LYMPHOID TISSUE III

Histology 2016-2017
Department of Anatomy &Histology: Dr.Rajaa Ali
*************************************************************
LYMPHOID TISSUE III
LYMPH NODE
GENERAL FEATURES
o Oval or bean-shaped structures situated along the course of the lymphatic vessels.
o They serve as filters of lymph, removing particulate matter and bacteria from lymph before it enters the CVS, thereby localizing and preventing the spread of infection.
o Lymph nodes are usually found in groups, especially in the axilla, inguinal region, root of lung, etc.
o Lymph node has many afferent lymphatic vessels which enter through the convex surface, whereas the efferent lymphatic vessels are one or two in number and leave through the concave depression, the hilum. The hilum also transmits nerves and blood vessels. The lymphatic vessels are provided with valves in such a way that lymph fl ows in one direction.
COMPONENTS/STRUCTURE
A. Connective tissue framework
1. Capsule
2. Trabeculae
3. Reticular stroma (fi bres)
B. Parenchyma
1. Cortex
2. Paracortex (inner cortex)
3. Medulla


Connective Tissue Framework
Capsule and Trabeculae
o The organ is surrounded by a thin connective tissue capsule which sends trabeculae into the interior.
o Beneath the capsule is the subcapsular sinus which is traversed by reticular fi bres and cells.
o The subscapsular sinus receives afferent lymphatic vessels and is continuous with trabecular sinuses found around the trabeculae.
o The trabecular sinuses become continuous with the medullary sinuses.

Reticular Stroma
o It is made of reticular fi bres and associated phagocytic reticular cells, forming a meshwork throughout the organ and is particularly dense in the cortex ( fig. ).
o Gives structural support to lymphoid cells (parenchyma).