6.2 blood system Flashcards
1
Q
what is the purpose of the circulatory system?
A
- helps to facilitate the movement of molecules, bringing them from the external surfaces to the inner tissues and vice versa
2
Q
what does human blood consist of?
A
- plasma and cellular components
- plasma:
• 90% water
• plasma proteins, blood electrolytes (ions), other dissolved products - cellular components:
• 2 main types of cells: red blood cells (erythrocytes), white blood cells (leukocytes for defence and immunity)
• platelets: not true cells; more like fragments of cells w no organelles (involved in blood clotting)
3
Q
what is the purpose of arteries?
A
- convey blood at high pressure from the ventricles to the tissues of the body
- in general, transport blood away from the heart towards the rest of the body
- contractions of the ventricles generate the necessary pressure to move the blood in the blood vessels
- as arteries are the blood vessels nearest to the heart, are of high pressures
• how?? -> heart ventricles have thick muscular walls
• why?? -> against gravity? - helps body to carry out the function of transporting substances around the body
4
Q
what is the structure of arteries?
A
FROM IN TO OUT:
BASEMENT MEMBRANE
- not made of cells; connective tissues protein
TUNICA INTIMA (intimate) - mainly made of endothelial cells and connective tissues
TUNICA MEDIA (medium) - smooth muscles and elastic tissues
TUNICA EXTERNA
- mainly made of collagen fibres
5
Q
how is blood pressure maintained in between pump cycles?
A
- muscle and elastic fibres assist
- heart beats in cycles
- periods between each contraction where the pressure with the blood vessels will drop
- smooth muscles (tunica media) in arterial walls contract
- cross sectional area of arteries decreases
- increases pressure
- maintains the pressure between pump cycles
- elastic fibres (tunica media) stretch when pressure in arteries increases during ventricular contraction
- in between pump cycles fibres recoil and push inwards,
- collagen fibres (tunica externa) prevent artery from bursting during ventricular contraction
6
Q
what are capillaries? (structure etc)
A
- blood vessels that have thin walls consisting of a single layer of endothelial cells
- very narrow in diameter; about the width of a red blood cell
- as red blood cells pass through capillaries, cells may flex a little; increases the surface available for gaseous exchange with red blood cells
- when arteries branch into arterioles and then into capillaries, increases total surface area of blood vessels, increased efficiency for diffusion
- 1 celled thickness & presence of pores within capillary wall allows for increased permeability to certain substances
- capillaries covered with basement membrane, basement membrane is permeable to many substances and allows them to pass through freely
7
Q
how do veins carry blood?
A
- collect blood at low pressure from the tissues of the body and return it to the atria of the heart
- as blood in arteries are distributed to numerous capillaries before flowing into the veins, pressure of blood that enters veins much lower than arteries
- lumen of veins are also much larger than that of arteries, to maximise the flow of blood that is already at low pressure, back to the heart
- walls of veins are also thinner with a lesser amount of elastic fibres and muscles present within
- due to low pressures in veins, movement of blood is also helped along with the contraction of skeletal muscles around them, as well as the valves present within
- veins often run parallel to arteries, and the expansion and contraction in arteries can help push the blood along in veins
8
Q
what is the structure of veins?
A
IN TO OUT
- large central lumen through which blood flows
- endothelium
- thin inner layer of muscle and elastic fibres
- thin outer wall
9
Q
how is backflow of blood prevented?
