Vascular System- Functions to transport vital materials between the external environment and the internal fluid environment of the body. It carries oxygen; nutrients; waste products , including carbon dioxide; hormones; defense elements; and cells involved in wound healing.
- Consists of the heart and vessels (arteries, capillaries, veins) that transport bloodthrough all parts of the body.
- Includes the lymphatic vessels, a set of channels that begin in the tissue spaces and return excess tissue fluid to the bloodstream.
| Circulatory loops |
Pulmonary circulation
- Transports blood from the right ventricle through the pulmonary arteries to the lungs for the exchange of oxygen and carbon dioxide and returns it to the left atrium of the heart through the pulmonary veins.
Systemic circulation
- Transports blood from the left ventricle through the aorta to all parts of the body and returns it to the right atrium through the superior and inferior venae cavae and the cardiac veins.
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| Heart |
- Is a hollow, muscular, four-chambered organ that pumps blood to two separate circulatory loops, the pulmonary circulation and the systemic circulation.
- Is regulated in its pumping rate and strength by the autonomic nervous system,which controls a pacemaker (i.e., sinoatrial node).
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| Blood vessels | - Carry blood to the lungs, where carbon dioxide is exchanged for oxygen.
- Carry blood to the intestines, where nutritive materials in fluid form are absorbed,and to the endocrine glands, where hormones pass through the vessel walls and are distributed to target cells.
- Transport the waste products of tissue fluid to the kidneys, intestines, lungs, and skin, where they are excreted.
- Are of four types: arteries, veins, capillaries, and sinusoids.
Arteries
- Carry blood away from the heart and distribute it to all parts of the body.
- Have thicker and stronger walls than do veins.
- Consist of three main types: elastic arteries, muscular arteries, and arterioles.
Capillaries
- Are composed of endothelium and its basement membrane and connect the arterioles to the venules.
- Are the sites for the exchange of carbon dioxide, oxygen, nutrients, and waste products between the tissues and the blood.
- Are absent in the cornea, epidermis, and hyaline cartilage.
- May not be present in some areas where the arterioles and venules have direct connections (arteriovenous anastomoses or arteriovenous shunts ), which may occur in the skin of the nose, lips, fingers, and ears, where they conserve body heat.
Veins
- Carry blood toward the heart from all parts of the body.
- Consist of the pulmonary veins , which return oxygenated blood to the heart from the lungs, and the systemic veins , which return deoxygenated blood to the heart from the rest of the body.
- Contain valves that prevent the reflux of blood and have venae comitantes that closely accompany muscular arteries in the limbs.
Sinusoids
- Are wider and more irregular than capillaries.
- Substitute for capillaries in the liver, spleen, red bone marrow, carotid body, adenohy-pophysis, suprarenal cortex, and parathyroid glands.
- Have walls that consist largely of phagocytic cells.
- Form a part of the reticuloendothelial system , which is concerned chiefly with phagocytosis and antibody formation.
Portal system
- Is a system of vessels in which blood traveling through one capillary bed passes through a second capillary network before it returns to the systemic circulation.
- Consists of the hepatic portal system in which blood from the intestinal capillaries passes through the hepatic portal vein and then hepatic capillaries (sinusoids) to the hepatic veins and the hypophyseal portal system in which blood from the hypothalamic capillaries passes through the hypophyseal portal veins and then the pituitary capillary sinusoids to the hypophyseal veins.
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