Cardiovascular Histology

Question 1

Small Artery / Small vein characteristics

Answer 1

Small Artery: thick media, contain internal and external elastic lamina, thin adventitia.

Small Vein: Thin media, thick adventitia, contain valves to prevent backflow.

Question 2

Elastic Arteries

Answer 2

Largest
Include Aorta, Subclavians, and Iliacs

Tunica intima: longitudinal smooth muscle cells in subendothelium, internal elastic lamina blends with tunica media
Tunica media: 40-70 fenestrated elastic laminae, smooth muscle, collagen type III***, vasa vasorum (vessels that supply walls of larger vessels)
Tunica adventitia: longitudinal type I collagen, elastic fibers, vasa vasorum, nerves, this layer limits expansion of the vessel

Question 3

Muscular Arteries

Answer 3

Medium size
Tunica intima: sparse subendothelial connective tissue, prominent internal elastic lamina (may be wavy, split or fused with basal lamina)
Tunica media: abundant smooth muscle in circular pattern (controls blood flow), type I collagen, elastic fibers, external elastic lamina
Tunica adventitia: longitudinal type I collagen, elastic fibers, vasa vasorum, nerves, this layer limits expansion of the vessel

Question 4

Arterioles

Answer 4

Tunica intima: endothelium with Weibel-Palade granules (von Willebrand’s factor), basal lamina, larger arterioles may have an internal elastic lamina
Tunica media: several layers of smooth muscle which control blood flow
Tunica adventitia: thin layer of connective tissue

Question 5

Capillaries (3 types)

Answer 5

7-9 um diameter (smallest)
Continuous: tight junctions between endothelial cells. No fenestrations.
Fenestrated: Leaky, contains pores with diaphragms
Sinusoidal: endothelium is discontinuous***. Incomplete basal lamina.

General Characteristics:
Tunica intima: endothelium, PERICYTES, basal lamina
Tunica media: NONE
Tunica adventitia: few reticular fibers

Question 6

Veins: Venules

Answer 6

Large Lumen, thin walls, pericytes, circular smooth muscle in media

Question 7

Small / Medium veins

Answer 7

Tunica intima: no internal elastic lamina*
Tunica media: HAS smooth muscle and collagen*
Tunica adventitia: thick, vasa vasorum
Contain valves

Question 8

Large Veins

Answer 8

Tunica intima: well developed
Tunica media: thin with smooth muscle and collagen
Tunica adventitia: large with smooth muscle and collagenous connective tissue