Structure and function of blood vessels

Question 1

3 layers of blood vessels

Answer 1

Intima: endothelium in contact with blood + some CT

media: smooth muscle + CT
adeventitia: mostly loose CT

Question 2

Arteries - histology

Answer 2

tunica media most prominent
concentric smooth muscle predominate in media
concentric elastic tissue laminae produced by smooth muscle cells

Question 3

Elastic (conduit) arteries

Answer 3

elastic recoil

expands in systole, recoil in diastole

Question 4

Muscular (distributing) arteries

Answer 4

prominent tunica media

adventitia has less elastic tissue, more collagen

Question 5

Arterioles

Answer 5

mainly regulate BP
<1 mm diameter
media has 1-2 layers of smooth muscles

Question 6

Veins - histology

Answer 6

thin and distensible
often collapsed in histologic sections 
collagen rather than elastin in media
relatively thick adventitia + vasa vasora 
flap-like valves to prevent backflow

Question 7

Large veins

Answer 7

capacitance vessels under low pressure

Question 8

Muscular veins

Answer 8

thin media
prominent adventitia: smooth muscle + collagen
lack elastin laminae
has vasa vasora
interior valves counter gravity

Question 9

Venules

Answer 9

Thin porous walls - diapedesis in inflammation

thinner walls, irregular lumens, discontinuous layer of smooth muscle cells in media

Question 10

Capillaries

Answer 10

single-layer flattened endothelial cells + pericytes on basement membranes.
Small diameter: 7-10 um, accommodates 1 RBC

Types:

• tight: tight junctions e.g. BBB
• fenestrated: allows for rapid transport of water and small molecules, e.g. in endocrine/renal tissues
• sinusoidal: large diameter, porous, discontinuous lining, no basement membrane e.g. liver/spleen/bone marrow