By the grace of Allah Almighty, a Master’s thesis entitled
“Comparative Histological Structure of the Adrenal Gland in Rabbits and Local Chickens at Different Ages (Histological, Histochemical, and Histometrical Study)”
was discussed at the College of Veterinary Medicine, Tikrit University, by the student Diana Mohammed Rajab, specializing in Veterinary Histology.
The examination committee consisted of:
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Prof. Dr. Idris Khalaf Thamer / Histology / Tikrit University – College of Medicine / Chairman
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Asst. Prof. Dr. Uday Alawi Jassim / Anatomy and Histology / Tikrit University – College of Veterinary Medicine / Member
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Asst. Prof. Dr. Rasha Hamed Ayyoub / Histology / University of Samarra – College of Education / Member
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Prof. Dr. Iyad Hamid Ibrahim / Anatomy / Tikrit University – College of Veterinary Medicine / Member and Supervisor
Thesis Summary:
The present study aimed to compare the developmental changes of the adrenal gland across different age periods in both rabbits and poultry. The study was conducted at the animal house of the College of Veterinary Medicine, Tikrit University, during the period from 1 September to 1 October 2024.
A total of 20 healthy female rabbits were obtained from the animal house of the College of Veterinary Medicine, Tikrit University, and divided according to age as follows:
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5 rabbits aged one month (200–500 g)
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5 rabbits aged three months (450–700 g)
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5 rabbits aged six months (750–1000 g)
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5 rabbits aged one year and older (1250–1500 g)
The animals were housed in standard plastic cages measuring 90 × 60 × 30 cm, under suitable environmental conditions with temperatures ranging between 20–25°C.
Similarly, 20 healthy female chickens were obtained and classified according to age as follows:
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Chickens aged one month (150 g)
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Chickens aged three months (1000 g)
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Chickens aged six months (1500 g)
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Chickens aged one year and older (2000 g)
The chickens were housed under the same environmental conditions as the rabbits. Animals were humanely euthanized and dissected at four age stages: one month, three months, six months, and one year for both rabbits and chickens.
Results:
In rabbits, the adrenal gland was surrounded by a fibrous capsule composed of elastic and collagen fibers. Beneath the capsule, spherical clusters of epithelial cells (6–8 cells per cluster) formed the zona glomerulosa. The capsule appeared thick and contained loosely arranged collagen fibers. Endocrine cells beneath the capsule were densely packed, with some cells showing brown-colored cytoplasm. Cells of the zona fasciculata were enlarged, with pale cytoplasm and small, dark, round nuclei.
Using Masson’s trichrome stain, the adrenal cortex was shown to be surrounded by a capsule composed of collagen fiber bundles, externally covered by loose connective tissue. Beneath the capsule, oval-shaped clusters of endocrine cells formed the zona glomerulosa, continuous with the zona fasciculata. The deeper cortical layer (zona reticularis) consisted of small endocrine cells arranged in rows, with large dark nuclei and faint brown-stained cytoplasm. Blood sinusoids extended toward the medullary vein.
In chickens, the adrenal gland was surrounded by a thin fibrous capsule. Beneath the capsule, clusters of glomerular cells with red-stained cytoplasm and small dark nuclei were observed. Groups of chromaffin cells were found near and around the zona glomerulosa, appearing as disc-shaped cells with pale cytoplasm and round nuclei. These groups extended throughout the cortex and around the zona fasciculata. Blood capillaries and sinusoids extended toward the medulla.
The adrenal capsule in chickens contained collagen fiber bundles, fibroblasts, and some leukocytes. Beneath the capsule, small groups of endocrine cells and numerous blood vessels with partially hemolyzed blood were observed. The zona glomerulosa cells exhibited acidophilic cytoplasm.
Using Masson’s trichrome stain, the adrenal capsule in chickens was externally surrounded by sympathetic ganglia containing large neurons and numerous supporting cells, encased by collagen fiber sheaths. The capsule contained few endocrine cells connected with subcapsular endocrine cells. The upper cortical layer showed bundles of unstained zona fasciculata cells. The adrenal capsule consisted of loosely arranged collagen fibers with endocrine cells surrounded by blood vessels, extending into the cortex. The cortex contained spherical clusters of endocrine cells encircled by collagen fibers, with zona fasciculata cells located between these clusters and zona glomerulosa cells surrounding them.
The thesis defense was held at Dr. Muhannad Maher Hall at the College of Veterinary Medicine, and was attended by a number of faculty members and students in a distinguished academic atmosphere.
