Study of anatomical, histological and cytological characteristics of the thymus of lambs

S Chaanbi,M A Lieshchova,D E Rahmoun,S Chergui

doi:10.32819/2020.82021

Abstract

Thymus of lambs of the Ouled-Djellal breed from eastern Algeria, aged one to 10 months, were used to study the anatomical, histological and cytological characteristics of these organs. Modern techniques have been used to demonstrate the morphometric parameters and masses of the thymus at different ages, a regression of the morphometric and mass indexes has been visualized according to the age of the lambs. Staining techniques with Hematoxylin and eosin revealed the normal structure of the thymus with its tissue components. The thymus is bilobed. The lobe is surrounded by a thin capsule and subdivided into lobules separated by septae, the cortical and medullary areas were clearly visible, the interlobular blood vessels enter the lobule in all its aspects to continue its way as interlobular blood vessels. From the changes observed in the involution of the thymus according to the age of the animals which occur relatively late, the percentage of the surface found for the capsule was very variable, which increases from the first to the tenth month, the demarcation of the cortex and the medulla beginning during the second month of age of the animal. The interlobular connective tissue (ILC) presents sums, the maximum of which was found in the fourth month of age of the animal, while the minimum was found in the thymus of ninth month lambs Concerning the Hassal corpuscles, their sums are in high extension until the tenth month, rich in T lymphocytes, whose use of immunohistochemistry, the anti-CD 157+ antibody allowed us to visualize to locate them clearly, which invade and form most of the thymus cortex. In conclusion, the significant changes in thymus development in sheep of the Ouled-Djellal breed are similar to those of other species.

Highlights

In mammals, the lymphatic system is made up of organized lymphoid structures, as cited by the authors (Datta et al, 2000), the thymus consists of two separate lobes, connected by an isthmus of connective tissue
The thymic frame consists of cross-linked epithelial cells between which evolve maturing T lymphocytes and macrophages (Moticka et al, 2016), in the superficial cortex, reticular epithelial cells or feeder cells are distinguished from lymphocytes only by their paler, ovoid nucleus, in the deep cortex, the reticular epithelial cells are involved in lymphocyte selection, the Hassal corpuscles, characteristic of the thymic medulla, consist of epithelial cells arranged concentrically in a bulb and undergoing a keratinization process from the periphery to the center, the outermost cells are less mature than the central cells loaded with keratin (Dijkstra et al, 1990)
Lobulation is well pronounced in fetuses and newborns; from 6 to 8 months, it is gradually lost. It is relatively large at birth, for older lambs, it begins to decrease and becomes very small, includes the thoracic and cervical lobes connected by an isthmus

Summary

Introduction

The lymphatic system is made up of organized lymphoid structures, as cited by the authors (Datta et al, 2000), the thymus consists of two separate lobes, connected by an isthmus of connective tissue. This thin capsule surrounds each lobe and, in most species, gives rise to partitions which partially subdivide the thymus into interconnected lobules of varying size and orientation, the lobules are often of geometric shape. The immune system is able to respond to external stimuli intervening anywhere in the body

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