Question

Bursa of fabricius is present in
A. Mammals
B. Birds
C. Reptiles
D. Amphibians

Answer 1

Hint: Bursa of Fabricius can also be called as blind sac on the cloaca in case of birds. It's lymphatic tissue produces B cells which are involved in antibody production and fighting against invading bacteria. Therefore, it is also called as cloacal thymus.

Complete answer:Bursa of Fabricius is important for the event of the postbursal B cell population, including the mature antigen-specific B cells and therefore the self-renewing postbursal stem cells. Neither of those populations is capable of homing, in contrast to the prebursal or bursal stem cells, to the cyclophosphamide-treated bursal reticulum, albeit they're capable of reconstituting antibody production. In other words, the postbursal cells have passed the stage of bursal development once and for all. The bursa of Fabricius functions as a central lymphoid organ, required for development of the antigen-specific B cell repertoire. It's necessary for the differentiation of prebursal stem cells into bursal stem cells present within the bursa until the 5th week after hatching. These cells are capable of reconstituting the bursal morphology and specific antibody production when transferred into birds with the bursal lymphoid structures destroyed with cyclophosphamide within the newly hatched period. They comprise a clearly defined stage within the stepwise maturation of the avian antibody-producing cells.
Bursa of Fabricius is vital for the diversification of the antibody repertoire by providing a site for extensive, high rate gene conversion, which occurs between only one functional V gene (VH1 or VL1) and a gaggle of V pseudogenes. The bursa of Fabricius is important for the event of the antigen-specific B cell repertoire. Prebursal stem cells with germline immunoglobulin genes rearranged are found within the intraembryonic mesenchyme from embryonic onwards. After arrival within the bursa of Fabricius they become bursal stem cells undergoing extensive, high rate gene conversion, which results in diversification of the germ line repertoire; these cells need the bursal microenvironment for further maturation. Post bursal cells, present both within the bursa and periphery, include mature antigen-specific B cells and self-renewing postbursal stem cells, capable of further maturation without bursal influence. The bursa of Fabricius, a lymphoid organ found only in birds, is a crucial tissue for B cell maturation. The interior surface of the bursa of Fabricius contains many folds and enormous numbers of lymphoid follicles. This surface is roofed with specialized epithelial cells which will take up luminal Ags.
Thus, the luminal surface of the bursa of Fabricius contains cells that resemble M cells. Wherever there are tendons moving across a bony surface, there's a bursa.

Additional information: There are approximately 150 bursa found within the body. Most are present at birth, but a bursa may form in a neighborhood where there's friction. Bursae are crammed with a skinny layer of thick fluid, just like the consistency of a raw albumen , and a lining of synovia , which also works as a shock for the joint and supplies molecules to the cartilage. This is often referred to as dissipating force. Normally, the bursae are thin and supply a really slippery surface so there'll be little or no friction when there's movement of the joint.

Note:Bursitis must be treated promptly although it isn't dangerous on its own, but infected bursae are often a big complication, which can cause future or permanent damage of the joint.