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Flip to reveal answersIn which direction does an artery carry blood?
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All 14 Flashcards — Structure of arteries and veins
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Question
In which direction does an artery carry blood?
Answer
**Away** from the heart (remember: **A**rtery = **A**way).
Question
In which direction does a vein carry blood?
Answer
**Towards** the heart (it returns blood to the heart).
Question
Describe the wall of an artery.
Answer
**Thick, muscular and elastic**, with a **narrow lumen** — built to withstand **high pressure**.
Question
Describe the wall of a vein.
Answer
**Thin**, with a **wide lumen** and **valves** — it carries blood at **low pressure**.
Question
How thick is the wall of a capillary?
Answer
**One cell thick** — this gives a short diffusion distance for **exchange**.
Question
Why is an artery wall thick, muscular and elastic?
Answer
To **withstand high pressure**: it **stretches** during each surge and **recoils** to push the blood onward.
Question
Why do veins have valves?
Answer
Blood in veins is at **low pressure**, so it could flow backwards — **valves close to stop backflow**.
Question
Why do arteries not need valves?
Answer
Their blood is at **high pressure**, which keeps it flowing forwards, so valves are not needed.
Question
How is a capillary adapted for exchange?
Answer
**Wall one cell thick** (short diffusion distance) and a **large surface area** close to every cell.
Question
What is the lumen of a blood vessel?
Answer
The **hollow space inside** the vessel through which the blood flows.
Question
Which vessel has the widest lumen relative to its wall — artery or vein?
Answer
The **vein** — thin wall and wide lumen; the artery has a thick wall and narrow lumen.
Question
How can you identify an artery on a micrograph?
Answer
It has the **thicker wall** and the **narrower lumen** of the two vessels.
Question
Why does the aorta show a smaller pressure change than the ventricle?
Answer
Its **elastic wall stretches** during the surge and **recoils** between beats, **smoothing** the pressure.
Question
Where in the circulation does exchange of materials with the tissues happen?
Answer
In the **capillaries** — the only vessels with a wall one cell thick.
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