Very slender, hair-like in shape.
Any one of the minute vessels that connect the arterioles and venules, forming a network in nearly all parts of the body. Their walls act as semipermeable membranes for the interchange of various substances, including fluids, between the blood and tissue fluid; called also vas capillare.
Small, thin-walled blood vessels connecting arterial and venous blood systems that allow the exchange of materials between blood and tissues.
The smallest blood or lymph vessel, formed of single layers of interconnected endothelial cells, sometimes with loosely attached connective tissue basement cells for added support, and, in some tissues, a few smooth muscle cells for special contractions. Capillaries allow the transport across their membranes and between their crevices of diffusable nutrients and waste products. Blood capillaries expand and contract, depending upon how much blood is needed in a given tissue and how much is piped into them by the small arteries that feed into them. They further maintain a strong repelling charge that keeps blood proteins and red blood cells pushed into the center of the flow. Lymph capillaries have many open crypts that allow free absorption of interstitial fluid that has been forced out of the blood; these capillaries further tend to maintain a charge that attracts bits of cellular garbage too large to return through the membranes of exiting venous capillaries.
A microscopic blood vessel that connects the smallest arteries (arterioles) and the smallest veins (venules) to complete the circulation of blood at a cellular level. The capillary walls are membranes through which nutrients and oxygen pass from the blood into body cells, while waste such as carbon dioxide passes out.
An extremely narrow blood vessel, approximately 5-20 /un in diameter. Capillaries form networks in most tissues; they are supplied with blood by arterioles and drained by venules. The vessel wall is only one cell thick, which enables exchange of oxygen, carbon dioxide, water, salts, etc., between the blood and the tissues.
Any of the minute blood vessels, averaging 0.008 mm in diameter, that connect the ends of the smallest arteries (arterioles) with the beginnings of the smallest veins (venules).
A tiny blood vessel that carries blood between arteries and veins and through which nutrients and waste pass into and out of the blood.
Any of the conduits that transport blood between the tiniest arteries, known as arterioles, and the tiniest veins, referred to as venules. Capillaries create an intricate network throughout the body’s organs and tissues. Their slender walls possess permeability, thereby facilitating the exchange of blood and cells, enabling the transfer of vital components such as oxygen, glucose, carbon dioxide, and water (as part of the process of respiration).
Capillaries possess the ability to dynamically adjust their blood flow based on the specific requirements of different organs for oxygen and nutrients. For instance, during a vigorous run, a majority of capillaries in the leg muscles remain open, whereas during rest, many of them are closed. The opening and closing of capillaries in the skin contribute to the regulation of body temperature. At the entrance of each capillary, a small circular muscle controls the blood flow traversing through it.
The impact of a forceful strike to a specific region of the body can lead to the rupture of capillary walls, resulting in bleeding beneath the skin. This, in turn, gives rise to swelling and the appearance of bruising.
In elderly individuals, those taking high doses of corticosteroid medications, and those afflicted with scurvy (a deficiency in vitamin C), capillaries tend to become more delicate and prone to damage. As a consequence, these individuals have an inclination to develop purpura, which manifests as reddish-purple patches resulting from small areas of bleeding beneath the skin.
Tiny blood vessels that connect arteries and veins; a small lymphatic vessel; related to capillaries.