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Sep 12, 2023 · The terminal branches enter the tissues, and pass towards the capillary beds of the tissues in vessels called arterioles. Gas exchange occurs between the blood and the tissues. The blood is collected from the capillaries by venules, which unite to form the veins of the systemic circulation. These veins ultimately drain to the right atrium via ...
Figure 20.3 Structure of Blood Vessels (a) Arteries and (b) veins share the same general features, but the walls of arteries are much thicker because of the higher pressure of the blood that flows through them. (c) A micrograph shows the relative differences in thickness. LM × 160.
Figure 18.2.2 18.2. 2: Structure of Blood Vessels. (a) Arteries and (b) veins share the same general features, but the walls of arteries are much thicker because of the higher pressure of the blood that flows through them. (c) A micrograph shows a similarly sized artery and vein.
Arteries transport blood away from the heart and branch into smaller vessels, forming arterioles. Arterioles distribute blood to capillary beds, the sites of exchange with the body tissues. Capillaries lead back to small vessels known as venules that flow into the larger veins and eventually back to the heart.
- Shared Structures. Different types of blood vessels vary slightly in their structures, but they share the same general features. Arteries and arterioles have thicker walls than veins and venules because they are closer to the heart and receive blood that is surging at a far greater pressure (Figure \(\PageIndex{2}\)).
- Arteries. An artery is a blood vessel that conducts blood away from the heart. All arteries have relatively thick walls that can withstand the high pressure of blood ejected from the heart.
- Arterioles. An arteriole is a very small artery that leads to a capillary. Arterioles have the same three tunics as the larger vessels, but the thickness of each is greatly diminished.
- Capillaries. A capillary is a microscopic channel that supplies blood to the tissues, a process called perfusion. Exchange of gases and other substances occurs between the blood in capillaries and the surrounding cells and their tissue fluid (interstitial fluid).
The cardiovascular system, is a closed-loop system, such that blood is pumped out of the heart through one set of vessels (arteries) and then returns to the heart in another (veins). More specifically, one can consider that there are two closed-loop systems which both originate and return to the heart: the pulmonary and systemic circulations (see Fig. 1).
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The function of blood vessels is to deliver blood to the organs and tissues in your body. The blood supplies them with the oxygen and nutrients they need to function. Blood vessels also carry waste products and carbon dioxide away from your organs and tissues. Each type of blood vessel serves a different function:
