Cardiovascular System Flashcards
Describe tunica externa
loose fibrous connective tissue, outer layer of vessel
describe the tunica media
layer of smooth muscle, 2 outmost layer
tunica intima
endothelial cells, innermost layer
Which type of artery delivers to specific organs
Muscular arteries
which type of artery is found nearest the heart?
elastic arteries
which type of artery is more active in vasoconstriction
muscular arteries
Describe the structure of arterioles
Single layer of spiralling smooth muscle
How to arterioles react in response to e.g. cold or shock
Can constrict so blood flow bypasses tissues
What are the two types of capillaries?
Fenestrated and continuous
Why type of capillary is least permeable?
Continuous
Where are continuous capillaries found?
Brain, lungs and muscles
What is the difference between fenestrated and continuous capillaries?
Fenestrated are ‘leakier’ - small pores and small gaps between cells - allow for exchange of larger molecules
What are the 3 layers of blood vessels?
- tunica externa/adventitia
- tunica media
-tunica intima
How many layers are veins made of?
three
Do arteries of veins have more smooth muscle/elastin?
Arteries have more
What are venules?
The smallest, post-capillary blood vessels
What percentage of blood is kept as reserve in veins?
65%
Why are there more venous valves in the lower limbs?
to stop blood flowing backwards
Are venules porous?
Yes, very
What are venous sinuses
Group of sinuses that drains venous blood circulating from cranial cavity
What is the venous return
the volume of blood flowing back to heart through veins
3 things that venous return is affected by?
- pumping of the heart
- skeletal muscle pump
- respiratory pump
What is the pericardium?
the fibrous sack surrounding heart
Describe 4 functions of the pericardium
- lubricated moving surfaces
- prevents ventricles over-expanding
- holds heart in position
- forms a barrier to prevent the spread of infections/cancer cells
What is pericarditis
Inflammation of pericardial sac
What is pericardial effusion
Build up of fluid in the sack
What is pericardial tamponade
Fluid build up in the sac causing problems with heart function
What is myocardium? What is it made of?
The muscle of the heart, made up of myocytes
Describe the 4 properties of the myocardium
- automaticity
- excitability
- conductivity
- contractability
What is automaticity?
The ability to initiate a response spontaneously
What is excitability?
The ability to respond to a stimulus
What is conductivity?
The ability to transmit an impulse from one cell to another
What is contractibility?
The ability to contract after an electrical stimulus
At what rate does the SA node conduct?
60-100BPM
At what does the AV junction conduct? Why would it do this?
40-60BPM. If the SA node stopped working
At what rate do the ventricular pacemaker cells conduct? Why would they do this?
<30-40 BPM. If SA node and AV junc. stop working
Describe the endocardium
lining of heart and valves. smooth membrane made up of flattened epithelial cells continuous with that of blood vessels
Why is the left ventricle thicker?
Forces oxygenated blood into aorta and through arterial system
Where is the pulmonary valve?
Between right ventricle and pulmonary artery
Where is the tricuspid valve?
Between right atrium and ventricle
Where is mitral valve?
Between left atrium and ventricle
Where is aortic valve?
Between left ventricle and aorta
Where does myocardium get it’s blood supply?
From coronary arteries
What is the function of coronary veins?
Return de-oxygenated blood from myocardium back into right atrium
What are the 3 stages of the cardiac cycle?
- Atrial and ventricular diastole
- Atrial systole
- Ventricular systole
What is the cardiac output?
amount of blood pumped by heart in 1 minute
How do you calculate cardiac output?
Heart rate x stoke volume
Define stroke volume
volume of blood pumped out of left ventricle during each systolic cardiac contraction
Approximate adult male and female cardiac outputs:
male at rest: 5.5L/min
female: 5L/min
Define preload
stretch of myocardium of ventricles at the end of diastole
Define afterload
the amount of resistance that the left ventricle must overcome to circulate blood
What may afterload be affected by?
cold, stress, hyperventilation
Define contractility
the strength of the contraction of the myocardium
Identify two things that may affect contractility
Heart failure, ischaemia
