Histomorphological study of the parathyroid gland in female Kuttanad ducks ( Anas platyrhynchos domesticus )

Introduction of the secretory cycle [3]. Parathyroid cells in most animals store relatively small amounts of preformed Calcium is essential for normal metabolic hormone but are capable of responding to minor flucprocesses in birds. Several hormonal systems exist to tuations in calcium ion concentration by rapidly altering regulate calcium levels in the body. Most important the rate of hormonal synthesis and secretion [4]. glands involved in avian calcium regulation are Kuttanad ducks native to Kerala are considered as Parathyroid (PTG) and Ultimobranchial glands (UBG). highly efficient in terms of egg production and egg size Calcium disorders can lead to a variety of clinical and are widely considered as an ideal layer duck breed problems in birds. The major physiological stimulus successfully launched in many other states of India. for parathyroid hormone secretion from the chief cells is a fall in plasma calcium concentration; while a rise in calcium suppresses it [1]. The hormone with the greatest involvement in calcium regulation in birds is parathyroid hormone, with calcitonin playing a minor and uncertain role [2]. The parathyroid chief cells undergo morphologic changes corresponding to different stages There exists a paucity of data with regards to duck parathyroid gland in general and that of Kuttanad duck in particular. Thus, our present work is targeted to give a normal morphological and histological picture of parathyroid gland which will serve as a platform for the allied disciplines to differentiate any deviations from normal. It can be further used for comparative studies of parathyroid gland between different species as well as breeds of domesticated and wild ducks. Veterinary World, EISSN: 2231-0916 Available at www.veterinaryworld.org/Vol.6/Nov-2013/23.pdf


Introduction
of the secretory cycle [3].Parathyroid cells in most animals store relatively small amounts of preformed Calcium is essential for normal metabolic hormone but are capable of responding to minor flucprocesses in birds.Several hormonal systems exist to tuations in calcium ion concentration by rapidly altering regulate calcium levels in the body.Most important the rate of hormonal synthesis and secretion [4].glands involved in avian calcium regulation are Kuttanad ducks native to Kerala are considered as Parathyroid (PTG) and Ultimobranchial glands (UBG).
highly efficient in terms of egg production and egg size Calcium disorders can lead to a variety of clinical and are widely considered as an ideal layer duck breed problems in birds.The major physiological stimulus successfully launched in many other states of India.for parathyroid hormone secretion from the chief cells is a fall in plasma calcium concentration; while a rise in calcium suppresses it [1].The hormone with the greatest involvement in calcium regulation in birds is parathyroid hormone, with calcitonin playing a minor and uncertain role [2].The parathyroid chief cells undergo morphologic changes corresponding to different stages There exists a paucity of data with regards to duck parathyroid gland in general and that of Kuttanad duck in particular.Thus, our present work is targeted to give a normal morphological and histological picture of parathyroid gland which will serve as a platform for the allied disciplines to differentiate any deviations from normal.It can be further used for comparative studies of parathyroid gland between different species as well as breeds of domesticated and wild ducks.

Materials and Methods
recorded using ocular micrometer.Nomina Anatomica Avium was used for nomenclature [6].

