Blood Vessels

Question 1

What are 3 properties a blood vessel must have?

Answer 1

• be resilient
• be flexible
• always remain open

Question 2

general blood vessel structure from the inside out

Answer 2

lumen
tunica intima
tunica media
tunica externa/adventitia

Question 3

tunica intima

Answer 3

• thinnest layer
• endothelium - simple squamous endothelium
• basal lamina (basement membrane) of epithelial cells
• subendothelial connective tissue

Question 4

tunica media

Answer 4

smooth muscle fibres in loose connective tissue
may contain elastic fibres

Question 5

tunica externa

Answer 5

connective tissue
merges with surrounding connecting tissue
may contain vaso vasorum - vessel within the tissue that provides it with blood

Question 6

arteries vs veins

Answer 6

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

Question 7

3 types of arteries

Answer 7

• elastic (conducting)
• muscular (distributing)
• arterioles (resistance vessels)

Question 8

elastic arteries adap and prop

Answer 8

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

Question 9

muscular arteries adap and prop

Answer 9

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

Question 10

arterioles struc and prop

Answer 10

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

Question 11

capillaries

Answer 11

• 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

Question 12

continuous capillaries

Answer 12

• majority are continuous
• no gaps between cells
• in skeletal/smooth muscle, CT and lungs

Question 13

fenestrated capillaries

Answer 13

• 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

Question 14

sinusoidal

Answer 14

• 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

Question 15

capillary beds and the important parts in it

Answer 15

Metarteriole
Precapillary sphinter
arteriovenous anastomoses

Question 16

metarteriole function

Answer 16

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

Question 17

precapillary sphincter function

Answer 17

guards entrance to each capillary
contractions narrow entrance = reduces flow
relaxation dilates entrance = inc fliw

Question 18

arteriovenous anastomoses function

Answer 18

form direct communication between arteriole and venule

when dilated, blood can bypass cap bed and flow direct to venous circulation

Question 19

venules

Answer 19

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

Question 20

veins: how are they classified, properties and struc adap

Answer 20

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

Question 21

how do valves work and how we stop backflow in lower limbs?

Answer 21

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

Question 22

order of vessels according to pressure (high to low)

Answer 22

aorta
elastic arteries (conducting)
muscular arteries (distributing)
arterioles (resistance vessels)
capillaries
venules
medium-sized veins
large veins
vena cavae

Question 23

what elastic artery is located beneath your collarbone

Answer 23

subclavian artery