Untitled Quiz

The endothelium facilitates molecule exchange, controls blood clotting, regulates vascular tone, is involved in inflammation & immune responses, and secretes growth factors.

The endothelium actively regulates the movement of molecules, including nutrients and waste products, into and out of the blood.

The endothelium prevents blood clotting and secretes factors like heparin and tissue plasminogen activator to manage clot formation.

Endothelium secretes substances that either relax or contract smooth muscle, adjusting blood flow and pressure.

Endothelial cells in venules influence white blood cell migration and activation at injury/infection sites, partly through interleukin secretion.

Endothelial cells produce growth factors that promote cell development and blood vessel formation, including VEGF.

Smooth muscle in larger vessels controls blood flow by constricting or dilating the vessel, important for blood pressure regulation.

Collagen and elastin fibers in the vascular wall offer structural support and resiliency, accommodating pressure changes, especially in larger arteries.

Capillaries have thin walls, a large surface area, and slow, pulsatile blood flow, facilitating fluid and solute exchange between blood and tissues.

Capillaries are classified into continuous, fenestrated, and discontinuous (sinusoidal) types, based on their endothelial cell structure and presence of fenestrations or perforations.

Continuous capillaries have tight junctions and are found in tissues requiring tight regulation of fluid and solute movement (muscle, connective, lungs)

Fenestrated capillaries have pores (fenestrations) and are found where faster exchange of substances is needed (kidneys, intestines, endocrine glands).

Discontinuous capillaries have large gaps and are found in tissues with high flow and large molecule exchange like the liver, spleen, bone marrow, and some endocrine organs.

Capillaries' blood flow is regulated by sphincters, causing pulsatile blood flow through the capillaries.

Postcapillary venules are the primary sites for leukocyte (white blood cell) adhesion to the endothelium and emigration from the bloodstream.

Cyclic opening and closing of capillary sphincters causes blood to pass through capillaries in a pulsatile manner, this is due to the intermittent constriction and dilation of precapillary sphincters that regulate blood flow.

Distribute blood to organs and regulate blood pressure; have a thin subendothelial layer and a prominent internal elastic lamina; media contains up to 40 layers of smooth muscle.

Small arteries, branching into capillary networks; have only a few smooth muscle layers; help regulate blood flow into capillaries.

Tiny blood vessels; allow metabolic exchange between blood and tissues; form networks around cells.

Capillaries vary in size but average 4-10 μm

Terminal branches of arterioles; control blood flow into capillaries by acting as precapillary sphincters.

Largest arteries/veins; aorta carries oxygenated blood away from heart; vena cava carries deoxygenated blood towards the heart.

Smooth muscle cells in arterioles act as sphincters, controlling blood flow. Muscle tone keeps arterioles partially closed.

Organs with high metabolic rates (like muscles and liver) have more capillaries; organs with low metabolic rates (like connective tissues) have fewer capillaries.