8.2 Blood Vessels Flashcards
What are the 3 key components within blood vessels?
Elastic fibres, smooth muscle and collagen
What are elastic fibres?
Fibres made of elastin that can stretch and recoil, providing the vessel walls with flexibility
What is the function of smooth muscle in a blood vessel?
Contracts or relaxes, changing the size of the lumen
What is the function of collagen in a blood vessel?
Provides structural support to maintain the shape and volume of the vessel.
Do arteries carry blood to or away from the heart?
Away, to bring it to the tissues of the body.
Do arteries carry oxygenated or deoxygenated blood?
Oxygenated (except in the pulmonary artery)
Is blood in the arteries under higher or lower pressure than blood in the veins?
Higher
What do elastic fibres allow arteries to do?
Withstand the force of the blood pumping, and to stretch to withstand the volume
Describe the endothelium of an artery
It is so smooth that the blood flows easily over it.
What happens to the elastic fibres of the arteries in-between contractions of the heart? Why?
The elastic fibres recoil and return to their original length, to help even out the surges of blood pumping, and to give a continuous flow.
What are arterioles?
Small blood vessels that link the arteries and capillaries
What is the name of the blood vessels that link the arteries and capillaries?
Arterioles
Describe the structure of arterioles.
Have more smooth muscle and less elastin in their walls than arteries, but can still constrict or dilate to control the flow of blood into individual organs.
What type of blood vessel can perform vasoconstriction and vasodilation?
Arterioles (and arteries)
What happens during vasoconstriction?
Smooth muscle in the arteriole contracts. This constricts the vessel, and prevents blood flowing into a capillary bed
What happens during vasodilation?
Smooth muscle in the arteriole relaxes, allowing blood to flow into the capillary bed.
What is a lumen?
The channel within the blood vessel
What are capillaries?
Microscopic blood vessels that link the arterioles and the venules.
What is the name of the blood vessel that links the arterioles and the venules?
Capillaries
How small are capillaries?
One cell thick
How do red blood cells travel through capillaries?
In a single file line
How do substances pass out of the capillaries?
Through the relatively large gaps between the endothelial cells that make up the capillary walls in most areas of the body,
Where do substances that pass out of the capillaries go?
Into the fluid surrounding the cells
Is the blood entering the capillaries oxygenated or deoxygenated?
Oxygenated, though by the time it exits it is deoxygenated
How are capillaries adapted for their function?
-Provide a large surface area for the diffusion of substances into and out of the blood
-The walls are a single epithelial cell thick, giving it a thin layer for diffusion
-Total cross-sectional area of the capillaries is greater than the arteriole supplying them, so blood flow falls.
Why is it good that blood flow falls while the blood passes through the capillaries?
Relatively slow movement of blood through capillaries gives more time for the exchange of materials by diffusion between the blood and the cells.
Do veins carry blood to or away from the heart?
To the heart, and away from the body.
Do veins carry oxygenated or deoxygenated blood?
Deoxygenated
What is the name for small veins?
Venules.
What are the two main vessels carrying deoxygenated blood back to the heart?
Inferior vena cava and superior vena cava
Where does the inferior vena cava take deoxygenated blood from?
The lower parts of the body
Do veins have a pulse? Why / why not?
No, because the surges from the heart pumping are lost as the blood passes through the narrow capillaries
Is blood pressure in the veins higher or lower than in the arteries?
Lower
What feature do medium-sized veins contain?
Valves, to prevent the backflow of blood
What do the walls of veins contain?
Epithelium, lots of collagen, and relatively little elastic fibre.
What is the lumen of a vein like?
Wide.
What is the epithelium of a vein like?
Smooth and thin, so the blood flows easily.
What are the 3 main adaptations of veins that allow them to overcome their low blood pressure, and moving against the force of gravity?
-Majority of veins have one-way valves at intervals
-Many of the bigger veins run between the big, active muscles in the body
-Breathing movements of the chest act as a pump
How does having valves help veins?
The valves open so that blood can pass through. If the blood starts to flow backwards the valves close to prevent this from happening.
How does having larger veins run between the big, active muscles in the body assist the flow of blood?
When the muscles contract, they squeeze the veins, forcing the blood towards the heart.
