8.2 Blood Vessels Flashcards Preview

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Flashcards in 8.2 Blood Vessels Deck (10):

What do arteries do?

Carry blood away from the heart to the tissues of the body

All carry oxygenate blood except the pulmonary artery


Describe the structure of arteries and how it helps them carry out their function

Walls contain :

Elastic fibres - withstand pressure as composed of elastin which allows stretch and recoil

Collagen - provides structural support to maintain shape and volume of vessel

Smooth muscle - contracts and relaxes which changes the size of the lumen

They also have a small lumen and corrugated / folded endothelium lining


What do arterioles do? Compare them to arteries.

They link the arteries and capillaries.

They have more smooth muscle and less elastin ( as they have little pulse surge ) but can constrict and dilate to control flow of blood to organs.


Define vasodilation and vasoconstriction

Vasoconstriction : when smooth muscle in arteriole contracts it constricts the vessel and prevents blood flowing into a capillary bed

Vasodilation : when smooth muscle in arteriole relaxes and blood flows through into capillary bed


What do capillaries do?

Microscopic blood vessels that link the arterioles with the venules

They form an extensive network through all the tissues of the body

Substances are exchanged through the capillary walls between the tissue cells and blood


Describe the structure of capillaries. How are they adapted?

Very small lumen - size of one cell

Gaps between endothelial cells are quite large

Large surface area for diffusion

Total cross - sectional area of capillaries is always greater than the arteriole supplying them so the rate of blood flow falls = enough time for exchange of materials

Walls are a single endothelial cell thick = very thin layer for diffusion


What do veins do?

Carry blood away from the cells to the heart

Always carry deoxygenated blood ( except pulmonary vein )


Describe the features of veins

Can carry a large volume of blood

Low blood pressure

Contain valves to prevent back flow

Walls contain lots of collagen and little elastic fibre

Wide lumen

Smooth thin lining ( endothelium )


What do venues do? Describe their structure

They link capillaries with the veins

They have very thin walls with little smooth muscle


How do veins carry blood to the heart if there is low pressure and it's against gravity?

Valves prevent back flow

Bigger veins run between the big, active muscles in the body. When the muscles contract they squeeze the veins, forcing blood towards the heart.

Breathing movements of the chest act as a pump. The pressure changes and the squeezing actions move blood in the veins of the chest and abdomen towards the heart.