UPSC Prelims 2004 Q13: Science & Technology – Biology
In which organ of the human body are the lymphocyte cells formed?
- (a) Liver
- (b) Long bone
- (c) Pancreas
- (d) Spleen
Answer: (b) Long bone
Explanation
Formation of lymphocytes
| Organ | Role |
|---|---|
| Bone marrow of long bones | Lymphocytes originate in the bone marrow |
| Spleen | Stores and matures them, a site of immune action |
| Liver | Not a main site |
| Pancreas | No |
Lymphocytes are formed in the bone marrow of long bones, then mature in lymphoid organs such as the thymus and spleen.
Answer: (b) Long bone.
Why each option is right or wrong
- (a) Incorrect. The liver is not the site of lymphocyte formation.
- (b) CORRECT. Lymphocytes are formed in the bone marrow of long bones.
- (c) Incorrect. The pancreas produces enzymes and hormones.
- (d) Incorrect. The spleen stores and filters, but the cells arise in the marrow.
Key point
All blood cells are formed in bone marrow; T cells mature in the thymus.
Remember
Lymphocytes are formed in the bone marrow.
Common mistakes
- Choosing the spleen because it is a lymphoid organ.
- Forgetting the role of bone marrow.
- Mixing the liver as a foetal site with an adult site.
Exam tip
Haemopoiesis: red marrow of bones in adults.
Sources
- NCERT Class XI Biology — Body Fluids and Circulation
- John E. Hall — Guyton and Hall Textbook of Medical Physiology (Resistance of the Body to Infection)