How Much Blood in the Human Body?

Which is the most accurate statement?

  1. Adults generally have 2-4 litres of blood.
  2. Adults generally have 3-5 litres of blood.
  3. Adults generally have 4-6 litres of blood.
  4. Adults generally have 5-7 litres of blood.

Correct answer: c.

About Blood (Saladin, 2018, p.671-673):

  1. It is a liquid connective tissue composed, like other connective tissues, of cells and an extracellular matrix.
  2. Its matrix is the blood plasma, a clear, light yellow fluid constituting a little over half of the blood volume.
  3. Suspended in the plasma are the formed elements — cells and cell fragments including the red blood cells, white blood cells, and platelets.
  4. The term formed element alludes to the fact that these are membrane-enclosed bodies with a definite structure visible with the microscope.
  5. Strictly speaking, they cannot all be called cells because the platelets are merely fragments torn from certain bone marrow cells.
  6. There are seven kinds of formed elements:
    1. Erythrocytes (red blood cells).
    2. Platelets
    3. Leukocytes (white blood cells): granulocytes (neutrophils, eosinophils, and basophils); and agranulocytes (lymphocytes and monocytes).
  7. The volume in an adult body varies between gender: 4-5 litres for women; and 5-6 litres for men.
  8. Blood is about 8% of bodyweight.
  9. Blood, by weight, is approximately 92% water.
  10. Sodium is more important than any other solute for the osmolarity of the blood. As such, it has a major influence on blood volume and pressure; people with high blood pressure are often advised to limit their sodium intake.

Reference

Saladin, K.S. (2018) Anatomy and Physiology: The Unity of Form and Function. 8th Ed. New York: McGraw-Hill Education.

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