Blood Vessels Flashcards
What are the components of blood vessels ?
- endothelium
- smooth muscle
- connective tissue
Describe the structure of endothelium
- thin and flat cells
- link together by cell junctions to form tubes
Explain the function of endothelium
- line the entire cardiovascular system
- keep blood in the system
- allow transfer between the vessels and the surroundings
What are the 2 circulatory systems ?
- pulmonary system (right side)
- systemic system (left side)
What is the overall strategy of blood vessels ?
Heart > elastic artery > muscular artery > arteriole > capillary > venule > vein (and back to the heart)
What is the function of the elastic arteries ?
- smooth blood flow
- at high pressure so the wall can stretch and the volume of the vessel can increase
What is the function of the muscular artery ?
Note - also known as distributing artery
- controls and distributes blood flow to different parts of the body
What is the function of arterioles ?
Pressure control to the capillaries
What is the function of the capillaries ?
- have very thin walls so majority of exchange takes place here
What is the function of the venules ?
- gathers blood from the capillaries
- fluid exchange between plasma and tissue fluid
What is the function of the veins ?
Return of the blood to the heart
What is the general structure of the blood vessels ?
(Except capillaries and sinusoids)
- they have 3 layers :
1) tunica intima
2) tunica media
3) tunica adventitia
What are the boundaries of the tunica media ?
- internal boundary is the internal elastic lamina
- external boundary is the external elastic lamina
Describe the structure of the tunica intima
- made of endothelium and little amounts of connective tissue
- innermost layer
Describe the structure of the tunica media
- made up of smooth muscle and connective tissue
- makes up the majority of the vessel
Describe the structure of the tunica adventitia
- made up of connective tissue
- outermost later
- holds the vessel together
Describe the orientation of smooth muscle in the blood vessels
- has a circular arrangement
- controls diameter of the vessel
Give some examples of elastic arteries
- aorta
- pulmonary artery
Describe blood supply to large arteries
- the walls of large arteries are too thick to receive adequate nutrient supply and waste disposal from the centre of the vessel
- so these vessels have blood vessels within their walls
- this is known as vasa vasora
What are terminal arterioles ?
- control blood flow to capillary beds
- the pressure within them is enough to get blood through but not too much to burst the capillaries
What are the 3 types of endothelium ?
- continuous
- fenestrated
- discontinuous
Describe the structure and function of continuous endothelium
- no gaps
- complete basement membrane
- line nearly all blood vessels and capillaries
- allow the exchange of solutes and gases
Describe the structure and function of fenestrated endothelium
- there are pores between the endothelial cells
- complete basement membrane
- found in the capillaries of endocrine glands
- allow the exchange of larger molecules such as hormones
Describe the structure and function of discontinuous endothelium
- there are gaps between the endothelial cells
- incomplete basement membrane
- found in sinusoids which occur in the bone marrow
- allow the exchange of whole cells
What are sinusoids ?
Big capillaries with very thin walls
Describe the structure of veins
- small tunica media and large tunica adventitia
- contain valves
Describe the structure and function of valves
- they are folds of the tunica intima
- they ensure one way flow of blood
Why do arteries and veins run together ?
- the blood flowing through the artery causes it to pulse
- the pulse causes the vein to be massaged and this allows blood to flow through the vein and back into the heart
What is the importance of muscle contraction in relation to veins ?
Muscle contraction squeezes veins and moves blood along
