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Biology · Grades 8–11

Circulation, vessels and blood components

Classify vessels by direction relative to the heart.

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Learn the idea

Arteries

Arteries carry blood away from the heart; oxygen content is not the defining rule.

Veins

Veins carry blood toward the heart; some contain valves.

Capillaries

Capillaries provide exchange pathways between blood and tissues.

Components

Red blood cells, white blood cells, platelets and plasma have different roles.

Worked examples

What defines an artery?

Direction relative to the heart is the defining rule.

It carries blood away from the heart.

What defines a vein?

Direction distinguishes veins from arteries.

It carries blood toward the heart.

Check your understanding

  1. Which vessels are associated with exchange with tissues?

    1. Only solid bone canals.
    2. Capillaries.
    3. Only the largest arteries.

  2. A supplied simplified model has 60 beats/min and 70 mL/beat. Find flow in mL/min.

  3. Which blood component is closely associated with oxygen transport?

    1. Red blood cells.
    2. Only platelets.
    3. Only dissolved salts.

Answers and marking notes

Answers and marking notes
  1. Capillaries.

    Thin capillary walls support exchange.

  2. 4200 mL/min

    60 × 70 = 4200 mL/min; these are supplied model values, not medical norms.

  3. Red blood cells.

    Hemoglobin in red cells carries much of the blood's oxygen.

Further reading and review references

These are reference links, not copied exercises, institutional endorsement or proof of independent review.

Independent educational review required. Grade bands are approximate; these are not officially aligned curricula.