Page 404 - Atlas of Histology with Functional Correlations

and teeth. Lymph capillaries also take up and deliver the absorbed lipids from

the intestines into the bloodstream.

Supplemental micrographic images are available at
www.thePoint.com/Eroschenko13e under Blood Vessels.

FIGURE 10.4 | Different Blood and Lymphatic

Vessels in Connective Tissue

This composite figure illustrates a section of irregular connective tissue with
nerve fibers, blood and lymphatic vessels, and adipose tissue. To illustrate

structural differences, the vessels have been sectioned in transverse, longitudinal,
or oblique planes.

A small artery (3) with its wall structure is shown in the lower left corner of
the illustration. In contrast to veins (11), an artery has a relatively thick wall and

a small lumen. In cross section, the wall of a small artery (3) exhibits the
following layers:

Tunica intima (4) is the innermost layer. It is composed of endothelium
(4a), a subendothelial (4b) connective tissue, and an IEL (membrane) (4c),
which separates the tunica intima (4) from the tunica media (5).

Tunica media (5) is predominantly composed of circular smooth muscle
fibers with a loose, interspersed network of fine elastic fibers.
Tunica adventitia (6) is the connective tissue layer around the vessel that

contains small nerves and blood vessels. In tunica adventitia (6), the blood
vessels are collectively called vasa vasorum (7), or “blood vessels of the
blood vessel.”

Arteries with about 25 or more layers of smooth muscle fibers in the tunica

media are called muscular or distributing arteries. Elastic fibers become more
numerous in the tunica media as thin fibers and networks.

A venule (9) and small vein (11) are also illustrated with a thin wall and a
large lumen. The thin wall, however, appears to have many cell layers when the
vein is sectioned in an oblique plane (9). In cross section, the wall of the vein

exhibits the following layers:

Tunica intima composed of endothelium (11a) and an extremely thin layer

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