A
- valves in veins and heart
- due to low pressures within veins, difficult for blood to flow against the forces of gravity
- to avoid backflow of blood due to gravity, numerous 1 way valves present in veins
- semi lunar valves made of connective tissues that fold flat against walls when blood flows in 1 direction, but open up when blood flows in opposite direction, closing vein and preventing backflow of blood
10
Q
compare structure of arteries, veins, and capillaries such that you can identify them from the structure of their walls
A
CAPILLARIES
- 1 cell thick
- generally small
ARTERIES
- thicker walls
- more elastic tissues and muscles
- small lumen
VEINS
- comparatively larger lumen
- thinner walls
11
Q
elaborate on william harvey’s discovery of the circulation of blood with heart acting as pump
A
- before harvey’s discoveries, people thought the supplies of arteries and veins were separate
- thought that arteries pump heat via heart to lungs for cooling, and veins pump natural blood from liver
- based on simple experiments, including those that dealt with the valves in veins, harvey discovered that:
• arteries and veins part of same network of blood vessels
• arteries brought blood from heart to rest of the body
• veins brought blood from rest of body back towards the heart
12
Q
explain the need and existence of separate blood circulation for lungs
A
- most land vertebrates have double circulation system, with separate circulation for lungs
- humans: 4 chambered heart split into left and right; left 2 handle taking in oxygenated blood from heart to pump to rest of body; right 2 take in deoxygenated blood to pump to lungs
- ensures that though blood flow is continuous (a red blood cell will alternate between pulmonary and systemic circuit), oxygenated and non- oxygenated blood do not mix
- circuits run at 2 pressures so ur lungs dont blow up lmao
- high pressure in systemic circuit so ur blood can run everywhere
- low pressure in pulmonary circuit so sensitive tissues in lungs are fine and so capillaries dont blow up;
- rbc move slower in lungs for more time for gaseous exchange
13
Q
why is double circulation needed for maintenance of different pressures?
A
- besides ensuring oxygenated and deoxygenated blood don’t mix, double circulation also allows for 2 different sets of pressures to be maintained
- blood pressure in pulmonary circuit much lower than systemic circuit, as blood has to travel shorter distance to lungs and back
- with lower pressure, blood also moves slower and have longer time in lungs for oxygen to diffuse into red blood cells
- systemic circuit needs much higher pressure to pump blood throughout body, especially in larger animals
- lower pressure needed means that muscle walls in right ventricles are much thinner
14
Q
briefly talk about the heart chambers
A
- atria (singular: atrium) receives blood from veins into heart, with left atrium receiving oxygenated blood from pulmonary vein and right atrium receiving deoxygenated blood from vena cavae
- atrioventricular (AV) valves prevent backflow of blood from ventricles to atria during ventricular contraction, with bicuspid valves in left and tricuspid valves in right
- semilunar valves present between arteries and ventricles to prevent backflow of blood into ventricles between cardiac contractions
15
Q
how is heart beat initiated?
A
- by group of specialized muscle cells in right atrium called sinoatrial node
- cardiac muscles contract under nervous stimulation (like most muscle cells), but unlike other muscles origin of the nerve impulses are NOT from brain
- all muscles are capable of transmitting impulses; muscle impulses trigger the muscle to contract
- sinoatrial node are a group of highly specialised muscle cells found in right atrium of heart
- can spontaneously produce electrical impulse that travels in a wave down throughout heart
- leads to contraction of cardiac muscles as expected during cardiac cycle
16
Q
how does the sinoatrial node act as a pacemaker?
A
- main function of the sinoatrial node is to send regular action potentials throughout heart, in place of direct regular impulses from brain
- hence acts as pacemaker, setting pace of cardiac contractions (heart rate)
- directly controls heart rate of individual
- however, 2 sets of nerves work together to increase or decrease the heart rate, hence bringing about regulation of heart rate
17
Q
detail the process of how sinoatrial node causes heart contractions?
A
- sinoatrial node sends out signal from right atrium, and is propagated to right atrium and across via bundles of his to left atrium
- results in contraction of atria of heart
- impulse moves down nervous pathways to another node in heart, known as atrioventricular (AV) node
- av node stimulated by nerve impulses from SA node, sends a signal across to septum and then down septum (between left and right ventricles) via purkinje fibres
- leads to ventricular contractions
18
Q
how can basal (resting) heart rate be altered?
A
- basal (resting) heart rate is determined and controlled by sinoatrial node
- can be altered directly with action of hormones on SA (sinoatrial) node, or via other receptors that detects changes in blood pH (carbon dioxide concentration and electrolyte levels) that sends nerve signal to SA node
19
Q
elaborate how 2 nerves (where are they from?) can increase / decrease heart rate?
