Читать книгу Anatomy and Embalming - Charles Otto Dhonau - Страница 50

—The arteries are cylindrical vessels which serve to convey the blood from both ventricles of the heart to every part of the body. They are called arteries from the Greek words which mean “to contain air,” and they were supposed, by our ancients, to have this function until the time of Galen, when he refuted this opinion and showed that these vessels, though for the most part empty after death, actually contained blood. The distribution of the arteries may be compared to a tree, the common trunk of which corresponds to the aorta, and the smallest twigs corresponding to the minute capillaries. When one artery communicates with another it is said to anastomose, and this communication is very free between the larger as between the smaller branches. Anastomosis between trunks of equal size is found where great activity of the circulation is requisite, as at the base of the brain, where the two vertebrals unite to form the basilar artery.

In the limbs and arms the anastomoses are more numerous and of larger size around the joints. The branches of the artery above, unite with branches, from the vessels below. These anastomoses are called collateral circulations. The principal ones of interest to the embalmer are those of the deep brachial uniting with the recurrent radial and ulnar arteries, forming the collateral circulation in the arm; the deep femoral uniting with the recurrent posterior and anterior tibials, forming the collateral circulation in the leg; the superficial and deep mammary arteries, branches of the subclavian artery uniting with the superficial and deep epigastric arteries, branches of the external iliac, forming the collateral circulation over the abdomen and chest, and may be considered the longest collateral circulation in the body.

A terminal artery is one which forms no anastomoses; such vessels are found in the heart, brain, spleen, kidneys, lungs and mesentery.

Structure.—An artery consists of an internal, a middle and an external coat.

The inner coat consists of endothelial cells and elastic fibrous tissue, sometimes arranged longitudinally, but usually they form a distinct fenestrated membrane (similar to a doorscreen).

The middle coat consists mostly of elastic tissue and white fibrous tissue.

The external coat is called the fibrous coat. It contains fibrous connective tissue and elastic tissues.

Vasa-Vasorum.—Running in the outer wall of the artery, we find small capillary vessels, and their function is that of nourishing the outer wall, for the blood which passes through the artery does not nourish the artery from within, but depends on these small capillaries, called vasa-vasorum, for their nutrition.

The individual sheath, or arterial sheath, the covering for the artery, is composed of connective tissue, and at places may adhere very tightly to the artery.

Fig. 9—Valves of the veins.

Fig. 10—Cross section through a small artery and vein. (Klein and Noble Smith)