the forces involved in circulating blood throughout the body, and on the blood vessels that constitute the major circulatory routes
carry blood away from the heart to the organs
small arteries that enter tissue. They regulate the flow of blood into capillary networks of the body's tissue
as the arterioles enter tissue they branch into these that allow the exchange of substances. They form the U-turn that connect the arterial outflow to the venous return. This network forms an enormous surface area to make contact with the body's cells. they lack tunica media and tunica externa
groups of capillaries reunite within a tissue to create 4 of these. They have thin walls that do not readily maintain their shape. They drain the capillary blood and begin the return flow of blood back toward the heart
venules form larger vessels that carry blood back to the heart. they have thin walls, they contain the same three layers as arteries but the relative thickness is different. The lumen is bigger.
forms the inner lining of a blood vessel and is in direct contact with the blood as it flows through the lumen.
interior opening of the vessel
is a muscular and connective tissue layer that displays the greatest variation among the different vessel types. In most vessels, it is a relatively thick layer comprised mainly of smooth muscle cells and substantial amounts of elastic fibers. The primary role of the smooth muscle tissue is to regulate the diameter of the lumen
the outer covering of a blood vessel consists of elastic and collagen fibers. It contains numerous nerves and, especially in larger vessels, tiny blood vessels that supply the tissue of the vessel wall.
a decrease in diameter of the lumen of a blood vessel stimulated by sympathetic fibes of the ANS
the increase in diameter of the lumen
are the largest arteries in the body. Their vessel walls are relatively thin. These vessels are characterized by well defined internal and external elastic laminea. They function to help propel blood onward while the ventricles are relaxed. Also called conducting arteries
medium sized arteries. Their tunica media contains more smooth muscle and fewer elastic fibers. They are capable of greater vasoconstriction or dialation to adjust the flow of blood. They are called distributing arteries. They do not have the ability to help propel blood
the terminal end of the arteriole. It tapers towards the capillary junction
at the metacapillary-capillary junction, the distal most muscle cell forms this, which monitors the blood flow into the capillaries
arterioles regulate this, the opposition of blood flow into the capillaries. It is due mainly to friction between blood and the inner walls of blood vessels
the flow of blood from a metarteriole through capillaries and into a postcapillary venule.
capillaries function as part of this, a network of 10-100 capillaries that arise from a single metarteriole
the distal end of the metarteriole has no smooth muscle, it resembles a capillary . it provides a direct route for blood from an arteriole to a venule, thus by passing capillaries
most capillaries are these, in which plasma membranes of endothelial cells form a continuous tube. They are found in the brain, lungs, skeletal and smooth muscle and connective tissue
the plasma membranes of the endothelial cells in these capillaries have many pores. They are found in kidneys, villi of the small intestine, choroid plexuses
are wider and more winding than other capillaries. Their endothelial cells may have unusually large fenestrations. They have very large intercellular clefts that allow proteins and in some cases even blood cells to pass from a tissue into the bloodstream. ex newly formed blood cells pass through these from the red bone marrow
in some parts of the body blood passes from one capillary network into another through a vein.