Talk:Draft 2016: Difference between revisions

Revision as of 18:07, 26 February 2016

Lymph Node Anatomy
Location throughout the entire body - concentrated in axilla, groin, lung, gastrointestinal tract mesenteries Small (1 mm - 2 cm) encapsulated organ (diffuse lymphoid tissue - no capsule) Antigen transformed lymphocytes from the blood In lymph vessel pathways “filter” lymph Afferent - towards node (A - arrives at the node) Efferent - away from node (E - exits the node)

Lymph Node Functions

Structure Overview

Connective tissue capsule (thin) with numerous trabeculae (septa)
- major blood vessels run in CT
Lobules containing cortex and medulla regions
- medullary regions are continuous (connected together)
NOT supplied by afferent lymph vessels

Blood-Thymic Barrier

Blood vessels are separated from thymus cortex by epithelioreticular cells.
impermeable to most macromolecules.
Barrier layers: capillary endothelium - endothelial basal lamina- perivascular CT sheath - basal lamina of epithelioreticular cells - epithelioreticular cell sheath

Thymus Epithelioreticular cells (TEC)	Macrophages	Lymphocytes
Abundant, eosinophilic, large, ovoid and light nucleus 1-2 nucleoli sheathe cortical capillaries form an epitheloid layer maintain microenvironment for development of T-lymphocytes in cortex (thymic epitheliocytes)	cortex and medulla difficult to distinguish from reticular cells in (Stain - Haematoxylin Eosin) remove auto-reactive T-lymphocytes	located in cortex and medulla more numerous (denser) in cortex majority are developing T-lymphocytes (= thymic lymphocytes or thymocytes)

Infant thymus

Fetal thymus	Young medulla	Young cortex

Adult Thymus
	Cortical lymphoid tissue is replaced by adipose tissue (involution) Increase in size of thymic corpuscles Thymic corpuscle - (Hassall’s corpuscle) mass of concentric epithelioreticular cells.

Connective Tissue

Capsule - dense connective tissue (irregular CT, some adipocytes))
Trabeculae - dense connective tissue
Reticular Tissue - Reticular cells and fibers, supporting meshwork (collagen type III)
- Reticular cell produces reticular fibers (collagen type III) and surrounds the fibers with its cytoplasm
- reticular fibbers can also be produced by fibroblasts

Important - Please note that the lymphocytes exit from the node by efferent lymphatic vessels.

‎‎Lymph Node 7

T and B motility

‎‎Lymph Node 8

T and B interaction

High Endothelial Venules

Links: Immunobiology - Figure 1.8. Organization of a lymph node

@@ Line 20: / Line 20: @@
 ! colspan=2|Lymph Node Functions&nbsp;
 |-
-| valogn=top|
+| valign=top|
-* specialised thymus microenvironments allow the production of self-tolerant T-cells (T lymphocytes) from immature precursors.
-** immature precursors enter the thymus
-** differentiate and undergo selection by thymic epithelial cell (TEC) subtypes
-** mature release into circulation of these cells
-* destruction of cells that recognise self antigens
-* T-cells kill infected and oncogenic cells
-'''T Cells  maturation within the thymus'''
+| [[File:Lymph_node_cartoon_01.jpg|Lymph_node_cartoon_01.jpg|600px]]
-# '''T cell progenitors''' enter the thymus at the cortex/medulla border via post–capillary venules
-# '''migrate''' toward the capsule in response to chemokine signalling.
-# '''cortex''' - thymocytes undergo positive selection by cTECs then migrate to the medulla
-# '''medulla''' - thymocytes are screened for reactivity to tissue-restricted self antigens expressed by mTECs.
-# '''Mature T cells''' exit the thymus via blood or lymphatic vessels in response to a sphingosine-1-phosphate (S1P) gradient.
-| [[File:Thymus structure and function cartoon01.jpg|600px]]
 |-
-| [[File:Mouse adult thymus 11.jpg|200px]]
-Macrophages phagocytosis of T cells
-{{Thymus Movie 1}}
-| [[File:T and B lymphocytes EM09.jpg|400px]]
-EM - T and B lymphocytes (look the same)
 |}