1. 淋巴小结（ lymphoid nodule ）： Definition: spherical or ovoid structures mainly composed of B C with clear boundaries Classification: primary LN →secondary LN : Composition: cap germinal center: light zone dark zone Function: humoral immunity
What we should find Lymph node （淋巴结）： cortex( three structures) medulla( two structures) Spleen （脾） : white pulp ( three structures) red pulp ( two structures) Thymus( 胸腺 ): cortex medulla (thymic corpuscle )
1 common features LO Abundance intensely lymphocytes 2 different arrangement of three types of LT lymph node and spleen thymus DLT LN LC How to recognize LO
1 capsule 2 Parenchyma
1.Lymph node At low power,the lymph nodes is 豆形,covered by capsule.with a dark-staining cortex at the periphery, pale-staining medulla in center. Possesses a depression-the hilum, a region where lymph leaves and blood vessels both arrive and leave. cortex medulla hilum capsule
Capsule (connective tissue) superficial cortex cortex paracortical zone cortical sinuses Parenchyma medullary cords medulla medullary sinuses General structure of lymph node
2. Spleen Capsule (CT, serous membrane) splenic corpuscle white pulp peri-arterial lymphatic sheath Parenchyma splenic cords red pulp splenic sinuses marginal zone
General structure of thymus Capsule (CT) cortex (periphera region, dark-staining) Parenchyma medulla (central portion (lobules) pale-staining,with Hassall's corpuscles)
white pulp : Dense accumulation of lymphocytes 1 periarterial lmyphatic sheath: Tcells 动脉周围淋巴鞘 around central artery 2 splenic corpuscle: lymphatic nodule B:periarterial lymphatic sheath A:spleenic corpuscle A B
Red pulp: dark red mass,occupies all the space except capsule and white pulp. 1 Splenic cords: Lymphatic cord with numerous erythrocytes 2 Splenic sinuses: Between splenic cords, composed of rod-shaped endothelial cells filled with blood.
Which organ ？ Which structure? Lymph node Lymphoid nodule
Which structure ? which organ? medulla cords medulla sinuses Lymph node
which organ? spleen
Which structurer? Hassall's corpuscles
Which organ? spleen
Which organ? spleen
Which organ? Lymph node
Which structurer? Subcapsular lymphatic sinuses
Immune cells: Lymphocytes (T-/B- lymphocytes) Antigen presenting cell Ohters: Plasma cells Granulocytes Mast cells, an so on Mononuclear phagocytic system
superficial cortex- lymphoid nodule Formed mainly by B lymphocyte. stimulated by antigen,the diameter can be much larger and germinal center(pale stained) can easily seen. lymphoid nodules are temporary structures,they may develop, disappear and redevelop. The size and number of nodules vary widely. Germinal center is temporary structure like lymph nodules.
Paracortical zone Lies in deep portion of cortex and on the border of medulla.Lies in deep portion of cortex and on the border of medulla. Compose of DLT, mainly with T lymphocyte.Compose of DLT, mainly with T lymphocyte. Postcapillary venules can be seen among them. Postcapillary venules can be seen among them.
Postcapillary venules High cuboidal epithelium
Subcapsular sinuses: Beneath the capsule Beneath the capsule Lymphatic sinuses Lymphatic sinuses Marcophage,plasma cell Marcophage,plasma cell
Medullary sinuses: Irregular space around medullary cords. Medullary cords Densely lymphatic strands.
This is the hilum region of a node where lymph leaves via efferent lymphatics and where blood vessels both arrive and leave. hilum
Capsule : (compare to lymph node) Thicker,covered by a serous membrane, more smooth muscle and elastic fibres. Enter into parenchyma and form trabeculae.
capsule Capsule: DCT, extend into the thymus and subdivid the thymus into lobules.
Cortex: Peripheral region, dark-staining, No lymphoid nodules Cortex capsule
Hassall's corpuscles (Thymic corpuscle) Medulla: Hassall's corpuscle, with concentric layers of keratinizing epithelial cells. Central cells often show degeneration and nucleus can not be seen.