6.2 The Blood System Flashcards
who was the first modern understanding of circulatory system based on?
William Harvey (De Motu Cordis)
what Greek views did scientist believe before Harvey? (3)
- arteries and veins were separate blood networks
- veins were pumped natural blood (produced by liver)
- arteries pumped to the heat via the lungs
what did Harvey propose? (3)
- arteries and veins were part of a single connected blood network
- arteries pumped blood from the heart
- veins returned blood to the heart
what does the heart consist of?
four chambered organs -
2 atria - reservoirs which blood returning to the heart is collected via veins
2 ventricles - pumps, expelling blood from the heart at high pressures
why are there 2 sets of atria and ventricles? (2)
- left side pumps oxygenated blood around the body (systemic circulation) -> thicker muscular walls
- right side pumps deoxygenated blood to the lungs (pulmonary circulation)
what is the function of arteries?
transport the blood at high pressures from the heart ventricles to the tissue of the body and lungs
what specialized structures do arteries have to accomplish the transport of blood at high pressures?
- narrow lumen (maintain high pressure)
- thick wall containing an outer layer of collagen to prevent the artery from rupturing
- arterial walls contains inner layer of muscle and elastic fibres to help maintain pulse flow
how is blood expelled from the heart?
by ventricular contractions by pulses
how are pulses caused? (2)
- muscle fibres form a rigid arterial wall that is capable of withstanding high blood pressure without rupturing
- they can also contract to narrow the lumen which increases the pressure between pumps and helped to maintain blood pressure throughout the cardiac cycle
what do elastic fibres allow the arterial wall to do? (3)
- to stretch and expand upon the flow of a pulse through the lumen
- the pressure exerted on the arterial wall is returned to the blood when artery returns to ts normal size (elastic recoil)
- elastic recoil helps to push the blood forward through the artery as well as maintaining arterial pressure between pump cycles
what is the function of the capillaries?
to exchange materials between the cells in the tissue and blood travelling at low pressures
how does blood network work? (3)
- arteries split into arterioles, which split into capillaries (decreases arterial pressure as vessel volume is increased)
- branching of arteries into capillaries ensures blood is moving slowly and all cells have a blood supply
- after material exchange has occurred capillaries will pool into venules which will collate into larger veins
what are the specialised structures of capillaries? (4)
- very small diameter (only one red blood cell at a time)
- the capillary wall is made from a single layer of cells to minimise the diffusion distance so it is permeable
- surrounded by a basement membrane which is permeable to materials
- may contain pores to aid in the transport of material between tissue fluid and blood
what are the unique structures of veins?
- wide lumen to maximise blood flow
- thin walls with a lot less muscles and elastic fibres for flow at low pressure
- valves to stop backflow
what is the heart chamber made up of? (2)
- 2 atria
- 2 ventricles
what are the heart valves? (2)
- atrioventricular (between atria and ventricles) - bicuspid valve (L) & tricuspid valve (R)
- semilunar valve (ventricles and arteries) - aortic valve (L) and pulmonary valve (R)
what are the heart blood vessels? (4)
- vena cava (inferior and superior) - into R atrium (returns deoxygenated blood)
- pulmonary artery connects R ventricle and sends deoxygenated blood from lungs
- pulmonary vein feeds into L atrium and returns oxygenated blood from lung
- aorta L ventricle and send oxygenated blood around body
what is the contraction of the heart?
myogenic (comes from heart muscles)
what does myogenic mean?
initiated by cardiomyocytes (not from brain)
what are the specialised cluster of cardiomyoctyes called?
sinoartial node (pacemaker)
how does the electrical conduction of a heart beat occur?
- sinoatrial node sends out electrical impulse that stimulates contraction of myocardium
- impulse directly causes the atria to contract and stimulates another noted at the junction between atrium and ventricle
- 2nd node -> atrioventricular node sends signals down septum via bundle of his (nerve bundle)
- bundle of his innervates nerve fibres in ventricular wall (causes ventricular contraction)
how do the pacemakers work?
- pacemaker is autonomic (involuntary) from brain and medulla oblongata
- sympathetic nerve releases neurotransmitter noradenaline
- parasympathetic nerc]ve (vagus nerve) releases the neurotransmitter acetylcholine to decrease heart rate
how does hormone sinalling on heart work?
- heart rate can undergo sustained increase in response to hormone signalling to prepare for physical activity
- adrenaline released from adrenal glands
- adrenaline increases heart rate by activating same chemical pathway as neurotransmitter noradrenaline
what is the systole cardiac cycles? (5)
- blood returning to heart flow into atria and ventricles as the pressure is lower
- when ventricles are 70% full and tria will contract increasing pressure in the artia ad forcing blood into ventricles
- as ventricles contract, ventricular pressure exceed trail pressure and AV valve prevent blood flow
- when both set of valve close, the pressure builds in contracting ventricle
- when ventricular pressure exceeds blood pressure in aorta, the aortic valve opened and blood is released into the aorta
what is the diastole cardiac cycle? (4)
- blood exists ventricle and travels down aorta, ventricular pressure fails
- ventricular pressure drops below aortic pressure, aortic valves close to prevent back flow
- ventricular pressure drops below atrial pressure, the AV valve opens and blood can flow from atria to ventricle
- throughout the cycle, aortic pressure remains quite high as muscle and elastic fibres in artery wall maintain blood pressure
what is atherosclerosis? (6)
hardening ad narrowing of arteries due to cholesterol deposition
- atheromas develop in arteries and significantly reduce the diameter of lumen
- restricted blood flow increase pressure and lead to damage to arterial wall
- damaged region is repaired with fibrous tissue which significantly reduce the elasticity of vessel wall
- smooth lining of artery is progressively degraded, lesions that restricts blood flow
- thrombus is dislodges it becomes an embolus and can cause a blockage in smaller arteriole
what are consequences of coronary occlusions? (3)
- myocardial tissue requires O2 and nutrients are transported via coronary artieris
- if coronary artery becomes completely blocked and myocardial infarction (heart attack) can result
- blockage of coronary arteries are treated by by-pass surgery or stent
what are risk factors of CHD (8)?
Age - become less flexible
Genetics - hypertension predisposes to develop CHD
Obesity - strain on heart
Disease
Diet - increases risk
Exercise - sedentary lifestyle increases risk of CHD
Sex - males have greater risk (due to low oestrogen level)
Smoking - nicotine causes vasoconstriction, raising blood pressure
