Morphological, Histometric and Histochemical Studies on the Adrenal Gland of the Dromedary Camel (Camelus dromedarius

Abstract

The aim of the present study was to investigate the morphology, histometry andhistochemistry of the adrenal gland in dromedary camel (Camelus dromedarius). Right and left adrenal glands of 45 apparently healthy adult dromedary camels of both sexes and nine foetuses were used in this study, specimens were obtained from AL-Salam and Tambul slaughterhouses, Sudan. The samples were collected during period (January 2015-May 2017).The gross anatomy of the adrenal glands was studied in foetuses and adult animals of both sexes; in adult animals the study included shape and measurements of weight and dimensions; observations of topography, blood supply and innervations were obtained by dissection of foetuses. Histological, histometric and histochemical studies were carried out using routinely processed histological sections from fixed specimens of adult animals of both sexes. The dromedary camel had paired adrenal glands, each lying cranio-medial to the poles of the corresponding kidney in a retroperitoneal position and embedded in the retroperitoneal adipose tissue. They were located at different levels in foetuses and differed in their shape, weight and dimensions. The right adrenal gland was oval or bean-shaped, whereas the left one ranged from rounded, triangular, pyramidal, to nearly heart- shaped. Generally, the right adrenal gland was larger, longer and thicker than the left one. Cuff was rounded or oval structure observed in the adrenal sections.The arterial blood supply of the adrenals came from renal, lumbar and directly from the aorta but the venous drainage differed according to the side of the gland. The right adrenal vein drained directly into the caudal vena cava, while the left adrenal vein joined the left renal vein. The adrenal gland was innervated by three nerve fibers from celiac, splanchnic, and renal nerves. The camel adrenal gland was surrounded by a capsule (Ca) and consisted of two distinct parts: an outer cortex (Co) and inner medulla (M). The capsule was vii thick and consistedof connective tissue containing all types of fibres and covered by pericapsular connective tissue withadipose tissue, blood vessels and nerves.The capsular tissue had two layers: outer thick loose layer and inner thin dense layer. The inner layer of the capsule extended to varying depths of the cortex as thin and thick branched septae. The adrenal cortex completely surrounded the medulla and it was usually dark in stain and had three concentric zones: outer zona glomerulosa (ZG), middle zona fasciculata (ZF) and inner zona reticularis (ZR). The zona glomerulosa was the smallest and it appeared morebasophilic than other parts; cells were arranged in cords, follicles, balls, clusters or in irregular groups. The zona glomerulosa contained two types of cells; dark small cuboidal or columnar cells and light large cells irregular in shape. The zona fasciculata was the broadest cortical zone.This zone was divided into an outer small part and an inner large part; the cells in the outer part were tightly packed and they were irregular in shape, lightly staining, some dark cells were found; the cells in inner part were arranged in long straight or branching and anastomosing cords. The cords were one or twocells in thickness flanked by long wide sinusoidal blood vessels. The cells in this zone were of two types; dark small cuboidal or polygonal cells and light large rounded or irregular cells.The microscopical distinction between the zona fasciculata and the zona reticularis was not as marked as the glomerulosa-fasciculata junction. However, the organization and cell morphology of the zona reticularis was quite distinct.The zona reticularis appeared to be the second largest layer in thickness of the cortex; its cells were small arranged in irregular anastomosing network or cords running in various planes separated by short sinusoidal blood vessels. The cells were of two types: dark small cuboidal or polygonal in shape and light large cells irregular in shape. The region of the zona reticularis that was adjacent to the medulla was more compact forming a ring-like structure or pseudo-capsule.The viii connective tissue fibres (collagenous, elastic and reticular) formed an incomplete layer around the medulla, otherwise no distinct boundary between the cortex and medulla was observed. The adrenal medulla was lighter than the cortex; its cells were much larger and lighter than those in the cortical zones. The medulla was rich in large blood vessels and sinusoids and possessed numerous large veins and also contained nerve fibres.The medullary cells showed four types; two types were large (light and intermediate) found in clusters, the third type was small dark and arranged around the clusters. The fourth type was ganglion cells in between the first two types in the clusters .The cuff was observed inside the medulla and it was composed of capsule, blood vessels and cortical tissue. The parenchymalconnective tissue of the gland contained all types of fibers (collagenous, elastic and reticular) but their distribution differed from one part to another. The histometry of the adrenal glands of the dromedary which was described for the first time in this study showed that the cortex was thicker than the medulla in both right and left glands. The glandular capsule, cortical zones and medulla of the right adrenal glands were collectively thicker than those in the left one. The mean thickness of the RCa was 0.242±0.281mm, whereas the mean thickness of the LCa was 0.238 ± 0.275mm.The mean thickness of the RCo was 2,616 ± 3.28mm, while in the LCo was 2.134±2.959mm and the mean thickness of the RM was 1.497±2.924mm, whereas in the LM was 1.265±2.304mm.The zona fasciculata (RZF was 1.425±1.94mm, LZF was 1.293±1.847mm) was the thickest zona in the cortex and zona reticulais (RZR was 0.553±0.787mm, LZR was 0.493±0.635mm) was the second layer in thikness. The zona glomerulosa (RZG was 0.421±0.613mm, LZG was 0.312±0.5mm) was the thinnest one in either side. PAS reaction was stronger in the capsule and in the cortical zones than in the medulla. PAS reaction after diastase treatment gave a positive reaction in the capsule, cortex and medulla of the adrenal ix gland. Alcian blue positive reaction was strong in the inner layer of the adrenal capsule and septae, strong to moderate in the cortical zones and medulla. PAS ∕Alcian blue sequence stains showed positive reaction in the gland. The distribution of lipids in the adrenal gland of the dromedary was very strong in the cortical cells, weak in medullary cells and weak to negative in the capsule and septae. The acid phosphatase positive reaction was strong in the adrenal capsule and septae, strong to moderate in the cortical zones and moderate in the glandular medulla. The alkaline phosphatase positive reaction was strong in the inner layer of the adrenal capsule and septae, strong, moderate to weak in the cortical zones and weak in the medullary tissue.