
Large vein
The tunica adventitia of large veins forms the thickest portion of the wall and completely fills the field of this image of the vena cava. Tunica adventitia is composed primarily of connective tissue, but often contains longitudinally orientated smooth muscle fibers as well. 400x

Location of image
The tunica adventitia of large veins forms the thickest portion of the wall and completely fills the field of this image. The tunica adventitia is composed primarily of connective tissue, but often contains longitudinally orientated smooth muscle fibers as well, as seen in this image of the vena cava. 400x

Connective tissue
The tunica adventitia of large veins forms the thickest portion of the wall and completely fills the field of this image. The tunica adventitia is composed primarily of connective tissue, but often contains longitudinally orientated smooth muscle fibers as well, as seen in this image of the vena cava. 400x

Longitudinal smooth muscle
The tunica adventitia of large veins forms the thickest portion of the wall and completely fills the field of this image. The tunica adventitia is composed primarily of connective tissue, but often contains longitudinally orientated smooth muscle fibers as well, as seen in this image of the vena cava. 400x