List the formed elements of blood (including specific leukocytes)

List the formed elements of blood (including specific leukocytes), their functions and abundance of each of the cell types.

The correct answer and explanation is:

Correct Answer:

The formed elements of blood include:

1. Erythrocytes (Red Blood Cells – RBCs)

• Function: Transport oxygen (via hemoglobin) and carbon dioxide.
• Abundance: ~4.5–6 million cells per microliter of blood (most abundant).

2. Leukocytes (White Blood Cells – WBCs)

• Function: Defend the body against infection and foreign invaders.
• Abundance: ~4,800–11,000 cells/µL (least abundant).
• Types of leukocytes include: a. Neutrophils (50–70%)
  • Function: Phagocytize bacteria and dead cells.
  b. Lymphocytes (20–40%)
  • Function: Produce antibodies (B cells), destroy infected or cancerous cells (T cells).
  c. Monocytes (2–8%)
  • Function: Become macrophages; phagocytize pathogens and debris.
  d. Eosinophils (1–4%)
  • Function: Combat parasites; involved in allergic responses.
  e. Basophils (0.5–1%)
  • Function: Release histamine during allergic reactions.

3. Thrombocytes (Platelets)

• Function: Help in blood clotting (hemostasis).
• Abundance: ~150,000–400,000 platelets/µL.

Explanation (300 words):

Blood is a connective tissue composed of plasma (fluid) and formed elements, which include erythrocytes, leukocytes, and thrombocytes. These elements are suspended in plasma and perform essential functions that maintain life.

Erythrocytes (RBCs) are the most abundant formed elements. Their primary function is to carry oxygen from the lungs to tissues and return carbon dioxide to the lungs for exhalation. They are biconcave, lack nuclei, and are rich in hemoglobin, which binds oxygen.

Leukocytes (WBCs) play critical roles in immune defense. Though they are fewer in number compared to RBCs, they are highly specialized:

• Neutrophils are the first responders to infection and use phagocytosis to neutralize pathogens.
• Lymphocytes include B cells (which produce antibodies) and T cells (which target infected or malignant cells).
• Monocytes migrate into tissues and transform into macrophages, cleaning up dead cells and pathogens.
• Eosinophils fight multicellular parasites and contribute to allergic reactions.
• Basophils release histamine and other chemicals during inflammatory and allergic responses.

Thrombocytes (platelets) are cell fragments that originate from megakaryocytes in the bone marrow. They are crucial for blood clotting. When a blood vessel is injured, platelets aggregate at the site, form a plug, and work with clotting factors to stop bleeding.

Each formed element has a distinct role, yet they all work together to transport gases, protect against disease, and prevent blood loss, maintaining homeostasis.