Study On Structure And Function Of The Skin Of Yaks (Bos Gruniens)

Healthy adult white yaks.and white yak embryo were studied by means of anatomi and histolog. The results showed that the skin of yaks could be divided into three parts like other livestock: epidermis, dermis and hypodermis. The epidermis consists mainly of a stratified squamous keratinized epithelium, but it also contains three less abundant cell type: melanocytes, langerhans cell, and merkel's cell. From the dermis outward, the epidermis consists of five layers of keratin-producing cell (keratinocytes): stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum.the color of the skin is the result of several factors, the most important of which are its content of melanin. The dermis consists mainly of loose connective tissue. It contains many collagenous fiber and elastic fiber. Epidermal derivatives include hairs, nails and sebaceous and sweat glands. The skin thickness is different in different part of the body, the dorsal and costal region skin of yaks are more thick than the region abdomen skin. The yak and white yak skin thickness are not different. The hypodermis consists loose connective tissue that binds the skins loosely to the subjacent organs, making it possible for the skin to slide over them. The hypodermis hairs are elongated keratinized structures derived from invaginations of epidermal epithelium. Each hair arises from an epidermal invagination, the hair follicle. The hair follicle has two type the primary hair follicle and the second hair follicle. The primary hair follicle is wide and long, the sebaceous gland, sweat gland and arrector pili muscle lie it's side. The second hair follicle is thin and short, it only have sebaceous gland by side. The yaks pili lane distribute evenly, mainly hair follicle is the primary hair follicle. The ratio of the primary hair follicle to the second hair follicle is called S/P. The yak and the white yak S/P is similar. The arrector pili muscle originates in the connective tissue sheath of the hair follicle and inserts into the papillary layer of the dermis, where it ends. The sebaceous glands are acinar glands that usually have several acini opening into a short duct. It contains secretory portion and duct portion the sweat glands are simple coiled tubular glands whose ducts open at the skin surface. The yak sweat glands is thin and long.