Gross and histomorphological observations of the testis and accessory genital glands of indigenous bull from prepubertal stage to adult

Abstract

A study was conducted in the post graduate laboratory of the Dept. of Anatomy and Histology, Sylhet Agricultural University and Dept. of Animal Husbandry and Veterinary Science, University of Rajshahi with aimed to evaluate the gross and histological features of testis and accessory genital glands in details and their chronological development of testes and accessory genital glands from prepubertal stage to adult during July 2012 to June 2014. Twenty eight bulls of three age groups were selected from the local market: the prepubertal group (<1 year n=4), pubertal group ((1.5-2.5 years, n=16) and post pubertal or adult group (above 3 years, n=8). Body weight and scrotal circumference were recorded before slaughter and various testicular and accessory glandular parameters were recorded after slaughter. The left testicular size of prepubertal bulls was slightly larger than the right. The left and right testicular weight was 18.57±1.40 gm and 16.10±1.64 gm respectively in prepubertal bull, 129.22±19.89 gm and 123.86±19.53 gm respectively in pubertal bull, 204.36±14.10 gm and 188.41±13.59 gm respectively in adult bulls. Among three layered testicular covering, the thickness of tunica albuginea varied among different age groups and the thickness increases with the advancement of age. The parenchyma of testis was divided into lobes and lobules by connective tissue septa originating from tunica albugenia. The testicular parenchyma of prepubertal bulls consisted of solid non luminated, coiled and straight tubular sex cord having basement membrane and filled up by the centrally placed large primordial germ cells with varying numbers and peripherally located small indifferent basal cells and interstitial tissue. The parenchyma of pubertal and adult bull consisted of interstitial tissue and seminiferous tubules containing complex stratified epithelium, the spermatogenic cells and Sertoli cells. The cells were four categories the spermatogonia, primary spermatocytes, secondary spermatocytes and spermatid arranged in chronological layers from outward to inward of the tubules. Spermatozoa are the mature form of spermatids contains oval shaped head and flagellated tail. All four types of cells were found within the fully luminated seminiferous tubules at or after 18 months of pubertal bull. The spermatogenic lineages were arranged in 5-8 layers in pubertal and 3-5 layers in adult bull. Whereas spermatozoa were less in early pubertal stage and increased along with the advancement of age. This observation revealed that spermatogenic cells and seminiferous tubules became functional at early pubertal stage and fully functions at late pubertal and adult bulls. The seminiferous tubules become more convoluted and intertubular space decreases with the advancement of age of the animals. The cross sectional lengths, breadths of the seminiferous tubules were higher in adult than the pubertal bulls. The interstitial tissues consisted of loose connective tissue, blood and lymph vessels, fibroblasts or fibrocytes, free mononuclear cells and the interstitial endocrine cells of Leydig lodged in the collagen fibrous network in between the seminiferous tubules. The interstitial cells of Leydig were large polymorphs, ovoid to polygonal in shape with spherical nuclei and granular cytoplasm remained singly or in groups. The weight, length, width and the thickness of the both left and right vesicular glands were recorded separately after slaughter of each animal. The left and right vesicular gland shows significantly different (p<0.01), in weight and length in every group. Left vesicular glands were slightly higher than the right in all parameters. The glandular unit of the vesicular gland showed folded mucosa, lined with pseudostratified columnar epithelium. Three types of cells were identified in the epithelium A, B and C cell. Type A cells were tall columnar cells having distinct cell boundaries with the oval, round or elongated nucleus. Type B cells were located in the basal lamina having round or oval nucleus with indistinct cell boundaries. Type C cells were narrow columnar cells interspersed between A cells with darkly stained cytoplasm. Lamina propria consisted of loose connective tissue surrounded the alveoli, tubules and some solid end pieces. The numbers of secretary end pieces were variable. The diameters of luminated or non-luminated acini of the glandular end pieces and ducts were increased gradually and significantly (p<0.01) with the advancement of age. The epithelial height of the duct and alveoli were increased with the advancement of age. Cytoplasmic secretary granules and secretion increased along with the advancement of age indicating the gland became more functional along with the advancement of age. The prostate glands of bull consisted of corpus prostate and pars disseminata portion. All three groups of bull showed the corpus prostate as band like structure. The both portions enclosed by the connective tissue capsule composed of mainly collagen and smooth muscle cells. Interlobular connective tissue decreased significantly (p<0.01) with the advancement of age. The secretary ends pieces were lined by simple cuboidal epithelium, simple low columnar epithelium and simple high columnar epithelium in prepubertal, pubertal and adult bulls respectively. The height of the lining epithelium increased with the advancement of age significantly (p<0.01). Cytoplasmic secretary granules and secretion increased along with the advancement of age as a result nuclei become flattened and pushed toward the basement membrane. The average diameters of the ducts, enfolding and the height of the lining epithelium increased significantly (p<0.01) with the advancement of age. These findings revealed that function of the prostate gland increased along with the advancement of age and reached maximum at adult stage. The left bulbourethral gland is larger than the right in all parameters in all three groups. The weight, length, width and the thickness of the both left and right glands were increased significantly (p>0.01) along with the age and reached maximum at adult stage. The thickness of the capsule increased significantly (p>0.01) with age whereas interlobular and intralobular com1ective tissue thickness decreased significantly (p>0.01) with the advancement of age. The gland was tubulo-alveolar type lined by pyramidal or columnar epithelium. In prepubertal bull epithelial height is least, cytoplasm having less cytoplasmic granules with rounded nuclei. In pubertal bull epithelial height and cytoplasmic granules increased, nuclei became oval and pressed toward the basement membrane. In pubertal bull the epithelial height and cytoplasmic granules further increased and nuclei became flatted and located near the basement membrane indicating the function of the gland increased along with the advancement of age and reached maximum stage at adult age. Above gross and histomorphological data will provide the database for the first time of testes and accessory glands of indigenous bull at different ages for making the ancestry of real scenario which may lead to the gateway for perspective future research. This information may help students, scientists and breeders for advance study, to select indigenous breeding bulls for quality tasty meat and to conserve our indigenous cattle