Rafii, J. Butler, and B. Ramasamy, A. Kusumbe, and R. Kusumbe, T. Itkin, S. Gur-Cohen, T. Lapidot, and R. Carmeliet and R. Trueta and J. View at: Google Scholar A. Kusumbe, S.
Ramasamy, and R. Maes, T. Kobayashi, M. Selig et al. Kusumbe, L. Wang, and R. S82—S89, Ferron, E. Hinoi, G. Karsenty, and P. Ferron, J. Wei, T. Yoshizawa et al.
Lee, H. Sowa, E. Hinoi et al. Mosialou, S. Shikhel, J. Liu et al. Oury, L. Khrimian, C. Denny et al. Yadav, J. Ryu, N. Suda et al. Kovacs and H. Panda, D. Miao, I. Bolivar et al. Kopp, S. Avecilla, A. Hooper, and S. Morrison and D. Crisan, S. Yap, L. Casteilla et al. Shi and S. Cumming and M. Ray, M. Kawabata, and J. An experimental method for the quantitative determination of bone blood flow. View at: Google Scholar M. Marenzana and T. Tomlinson and M. Kusumbe, M. Schiller et al. Kopp, A.
Hooper, S. Avecilla, and S. Nombela-Arrieta, G. Pivarnik, B. Winkel et al. Ramasamy, T. Itkin et al. Gur-Cohen, J. Spencer et al. Spencer, F. Ferraro, E. Roussakis et al. Parmar, P. Mauch, J. Vergilio, R. Sackstein, and J. Winkler, V. Barbier, R. Wadley, A. Zannettino, S. Williams, and J. Suda, K. Takubo, and G. Ejtehadifar, K. Shamsasenjan, A. Movassaghpour et al. Keith and M. Takubo, N. Goda, W. Yamada et al. Provot, D. Zinyk, Y. Gunes et al. Schipani, H. Ryan, S. Didrickson, T.
Knight, and R. View at: Google Scholar N. Ferrara, H. Gerber, and J. Zelzer and B. Maes, P. Carmeliet, K. Moermans et al. Zelzer, R. Mamluk, N. Ferrara, R. Johnson, E. Schipani, and B. Schipani, C. Maes, G. Carmeliet, and G. Wan, S. Gilbert, Y. Wang et al. Rankin, C. Wu, R. Khatri et al. North, W. Goessling, M. Peeters et al. Dinenno, P. Jones, D. Seals, and H. Wang, F. Zhou, P. Zhang et al. Griffith, D. Yeung, P. Tsang et al. Capillaries are very tiny blood vessels — so small that a single red blood cell can barely fit through them.
They help to connect your arteries and veins in addition to facilitating the exchange of certain elements between your blood and tissues.
This is why tissues that are very active, such as your muscles, liver , and kidneys , have an abundance of capillaries. Capillaries connect the arterial system — which includes the blood vessels that carry blood away from your heart — to your venous system. Your venous system includes the blood vessels that carry blood back to your heart.
The exchange of oxygen, nutrients, and waste between your blood and tissues also happens in your capillaries. This happens through two processes:.
Additionally, white blood cells from your immune system can use capillaries to reach sites of infection or other inflammatory damage. There are three types of capillaries. Each has a slightly different structure that allows to function in a unique way. These are the most common types of capillaries. They contain small gaps in between their endothelial cells that allow for things like gases, water, sugar glucose , and some hormones to pass through. The continuous capillaries in the brain are an exception, however.
These capillaries are part of the blood-brain barrier, which helps to protect your brain by only allowing the most essential nutrients to cross. They contain small pores, in addition to small gaps between cells, in their walls that allow for the exchange of larger molecules.
This type of capillary is found in areas that require a lot of exchange between your blood and tissues. Examples of these areas include:. Sinusoid capillaries allow for the exchange of large molecules, even cells. The surrounding basement membrane is also incomplete with openings in many places. These types of capillaries are found in certain tissues, including those of your liver , spleen, and bone marrow. For example, in your bone marrow, these capillaries allow newly produced blood cells to enter into the bloodstream and begin circulation.
While capillaries are very small, anything unusual in their functioning can cause visible symptoms or even potentially serious medical conditions.
Port wine stains are a type of birthmark caused by the widening of capillaries located in your skin. This widening causes the skin to appear pink or dark red in color, giving the condition its name.
Over time, they can darken in color and thicken. Petechiae are small, round spots that appear on the skin. They happen when capillaries leak blood into the skin. One system , the pulmonary vessels, transports blood from the right ventricle to the lungs and back to the left atrium. The other system, the systemic vessels, carries blood from the left ventricle to the tissues in all parts of the body and then returns the blood to the right atrium.
Based on their structure and function, blood vessels are classified as either arteries , capillaries , or veins. Arteries carry blood away from the heart. Pulmonary arteries transport blood that has a low oxygen content from the right ventricle to the lungs. Systemic arteries transport oxygenated blood from the left ventricle to the body tissues. Blood is pumped from the ventricles into large elastic arteries that branch repeatedly into smaller and smaller arteries until the branching results in microscopic arteries called arterioles.
The arterioles play a key role in regulating blood flow into the tissue capillaries. About 10 percent of the total blood volume is in the systemic arterial system at any given time. The wall of an artery consists of three layers. The innermost layer, the tunica intima also called tunica interna , is simple squamous epithelium surrounded by a connective tissue basement membrane with elastic fibers.
The middle layer, the tunica media , is primarily smooth muscle and is usually the thickest layer. It not only provides support for the vessel but also changes vessel diameter to regulate blood flow and blood pressure.
0コメント