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Blood and Organs
Functions of the Blood:
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Blood has four main components:
o Plasma, platelets, red blood cells and white blood cells
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Digested food products from the gut to all over the body
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Urea from the liver to the kidneys
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Platelets:
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When you damage a blood vessel, platelets clump together to plug up the damaged
area
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Blood clots stop you losing blood and prevent
microorganisms from entering the wound
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Reb Blood Cells:
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They transport oxygen from the lungs to all the cells in the body
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They contain haemoglobin, which is what gives blood its colour
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In body tissues the
reverse reaction happens
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White Blood Cells and Immunity:
The Immune System:
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Pathogens are microorganisms that cause disease
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White blood cells do this
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Phagocytes:
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Phagocytes detect things that are foreign in the body
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Phagocytes are non-specific – they attack anything that’s not meant to be there
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When certain white blood cells come across a foreign antigen, they will start to
produce proteins called antibodies
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The antibodies produced
are specific to that type of antigen
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Some of the lymphocytes stay in the blood as memory cells after the original
infection has been fought off
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That’s why you’re immune to most diseases after
having them
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The heart pumps the blood out at high pressure so the
artery walls are strong and elastic
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They contain thick layers
of muscle to make them strong
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Capillaries:
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Involved in the exchange of materials at the tissue
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Capillaries are really tiny – too small to see
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They have permeable walls, so substances can diffuse in and out
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Their walls are usually only one cell thick
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Veins:
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Carry blood to the heart
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The blood is at lower pressure in the veins, so the
walls don’t need to be as thick as artery walls
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They also have valves to help make sure the blood is flowing the right direction
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The Heart:
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The right atrium of the heart receives
deoxygenated blood from the body
through the vena cava
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The left atrium receives oxygenated blood
from the lungs through the pulmonary
vein
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The left ventricle has a much thicker wall than the right ventricle
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This also means that the blood in the left
ventricle is under higher pressure
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Exercise:
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When you exercise, your muscles need more energy, so you respire more
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For
this to happen the blood has to flow faster, so you heart rate increases
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High levels of blood carbon dioxide are detected by receptors in the aorta and
carotid artery
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The brain sends signals to the heart, causing it to contract more frequently and with
more force
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Adrenaline binds to specific receptors in the heart
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This increases oxygen supply to the tissues, getting the body ready for action
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They perform three main roles:
o Removal of urea from the blood
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o Adjustment of salt levels in the blood
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They do this by filtering stuff out of the blood under high pressure, and then
reabsorbing the useful things
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Nephrons:
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Each kidney contains thousands of nephrons
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o A high pressure is built up which squeezes water, urea, salts and glucose out
of the blood and into the Bowman’s capsule
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They stay in the
blood
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Reabsorption:
o As the filtrate flows along the nephron, useful substances are selectively
reabsorbed back into the blood
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This
involves the process of active transport
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Excess salt isn’t
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Release of waste:
o The remaining substances form urine
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Osmoregulation – The Kidneys:
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Water is taken into the body as food and drink and is lost from the body through
perspiring, urinating and breathing
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One way that it can do this is by adjusting the amount of water that is excreted by
the kidneys in the urine
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It
makes the nephron more permeable so more water is reabsorbed back into the
blood
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The whole process of osmoregulation is controlled by a mechanism called negative
feedback
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