Lymphatic system (practicum) (1st Faculty of Medicine, UK)

In the practical exercise, the following preparations are microscoped:

• G1 - Lymph Node
• G2 - Spleen
• G3 - Spleen (impregnation)
• G4 - Thymus of the child
• G5 - Thymus of an adult human
• B5 - Palatine tonsil

G1 - Lymph node

A lymph node is a bean-shaped organ embedded in thin connective tissue. The knot itself is surrounded by a hard fibrous capsule capsule made of dense collagen fibers, elastic fibers and a minimum of smooth muscle cells. Capsula fibrosa sends out trabeculae inwards, which at the same time branch blood vessels inwards. The stroma is made up of a network of reticular fibers and cells (reticular fibroblasts) and 3 areas can be distinguished in it on a section - the cortex (cortex), the medulla (medulla) and the paracortex.

Bark it contains oval accumulations of lymphatic tissue, the so-called lymphatic follicles. We recognize 2 types of follicles:

• Primary follicles are formed by the accumulation of B-lymphocytes with a strongly staining nucleus and only a small amount of cytoplasm, therefore they have a dark appearance.
• Secondary follicles have a germinal (reaction) center of different sizes in the middle. The lighter coloration is due to activated B-lymphocytes with a finer chromatin structure and a larger amount of cytoplasm.

The cortex usually does not reach the hilum of the nodule.

In the marrow there is a smaller amount of lymphocytes, but in contrast to the cortex there are numerous macrophages, plasma cells and rarely heparinocytes.

G2 - Spleen

The spleen is a large lymphatic organ, which, due to its functions ("cemetery" of erythrocytes, a reservoir of blood platelets, etc.), is richly supplied with blood.

B5 - Palatine tonsil

The palatine tonsil is an accumulation of cells of the lymphatic line in the mucosa between the arcus palatoglossus and the arcus palatopharyngeus.

Tonsil Surface:

• is covered with stratified squamous epithelium non-keratinizing (epithelium oral cavity);
  • the covering epithelium is clearly visible in some places, in other places, especially in the crypts, it is fibrous due to the infiltration of lymphocytes and therefore difficult to distinguish under the microscope;
• furrowed into pits that lead to variously deep crypts;
  • in the crypts there is 'detritus - a mixture of desquamated epithelial cells, bacteria, food remains and numerous lymphocytes that have traveled here from the epithelium.
    

Lymphatic Component

• forms variously numerous and close to each other lymphatic follicles
• we will often observe bright germinal centers showing slight eosinophilia. The germinal centers are the expression of the organism's immune system activation.

Tonsils have no afferent lymphatic vessels, but are drained by efferent lymphatic vessels.