Blood vessels 8.2 Flashcards
What are the different components utilised in blood vessels
Elastic fibres
Smooth muscle
Collagen
What are the features of elastic fibres found in blood vessels
these are composed of elastin and can stretch and recoil, providing vessel walls with flexibility
what are the features of smooth muscle found in blood vessels
contracts or relaxes, which changes the size of the lumen
what are the features of collagen
provides structural support to maintain the shape and volume of the vessel
what is the function of arteries
The arteries cary blood away from the heart to the tissues of the body. They carry oxygenated blood expect in the pulmonary artery, which carries deoxygenated blood from the heart to the lungs and (during pregnancy)the umbilical artery, which carries deoxygenated blood from the foetus to the placenta.
What is the pressure of the blood in arteries
The blood in the arteries is under higher pressure than the blood in the veins
What layers make up an artery from the inside to the outside
Describe the structure of an artery
The elastic fibres enable them to withstand the force of the blood pumped out of the heart and stretch (within limits maintained by collagen) to take larger blood volume.l
In between contractions of the heart, the elastic fibres recoiled return to their original length. This helps to even out the surges of blood pumped from the heart to give a continuous flow. However you can still feel a pulse (surge of blood) when the heart contracts, which the elastic fibres cannot completely eliminate. The lining of an artery (endothelium) is smooth so the blood flows easily over it
what is the role of arterioles
Arterioles line the arteries and the capillaries
Describe the structure of arterioles
They have more smooth muscle and less elastin in their walls than arteries ( as they have little pulse surge)
They can constrict and dilate to control the flow of blood into individual organs
Explain how vaso-constriction and dilation are connected to arterioles
when the smooth muscle in the arteriole contracts it constricts the vessel and prevent blood flowing into a capillary bed (vasoconstriction).
When the smooth muscle in a wall of an arteriole relaxes, blood flows through into the capillary bed (vasodilation)
what is an aneurysm
A bulge or weakness in a blood vessel
what are capillaries
The capillaries are microscopic blood vessels that link the arterioles with the venules
Describe the structure & function of a capillary
they form an extensive network through all the tissues of the body
The lumen of a capillary is so small that red blood cells have to travel through in single file.
Substances are exchanged through the capillary walls between the tissue cells and the blood.
The gaps between the endothelial cells that make up the capillary walls in most areas of the body are relatively large. This is where many substances pass out of the capillaries into the fluid surrounding the cells.
The exception is the capillaries in the central nervous system, which have very tight junctions between the cells
describe the oxygenation of the blood going into and out of the capillaries
In most organs of the body the blood entering the capillaries from the arterioles is oxygenated.
By the time it leaves the capillaries for the venules it deoxygenated.
the lungs and the placenta are exceptions with deoxygenated blood entering the capillaries and oxygenated blood leaving in the venules
what are the layers of a vein in order from inside to out
what are the 3 main adaptations that enable veins to overcome low blood pressure
- have one-way valves at intervals.
^prevent backflow of blood - bigger veins run between big, active muscles in the body
^muscles contract, squeeze veins, force blood towards heart - breathing movements of the chest act as a pump.
^pressure changes and squeezing actions move blood in veins in chest and abdomen towards heart
