Vessel Wall - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 356

Fig. 7.4 Limb valved vein
network, with a superficial
vein and a deep vein
anastomosed by a
communicating vein
equipped with ostial valves
for one-way circulation from
superficial to deep vein.

deep vein superficial vein

perforating vein

Endothelial cell density is significantly higher on the surface of valve leaflets
(about 10 cells per 1000 m 2 ) than on other venous surfaces (about 7 cells/1000

m 2 )[ 666 ]. Endothelial cells on the medial surface and on the lateral surface
of the valve leaflet are oriented parallel to the vein axis and perpendicular to it,
respectively.

7.3.2 Small Vessels

Small blood vessels of the microcirculation comprise perfusing arterioles, capillar-
ies (caliber 5-10 m), and draining venules (caliber 8-100 m).

7.3.2.1 Arterioles

Arterioles are composed of an endothelium surrounded by one or a few concentric
layers of smooth myocytes that regulate blood flow (Table 7.6 ). Arterioles thus have
a thin wall. Arterioles receive both sympathetic and parasympathetic innervation.