Blood: Formed Elements

What is the function of erythrocytes (red blood cells)?

To transport oxygen around the body via hemoglobin molecules.

How is the structure of erythrocytes well-suited for their function?

• Biconcave shape allows for greater surface area.

• Round sides enable efficient flow through blood vessels.

• Lack of nucleus and few organelles ensures oxygen isn’t used during transport.

Why must oxygen be carried by erythrocytes?

Oxygen is nonpolar and not soluble in blood.

How does hemoglobin carry oxygen?

• Hemoglobin is made of 4 globin chains.

• Each globin contains a “heme” with an Iron atom.

• Each Iron atom binds to one O₂ molecule.

• One hemoglobin can carry up to 4 O₂ molecules.

What is the function of leukocytes (white blood cells)?

To protect the body from foreign cells or substances.

How do erythrocytes and leukocytes differ?

• Erythrocytes:

  • Outnumber leukocytes 1,000 to 1.

  • No nuclei when mature.

  • Lifespan: 100–120 days.

  • Confined to the bloodstream.

  • Concentration remains constant.

• Leukocytes:

  • Less numerous than erythrocytes.

  • Always contain nuclei.

  • Lifespan: a few days to several years.

  • Can move through plasma and leave blood vessels (diapedesis).

  • Concentration changes as needed.