PRACTICUM IN HISTOLOGY, CYTOLOGY AND EMBRYOLOGY - 2016

Chapter 5. SPECIAL HISTOLOGY

Organs of Hematopoiesis and Immune Defense

Slide 85. Lymph node.

Staining: hematoxylin and eosin.

Magnification: x80.

With the naked eye, a bean-shaped section is visible, featuring a dark periphery (cortex) and a lighter center (medulla). At low magnification, select an area that encompasses both the cortical and medullar regions in the field of view.

Externally, the Lymph node is covered by a Connective Tissue capsule (1) stained pink. The capsule contains adipocytes, smooth myocytes, small Blood Vessels, and afferent Lymphatic vessels. Trabeculae (2) extend from the capsule deep into the node. Beneath the capsule lies the cortex (3), which consists of rounded lymphoid nodules (4) colored purple due to the intense staining of lymphocyte nuclei. A lighter area (5), known as the germinal center (reactive center, center of proliferation), may be visible in the center of the nodule.

The medulla (6) is represented by cord-like accumulations of lymphocytes (medullary cords).

Lymphoid nodules, medullary cords, and trabeculae are covered with a layer of reticuloendothelial Cells. Narrow cleft-like spaces, known as lymph node sinuses, lie between these cells. The following sinuses are distinguished within a lymph node: a) subcapsular (marginal) sinus (7) located between the capsule and the periphery of the lymphoid nodule; b) interfollicular cortical sinus (8) located between the trabeculae and the lymphoid nodule; c) medullary sinus (9) located between the trabeculae and the medullary cords; d) hilar sinus located in the hilum of the node, which continues into the efferent lymphatic vessel.

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Slide 85. Lymph node.