Interferons

A. The popliteal vein:The popliteal vein is a major vein of the lower limb, located behind the knee, and drains blood from the leg into the femoral vein.

B. The medial plantar artery:The medial plantar artery is a branch of the posterior tibial artery that supplies blood to the plantar aspect of the foot, making it part of the lower limb vasculature.

C. The posterior tibial artery:The posterior tibial artery runs along the posterior compartment of the leg and supplies the lower leg and foot, classifying it as a lower limb vessel.

D. The fibular vein:The fibular (peroneal) vein accompanies the fibular artery in the lateral leg and drains the lower leg, making it a vessel of the lower limb.

E. The axillary vein:The axillary vein is located in the upper limb, draining blood from the arm into the subclavian vein. It is not part of the lower limb vasculature.

A. Thymus:The thymus is essential for the development and maturation of T lymphocytes, particularly in infants and young children. Removing the thymus at one year of age would severely impair adaptive immunity, leaving the child highly susceptible to infections.

B. Spleen:While the spleen plays a significant role in filtering blood and mounting immune responses, its removal is less immediately catastrophic in a one-year-old than removal of the thymus. Children can survive with partial immune support from other lymphoid tissues.

C. Appendix:The appendix contains lymphoid tissue but is not essential for immune function. Its removal has minimal long-term impact on immunity, even in young children.

D. Lymph node:Lymph nodes contribute to local immune responses, but their removal does not drastically impair systemic immunity. Other nodes can compensate for the loss of individual lymph nodes.

E. Palatine tonsil:Tonsils provide localized immune surveillance in the oropharynx. Removal may slightly reduce immune defense in that area, but systemic immunity remains largely intact.