8.2 Blood Vessels Flashcards
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.
