Henry Gray (18251861). Anatomy of the Human Body. 1918.
or lymph sinus(Fig. 597). Running across it are a number of finer trabeculæ of retiform connective tissue, the fibers of which are, for the most part, covered by ramifying cells.
On account of the peculiar arrangement of the frame-work of the organ, the gland pulp in the cortical portion is disposed in the form of nodules, and in the medullary part in the form of rounded cords. It consists of ordinary lymphoid tissue (Fig. 598), being made up of a delicate net-work of retiform tissue, which is continuous with that in the lymph paths, but marked off from it by a closer reticulation; it is probable, moreover, that the reticular tissue of the gland pulp and the lymph paths is continuous with that of the trabeculæ, and ultimately with that of the capsule of the gland. In its meshes, in the nodules and cords of lymphoid tissue, are closely packed lymph corpuscles. The gland pulp is traversed by a dense plexus of capillary bloodvessels. The nodules or follicles in the cortical portion of the gland frequently show, in their centers, areas where karyokinetic figures indicate a division of the lymph corpuscles. These areas are termed germ centers. The cells composing them have more abundant protoplasm than the peripheral cells.
The afferent vessels, as stated above, enter at all parts of the periphery of the gland, and after branching and forming a dense plexus in the substance of the capsule, open into the lymph sinuses of the cortical part. In doing this they lose all their coats except their endothelial lining, which is continuous with a layer of similar cells lining the lymph paths. In like manner the efferent vessel commences from the lymph sinuses of the medullary portion. The stream of lymph carried to the gland by the afferent vessels thus passes through the plexus in the capsule to the lymph paths of the cortical portion, where it is exposed to the action of the gland pulp; flowing through these it enters the paths or sinuses of the medullary portion, and finally emerges from the hilus by means of the efferent vessel. The stream of lymph in its passage through the lymph sinuses is much retarded by the presence of the reticulum, hence morphological elements, either normal or morbid, are easily arrested and deposited in the sinuses. Many lymph corpuscles pass with the efferent lymph stream to join the general blood stream. The arteries of the gland enter at the hilus, and either go at once to the gland pulp, to break up into a capillary plexus, or else run along the trabeculæ, partly to supply them and partly running across the lymph paths, to assist in forming the capillary plexus of the gland pulp. This plexus traverses the lymphoid tissue, but does not enter into the lymph sinuses. From it the veins commence and emerge from the organ at the same place as that at which the arteries enter.
FIG. 598 Lymph gland tissue. Highly magnified. a, Trabeculæ. b. Small artery in substance of same. c. Lymph paths. d. Lymph corpuscles. e. Capillary plexus. (See enlarged image)
The lymphatic vessels are arranged into a superficial and a deep set. On the surface of the body the superficial lymphatic vessels are placed immediately beneath the integument, accompanying the superficial veins; they join the deep lymphatic vessels in certain situations by perforating the deep fascia. In the interior of the body they lie in the submucous areolar tissue, throughout the whole length of the digestive, respiratory, and genito-urinary tracts; and in the subserous tissue of the thoracic and abdominal walls. Plexiform networks of minute lymphatic vessels are found interspersed among the proper elements and bloodvessels of the several tissues; the vessels composing the net-work, as well as the meshes