b. Blood Matching. There are a number of substances (antigens) on the
surfaces of RBCs that vary among individuals. The blood of other individuals may
contain or develop antibodies to these antigens. Before blood transfusions, the blood of
the recipient and the donor must be matched to avoid potentially fatal reactions.
Important systems of such antigens include the ABO system and the Rh system.
Section III. THE BLOOD VESSELS--THE CONDUITS OF THE
The blood vessels are tubular structures throughout the entire body. Since this
tubular system is continuous (without interruption or opening), we sometimes refer to it
as a closed system.
10-19. TYPES OF BLOOD VESSELS AND THEIR CONSTRUCTION
In general, there are three types of blood vessels--arteries, veins, and
capillaries. We use the following abbreviations:
A. = artery
V. = vein
Aa. = arteries
Vv. = veins
NAVL = nerve(s), artery(ies), vein(s), lymphatic(s)
a. Three General Layers. In general, a blood vessels has a wall composed of
(1) Intima. The innermost layer is the intima. The intima is a simple
epithelium made up of a single layer of flat epithelial cells.
(2) Media. The main portion of the wall is the media. It is made up of a
combination of FCT and smooth muscle tissue.
(3) Adventitia. The outer surface of the blood vessel is the adventitia. It is
an FCT layer.
b. Comparison of the Structures of Arteries and Veins. Given an artery and
a vein with similar inner diameters, the artery will have a thicker wall than the vein. This
greater thickness is due to the presence of more smooth muscle tissue and the
presence of elastic FCT as a significant element.