Unit 3: Vasculature - 20.1; 20.6-20.8 Flashcards
arteries
efferent vessels of the cardiovascular system; vessels that carry blood away from the heart; considered resistance vessel due to strong, resilient tissue structure; heart beat creates surge of pressure as blood is ejected into them; retain round shape when empty, appear relatively circular or elliptical in tissue sections
veins
defined as the afferent vessel that carry blood back to the heart
what are does not define arteries and veins
high or low oxygen in the blood they carry
capillaries
microscopic, thin walled vessels that connect the smallest arteries to the smallest veins
walls of arteries and veins are composed of three layers called
tunics
tunica interna
aka tunica intima; lines inside of the vessel and contacts the blood; simple squamous epithelium (endothelium) overlaying a basement membrane and a sparse layer of loose connective tissue; continuous with the endocardium of the heart; endothelium acts as selective permeable barrier to materials entering or leaving blood stream; secretes chemicals that stimulate dilation/constriction of the vessel; typ. repels blood cells and platelets so they flow freely without sticking to vessels wall; when tissue around a vessel is inflamed, endothelium produces cell-adhesion molecule to cling leukocytes to vessel wall which brings them to the tissues where defensive actions are needed
endothelium
simple squamous epithelium tissue that lines lumen of blood, heart, and lymphatic vessels
tunica media
strengthens vessels and prevents blood pressure from rupturing them, regulates diameter of a vessel; middle layer of blood vessel wall; usually thickest; smooth muscle and collagen tissue and some times elastic tissue; ratio of smooth vessel and elastic tissue differ and are a characteristic that is used to distinct vessels from one another
tunica externa
aka tunica adventitia; anchors vessel of adjacent tissue and provides passage for small nerves, lymphatic vessels and smaller blood vessels that supply the tissues of the larger ones; consists of loose connective tissue that often merges with neighbouring blood vessels, nerves or other organs
vasa vasorum
network of smaller blood vessels that provide the nutrition, oxygenation and waste removal for the larger and medium blood vessels that dont have their needs fully met by the blood they are carrying; most visible tunica externa since loose organization of tissue doesnt hide them; supplies to outer half of vessel wall
3 classes of arteries
conducting (elastic/large), distributing (muscular/medium), resistance (small)
conducting artery
elastic/large arteries - biggest, duh - layer of elastic tissue internal elastic lamina at the border ex: aorta, common carotid and subclavian arteries, pulmonary trunk, common iliac arteries.
Why do arteries have so much more elastic tissue than veins?
Allows it to stretch and recoil - when recoiling they maintain that pressure surge from the heart and keep pushing that blood throughout the body.
Valves in veins keep the blood from flowing backwards.
Distributing (muscular/medium) arteries
Distributing (muscular/medium)
distributes blood to specific organs
i.e. brachial, femoral, renal, splenic Smooth muscle layers 3/4 of wall thickness
resistance arteries (Small arteries)
resistance (Small arteries)
arterioles: Smallest arteries
major point of control over how much blood an organ or tissue receives
aneurysm
weak point in artery or heart wall; thin walled bulging sac that pulsates with each beat of the heart and may rupture
capillaries
exchange vessels between blood and tissue fluid; all have endothelial cells and most have basal lamina a thin protein carb layer that separates adjacent connective tissue
3 types of capilliaries
continuous, fenestrated, sinusoids
Continuous capillaries
In most tissues
Endothelial cells tight junctions forming continuous tube
Intercellular clefts allow passage of small solutes such as glucose
Large molecules (Proteins, platelets, RBCs) held back.
Pericytes wrap around capillaries contain contractile proteins regulate blood flow