A healthy adult man has, on an average, how many (in millions) red blood cells per cubic millimetre (mm^3) of blood?

Introduction / Context:

The number of red blood cells, also called erythrocytes, present in a given volume of blood is an important parameter in human physiology and medicine. It influences oxygen transport capacity and is routinely measured in blood tests. A normal range differs slightly between men and women, and exam questions often ask for the approximate red blood cell count in a healthy adult man. Knowing this typical range helps students interpret basic clinical information and answer general knowledge questions correctly.

Given Data / Assumptions:

• The subject is a healthy adult male, not a child or woman.
• The measurement unit is millions of red blood cells per cubic millimetre (mm^3) of blood.
• Options provide several different ranges of millions per mm^3.
• We assume standard physiological values given in school and entrance exam textbooks.

Concept / Approach:

In an average healthy adult man, the red blood cell count is approximately 5.0 to 5.5 million cells per mm^3 of blood. Women typically have a slightly lower count, around 4.5 to 5.0 million per mm^3. These are approximate values, and exact numbers can vary with health, altitude, and other factors. In exams, the accepted range for men is usually stated as about 5 to 5.5 million per mm^3. Values that are much lower or higher may indicate anaemia or polycythaemia. Therefore, the option that gives 5.0 to 5.5 million per mm^3 matches the standard textbook value.

Step-by-Step Solution:

Step 1: Recall the typical normal red blood cell count for adult males from physiology tables. Step 2: Remember that this value is around five to five and a half million cells per mm^3 of blood. Step 3: Check the options for a range that includes values close to five million and slightly above. Step 4: Identify that 5.0 to 5.5 million per mm^3 matches this remembered range. Step 5: Select 5.0 to 5.5 million per mm^3 as the correct answer.

Verification / Alternative check:

Physiology charts in textbooks list normal blood cell counts and clearly state that adult males typically have about 5 to 5.5 million red blood cells per mm^3. Laboratory reference values given on test reports show similar ranges, often with minor variation. Comparisons between male and female values consistently show male counts slightly higher, supporting the given range. These independent sources confirm that the correct range for a healthy adult man is approximately 5.0 to 5.5 million per mm^3.

Why Other Options Are Wrong:

Option B, 4.0 to 4.5 million per mm^3, is more typical of female counts and is slightly low for healthy adult men. Option C, 3.0 to 3.5 million per mm^3, would generally be considered abnormally low and may indicate anaemia. Option D, 6.0 to 6.5 million per mm^3, is higher than normal and may suggest polycythaemia or adaptation to extreme altitude. Option E, 2.0 to 2.5 million per mm^3, is far below normal and would not represent a healthy adult.

Common Pitfalls:

Students may remember that the normal value is in millions but forget the exact range and choose a rounded number that sounds familiar. Others may mix up values for men and women or incorrectly recall white blood cell counts, which are much lower. To avoid such mistakes, learners should memorise a small set of key numbers: about 5 million red blood cells per mm^3 in men, about 4.5 million in women, and much lower counts for white blood cells and platelets.

Final Answer:

A healthy adult man has on average 5.0 to 5.5 million per mm^3 red blood cells in his blood.