Морфологічні особливості кровоносних судин тимуса новонароджених телят

The blood vessels of thymus of newborn calves were studied by using a complex of histological methods and methods of injection of blood vessels. Calf thymus gland is an unpaired organ consisting of a pair of cervical, unpaired cervical and thoracic lobes. Radiating insertions (septa) extrude from the capsule, dividing organ on lobules. Stroma (6.53 ± 2.33%) consists of loose connective tissue. The base of the lobules is formed by a lymphoid tissue (epithelial with cells of the lymphoid series). The area of the parenchyma of the diurnal calves’ thymus is 80.57 ± 3.46%. The thymus lobes consist of cortex (57.97 ± 3.38%) and medulla (22.60 ± 2.71%). There are concentric, nest-like bodies called Hassall's corpuscles in the medulla. The blood vessels of the thymus are interlobular and intralobular. Interlobular arteries are a continuation of extraorganic arteries. The diameter, caliber and thickness of the wall of arteries and veins, as well as microcirculatory vessels are different, which is due to functional activity. Some blood vessels branch out in the interlobular stroma, while others penetrate into the lobules, where they branch into microcirculatory vessels. In the cortex the blood vessels are radially branched, and in the medulla they form polygonal plexuses. Blood vessels of the thymus are represented by arteries, veins and microcirculatory vessels. The parameters of the wall of intralobular vessels are less than interlobular. The total area of the blood vessels of the thoracic part of the thymus is 12.89 ± 0.97%, interlobular – 4.28 ± 0.61% and intralobular – 8.61 ± 0.54%. The area of interlobular arteries is 11.71 ± 0.41%, which is slightly smaller than the area of interlobular veins (19.09 ± 0.86%).Microcirculatory vessels occupy the smallest area – 2.33 ± 0.05%. The area of intralobular arteries (9.60± 0.83%) is less, and the veins (22.08 ± 0.45%) are larger than interlobular. Microcirculatory vessels occupy the largest area in the lobe – 35.14 ± 0.88%. The wall of arteries and veins consists of intima, media and adventitia. Microcirculatory vessels are represented by arterioles, precapillaries, capillaries, postcapillaries and venules. The wall of arterioles consists of an intima, which is formed by endotheliocytes on the basement membrane, a media, which is made up principally of smooth (involuntary) muscle cells and elastic fibers arranged in roughly spiral layers, and an adventitia. The structure of the precapillary wall is similar to such in arterioles, but only single smooth muscle cells are in the media. The wall of capillaries and venous section of microcirculatory vessels are formed by endotheliocytes and the basement membrane.