1. Immune response (lymphoid) system

2. Immune response system includes: Diffuse lymphoid infiltration Lymphoid follicles (nodules) MALT, GALT, BALT Tonsils (Waldeyer’s ring) Lymph nodes Spleen Thymus gland Red bone marrow

5. Waldeyer’s ring: Palatine tonsils (paired) Tubal tonsils (paired) Pharyngeal tonsil (single) Lingual tonsil (single) Laryngeal tonsil (occasional) Tonsillar structure: Crypts Epithelial lining Lymphoid nodules (follicles) surrounding crypts

8. Lymph node structure: Cortex (Lymphoid nodules with germinal centers) Paracortex (Deep cortex, T-lymphocytes) Medulla (Medullary cords) Sinuses: Marginal (subcapsular) Cortical (paratrabecular) Medullary Hilary

13. Spleen structure: White pulp Lymphatic nodules with central arteries Periarterial lymphatic sheaths (PALS) Red pulp Trabecules with arteries and veins Cords of Billroth

18. Thymus gland structure: Thymic lobule is a structural unit, consisting of epithelioreticulocytes infiltrated with thymocytes (T-lymphocytes). Each lobule includes: Cortex + Medulla (including Hassal corpuscles) During ageing thymus undergoes involution resulting in transformation into corpus adiposum Under stressfull conditions thymus undergoes accidental involution

22. Red bone marrow: Location: flat bones and epiphysial parts of long bones Structure: Osseous trabecules of spongy bones Reticular connective tissue Pluripotent hemopoetic cells with clasters of differentiating red and white blood cells