Lymphoid Organs Lymphocytes (B,T) Macrophages Antigen presenting cells Capsule (D.C.T. ), Trabecula Stroma: Reticular connective tissue

Lymphoid Organs 1-Central (primary) lymphoid Organs a- Thymus (T lymphocyte) b- Bonemarrow (B lymphocyte) 2- Peripheral (secondary) lymphoid organ a –Tonsil b - Lymph node C- spleen

Thymus=central ( primary lymphoid Organs) Mediastinum Epithelio –reticular cell

Epithelio – reticular cell in cortex Type I : between capsule & cortex,around cortical vessels (Tight Junction) Type II : In Cortex (Desmosome,Tonofilaments ) Type III: between cortex & medulla(Tight Junction)

Epithelio – reticular cell in Medulla Hassals corpuscles

Blood Circulation Medulla A-capillary B-post capillary venule cortex continues capillary Thick basal lamina Epithelio – reticular cell Blood-thymic barrier (Cortex) (High endothelial cell) Receptor T-lymphocyte

Thymic functions : Production and differentiation of T cells Epithelio – reticular cells secret: - thymic humeral factor - thymolin - thymosin – α -thymopoietin differentiation of T-cells Digeorge syndrome (no thymus development)

Lymph nodes

Lymph node Cortex Medulla

Cortex *outer cortex lymphatic follicule B cells * inner cortex (para cortical zone) T cells

inner cortex (T-cell) subcapsular sinus (para cortical zone) outer cortex(B-cell )

Medulla medullary cord B-cell plasma cell Macrophage medullary sinus (lymph)

Lymph Circulation Capsule afferent lymphatic vessel subcapsular sinus pretrabecular sinus (Intermediate sinus ) Medullary sinus efferent lymphatic vessel Hilum

Post capillary venule Lymphocyte(selectin) Recognition High endothelial cell (ligand)

Lymph node Functions : -Production of lymphocyte -Defense -Filteration of lymph Metastasis

Mucosal Associated Lymphoid Tissue (MALT) Digestive duct Respiratory duct Uro-genital duct 1-Diffuse T-cell, B-cell, Plasma cell 2-Solitary 3-Aggregate(pyers patches&Tonsils)

Tonsils palatin tonsil pharyngeal tonsil lingual tonsil Type of epithelium, number of crypt

Tonsils - Capsule+Trabecula: Dense connective tissue incomplement capsule = organ Epithelium,crypt Stoma: Reticular connective tissue Lymphocyte: T-cell( Diffuse) B-cell (lymphoid follicle)

Palatine tonsils lateral part of oropharynx Number: pairs (2) Epithelium stratified squamous Crypt : 10-20

Lingual tonsils Small, numerous Crypt: one Location: Base of tongue Epithelium: stratified squamons

pharyngeal tonsil Number: 1 Location: supero-posterior of pharynx Adenoid : hypertrophy of tonsil crypt : no crypt epithelium :pseudo stratified

Spleen location Left of abdominal cavity hilum

Structure Capsule+ Trabecula:- Dense connective tissue - smooth muscle cell Stoma: Reticular connective tissue Origin: Mesoderm Cells: Lymphocyte: T-cell, B-cell APC, Macrophage, reticular cell Blood cells

Trabecular artery Trabecular vein

Stoma: Reticular connective tissue Origin: Mesoderm

Parenchyme=pulp Pulb: Reticular cell, lymphocyte, macrophage, APC, blood cells recticular C.T 1-white pulp 2-red pulp

white pulp lymphatic follicule (B-lymphocyte) centeral arteriol

White pulp Central arteriol Peri Arterial lymphatic sheath (PALS ) T-lymphocyte Marginal sinus: (loose C.T) Lymphocyte active macrophage APC interdigitaling dendritic cell blood antigen = immunologic activity

Red pulp - splenic cord (billroth's cord) reticular cell T lymphocyte B lymphocyte blood cells -Sinusoids

Sinusoids elongated endothelia cell long axes parallel long axes of sinusoids) reticular fiber (transvers direction )

Blood circulation splenic artery trabecular artery (PALS) centeral artery(white pulp) pulp arteriol penicillar arteriol sheated arteriol terminal arteriol sinusoids open circulation close circulation pulp venule trabecular vein

Function -production of lymphocyte -defense -destructon of erythrocyte (active macrophage) :RBC heme + globin -production of granulocyte & erythrocyte (pathologic condition) = myeloid metaplasia ) Normal :embryonic period Abnormal: splenomegaly (Anemia, platlet disorders turomato abdomen)

When god says yes, he give you what you want When he says wait, he gives you something better When he says no, he wishes to give you the best