Immune System

Chapter 10

Immune System

Components Immunological molecules  Immune cells  lymphoid tissues  lymphoid organs 

Functions Immune reactions

Immune cells 

Lymphocytes T- lymphocytes B- lymphocytes LGL

K - lymphocytes NK- lymphocytes

Macrophages

& Mononuclear phagocytic system Monocytes Macrophages (C.T. & L.T.) Osteoclasts Microglia Macrophages (liver & lung)

Antigen

presenting cells

Dendritic cells Macrophages

Lymphoid tissue A specialized C.T. 

Components Reticular tissue A large number of

lymphocytes and a few antigen presenting cells



Two patterns Diffuse lymphoid tissue Lymphoid nodules

Diffuse lymphoid tissue 

No distinct boundary  Mainly T-lymphocytes  Postcapillary venules  It can increase and occur new lymphoid nodules by stimuli of antigen

Lymphoid nodule 

oval in shape with a distinct boundary

-Mainly B-lymphocytes

-A pale center — germinal center

Lymphoid organs Mainly compose of lymphoid tissue  Classification 

Central lymphoid

organs Thymus, Bone marrow Peripheral lymphoid organs Lymph nodes, Spleen, Tonsils

Thymus In the puberty the thymus begins to involute and is gradually replaced by the C.T. It can generate T-cells.

Lymph node Capsule Cortex Medulla

1.Structure 1.1 Capsule C.T. , Trabeculae Afferent lymphatic vessels Hilum: C.T. , Blood vessels, Efferent lymphatic vessels

1.2. Cortex Superficial cortex Paracortex zone Cortical sinus

1.2.1.Superficial cortex Lymphoid nodules 95% of B-lymphocytes germinal center

Diffuse lymphoid tissue inter-nodular region

1.2.2. Paracortex zone Diffuse lymphoid tissue T- lymphocytes Postcapillary venules

Structure: Endothelium--simple tall cuboidal Function: Lymphocytes in the blood stream → lymphoid tissue

1.2.3. Cortical sinuses Subcapsular sinus Peritrabecular sinus

Structures 

Sinusoidal wall  endothelium  basal lamina& reticular fiber  reticular cells



Lumen  lymphocytes  macrophages  reticular cells

Functions To filtrate the lymph

1.3. Medulla Medullary cords Plasma cells, B-lymphocytes, Macrophages

Medullary sinus

Lymph circulation

Recirculation of lymphocyte Postcapillary venules

L.N.

Heart

lymphatic vessels

Blood vessels

Postcapillary venules Lymphocytes

lymphoid organs or tissue Lymphocytes

Blood vessels

Lymphatic vessels

2. Function To filtrate lymph  To give rise to immune response 

Spleen Capsule White pulp Red pulp Marginal zone

1. Structure 1.1 Capsule mesothelium dense

C.T. , smooth muscle cells and elastic fibers trabeculae

1.2. White pulp Splenic corpuscles---lymphoid nodules B-lymphocytes

Periarterial lymphatic sheath Central artery Thick diffuse L.T.: T-lymphocytes

1.3.Red pulp Splenic cords Blood cells  B-lymphocytes, plasma cells, 

Macrophages,

etc.

Splenic sinus Endothelial

cells

Incompleted Reticular

basement membrane

fibers

1.4. Marginal zone between the white pulp and red pulp B, T-lymphocyte and macrophages

--Marginal (blood ) sinus Passage for antigen and lymphocytes of blood entering the white pulp 

2. Function    

To filtrate blood Immunological defense Production of blood cells Blood storage: 40ml