Comparative Anatomy of Blood Vessels Flashcards
the simplest circulatory route takes blood from
the heart to arteries to arterioles to the capillaries to the venules to veins and back to heart
a portal system allows blood to
flow through two separate capillary networks before returning to the heart
anastomosis
the union of two or more blood vessels in the same body region
shunt allows blood to flow
from artery to vein and bypass capillaries
shunts are common in
ears, fingers, toes
they can lead to frostbite as a consequence of exposure to extreme cold
arterial anastomoses provide
collateral circulation by providing alternative routes for blood to reach a capillary network
venous anastomoses provide
several routes for blood to drain from an organ
arteries carry blood
away from the heart
arteries are colored
red , since arteries transport oxygen rich blood
arteries have thick walls composed of _____ layers
name them
3:
tunica externa
tunica media
tunica intima
tunica externa consists of
loose connective tissues
tunica media consists of
smooth muscle, collagen fibers, and elastic fibers
-sympathetic motor nerves innervated smooth muscle
tunica intima consists of
a lining of squamous endothelium attached to basement membrane that underlies connective tissue
the smooth surface of the endothelium of the tunica intima
inhibits intravascular coagulation
intracellular clefts between endothelial cells of the tunica intima
allow substances to freely move in and out of blood
endothelial cells of tunica intima can
replace damaged cells and also produce cells that will contribute to new blood vessels
arteries are classified according to
size
conducting (elastic) arteries are
large. and they help propel blood through systemic circulation while ventricles are relaxing (ex. pulmonary trunk and aorta)
distributing (muscular) arteries are
smaller than conducting arteries. adjust rate of blood flow to organ or limb
resistance (small) arteries are
variable and include arterioles. metarterioles are short vessels that link arterioles to capillary network
capillaries are
microscopic blood vessels where gases, nutrients, and wastes are exchanged between the blood and the tissue cells
capillary walls consist of
a single layer of endothelium and a basement membrane
lumen is so narrow that
red blood cells must pass through capillary in single file
blood flows through a metarteriole into
a capillary bed
metarteriole passes through the capillary bed as
a thoroughfare channel
flow of blood into capillary bed is controlled by
pre-capillary sphincters comprised of smooth muscle
continuous capillaries
have endothelial cells that form an uninterrupted tube to allow passage of small solutes, but not passage of plasma proteins and formed elements
fenestrated capillaries
are riddled with small holes, so they allow rapid passage of wastes and small molecules
sinusoids
are large, twisted spaces with very thin walls, so they allow plasma proteins and formed elements to leave blood
capillaries unite at
the distal end of a thoroughfare channel to form a venule
veins carry blood
toward the heart
most veins are colored coded
blue since most veins transport de-oxygenated blood
veins have the same three layers in their walls as arteries but
their walls are thinner and contain less smooth muscle and elastic tissue so they expand and collapse more easily than arteries
many veins, especially in the limbs, contain
one way valves that prevent blood from flowing backward against the force of gravity
a venous sinus has
thin walls, a large lumen, and no smooth muscle
