Development of the adrenal gland in the crossbred goat
| dc.contributor.advisor | Harshan, K R | |
| dc.contributor.author | Ashok, N | |
| dc.contributor.author | KAU | |
| dc.date.accessioned | 2019-05-07T10:12:10Z | |
| dc.date.available | 2019-05-07T10:12:10Z | |
| dc.date.issued | 1999 | |
| dc.description | PhD | en_US |
| dc.description.abstract | Studies on the prenatal and postnatal development of the adrenal gland in crossbred goats were conducted using 55 embryos/ foetuses of varying gestational ages and 45 goats from day old to 180 days postpartum. The project was taken up to trace the normal growth and developmental pattern of the glands and their relationship with age, body weight and the physiological status. After recording gross relations and measurements, the material was fixed using various fixatives for studying the cellular details, arrangement of cells, connective tissue framework, micrometry and histochemistry. The glands attained their characteristic shapes even during early development and were located cranial to the kidneys in the retroperitoneum. During the prenatal period weight of the adrenals increased steadily upto 141 days followed by a spurt thereafter due to the hypertrophy and hyperplasia of the cortex. After birth also an increasing trend was noticed in adrenal weight from birth to 180 days with a slight decrease at 45 days. The glandular weight was positively correlated with age and body weight. The proportion of the adrenal to body weight percentage showed a decreasing trend in both the groups studied. The left gland was slightly heavier and longer than the right while the right one was broader and thicker. The length, breadth and thickness were positively correlated with the age of foetuses and kids. The cortical primoridum was first detected at 33 days of embryonic development. By 36 days , these cells began to organize into cords and dense aggregations. Though a thin .'. collagenous capsule began to develop by 42 days, it became conspicuous with outer more fibrous and inner more cellular layers by 70 days. Reticular fibres appeared by 58 days and elastic fibres by 74 days of foetal life. By 42 days, histological differentiation started with organization of cells into small groups and clusters separated by irregular spaces. The central vein also started development at this stage. Differentiation of zona glomerulosa was noticed by 58 days and was completed by 95 days. Zona fasciculata and zona reticularis became apparent by 129 days. A distinct corticomedullary junction appeared at 95 days eventhough interdigitations of cortex and medulla were seen at the junction throughout the study period. Towards the centre of the gland intermingling of cortical and medullary cells were seen upto 104 days. Patches of cortical cells were seen in the medullary region and also around the central vein throughout the period of study. Neural crest cells invaded the cortical primordium by 50 days and this process was completed by 70 days. Chromaffin reaction appeared in the medullary cells by 50 days. Even though norepinephrine cells were detected in the gland at this stage, epinephrine cells made their presence only by 98 days. Follicles containing colloid material were encountered in the medulla during both the advanced foetal and the postnatal periods. In goats, the glands were covered by highly vascular' connective tissue capsule composed of collagen, reticular and elastic fibres with a few smooth muscle cells. An outer more fibrous and an inner more cellular layers were recognizable. The capsule contained undifferentiated cells, differentiated cortical type cells, fibroblasts, neurons and melanocytes. The parenchyma was divisible into a cortex and a medulla. Cortex was further subdivided into zona glomerulosa, zona fasciculata and zona reticularis. Each zone had distinct pattern of cellular arrangement and cytological characteristics. Mast cells were occasionally detected in all the cortical zones. Mitotic figures were also recorded throughout the cortex. A zona intermedia was observed between the zona glomerulosa and the zona fasciculata. Capsule, trabeculae and the parenchyma were all PAS positive.Acid mucopolysaccharides and glycogen were also detected in the cortex. They were seen at varying intensities in the cortex and medulla of the prenatal and the postnatal subjects. Intensity of phosphatase enzymes was lower in the cortical cells between third and fourth month of gestation after which the same increased till term. After birth a higher activity upto 30 days and a reduced activity at 45 days were recorded especially in the zona fasciculata. Medullary cells revealed moderate alkaline phosphatase and intense acid , phosphatase activities during the study period. Lipid was first detected by 50 days, and upto 74 days a uniform distribution was seen throughout the cortex. Afterwards, it concentrated more in the clusters of cells in the subcapsular region. Between 84 and 122 days, a low lipid content was noticed in the cortical cells, the concentration of which gradually increased towards term. After 141 days a heavy accumulation was observed in the cortex. During the postnatal period, the inner two cortical zones showed heavy lipid accumulation upto 15 days and a slight depletion at 30 days. This was followed by a very heavy accumulation in all the three cortical zones at 45 days. Following this, a gradual depletion was noticed from all the cortical zones. In the prenatal group, capsular thickness, width of the entire cortex as well as the various cortical zones and diameter of the medulla showed positive correlation with foetal age. In the postnatal group, excepting the width of zona reticularis, all other parameters were positively correlated with age. After 135 days of gestation, width of the cortex, especially of the inner two cortical zones increased significantly till term. During postnatal period, a decrease was noticed in the width of outer two cortical zones by 45 days, however the diameter of medulla increased steadily upto 180 days. Growth rate of zona glomerulosa was higher than that of zona fasciculata till 60 days, after which the latter grew faster. The medulla grew faster than the cortex upto 45 days and thereafter no significant difference in growth rates could be detected. Percentage contribution of zona glomerulosa to the entire cortex was more during the foetal period compared to the postnatal animals. On an average, during the postnatal period the zona glomerulosa contributed 16.71 per cent, zona fasciculata 74.16 per cent and zona reticularis 9.13 per cent to the total cortical width. It was concluded that the stress induced on the growing foetus towards the end of gestation due to the insufficiency of placenta resulted in a higher activity of the cortex, particularly of the zona fasciculata under the influence of foetal ACTH. At parturition, exposure of the new born to the external environment induced severe stress which was responsible for the higher activity of the gland during early neonatal period. When the young one got acclimatized to the new surroundings, the stress was relieved which in turn resulted in the reduced activity of the gland by 45 days postpartum. | en_US |
| dc.identifier.citation | 171450 | en_US |
| dc.identifier.uri | http://krishikosh.egranth.ac.in/handle/1/5810102255 | |
| dc.keywords | Anatomy, adrenal gland, crossbred goat | en_US |
| dc.language.iso | en | en_US |
| dc.publisher | Department of Anatomy, College of veterinary and animal sciences, Mannuthy | en_US |
| dc.sub | Veterinary Anatomy | en_US |
| dc.subject | null | en_US |
| dc.theme | Adrenal gland in the crossbred goat | en_US |
| dc.these.type | Ph.D | en_US |
| dc.title | Development of the adrenal gland in the crossbred goat | en_US |
| dc.type | Thesis | en_US |