Blood vessels and their functions Flashcards
What is the function of the arteries?
Arteries transport blood rapidly under high pressure away from the heart and into the arterioles towards the tissue
What is the function of the arterioles?
Arterioles carry blood under lower pressure than arteries and control blood flow between the arteries to the capillaries
What is the function of capillaries?
Capillaries link arterioles to veins and allow the exchange of metabolic materials (oxygen, carbon dioxide and glucose) between the blood and body cells
What is the function of veins?
Veins transport blood slowly, under low pressure, from capillaries in the tissues back to the heart
What is the basic structure of arteries, arterioles, and veins? (from outermost to innermost) (5pts)
- The tough fibrous outer layer - which resists pressure changes
- Muscle layer - which contracts to control blood flow
- Elastic layer - which maintains blood pressure by stretching and recoiling
- Thin inner lining (endothelium) - which is smooth to reduce friction + thin for diffusion
- Lumen - which has the central cavity for blood flow
How do arterioles differ from arteries?
Arterioles have a smaller diameter, a relatively larger muscle layer and a larger lumen compared to arteries
How do arteries and veins differ in structure?
Arteries have a thicker muscle layer and elastic layer to maintain high blood pressure
Vein shave a thinner muscle and elastic layer since blood pressure is lower
Veins have pocket valves to prevent backflow of blood
Why do arteries have a thick muscle layer compared to veins?
A thick muscle layer allows smaller arteries to constrict and dilate, controlling the volume of blood passing through them
Why do arteries have a thick elastic layer compared to veins?
A thick elastic layer helps maintain high blood pressure by stretching during systole and recoiling during diastole, smoothing pressure surges
How does the overall wall thickness of arteries relate to their function?
The thick wall helps resist the vessel bursting under high pressure
Why do arteries (except those leaving the heart) not have valves?
Blood is under constant high pressure due to the heart’s pumping action, so it tends not to flow backwards
Why is the muscle layer in arterioles relatively thicker than in arteries?
A thicker muscle layer allows the arteriole to constrict its lumen, restricting blood flow and controlling movement into capillaries
Why is the elastic layer in arterioles thinner than in arteries?
The elastic layer is thinner because blood pressure in arterioles is lower than in arteries
Why is the muscle layer in veins relatively thin compared to arteries?
Veins carry blood away from tissues, so their constriction and dilation cannot control blood flow to the tissues
Why is the elastic layer in veins thinner than in arteries?
Blood pressure in veins is low, so there is no risk of bursting, and the pressure is too low to create a recoil action
Why is the overall wall thickness of veins small?
The pressure is too low to cause bursting, and the thin walls allow veins to be flattened easily, aiding blood flow
Why do veins have valves, and how do they help blood flow?
Valves prevent backflow of blood due to the low pressure. When body muscles contract, veins are compressed and valves ensure blood moves only towards the heart
Why is blood flow in capillaries slow?
Slow blood flow allows more time for the exchange of material between the blood and the cells
How does the thin capillary wall aid in diffusion?
The walls consist mostly of the lining layer, making them extremely thin, which shortens the diffusion distance and allows rapid exchange of materials
How does the large number of branching help with their function?
They provide a large surface area for the exchange of materials
Why is the narrow diameter of capillaries important?
It allows capillaries to permeate tissues so that no cell is far from a capillary, ensuring a short diffusion pathway
How does the narrow lumen of capillaries aid oxygen delivery?
It squeezes red blood cells against the capillary walls, reducing diffusion distance and bringing oxygen closer to the cells
Why do capillaries have spaces between endothelial cells?
These spaces allow white blood cells to escape and deal with infections in tissues
Why can’t capillaries directly serve every single cell?
The final journey of metabolic materials occurs in tissue fluid, which bathes the cells and facilitates exchange.
