Human Health And Systems Flashcards
Ingestion/Eating
Food is taken in by the body
Digestion
Food is broken down
Absorption
Digested food passes into the bloodstream
Assimilation
Using the food In the cells of the body
Elimination
Getting rid of undigested food
Physical digestion
Mouth (teeth) stomach (churning)
Chemical digestion
Uses enzymes to break down food. Enzymes are chemicals that speed up reactions without being used in the reaction
Plasma
Liquid part of the blood
Pale yellow - mostly water
Function : to transport chemicals and heat
Also carries the red blood cells, white blood cells, and platelets
Red blood cells
Round, flattened discs, curve inward near centre
• Small, no nucleus, formed in bone marrow
• Very numerous – approx 5million per drop blood
• Function : transport oxygen to cells
• Red colour comes from haemoglobin
they contain.
• Haemoglobin picks up oxygen in the lungs
• It later releases it in other parts - e.g. muscle
White blood cells
Larger than Red Blood Cells but fewer in number
• No definite shape – shape can change
• They are also made in the bone marrow
• Function : to fight infection
• Some can surround micro-organisms and destroy them
• Others produce proteins called antibodies
• Antibodies help to destroy micro-organisms such as bacteria
Platelets
• Smaller than red or white blood cells
• They are formed in the bone marrow
• They are formed from larger cells breaking down into pieces
• Function: help to form blood clots
• When a blood vessel is injured, platelets help to form a clot
• Clotting prevents loss of blood, and prevents micro- organisms getting in
• Clots are temporary barriers while repair and healing is taking place
System of Tubes + Pump
• Blood being a fluid, needs tubes in which to flow
• These tubes are called blood vessels
• They come in three main types:
– Arteries
– Veins
– Capillaries
• Good blood flow requires the aid of a good pump
• In the human circulatory system this pump is the heart
• In an average lifetime, the heart beats more than 2.5 billion times, without ever pausing to rest
Arteries
• Carry blood AWAY from the heart
• Flow of blood is strong and at high pressure
• Artery walls are thick and strong to withstand this pressure
• Blood is under pressure – forced to move in one direction
• There is no need for valves in arteries to prevent backwards flow
• All arteries (except pulmonary artery) carry oxygenated blood
Veins
Carry blood BACK to the heart
• Flow of blood is weaker and pressure is low
• Vein walls are thinner and weaker than artery walls
• Pressure is low, so there is a danger of backward flow of blood, especially when flow direction is against gravity
• Valves in veins at regular intervals, allow blood to flow forwards, but prevent reverse flow
• All veins (except pulmonary vein) carry deoxygenated blood
Capillaries
These are tiny blood vessels
• There are a huge number of them in the body
• Capillaries are found between arteries and veins
• Capillaries have very thin walls which allow materials to pass in and out with the surrounding cells and tissue.