The fewest of the formed elements are
A. viscosity
B. fibrinolysis
C. stem
D. white blood cells WBCs leukocytes
The correct answer and explanation is:
The correct answer is D. white blood cells (WBCs or leukocytes).
Explanation:
Blood is made up of formed elements suspended in plasma. The formed elements include:
- Red blood cells (RBCs or erythrocytes) – These are the most abundant formed elements and are responsible for carrying oxygen to tissues and removing carbon dioxide.
- Platelets (thrombocytes) – These are small cell fragments involved in blood clotting.
- White blood cells (WBCs or leukocytes) – These cells are part of the immune system and defend the body against infection and foreign invaders.
Among these formed elements, white blood cells are the fewest in number.
- Red blood cells typically number around 4.5 to 6 million per microliter of blood.
- Platelets number around 150,000 to 450,000 per microliter.
- White blood cells are far fewer, usually ranging from 4,000 to 11,000 per microliter.
This means WBCs are the least numerous formed elements in the blood.
Why the other options are incorrect:
- A. Viscosity is not a formed element; it is a physical property of blood describing its thickness or resistance to flow.
- B. Fibrinolysis is a biological process where the body breaks down clots; it is not a formed element.
- C. Stem cells are precursor cells found mainly in the bone marrow that develop into the different types of blood cells, but they are not considered formed elements circulating in the blood.
Summary:
The formed elements of blood are red blood cells, platelets, and white blood cells. Of these, white blood cells are the fewest in number but play a crucial role in immune defense. The other options (viscosity, fibrinolysis, and stem cells) either describe blood properties, processes, or precursor cells, not the circulating formed elements themselves.