxygenated blood back to the heart and digested food from the liver around the body

Hepatic portal vein

carries digested food from the small intestine to the liver

Renal artery

carries oxygenated blood rich in urea to the kidneys for excretion

Renal vein

carries deoxygenated blood low in urea back to the heart

Hepatic

liver

Renal

kidneys

Increased respiration during exercise

muscles contract more, requiring more energy, so blood flow increases (raises pulse rate)

Benefits of regular exericse

• strengthens heart muscle

• increases cardiac output at rest

• reduces chance of heart attack

• reduces recovery rate