Unit 15 - Vessels and Circulation Flashcards
three classes of blood vessels
Arteries, Capillaries, Veins
where the exchange of nutrients and gasses takes place between the tissue cells and the blood.
Capillaries
The site where two or more arteries (or two or more veins) merge to supply the same body region is called an
“anastomosis”
provide alternate blood supply routes to body tissues or organs.
Arterial anastomoses
Veins form many more anastomoses than arteries.
True
Some arteries do not form anastomoses; in these so-called ____, there is only one pathway through which blood can reach an organ (i.e. - renal artery of the kidney or splenic artery of the spleen).
“end arteries”
Often, an artery will travel with a corresponding vein and these vessels are called
______ because they service the same body region and tend to lie next to
one another
“companion vessels”
Both arteries and vein walls have three layers, called “____ (Latin for “coats”).
tunics”
The tunics surround the “_____”, or inside space, of the blood vessel through which blood flows.
lumen
The innermost layer of a blood vessel wall is the _____
tunica intima
Tunica Intima is composed of _____ and a subendothelial layer made up of a thin layer of connective tissue
“endothelium”
The tunica intima in veins has one-way valves. This is not seen in arteries.
True
The _____ (Latin for “coat” and “middle”) is the middle layer of the vessel wall.
“tunica media
Sympathetic innervation causes the smooth muscles to contract, resulting in
“vasoconstriction” (narrowing of the blood vessel lumen); when the fibers relax,
“vasodilation” (widening of the blood vessel lumen) results.
True
The ______ (Latin for “coat” and “outside”) is the outermost layer of a blood vessel wall.
“tunica externa”
In arteries, the thickest layer is the _____, while veins have a thicker _____.
tunica media, tunica externa
The lumen in an artery is narrower than in a vein of the same size
True
Arteries tend to have more elastic and collagen fibers in all their tunics, which means that artery walls remain open (patent) and can spring back to shape.
In contrast, vein walls tend to collapse if there is no blood in them
True
Capillaries contain only the _____, but this layer consists of a basement membrane and endothelium only.
tunica intima
This allows for easy exchange of materials between the blood in the vessels and the fluid surrounding the tissue cells (interstitial fluid)
In general, as an artery’s diameter decreases, there is a corresponding decrease in
the amount of elastic fibers and a relative increase in the amount of smooth
muscle.
True
_____ are the largest arteries, with diameters ranging from 2.5 to 1 centimeter.
“Elastic arteries”
There are several examples of elastic arteries.
- Aorta
- Pulmonary
- Brachiocephalic
- Common carotid
- Subclavian
- Common iliac arteries
True
Elastic arteries branch into
muscular arteries.
typically have diameters ranging from 1 centimeter to 3
millimeters
muscular arteries.
Muscular arteries have a proportionately thicker _____, with multiple layers of smooth muscle that give them better ability to vasoconstrict and vasodilate
tunica media
______ are the smallest arteries, with diameters ranging from 3 millimeters to 10 micrometers
Arterioles
Three basic types of arteries
Elastic arteries, muscular arteries, arterioles
In general, arterioles have less than ______ of smooth muscle in their tunica media
six layers
Larger arterioles have all three tunics, whereas the smallest arterioles have fewer.
True
By vasocontricting or vasodilating the arterioles can increase or decrease the arterial
blood pressure and also regulate blood flow through the capillaries.
True
the smallest blood vessels, connect arterioles to venules
capillaries
The average capillary diameter is ____ micrometers, just slightly larger than the diameter of a single erythrocyte (7 micrometers)
8-10
The narrow vessel diameter means erythrocytes must travel in single file through
each capillary
______” causes blockages and infarctions in body organs
“Sickle-cell disease
Sickle cell disease is caused by inheritance of a gene for abnormal hemoglobin (_______)
hemoglobin-S
Thus, capillaries are called the ____ of the cardiovascular system.
functional units
Three different structural types of capillaries
continuous capillaries, fenestrated capillaries, sinusoids
the most common type of capillaries, endothelial cells form a complete, continuous lining and are connected by tight junctions.
continuous capillaries
Materials can pass through the endothelia cells or the intercellular clefts to and from
the surrounding interstitial fluid.
have fenestrations within each endothelial cell and are
seen where a great deal of fluid transport occurs between the blood and interstitial
fluid of the tissues (i.e.-intestines, endocrine glands, and kidneys).
fenestrated capillaries
_____ tend to be wider, larger vessels with openings that allow for transport
of larger materials, such as proteins or cells (i.e. - blood cells).
“Sinusoids”
Sinusoids are found in the bone marrow, the spleen, the anterior pituitary, the liver, and at several other locations in the body
“Veins” drain capillaries and return blood to the heart
True
At rest, the body’s veins hold about ____ of the body’s blood.
(a) Thus, veins function as “blood reservoirs”
60%
_____” are the smallest veins, measuring from 8 to 100 micrometers in diameter.
Venules
A venule becomes a “vein” when its diameter is greater than _____
100 micrometers.
Smaller and medium-sized veins typically travel with muscular arteries, while the largest veins travel with (correspond to) elastic arteries
True