With regard to the medullary sinuses of the lymph node: They contain blood.

Correct Answer: B

Rationale: Medullary sinuses contain lymph, not blood; blood is found in vascular structures like sinuses of the spleen.

Correct Answer: C

Rationale: Afferent vessels enter at the convex surface, efferent vessels and veins exit at the concave hilum of the lymph node.

Correct Answer: C

Rationale: PALS (periarteriolar lymphatic sheath) contains only T-lymphocytes.

Correct Answer: D

Rationale: Epithelial reticular cells secrete hormones , form barriers , and nurse T-cells ; all apply.

Correct Answer: D

Rationale: Malpighian corpuscle (white pulp) has a follicular zone with B-lymphocytes ; it's lymphoid, not epithelial , arteriole is central (B is misphrased), mitoses are in germinal centers .