Immunity
Read the following passage carefully and answer the given questions.
On daily basis, large number of pathogens are entering our body from the air we breathe in or the food we eat but we are not falling ill daily. It is because of the reason that our body can fight with most of these pathogens entering our body and kill them. Immunity is of two types - acquired or innate immunity. Innate immunity is non specific type of defence which is present from the birth. It is provided by four kinds of barriers - physical, physiological, cellular and cytokine barrier. It is a non specific type of defence. Acquired immunity is acquired when pathogen enters the body. It is pathogen specific and is characterised by memory of the immune system. Acquired immunity is carried out by two special type of lymphocytes called as B-cells and T-cells. B-cells produce antibodies and are responsible for humoral response whereas T-cells produce cell-mediated immune response.
The secondary lymphoid organ which acts as filter of blood is:
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → Spleen
The secondary lymphoid organs are the places where lymphocytes meet the antigen and multiply to form effector cells. They include the spleen, lymph nodes, tonsils, Peyer’s patches and the appendix. Each filters or traps a different thing.
(1) Tonsils — Incorrect. The tonsils are secondary lymphoid organs, but they do not filter blood.
(2) Spleen — Correct. It is a large, bean-shaped organ that has many lymphocytes and phagocytes. It acts as a filter of the blood by trapping blood-borne micro-organisms. It also stores a large reserve of red blood cells.
(3) Lymph nodes — Incorrect. These small structures trap micro-organisms and antigens that reach the lymph and tissue fluid. They filter lymph, not blood.
(4) Appendix — Incorrect. It is a secondary lymphoid organ of the gut, but it does not filter blood.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.
NCERT Extract:
Lymphoid Organs – “… The bone marrow is the main lymphoid organ where all blood cells including lymphocytes are produced. The thymus is a lobed organ located near the heart and beneath the breastbone. The thymus is quite large at the time of birth but keeps reducing in size with age and by the time puberty is attained it reduces to a very small size. Both bone-marrow and thymus provide micro-environments for the development and maturation of T-lymphocytes. The spleen is a large bean-shaped organ. It mainly contains lymphocytes and phagocytes. It acts as a filter of the blood by trapping blood-borne micro-organisms. Spleen also has a large reservoir of erythrocytes.”