Vessel Wall - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 355

Tabl e 7. 5. Vein wall structure.

Vein type Caliber Wall

Microvenule 15-100 m Endothelium,

thin layer with CnFs,

± FBs,

SMCs if caliber > 50 m

Minivenule 100-300 m Continuous layer of SMCs,

± postcapillary sphincter

Venule 300-500 m e ia,

thin adventitia (EnFs, CnFs, FBs)

Drainage vein 0.5-2 mm Intima with subendothelium,

± EnF network,
adventitia

Collecting vein 2-9 mm Intima sometimes bounded

by EnF network,
media poorly developed,
except in inferior limbs,
thick adventita,
valves in zones of
greater caliber

Central vein 20-30 mm Adventitia of vena cava

with CMCs in the heart vicinity

7.3.1.4 Venous Valves

Perforating veins usually contain venous valves that prevent reflux of blood from
the deep veins into the superficial veins ( ostial valve ).
Although venous drainage in the human head and neck commonly does not
counter gravity, venous valves are also found throughout veins of these body
parts [ 660 ].
Vieussens valve is the ostial valve of the great cardiac vein located near the
coronary sinus that is provided at its ostium by the Thebesian valve [ 661 ].
Venous valves most often are bicuspid and located in stiffer expanded segments
(Figs. 7.2 and 7.4 ). Venous valves are made of connective tissue with elastic fibers
and few smooth myocytes, covered by the endothelium.
Veins usually have elliptical cross-sections. Valve leaflets are inserted on each
face of the vein wall, 15 whereas vein edges receive perforating and tributary

veins [ 665 ].

15 Valvular free borders of the superficial veins of inferior limbs are parallel to the skin surface.