B1 The cardiovascular system Flashcards
(42 cards)
What is the cardiovascular system and what is it’s function?
It consists of the heart, blood vessels and blood. The function is to transport important substances around the body eg oxygen, glucose.
The heart is part of a double circulatory system meaning?
Blood passes through the heart twice per cycle.
What is pulmonary circulation?
The blood passes through the heart and is pumped to the lungs returning back to the heart.
What is systematic circulation?
The blood then passes through the heart a second time (blood is repressurised) and pumped around the body organs before returning to the heart.
What is mass flow? Give an example.
Blood moves around the body due to pressure difference between the pressure in the heart (high) and the pressure in the blood vessels (low).
Heart structure
The heart is a pump made of cardiac muscle (myogenic) - will beat/contract without any nervous stimulation. Muscle cells- are able to depolarise/generate own electrical pulses.
The heart has 4 chambers: seperated by muscular wall called septum, each side consists of upper chamber (atrium) and lower chamber (ventricle).
Describe the route that blood flows through the heart and around the body.
1) deoxygenated blood returns from the body in the vena cava and enters the right atrium.
2) the blood then passes via atrioventricular valve (tricuspid) into the right ventricle and out, via semilunar valve, into the pulmonary artery.
3) The blood now passes through the lungs and returns to the left atrium via the pulmonary vein.
4) the blood passes through a second AV valve (bicuspid) into left ventricle and then through semi lunar valve into the aorta and then body tissues.
Suggest the purpose of the valves in the heart
To prevent back flow of blood/ ensures that blood flows in one direction/ smooth flow of blood and maintains high blood pressure.
Role of the atrioventricular valves
- Left AV valve prevents back flow to left atria/ ensures blood pumped to aorta/ body.
- Right AV valve prevents back flow from right ventricle to right atria/ ensures blood is pumped to the lungs.
Role of semi-lunar valves
These are at the base of the arteries leaving the heart, they prevent blood from returning to the ventricle during diastole (heart at rest).
Characteristics of arteries (blood vessel)
- Transports blood from heart to organs (blood under high pressure).
- Thick walls made of fibrous proteins to resist damage due to high pressure of the blood, many muscle tissue (strengthening) and elastin fibres to withstand the high pressure generated by left ventricle during contraction.
- endothelium- reduced friction and gives a smooth flow
- narrow lumen- maintains pressure
Characteristics of capillaries
- wall has endothelial layer, one cell thick
- it’s involved in exchange of materials between blood and the tissue sells (site of diffusion)
- diameter very small + large number of capillaries- this creates greater friction and high surface area, reducing blood pressure and blood flow
-very thin walls- increased rate of diffusion - wall spaces- gaps between cells of the endothelial cells which allow rapid formation of tissue fluid and WBC to pass tissue spaces.
Characteristics of veins
- veins carry blood back to the heart from the tissue. (Blood is under low pressure) the vein wall doesn’t need to be thick.
- large lumens- to give low resistance
- thinner muscle layer- no need for vaso constriction as all blood going back to heart
- thinner elastic layer- as pressure is very low and wall does not need to stretch/ recoil
- semilunar valves- the residual blood pressure is very low, blood is moved along the vein when skeletal muscles contract.
Pressure changes in the arteries
Flow is fast and pressure is high and flunctuating due to the contraction of the left ventricle.
Pressure changes in the capillaries
Increased cross-sectional area causes increased friction which reduces blood pressure and flow changes from pulsar to smooth and speed of flow decreases.
Pressure in the veins
Pressure is low and flow is smooth and non-pulsar.
The chart shows the change in speed of flow and pressure of blood from the start of the aorta into the capillaries. Describe and explain the changes in the speed of flow of the blood in shown in the chart. (3 marks)
It shows a slow decrease in speed until it reaches the arterioles then a rapid decrease as there is an increase in cross sectional area of blood vessels leading to more friction in smaller blood vessels.
Explain how the structures of the walls and arteries and arterioles are related to their functions. (6 marks)
The arteries have many muscle and elastin fibres to withstand high pressure generated by the left ventricle during contraction and recoiling. The muscle also reduces diameter of lumen. It has a smooth epithelium layer which reduces friction and has less resistance.
Pressure changes in a graph
A- closed (Av): pressure in ventricle rises above that in atria
B- open (SL): pressure in ventricle rises above that in aorta
C- closed (SL): pressure in ventricle falls below that in aorta
D- open (AV): pressure in atrium rises above that in ventricles
What is blood composed of?
-Redblood cells
- white blood cells
- platelets: cell fragments that aid in clotting
What are the risks of blood transfusion (donating blood) ?
- Transfusing the wrong blood group
- infection
- reaction to the blood product
When a unit of blood has been donated, before it has been transfused what does it undergo?
- testing of blood for risk of infection
- testing for blood grouping
- taken to processing facility where wbc are removed and get split into rbc, platelets and plasma.
What causes the different blood group types (A,B,AB,O)?
Variations in the antigens on RBC membranes.
What are antigens?
They are proteins which are produced by the immune system that bind to antigens.
