Capillaries, blood components, and arterial structure

What are blood vessels?

Tubular structures that transport blood.

What are capillaries?

Blood vessels that connect arteries with veins and allow exchange of materials between blood and the internal or external environment.

Why do capillaries operate under low pressure?

To allow efficient exchange of materials by diffusion.

How do capillaries increase surface area for exchange?

They form a network of branches.

What is the diameter of capillaries?

Approximately 10 micrometres.

Why does a narrow capillary diameter increase diffusion efficiency?

It decreases the diffusion pathway of gases.

What type of cells surround capillaries?

Thin endothelial cells.

What can leak out of capillaries?

Blood plasma and nutrients.

What cannot leak out of capillaries?

Blood cells and larger proteins.

What is tissue fluid?

Fluid that leaks out of capillaries containing plasma and nutrients.

List three substances transported by the transport system.

Gases, soluble nutrients, and waste products.

Name two examples of soluble nutrients transported in blood.

Sugars and proteins.

What waste product is transported by the blood?

Urea.

How does the transport system help regulate body temperature?

By distributing heat.

What is plasma?

The liquid component of blood.

What does plasma transport?

Nutrients, excretory products, hormones, and heat.

What are erythrocytes?

Red blood cells.

What is the function of erythrocytes?

Transport oxygen and carbon dioxide.

What are leucocytes?

White blood cells.

What is the function of lymphocytes?

They form antibodies.

What is the function of phagocytes?

They ingest bacteria or cell fragments.

What are platelets?

Blood components involved in clotting.

What is the function of arteries?

Transport blood away from the heart at high pressure.

What structural feature allows arteries to withstand high pressure?

Thick walls with elastic and smooth muscle fibres.

What is the tunica externa?

An outer layer made of connective tissue and collagen.

Why does the tunica externa need to be strong?

To withstand high blood pressure without bursting.

What is the function of the tunica media?

Stretching and recoiling with pulsating blood pressure.

What is the tunica intima?

A thin smooth inner layer of the artery.

What happens to arteries during systole?

The wall stretches and elastic fibres store potential energy.

What happens during diastole?

Elastic fibres recoil and push blood forward.