Results
In female Kuttanad ducks, the paired parathyroid glands lay just caudal to the division of the innominate artery into the subclavian and common carotid arteries.Lying in contact with the thyroid at or near the posterior Histomorphological studies on parathyroid gland pole, parathyroids were oval to spherical in shape, were carried out in twelve adult female Kuttanad ducks yellow in colour and smaller than thyroid gland of the (Anas platyrhynchos domesticus) of 20 weeks of age.
representative sides (Fig. 1).The length, breadth, and Birds reared semintensively were procured from thickness of the cranial parathyroid glands were Kerala Veterinary and Animal Sciences University approximately 1.92 ± 0.3 mm, 1.4 ± 0.3 mm and 1.1 ± Poultry and Duck Farm and sacrificed humanely.0.4 mm, respectively; whereas, the corresponding Glands were collected and gross parameters like length parameters of the caudal parathyroid glands were 1.13 and breadth were taken by Vernier's caliper.Weights of ± 0.23 mm, 0.94 ± 0.21 mm and 0.59 ± 0.16 mm, parathyroid glands were taken by Digital weighing respectively.The arterial blood supply was from balance (Shimadzu-ELB 300).After recording the parathyroid arteries which branched out from the morphometric parameters, the glands were fixed in 10 common carotid artery and blood from gland was percent neutral buffered formalin.The small sized drained directly into jugular vein (Fig. 2).Although it glands were processed as such by routine histological lied close to the thyroid, thymus and ultimobranchial methods, paraffin blocks were prepared and sectioned gland, parathyroid tissue did not merge to any of the to a thickness of 5µ.The tissues were stained by Haeabove mentioned three glands (Fig. 3).matoxylin and Eosin (H&E) for routine histological Histologically, Parathyroid glands were enclosed studies and Gomori's rapid one step trichrome method by a well-developed connective tissue capsule made of for connective tissue fibres [5].Using Olympus 16 mega predominant collagen fibers with some elastic and pixel digital camera macroscopic and microscopic reticular fibers (Fig. 4).From the capsule fine connective findings were recorded.Micrometric parameters were tissue trabaculae extended inwards constituting stroma Since the present work was done in parallel with work on the thyroid gland, the same healthy birds were utilized for sample collection as sanctioned by Animal ethics committee with sanction order IAEC-12-08 with humane view to limit the use of total number of birds for the study. of the gland (Fig. 5).Arteries which supplied parathyroid stroma were reported in laying hens [20].Parenchyma gland entered the fibrous capsule at different angles.
of parathyroid gland was composed of a single cell type Parenchyma of the parathyroid gland was composed in chicken [21].In humans, chief cells undergo of irregular anatomizing cords of cells supplied by morphologic changes corresponding to different stages connective tissue stroma penetrated by blood capillaries.
of the secretory cycle.The oxyphil cells of the Parenchyma was predominantly made of lightly parathyroid gland derived from chief cells on aging and stained cells, the chief cells (Fig. 6).The shapes of the due to some metabolic derangements have the potential chief cells were cuboidal and measured 16-20µm along to produce parathormone (PTH), PTH -related protein, their longitudinal axis.The parenchymal cells were and calcitriol.However, Oxyphil cells were reported to separated from adjacent blood capillaries by a be absent in the avian parathyroid gland [22].relatively thick basal lamina.The nuclei were round The hypercalcemic effects of PTH were greater in with approximately 4 µm in diameter and contain one egg laying hens than in cockerels.The fact may be or two nucleoli.Oxyphil cells, as present in parathyroid attributed either calcium binding by yolk proteins in glands of other mammals were not seen in present study.
the plasma or to the presence of additional PTH receptors in medullary bone and oviduct.The major Discussion physiological stimulus for PTH secretion from the In birds, the regulation of calcium and phosphate chief cells was a fall in plasma calcium concentration, homeostasis was typically mammalian with only minor while a rise in plasma calcium suppressed the hormone differences [7].Number of parathyroid glands varied secretion [23].between two and four in birds.In chicken there were Conclusion two pairs of parathyroid glands often fused together located slightly caudal to the thyroid, whereas only one Histomorphological features of Parathyroid gland pair was found in the Japanese quail [8,9,10].In mice, in female Kuttanad duck were documented.Cranial there was only one pair of parathyroid glands developed parathyroids were larger in size as compared to the with the thymus from the endoderm of 3rd pharyngeal caudal parathyroids.However, cranial as well as caudal pouch at the beginning which was homologous to parathyroids showed strong similarity in their inferior parathyroid glands in humans [11][12][13].Accessory microanatomy.Parenchyma of the parathyroid gland parathyroid tissues had been reported in adjacent areas was composed of irregular anatomizing cords of cells in birds, included within the thyroid, thymus and supplied by connective tissue stroma penetrated by ultimobranchial gland [14-16].In Falconiformes, the blood capillaries.Oxyphil cells were absent similar to parathyroid glands were supplied by one to three other aves.Parathyroid gland is very vital in parathyroid arteries.The average number of thyroid and maintaining the homeostasis of the plasma calcium.parathyroid arteries in common buzzard was Both hypo and hypercalcemic condition affect the significantly higher than those in common kestrel [17].
body growth and production potential of the birds.In Kuttanad ducks, paired parathyroid glands lay Findings of this study will contribute to the anatomy just caudal to the division of the innominate artery literature as a valuable resource for future researchers supplied by three arteries and drained by jugular vein.
focused on this subject and will also help other allied No accessory parathyroid glands were seen that were subjects on comparative basis.closely associated with thyroid, thymus and ultimo-