A
- basal heart rate can be altered via other receptors that detects changes in blood pH (carbon dioxide concentration and electrolyte levels) that sends nerve signal to SA (sinoatrial) node
- 2 sets of nerves that originate from the medulla of the brain can alter heart rate of an individual
- sympathetic nerve can secrete a neurotransmitter, NORADRENALINE, to increase heart rate
- parasympathetic nerve (vagus nerve) can secrete a neurotransmitter, ACETYLCHOLINE, to reduce heart rate
20
Q
what is the effect of epinephrine on heart rate?
A
- several hormones can affect SA (sinoatrial) node directly to increase heart rate
- epinephrine (adrenaline) secreted by adrenal glands in response to various environmental changes, including sudden shock or the presence of toxins or chemicals like caffeine in the bloodstream (endocrine system)
- acts in similar manner as noradrenaline secreted by sympathetic nerves, and causes SA node to increase heart rate
- situations where there is stress, adrenaline secreted increases heart rate, increasing transport of oxygen and other substances needed for vigorous physical activity
21
Q
how does diastole work?
A
- cardiac cycle split into 2 series of events, diastole (relaxation of heart muscles) and systole (contraction)
DIASTOLE: - heart muscles relax
- blood flows from veins into atria of heart
- relaxation of ventricular muscles results in fall of pressure within ventricles, to below than aorta and pulmonary arteries
- causes the semilunar valves to close to prevent excessive backflow of blood back into the heart
- low pressures in ventricles also mean that atrioventricular valves will open and some blood can flow from atria into ventricles
22
Q
how does systole work?
A
- cardiac cycle split into 2 series of events, diastole (relaxation of heart muscles) and systole (contraction)
SYSTOLE: - due to pressure differences, blood will normally flow from veins into atria, across open atrioventricular valves into ventricles
- when ventricles about 70-80% full, atria contraction takes place, increasing atrial pressure and forcing blood to flow into ventricles
- ventricles will subsequently contract, leading to huge increase of ventricular pressure
• ventricular pressure exceeds atrial pressure and AV (atrioventricular) valves close
• ventricular pressure exceeds aortic (and pulmonary arterial) pressure and semilunar valves open - blood pumped from heart into arteries
23
Q
give a brief overview of atrial + ventricular systole + diastole (chambers, blood flow, valves)
A
ATRIAL SYSTOLE chambers: - atrium contracts - ventricle relaxed blood flow: - atrium to ventricle valves - av (atrioventricular) valve open - aortic valve closed
VENTRICULAR SYSTOLE chambers: - atrium relaxed - ventricle contracts blood flow: - ventricle to aorta valves: - av valve closed - aortic valve open
DIASTOLE chambers: - atrium relaxed - ventricle relaxed blood flow: - passive flow into atrium and ventricle valves: - av valve open - aortic valve closed
24
Q
what are the causes (main cause) of occlusion of coronary arteries?
A
- occlusion refers to blockage of a tube
- main cause of occlusion in coronary arteries is
atherosclerosis - atherosclerosis mainly due to deposition of cholesterol in arteries
- atheromas, or fatty deposits, develop in arteries over time and reduce cross sectional diameter of arteries
- results in damage to arterial walls, and body tries to heal damage by repairing area with fibrous tissues
- fibrous tissues over time will lead to formation of plaque on arterial walls
- when plaque ruptures, blood clotting can be triggered forming a thrombus that can restrict blood flow
- thrombus can also move to other arterioles and can lead to blockages of other blood vessels
25
Q
what are the consequences of occlusion of coronary arteries?
A
- occlusion refers to blockage of a tube
- main cause of occlusion in coronary arteries is
atherosclerosis - narrowing of coronary arteries due to atherosclerosis can cause blockage or result in increased blood clot formations there leading to blockage
- direct consequence would be reduced blood flow to the cardiac muscles, meaning that less oxygen and nutrients are brought to heart muscles
- can lead to muscle damage, and in acute situations lead to heart attacks (myocardium infarctions) to occur
