Histology Of The Lymphoid System

function: keeping the own antigen environment, eliminating the foreign substances/antigens lymphoid tissue lymphoid organs: primary (red bone marrow, thymus): development of lymphocytes secondrary(lymph node, spleen, tonsils, Peyer s patches, appendix): mature lymphocytes can be found here basic tissue: lymphoreticular- reticular connective tissue, reticular fibers, reticular cells; thymus: epithelial reticular cells main cell types: lymphocytes, macrophages, dendritic cells, endothelial cells

unit of the lymphoid tissue round, oval structure, many lymphocytes primary: dark, ruond, little lymphocytes, intrauterine secondary: bigger (200-400 m), originating from the primary, in the middle: light area- germinal center (centroblasts, centrocytes, FDC), peripheral: cap zone

structure of a lymphoid follicle cap zone

germinal center

along the course of lymphatic vessels bean-shaped, encapsulated organs afferent lymphatic vessels efferent lymphatic vessels connective tissue capsule trabeculae hilus among trabeculae: reticular connective tissue cortex: lymphoid follicles (B dep. zone) paracortex: no lymphoid nodules (T dep. zone) medulla: medullary lymphoid sinuses, medullary cords marginal sinus intermediate sinus medullary sinus efferent lymphatic vessels (hilus)

cortex

paracortex

trabecula medulla

lymphoid follicle

24. lymph node (HE)

epithelial, lymphatic, adipose form during life 2 lobes+ capsule lobules cortex: peripheral, darker, thymocytes, macrophages, epithelial reticulum cells medulla: central, lighter, more epithelial reticulum cells, Hassal-corpuscules (eosinophil,concentrically arranged,flattened epithelial cells with keratohyalin granules), neuroendocrine cells, myoid (Hammar) cells no lymph follicles function: mature and differentiation of T lymphocytes blood-thymus barrier: pericytes, capillary basal lamina, basal lamina of the epithelial reticular cell, cells of the endothelium, epithelial reticular cells

interlobular connective tissue

medulla

cortex

25. Thymus,HE

medulla

Hassal s corpuscles

25. Thymus,HE

intraperitoneal organ connective tissue capsule trabeculae parenchyma (pulp) red pulp (80%), white pulp (20%) reticular connective tissue, reticulum cells, reticular fibers red pulp: Billroth s cords, sinuses white pulp: PALS (A. centralis- T dep. zone), lymhoid follicles Malpighi (B dependent), marginal zone open and closed circulation

red pulp

capsules white pulp

trabecules

26. Spleen, HE

PALS

26. Spleen, HE

lymhoid tissue in the mucosa Waldeyer s lymphatic ring: pharyngeal tonsils palatine tonsils tubal tonsils lingual tonsils tonsillary epithelium+ lymhoid tissue (lymphoreticular connective tissue) tubal and pharyngeal t.: ciliated pseudostratified epithelium with goblet cells lingual and palatine t.: stratified squamos nonkeratinized epithelium epithelium crypts: lingual t.- shallow, wide// palatine t.: narrow, deep lingual t.: seromucous glands crypts, strited muscle fibers follicles (B dep.), interfollicular area (T dep.) epithelium is often infiltrated with lymphocytes

crypt

tonsillary epithelium

lymphoid follicles

27. Palatine tonsil, HE

crypt stratified squamous nonkeratinized epithelium

lymphoid follicle

27. Palatine tonsil, HE

crypt lymphoid tissue

tonsillary epithelium

seromucous glands

28. Lingual tonsil, HE

stratified muscle fibers

seromucous glands

28. Lingual tonsil, HE