SBA — Single Best Answer · Review
Question 616
Immunology → General
Classification
Question
SSBAQuestion Header
Which of the following statements about the thymus is correct?
Question Stem
Select the single best answer.
Options
A
It is principally derived from the third pharyngeal pouch.
B
It is a secondary lymphoid organ responsible for antigen capture.
C
B lymphocytes mature within it in humans.
D
It normally remains in the neck throughout development.
E
Hassall’s corpuscles are characteristic of the spleen.
Explanation
The thymus is principally endodermal in origin and develops from the third pharyngeal pouch. It descends into the anterior mediastinum and is a primary lymphoid organ in which T lymphocytes mature.
Option Validity
B) The thymus is a primary lymphoid organ; the spleen and lymph nodes are secondary lymphoid organs involved in antigen capture and lymphocyte activation.
C) B lymphocytes arise and mature in bone marrow in humans.
D) The thymus descends into the anterior mediastinum.
E) Hassall’s corpuscles are characteristic structures of the thymus.
Further Reading
Saxena MRCOG-1 Basic Sciences — Immunology: Organisation of the Immune System, printed page 208.