Henry Gray (18251861). Anatomy of the Human Body. 1918.
each containing numerous nuclei or one compound nucleus. Nucleated red-blood corpuscles have also been found in the spleen of young animals.
Bloodvessels of the Spleen.The lienal artery is remarkable for its large size in proportion to the size of the organ, and also for its tortuous course. It divides into six or more branches, which enter the hilum of the spleen and ramify throughout its substance (Fig. 1190), receiving sheaths from an involution of the external fibrous tissue. Similar sheaths also invest the nerves and veins.
Each branch runs in the transverse axis of the organ, from within outward, diminishing in size during its transit, and giving off in its passage smaller branches, some of which pass to the anterior, others to the posterior part. These ultimately leave the trabecular sheaths, and terminate in the proper substance of the spleen in small tufts or pencils of minute arterioles, which open into the interstices of the reticulum formed by the branched sustentacular cells. Each of the larger branches of the artery supplies chiefly that region of the organ in which the branch ramifies, having no anastomosis with the majority of the other branches.
The arterioles, supported by the minute trabeculæ, traverse the pulp in all directions in bundles (pencilli) of straight vessels. Their trabecular sheaths gradually undergo a transformation, become much thickened, and converted into adenoid tissue; the bundles of connective tissue becoming looser and their fibrils more delicate, and containing in their interstices an abundance of lymph corpuscles (W. Müller).
The altered coat of the arterioles, consisting of adenoid tissue, presents here and there thickenings of a spheroidal shape, the lymphatic nodules (Malpighian bodies of the spleen). These bodies vary in size from about 0.25 mm. to 1 mm. in diameter. They are merely local expansions or hyperplasiæ of the adenoid tissue, of which the external coat of the smaller arteries of the spleen is formed. They are most frequently found surrounding the arteriole, which thus seems to tunnel them, but occasionally they grow from one side of the vessel only, and present the appearance of a sessile bud growing from the arterial wall. In transverse sections, the artery, in the majority of cases, is found in an eccentric position. These bodies are visible to the naked eye on the surface of a fresh section of the organ, appearing as minute dots of a semiopaque whitish color in the dark substance of the pulp. In minute structure they resemble the adenoid tissue of lymph glands, consisting of a delicate reticulum, in the meshes of which lie ordinary lymphoid cells (Fig. 1191). The reticulum is made up of extremely fine fibrils, and is comparatively open in the center of the corpuscle, becoming closer at its periphery. The cells which it encloses are possessed of ameboid movement. When treated with carmine they become deeply stained, and can be easily distinguished from those of the pulp.
The arterioles end by opening freely into the splenic pulp; their walls become much attenuated, they lose their tubular character, and the endothelial cells become altered, presenting a branched appearance, and acquiring processes which are directly connected with the processes of the reticular cells of the pulp (Fig. 1192). In this manner the vessels end, and the blood flowing through them finds its way into the interstices of the reticulated tissue of the splenic pulp. Thus