- Diastole(relaxation of heart)
- blood enters atria from pulmonary vein (from lungs) and vena cava (from body)
- as atria fills, pressure rises
- when pressure exceeds that in ventricles, the atrioventricular valves open allowing blood to pass into the ventricles
- the passage of blood is aided by gravity
- muscular walls of atria and ventricles are relaxed
- relaxation of ventricles walls causes them to recoil and reduces pressure within ventricle so pressure is lower than in aorta and pulmonary artery
- semi-lunar valves in aorta and pulmonary artery close
- Contraction of atria(atrial systole)
- contraction of atrial walls, along with recoil of ventricle walls forces the remaining blood into ventricles from atria
- muscle of ventricle walls remain relaxed
- Contraction of ventricles(ventricular systole)
- walls contract simultaneously after ventricles fill with blood
- ventricles increase blood pressure, forcing shut the atrioventricular valves and preventing backflow of blood into atria
- the shut valves increase ventricle pressure
- once pressure exceeds aorta and pulmonary artery, blood is forced from ventricles into them(creates high pressure to pump blood round body)
control of blood flow
when pressure difference favours the backflow of blood (wrong direction), valves are designed to shut
atrioventricular valve
between left atrium and ventricle(bicuspid valve)
between right atrium and ventricle(tricuspid valve)
semi-lunar valves
in aorta and pulmonary artery
close when elastic walls of vessels recoil, increasing pressure within them and ventricle walls relax reducing pressure within ventricles
pocket valves
when veins are squeezed, blood flows towards heart rather than away
design of valves
made up of flaps of tough, but flexible, fibrous tissue which are cusp shaped
when pressure is greater on convex side of cusps, they move apart to let blood pass between cusps
when pressure is greater on concave side, blood collects within the cusps, this pushes them together to form a tight fit to prevent passage of blood
cardiac output
volume of blood pumped by one ventricle of the heart in one minute
heart rate x stroke volume
arteries
carry blood away from heart and into arterioles
arterioles
smaller arteries that control blood flow from arteries to capillaries
capillaries
tiny vessels that link arterioles to veins
veins
carry blood from carpillaries back to heart
5 basic structures in blood vessles
- tough fibrous outer layer that resists pressure changes
- muscle layer that can contract and control flow of blood
- elastic layer that helps to maintain blood pressure by stretching
- thinner inner lining(endothelium) that is smooth to reduce friction and thin to allow diffusion
- lumen is central cavity which blood flows
artery structure
- muscle layer is thick compared to veins (constricts and dilates to control volume of blood passing through)
- elastic layer is thick (maintains high pressure)
- overall thickness of wall is great which resists vessel bursting under pressure
- no valves as blood doesn’t flow backward
arteriole structure
- muscle layer thicker than arteries which restricts flow of blood so controls movement into capillaries
- elastic layer is thinner than arteries because blood pressure is lower
Vein structure
- muscle layer thin because veins carry blood away from tissues so cannot control flow of blood
- elastic layer is thin because pressure is low so vessels won’t burst
- wall thickness is small as it allows them to be flattened easily aiding the flow of blood within them
- valves at intervals throughout so blood doesn’t flow backwards because pressure is low
Capillary structure
- walls consist mostly of lining so they’re very thin so diffusion is short
- numerous and highly branched providing large SA
- lumen is narrow so that red blood cells are squeezed flat against side of capillary, bringing them closer to cells reducing diffusion distance
- spaces between lining cells that allow white blood cells to escape in order to deal with infections within tissues
tissue fluid
watery liquid containing glucose, amino acids, fatty acids, ions in solution and oxygen
supplies those substances to tissues and receives Co2 and other waste materials
hydrostatic pressure
caused by pumping of heart
at arterial end of capillaries
causes tissue fluid to move out of blood plasma
Forces that push tissue fluid out of capillaries at arterial end
- hydrostatic pressure of tissue fluid outside capillaries, which resists outward movement of liquid
- lower water potential of blood due to plasma proteins that causes water to move back into blood within carpillaries
ultrafiltration
The pressure that forces small molecules out of capillaries, leaving all cells and proteins in the blood because they are too large to cross membranes
Return of tissue fluid
- loss of tissue fluid from carpillaries reduces hydrostatic pressure inside them
- by time blood reaches venous end of capillary network the hydrostatic pressure is lower than tissue fluid outside it
- tissue fluid is forced back into capillaries down pressure gradient
- plasma has lost water and still contains proteins(lower wpt than tissue fluid)
- water leaves tissue by osmosis down wpt gradient
- remainder of tissue fluid is carried back via lymphatic system
lymphatic system movement
gradually merge into larger vessels that form network through body
they drain contents back into bloodstream via two ducts that join veins close to heart
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3.1->3.3 Microscope19
-
3.4 Eukaryotic Cell structure31
-
3.5->3.6 Cell specialisation and Prokaryotic cell19
-
3.7->3.819
-
4.1 Structure of cell surface membrane14
-
4.2 Diffusion and Osmosis13
-
Active transport6
-
5.1 and 5.29
-
5.3->5.523
-
5.6 and 5.718
-
8.1 -> 8.2 dna10
-
8.3 -> 8.512
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9.1 gene mutation13
-
9.2 meiosis and genetic variation15
-
9.3+ 9.4 genetic diversity and selection8
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10.1 species19
-
10.2 -> 10.310
-
10.411
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7.1 + 7.2 Haemoglobin19
-
7.3 + 7.412
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7.5 + 7.625
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7.714
