Lymphoid System Flashcards
Name the primary lymphoid organs
Bone marrow
Thymus
Name the secondary lymphoid organs
Lymph nodes Spleen Tonsils Epithelia-lymphoid tissues Bone marrow
What are the functions of lymphatics?
Fluid homeostasis
Allows cell traffic and trapping
Allows interaction with cells and the immune system
Describe the structure of lymph nodes
Small oval bodies located along the course of lymphatic vessels
Afferent channels
Efferent vessels
Medulla and follicles surrounding a hilum
Where do the efferent vessels drain?
Cisterna chyli/thoracic duct
R/L jugular, subclavian or brachomediastinal trunks
Into venous system at junction of subclavian and jugular veins
Where is lymph filtered?
Node parenchyma
What does lymph filtration allow?
Traffic of cells
Immune interactions
What role does lymph play in the immune system?
Houses cells of innate immune system
Traffic of APCs links innate and adaptive
Adaptive immune response
What immune cells can be found in a lymph node?
Lymphocytes Mononuclear phagocytes APCs Dendritic cells Endothelial cells
Where are B cells found?
Follicles
Germinal centres
Interfollicular area
Plasma
What can cause lymphadenopathy?
Local inflammation
Systemic inflammation
Malignancy
Others - sarcoid, castleman’s
What is lymphangitis?
Red lines extending from an inflamed lesion of superficial infection
Describe how cell pattern can indicate cause
Predominant B cell - autoimmune/infection
Predominant phagocyte - tumour
Predominant T cell - virus/drugs
Where is the spleen?
Upper left quadrant of abdomen
Name the two surfaces of the spleen
Diaphragmatic surface
Visceral surface
What makes up the visceral surface?
Left kidney, gastric fungus, tail of pancreas, splenic flexure of colon
Describe the vasculature of the spleen
Supplied by the splenic artery - branch of coeliac
Drained by splenic vein (contributes to SMV to portal vein)
Name the two key parts of the spleen
Red pulp
White pulp
What is found in the red pulp?
Sinusoids
Cords
What supports the sinusoids?
Hoops of reticulin
What do cords contain?
Macrophages, fibroblasts, cells in transit
What makes up the white pulp?
Peri-arteriolar lymph sheath (PALS). APCs in white pulp present antigen to immune reactive cells
What is the function of the spleen?
Detect, retain and eliminate unwanted foreign/damaged material
Facilitate immune responses to blood borne antigens
State the hypersplenism triad
- splenomegaly
- fall in one or more cellular components
- correction of cytopenias by splenectomy
How does splenomegaly present?
Dragging sensation in LUQ
Discomfort with eating
State the causes of splenomegaly
Infection Congestion - portal Haematological Inflammatory Storage disease Miscellaneous (amyloid, tumours, cysts)
What can cause hyposplenism?
Splenectomy
Coeliac, sickle cell, sarcoidosis, iatrogenic
What cells can be seen in reduced red pulp?
Howell Jolly bodies
