Blood Vessels Flashcards
What are 3 properties a blood vessel must have?
- be resilient
- be flexible
- always remain open
general blood vessel structure from the inside out
lumen
tunica intima
tunica media
tunica externa/adventitia
tunica intima
- thinnest layer
- endothelium - simple squamous endothelium
- basal lamina (basement membrane) of epithelial cells
- subendothelial connective tissue
tunica media
smooth muscle fibres in loose connective tissue
may contain elastic fibres
tunica externa
connective tissue
merges with surrounding connecting tissue
may contain vaso vasorum - vessel within the tissue that provides it with blood
arteries vs veins
this is when comparing corresponding vessels
A:
- blood under high pressure
- thick walls
-smaller lumen
- more resilient, maintains shape
V:
- blood under low pressure
- thin walls
- may have valves to prevent backflow
3 types of arteries
- elastic (conducting)
- muscular (distributing)
- arterioles (resistance vessels)
elastic arteries adap and prop
aka conducting
e.g. aorta, brachiocephalic, common carotid
diameter - up to 2.5cm
withstand changes in bp during cardiac cycle
ensure cont bloof flow
adaptations:
thick tunica media w/ many elastic fibres - recoil ensure cont blood flow
few smooth muscle cells
muscular arteries adap and prop
aka distributing
e.g. brachial, femoral
diameter 0.5mm-0.4cm
distributes blood to muscles and organs (branches off from aorta)
capable of vasodilation and vasocontriction to control rate of flow
to suit needs of organ
struc adap:
loads of smooth muscle cells in tunica media
distinct internal and external elastic laminae
thick tunica media
arterioles struc and prop
capable of vasocontriction and vaso dilation
controls blood flow to organs
involved in bp control
diameter <30 micrometres
struc adap
1-2 layers of smooth muscle cells in tunica media
poorly defined tunica externa
capillaries
- connect arterioles & venules
(micro circulation) - gas exchange
- thin walls = diffusion
- slow blood flow to allow time for exhange
- struc permits 2 way exchange
- 8micrometres in diamter
- found near almost every cell
continuous capillaries
- majority are continuous
- no gaps between cells
- in skeletal/smooth muscle, CT and lungs
fenestrated capillaries
- pores penetrate endothelial lining
- used in rapid exchange of water/large solutes (e.g. small peptide)
- or in absorption (kidney, endocrine glands, choroid plexus (makes the cerebrospinal fluid))
- there are intercellular clefts - gaps between adjacent cells
further allows ions to pass through
sinusoidal
- spaces between endothelial cells
- incomplete/absent basement memb
- exhange of large solutes (plasma proteins)
- in the specialised lining cells (liver for absoribing things like proteins, or damaged blood cells that are engulfed by phagocytic cells)
- blood moves slowly through sinusoids to allow this
capillary beds and the important parts in it
Metarteriole
Precapillary sphinter
arteriovenous anastomoses
metarteriole function
supplies single capillary bed
has a ‘thoroughfare channel’ which leads to the vein on the other side
has numerous caps leading off it
constriction of this can reduce floe to a whole cap bed
precapillary sphincter function
guards entrance to each capillary
contractions narrow entrance = reduces flow
relaxation dilates entrance = inc fliw
arteriovenous anastomoses function
form direct communication between arteriole and venule
when dilated, blood can bypass cap bed and flow direct to venous circulation
venules
collect blood from cap beds and deliver it to small veins
diameter ~ 20micrometres
stuc adap:
small ones have endothelium on BM
larger ones have inc numbers of smooth muscle cells on outside of endothelium
veins: how are they classified, properties and struc adap
calssified according to size:
- small <2mm
- med 2-9mm
- large >9mm (e.g. sup & inf vena cavae)
low pressure system
easily distensible (capacitance) - can stretch and expand
struc adap:
- thin walled
- tunica externa is predominant
- some have valves
how do valves work and how we stop backflow in lower limbs?
open and close depending on contraction,
prevents bakflow
musculovenous pump is the thing in legs that will contract and force blood upwards, the valves then stop backlfow
order of vessels according to pressure (high to low)
aorta
elastic arteries (conducting)
muscular arteries (distributing)
arterioles (resistance vessels)
capillaries
venules
medium-sized veins
large veins
vena cavae
what elastic artery is located beneath your collarbone
subclavian artery
