1- INTRODUCTION- DEFINITION :
- Lymph nodes are small, kidney-shaped organs, encapsulated, a few mm long (5mm à 10mm), along the route of lymphatic channels (lymph circulation).
- Lymph nodes are peripheral lymphoid organs (said secondary ) ,sites d’immunopoièse c.a. of production dependent lymphoid cells of the & rsquo; antigen as opposed to central lymphoid organs are lymphopoiesis ie sites producing lymphoid cells independent of any antigenic stimulation.
- They are filter lymph and play a big role in the defense of the & rsquo; vis-a-vis body microorganisms (virus, bacteria etc.…) and the spread of cancer cells.
2- LOCATION :
- cervical Regions, axillary, inguinal.
- pre-vertebral regions or they accompany large thoracic and abdominal vessels.
- Folds bending members.
- In the hilum of the thoracic and abdominal viscera.
- At the root and between the layers of the mesentery.
3- HISTOLOGICAL STRUCTURE :
Each lymph node has to describe the four components :
- A conjunctiva frame
- A lymphoid parenchyma
- The lymphatics
- A blood Network
A- FRAMING CONJUNCTIVA : constituted by :
a- A tissue capsule :
– made of collagen fibers and elastic fibers of a few.
– lets lymphatic vessels afferent and efferent.
b- Conjunctive bays :
– interfolliculaires : that detach from the capsule, penetrate the cortical and delimit cubicles which communicate with each other in their deep part.
– intercordonnales : irregular arrangement, extend interfollicular spans and meet in a fibrous core = the HILUM.
c- a crosslinked tissue :
- s & rsquo; inserts on the conjunctiva frame.
- draws a large mesh frame which supports the lymphoid formations .
- He understands : * reticulated cells = Fixed macrophages (able to mobilize and become free macrophages).
B- PARENCHYMA LYMPHOID :
On he distinguishes two zones duties to the distribution inégale des lymphocytes.
a- Peripheral zone = ZONE CORTICAL :
- Dense, occupies the node peripheral region.
- It is split into two parts :
1- an outer cortical :
- On its surface is the SINE UNDER- CAPSULE marginal or consisting of & rsquo; a loose network of reticulated cells, reticulin fibers and macrophages.
- The subcapsular sinus communicates with the medullary sinuses by & rsquo; intermediate cortical sinus who walk on the surface of trabeculae.
- The outer cortical region is formed of & rsquo; lymphoid tissue into organized structures called spherical : FOLLICLES LYMPHOIOES.
2- an inner cortical : called para-cortical areas :
- It is continuous with the outer cortical.
- It corresponds to the thymus-DEPENDENT area or lymphocytes are T-type (LT).
- It is devoid of lymphoid follicles.
- It is characterized by its particular vascularization made veinlets POST- HAIR (Cubic endothelial cells) through which the cells migrate from the blood flow to the deep cortex.
3- FOLLICLES LYMPHOID :
- They are arranged in a single layer at the periphery of the outer cortex.
- These are spherical formations or free cell density is higher than in other regions
- On distingue :
– primary follicles = rounded cell clusters, dense, consisting of & rsquo; LB population (in these follicles is n & rsquo; not observed immune response but an increased proliferation of LB).
– secondary follicles : correspond to modified primary follicles.
They have a clear center called germinal center ( at which the immune reaction is taking place ) surrounded d & rsquo; a dense lymphocytic crown.
b- CENTRAL ZONE ZONE = MEDULLARY :
- Claire, it occupies the center of the node and the hilar region.
- It consists of :
1- CORDS MEDULLARY :
*which appear as extensions of the medial cortex.
*they contain LB, plasma cells and macrophages.
*they are separated by dilated medullary cavities called Sinus .
2- SINUS MEDULLAIRES :
Their structure is comparable to that in sinus- capsular .
3- TRAVEES INTER CORDON menores :
4- SUB FUNCTIONAL PU LYMPH :
The lymphoid parenchyma of the lymph nodes is divided into three functional compartments :
A- ZONE dependent B or Zone B :
- Corresponds to the territory of the outer cortical.
- Colonized by the LB (largely) which are grouped into lymphoid follicles that are related to a cell array cytoplasm highly branched cells called DENDRITIC.
- Before antigenic stimulation :
- Zone B is organized lymphoid follicles primary (resting)
- these follicles are made of : – small lymphocytes B
– a loose network of dendritic cells
- After antigenic stimulation :
*appearance of lymphoid follicles with germinal center side.
*these structures have :
– a peripheral area formed as the primary follicle small LB and & rsquo; a loose network of dendritic cells .
– A central zone : characterized by :
- LB activated : centroblastes you centrocytes
- A denser network of dendritic cells
- LT (5 at 10%)
B- ZONE THYMO-depending ou zone T :
- Represented by the para-cortex or predominantly LT,
- Characterized by the presence of dendritic cells (presenting cells d & rsquo; antigens)
- The vascularization of this area is special, made of post-capillary venules through the wall which the cells migrate from the bloodstream to the para-cortex.
C- ZONE MEDULLAIRE : rich plasma cells and macrophages .
5- VASCULARISATION :
A- VASCULARIZATION LYMPHATIC :
- The lymph enters the lymph node by 5 at 6 RELATED lymphatic vessels which lead into the sinus under- capsular.
- She then won the cortical sinuses that continues for medullary sinuses.
- These confluence to form the efferent lymphatic vessel that leaves the lymph node by the hilar region.
B- VASCULARIZATION BLOOD:
- The arteries enter the hilum, head to the follicles while walking in the trabeculae inter-cordonnales and divide into arterioles peri-follicular which in turn provide many capillaries that reach the center of each follicle and then return to the periphery and flow into a post-venule capillary.
- Venules post- capillaries : are characterized by an endothelium (to cuboid cells) that lets the cells of venous blood into the parenchyma of the lymph node.
The lymph node performs several functions :
- Filtration of lymph : capacity & rsquo; stop foreign bodies.
- Devices not specific : phagocytosis of foreign bodies by macrophages.
- humoral immunity : developing & rsquo; circulating antibodies by LB.
- Cell-mediated immunity : provided by LT.
7- THE CYTOPUNCTIQN GANGLIONAIRE :
The lymph node aspiration biopsy is a simple gesture, non invasive, bit painful, easy to achieve before any lymphadenopathy ( ie any increase in size & rsquo; a ganglion ).
- INTEREST : it often allows rapid diagnostic referral to Benin context or reaction to a tumor while imposing the realization d & rsquo; a biopsy for histological analysis .
- TECHNIQUE : it consists of introducing a thin and short needle (25G) in & rsquo; lymphadenopathy after immobilize it between two fingers and do some back and forth accompanied by & rsquo; s rotation & rsquo; needle and achieve some smear with lymph node collected.
- In all cases the lymph node FNA allows & rsquo; quickly orient the Diagnostic and assists in the selection of additional tests to perform.
DR N course. AFOUTNI – Faculty of Constantine