Immune-Lymphatic System – 2 Lymphatic Organs ANHB 2212 – 2006 – Week 9 Avinash Bharadwaj

Mechanisms  Nonspecific defence  Specific defence  Cellular attack  Molecular (“humoral”) attack More than one mechanisms may be operating at a time!  Cells involved  White blood cells  Macrophages  Lymphocytes T and B  Others  Intricate interactions between cells – molecular messengers

Lymphoid (Lymphatic) Tissues  Scattered lymphocytes and other cells  Lymphatic nodule – structural organisation  Lymphocytes, macrophages, plasma cells, other leucocytes  Outer zone (corona) and germinal centre  Aggregates of lymphatic nodules  Mucosa of GI Tract, respiratory system and other sites  Larger aggregates – Peyer’s patches (ileum), tonsillar tissue.  Organised, encapsulated structures  Lymph nodes  Spleen – special functions  Thymus – the academy

Lymphatic Nodule  “Non-capsulated”  Single or aggregated  Independent OR parts of other lymphoid organs  Outer dark zone  (Corona or cap)  Germinal centre

Lymphocyte Training - Thymus  Lymphoid organ  Anterior Mediastinum  Foetal life  Childhood  Puberty  Involution in adult life

Thymus  Capsule  Lobules  Cortex  Medulla  Hassal’s Corpuscles

Regions and Cells Capsule Cortex Medulla Epithelial reticular cells Lymphocytes Stages of maturation Blood vessels Barrier

Lymphocyte Training  CFU-L  Recognise antigen – pass/fail  Recognise self/non-self – pass/fail  Cytotoxic / Helper T cells

B Lymphocytes  Bursa of Fabricius  Lymphoid organ in birds  Bursa equivalent structures  Bone marrow  Gut and other mucosa-associated structures

Tonsil  A group of lymphoid structures  Around the pharynx (GIT and RS)  Lingual, “palatine”, tubal, nasopharyngeal  Structurally similar

Palatine Tonsil Epithelium of the pharynx “Crypts” Lymphatic nodules Connective tissue and pharyngeal muscle.

Peyer’s Patches  Ileum – “antimesenteric border”  Lamina propria  submucosa

Lymph Node  Capsulated  Afferent lymphatics  “subcapsular sinus”  Hilum – blood vessels, efferent lymphatic  Cortex and medulla  Cortex  Lymphatic nodules, germinal centres  “Paracortex”  Medulla  Medullary cords and sinusoids

C M

Lymph Node Lymphatics  Afferent  Efferent Blood vessels  Lymphocytes  Cortex  Nodules (B)  Deep cortex (T zone) Medulla (Cords, sinuses) A A A A E

Function Antigens etc APCs Nodule : B High Endothelial Vv Medulla : Plasma cells etc

Spleen  Lymphatic function – lymph nodules (white pulp) around arterioles.  Red pulp  Sinusoids

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