Why do we need a circultory systek
Cells in our body need nutrients and oxygen and it the circulatory system that
transports these to our cells.
• Blood picks up oxygen from the lungs and nutrients from the small intestine and
transports them around the body to all the cells.
• The circulatory system is also responsible for removing waste products from cells
(carbon dioxide and water).
• The circulatory system consists of arteries, veins, capillaries
Blood
Blood is a tissue as it consists of a group of cells with a similar structure and
function.
• Blood is made up of 4 components:
1. Plasma
2. Red blood cells
3. White blood cells
4. Platelets.
Plasma
• The liquid part of the blood.
• It is actually a straw yellow colour that is mostly made of water.
• Functions: To transport dissolved chemicals (CO2, nutrients, waste) and heat
around the body. Plasma is an excellent solvent as it is 90% water.
Red blood cells
• Contain a protein pigment (haemoglobin).
• Haemoglobin helps carry oxygen around the body.
• RBC’s are bioconcave shaped to allow for maximum surface area so that as much
oxygen can be carried around.
• RBC’s are slightly elastic to prevent being damaged easily as they move around
the body.
• RBCs are made in the bone marrow and broken down by the liver.
White blood cells
WBC’s fight infection by surrounding and engulfing micro-organisms.
• WBCs are made in the bone marrow.
Platelets
• Platelets form blood clots e.g. a scab.
• Blood clotting has two purposes:
1. To prevent blood loss.
2. To prevent the entry of micro organisms into the body.
Blood vessels
• Blood vessels are the network of connecting arteries, veins and capillaries.
• Each have a similar function - to transport blood but there are differences.
• Arteries carry blood away from the heart.
• Veins carry blood towards the heart.
• Capillaries connect arteries and veins and it is also in capillaries where nutrients,
gases and waste substances are exchanged in cells.
Arteries
Carry blood AWAY (think a)
Strong blood flow pressure so thicker wall
No valves
Carries oxygenated blood
Viens
Carry blood towards the heart
Low blood flow pressure so thinner wall
Valves prevent blood backflow due to low blood pressue
Dexoygenated blood
Cappilaries
Cappillaries are tiny blood vessels that connect arties and viens
They’re thin walled which allow substances to diffuse in and oit of the blood into body cells
The heart
The size of a fist
- label heart and draw diagram.
Made of cardian muscle
Average 70bpm
Located in the centre of the chest but felt ln the left side
Four chambers in the heart
The left & right ventricles and the left and right atriums.
• The left ventricle is thicker due to it pumping blood all around the body. Hence
why we feel it more on the left hand side.
• The septum divides the two sides of the heart.
• Heart valves ensure blood moves in one direction only.
• The coronary artery provides nutrients and oxygen to the cardiac muscle of the
heart itself.
Major blood vessels
Four major blood vessels connected to the heart.
• Vena cava: Carries deoxygenated blood to right
atria.
• Pulmonary artery: Carries deoxygenated blood
to the lungs.
• Pulmonary vein: Carries oxygenated blood to left
atria.
• Aorta: Carries oxygenated blood to rest of body.
Heart disease
Caused by eating too much fatty foods, not exercising and smoking.
