What is the role of Peyer's patches in immunity?

Correct Answer: B

Rationale: Peyer's patches monitor gut pathogens; blood is spleen, B cells are marrow, T cells are thymus.

Correct Answer: C

Rationale: Tunica adventitia contains longitudinal smooth muscle and vasa vasorum in larger lymphatic vessels; stratum basale is epithelial.

Correct Answer: A

Rationale: Spleen trabeculae divide it into irregular compartments, not regular or cortex/medulla like lymph nodes.

Correct Answer: D

Rationale: Thymus stroma has a thin C.T. capsule , incomplete trabeculae , and reticular C.T. ; it does not have a thick capsule (D is incorrect).

Correct Answer: B

Rationale: Billroth cords in spleen red pulp are infiltrated with blood and lymphoid cells ; they're not in lymph nodes or between follicles , and lack central arterioles .