BV chpt 20:pt 1
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51 Terms
What are the three major types of blood vessels?
Arteries, capillaries, and veins.
What are companion vessels?
Arteries and veins that travel together serving the same body region.
How do arteries differ from veins structurally?
Arteries have thicker tunica media and narrower lumens than veins.
Why are arteries more resistant to pressure changes?
They contain more elastic and collagen fibers.
What happens to veins when they contain no blood?
Their walls collapse.
Which vessel type has the thickest tunica externa?
Veins.
Which vessel type has the thickest tunica media?
Arteries.
What is the lumen?
The inner open space of a blood vessel where blood flows.
What layers make up blood vessel walls?
Tunica intima, tunica media, and tunica externa.
Which vessel type contains only tunica intima?
Capillaries.
What composes capillary walls?
Endothelium and basement membrane.
Why are capillary walls thin?
To allow rapid gas and nutrient exchange.
What are muscular arteries?
Medium-sized distributing arteries that send blood to specific body regions.
What is the diameter range of muscular arteries?
About 1 cm to 0.3 mm.
What allows muscular arteries to vasoconstrict and vasodilate?
Smooth muscle in the tunica media.
What is the internal elastic lamina?
Elastic tissue layer between tunica intima and tunica media.
What is the external elastic lamina?
Elastic tissue layer between tunica media and tunica externa.
What are examples of muscular arteries?
Brachial artery and coronary arteries.
What are arterioles?
The smallest arteries that regulate blood pressure and blood flow.
What is the diameter range of arterioles?
0.3 mm to 10 micrometers.
What is vasomotor tone?
Partial constriction of arteriole smooth muscle.
What maintains vasomotor tone?
Sympathetic nervous system activity.
What is the main function of arterioles?
Regulate systemic blood pressure and blood flow.
What are capillaries?
Small vessels connecting arterioles to venules.
What is the average length of a capillary?
About 1 mm.
What is the average diameter of a capillary?
8–10 micrometers.
What are the three types of capillaries?
Continuous, fenestrated, and sinusoid capillaries.
What are continuous capillaries?
Capillaries with a continuous endothelial lining.
What are intercellular clefts?
Gaps between endothelial cells in continuous capillaries.
Can large proteins pass through continuous capillaries?
No.
What substances can pass through continuous capillaries?
Small molecules like glucose.
Where are continuous capillaries commonly found?
Muscles, skin, lungs, and central nervous system.
What are fenestrated capillaries?
Capillaries with pores called fenestrations.
What do fenestrations allow?
Movement of smaller plasma proteins and fluids.
Where are fenestrated capillaries found?
Intestines and kidneys.
Why are fenestrated capillaries useful in kidneys?
They help filter blood to form urine.
What are venules?
The smallest veins that receive blood from capillaries.
What is the diameter range of venules?
8–100 micrometers.
What are postcapillary venules?
The smallest venules directly connected to capillaries.
What do venules eventually form?
Veins.
Where is most blood located at rest?
In systemic circulation.
Approximately what percentage of blood is in systemic veins at rest?
About 55%.
Approximately what percentage of blood is in systemic arteries at rest?
About 10%.
Approximately what percentage of blood is in systemic capillaries at rest?
About 5%.
Approximately what percentage of blood is in pulmonary circulation?
About 18%.
Approximately what percentage of blood is in the heart?
About 12%.
Why are systemic veins called blood reservoirs?
Because they contain most of the blood volume at rest.
What is an aneurysm?
A weakened bulging area in an arterial wall.
Why are aneurysms dangerous?
They may rupture and cause massive bleeding.
Where do aneurysms commonly occur?
In the aorta or arteries at the base of the brain.
Why does aneurysm risk increase with age?
Arteries become less able to withstand pulsating blood forces.