Vessel Wall - Tissue Functioning and Remodeling in the Circulatory and Ventilatory Systems - page 353

Tabl e 7. 4. Comparison bet ween a vein and its associated artery wal ls.

Artery Vein

Shape Circular Elliptical

Wall Thick Thin

Intima Very thin

Media Prominent Weak

IEL Quasi-absent

1

2

1

3

q q

Fig. 7.2 Bicuspid venous valves. ( Left ) Cross and axial cut of a vein. ( Right ) Open and spread
vein after axial incision of a wall edge (1: orifice of communication vein at the vein edge; 2: cusp
free border in front of the vein face; 3: valve insertion lines). The valvular sinuses are behind the
cusps. The luminal face is smooth; the parietal face is rough.

7.3.1.3 Veins

Vein walls are thinner than artery walls, whereas the bore is larger (Table 7.4 ). The
intima is very thin. Internal and external elastic laminae are either absent or very
thin. The media is thinner than the adventitia.
Medium-sized veins are characterized by the presence of valves to prevent
transient blood return to upstream segments during muscular compression (Figs. 7.2
and 7.3 ).
The largest veins of the abdomen and thorax have very thick adventitia that
contains bundles of longitudinal SMCs and vasa vasorum. Valves are absent. The
main features of the wall are given for different kinds of veins, sorted by their bore,
in Table 7.5 .
Different gene expression occurs between arterial and venous walls that are
exposed to different mechanical stress magnitudes. γ -Catenin (or plakoglobin),