21.1 Structure and Function of Blood Vessels Flashcards
arteries
- one of the five main types of blood vessels
- pressurized vessels which carry blood away from the heart to other organs
arterioles (resistance vessels)
- one of the five main types of blood vessels
- small vessels which are carrying blood away from the heart
- intermediate step between arteries and capillaries
- regulate blood flow by altering resistance of blood flowing through them before hitting the capillaries
capillaries (exchange vessels)
- one of the five main types of blood vessels
- very small hairlike vessels inside tissues
- have thin walls, allowing the exchange of substances between blood and body tissues
- only vessels which lack a tunica externa and tunica media
venules
- one of the five main types of blood vessels
- small vessels which are formed when several capillaries merge together as they are leaving tissue
- intermediate step between capillaries and veins
veins
- one of the five main types of blood vessels
- depressurized vessels which carry blood from organs back to the heart
tunica interna (or tunica intima)
-inner lining of a blood vessel which is in contact with blood flowing through the lumen
lumen
-the opening in a blood vessel through which blood flows
endothelium
- the innermost layer of the tunica interna
- a tissue composed of flattened cells which line the inner surface of the entire cardiovascular system
basement membrane
- the second component of the tunica interna, which is deep to the endothelium
- provides tensile strength to the tunica interna as well as resistance to stretch and recoil
- anchors the endothelium to underlying connective tissue
internal elastic lamina
- the outermost layer of the tunica interna
- a thin sheet of elastic fibers with many holes like swiss cheese which facilitate diffusion of materials from the tunica interna to the tunica media
tunica media
- the middle layer of a blood vessel
- made of muscular and connective tissue
- has greatest variation amongst different types of vessels
vasoconstriction
-a decrease in the diameter of the lumen of a blood vessel
vasodialtion
-an increase in the diameter of the lumen of a blood vessel
vascular spasm
-the contraction of a small artery or arteriole to prevent the loss of blood when damaged
external elastic lamina
-swiss cheese like layer separating the tunica media from the tunica externa
tunica externa
- the outermost layer of a blood vessel
- consists of elastic and collagen fibers, as well as nerves controlling contraction of the tunica media
- helps anchor vessels to surrounding tissues
vasa vasorum
- name means vessels of the vessels
- small vessels which supply blood to the tissue of large vessels like the aorta
compliance
- the ability of vessels to stretch easily or expand without tearing in response to increase in pressure
- normally high in arteries
elastic arteries (conducting arteries)
- the category of arteries including the largest arteries in the body, like the aorta, pulmonary trunk and their branches
- named for their well defined internal and external elastic laminae
- propel blood onward while ventricles are relaxing
elastic lamellae
-stretchy fibers which dominate the tunica media of the conducting arteries
pressure resevior
-the function of the elastic arteries when their elastic fibers are stretched, just after the ventricles have contracted and are starting to relax
muscular arteries (distributing arteries)
- the category of arteries containing medium arteries like the femoral, brachial, and radial arteries
- contain more smooth muscle and fewer elastic fibers
- have a thick tunica media, with as many as 40 layers of smooth muscle cells, making up 25% of total vessel thickness
vascular tone
- the ability of smooth muscle in vessels to contract and maintain a state of partial contraction
- stiffens the vessel wall, important for maintaining vessel pressure and efficient blood flow
anastomosis
- the union of the brances of two or more ateries supplying the same region of the body
- provide alternative routes for blood to reach an area in case one is closed by normal movements compressing it shut, or injury/disease
collateral circulation
-the alternative route of blood flow to a body part through an anastomosis
end arteries
- arteries that do not anastomose
- obstruction of one of these arteries will interrupt all blood flow to an organ, leading to necrosis
metarteriole
- the terminal end of an arteriole
- here the vessel tapers toward the capillary junction
precapillary sphincter
- the distal-most muscle cell in the metarteriole-capillary junction
- monitors the blood flow into a capillary
resistance
- the opposition of blood flow due to friciton between blood and the walls of blood vessels
- actively controlled by arterioles by vasoconstriction and vasodilation before hitting the capillaries
postcapillary venule
- the venule that receives blood from a capillary
- extremely porous, allowing for significant exchange of nutrients and wastes as well as white blood cell emigration
microcirculation
-the flow of blood from a metarteriole through a capillary and into a postcapillary venule
capillary bed
-the network of 10-100 capillaries that arises from a single metarteriole
capillary route
- one of the two ways in which blood can flow through an arteriole and into a venule
- happens when precapillary sphincters are relaxed, allowing blood to flow through all parts of the capillary bed
vasomotion
- the intermittent contraction and relation of the smooth muscle of metarterioles and precapillary sphincters to encourage blood flow through the capillary bed
- occurs 5-10 times per minute
thoroughfare channel
- one of the two ways in which blood can flow through an arteriole and into a venule
- happens when the precapillary sphincters are contracted, forcing blood directly from arteriole to venule without going into the capillary bed
continuous capillaries
- one of the three types of capillaries
- has endothelial cells which are an unbroken tube, aside from intercellular clefts between cells
- found in the CNS, lungs, muscle tissue, and skin
intracellular clefts
- the gaps between neighboring epithelial cells
- the only spaces through which diffusion can occur in continuous capillaries
fenestrated capillaries
- one of the three types of capillaries
- have small (~70-100nm) holes in their endothelial cells to allow for diffusion of larger compounds out of the blood
- found in kidneys, small intestine, choroid plexuses of ventricles in the brain, ciliary processes of the eyes, and endocrine glands
sinusoids
- one of the three types of capillaries
- have large holes in their endothelial cells allowing proteins and sometimes even blood cells to pass from a tissue into the bloodstream
- present in red bone marrow, liver, spleen, anterior pituitary, and parathyroid and adrenal glands
portal vein
-a vein connecting two capillary beds together, rather than a capillary bed back to the heart
portal system
- a two of capillary beds and the portal vein which connect them
- named for the location of the second capillary
muscular venules
- thicker venules one with one or two layers of smooth muscle cells
- walls are too thick to allow for exchanges with interstitial fluid
- connect postcapillary venules to veins
valves
-thin folds of tunica interna that form flaplike cusps, preventing backflow of blood in veins
vascular sinus
-a vein with a thin endothelial wall that has no smooth muscle to alter its diameter
anastomatic veins
- the veins which connect the double set of veins which accompany medium-small sized arteries
- the rungs of ladderlike structures alongside those arteries
superficial veins
- the veins which course through the subcutaneous layer, unaccompanied by parallel arteries
- the major pathway for blood to return to the heart in the upper limbs
deep veins
- veins which travel between the skeletal muscles
- the major pathway for blood to return to the heart in the lower limbs
blood distribution
- 64% in systemic veins and venules
- 13% in systemic arteries and arterioles
- 7% in systemic capillaries
- 9% in pulmonary blood vessels
- 7% in the heart
blood reservoir
- a place where a large blood volume is stored in the cardiovascular system for quick distribution if the need arises
- systemic veins and venules function as one of these for the body
venoconstriction
-the constriction of veins to allow for less blood in the resevoirs of systemic veins, forcing more into skeletal muscles, such as during exercise
