| Objects:At high altitude, strongly ultraviolet and cold environment, habitat yak on the Tibetan Plateau was considered as one of the best high altitude adaptation cattle. The skin which coveres the whole body is responsible for protecting the deep tissue from mechanical stimulation, ultraviolet and cold environment. Therefore, the experiment explores the change of skin thickness in different body regions and different age detailedly, which can provide the basis for the further study of yak skin growth.Methods:In this study, 15 healthy yaks from Gannan Prefecture Gansu Province(newborn, 6-month-old and adult) were used for quickly gathering fresh skin samples. Skin samples were fixed in 40 g/L paraformaldehyde phosphate buffer for two weeks. The whole skin thicknesses were measured by micrometer, then embedding in the paraffin and making the consequent sections at 10μm thickness. The thickness of epidermis、stratum corneum、viable epidermis and dermis were measured by Olympus DP71 Microscope system(Olympus DP Control and Image-Pro Express) after H.E staining and Masson’s staining.Results:1. The whole skin thicknesses in newborn, 6-month-old and adult yak were respectively ranged from 624μm to 1538μm, 976μm to 2346μm and 2052μm to 5934μm. The average values were respectively 982μm, 1575μm and 3953μm. The thickest samples were cheek, ventral cervical and dorsum, while the thinnest were inguen in newborn and 6-month-old, axilla in adult. 2. The thicknesses of epidermis in newborn, 6-month-old and adult were respectively ranged from 16.030μm to 29.207μm, 22.458μm to 63.594μm and 34.211μm to 78.276μm. The average values were respectively 20.604μm, 34.342μm and 51.526μm. The thickest samples in epidermis were metacarpus in each age, while the thinnest were lateral of crural, costal region and inguen. 3. The thicknesses of stratum corneum in newborn, 6-month-old and adult were respectively ranged from 3.679μm to 9.791μm, 4.082μm to 18.744μm and 6.234μm to 21.201μm. The average values were respectively 5.807μm, 7.694μm and 11.067μm. The thickest samples in stratum corneum were costal region in newborn, metacarpus in 6-month-old and adult, while the thinnest were lateral of crural, costal region and cheek. 4. The thicknesses of viable epidermis in newborn, 6-month-old and adult were respectively ranged from 10.890μm to 23.151μm, 18.364μm to 43.211μm and 25.372μm to 63.516μm. The average values were respectively 15.248μm, 25.305μm and 43.547μm. The thickest samples in viable epidermis were metacarpus in newborn and 6-month-old, dorsum in adult, while the thinnest were scapula, costal region and inguen. 5. The thicknesses of dermis in newborn, 6-month-old and adult were respectively ranged from 389.956μm to 948.520μm, 507.742μm to 1210.813μm and 826.451μm to 2181.566μm. The average values were respectively 596.430μm, 811.597μm and 1517.440μm. The thickest samples in dermis were dorsum in newborn and 6-month-old, metacarpus in adult, while the thinnest were metatarsus, inguen and axilla. 6. The epidermis of haired skin from shallow to deep were stratum corneum, stratum granulosum, stratum spinosum and stratum basale,stratum lucidum not included.Conclusion:The skin thicknesses showed a growth trend with aging. The increased trend was more obvious in dermis thickness, while the growth trend in epidermis was relatively insignificant, the epidermis thickness was mainly influenced by the growth of viable epidermis with ages. The skin thickness had a decreasing trend from dorsum to abdomen and from the lateral surface to the medial surface of the body. The epidermis, viable epidermis and stratum corneum of skin in dorsum, metacarpus and metatarsus were thicker than other samples. The stratum corneum in some samples did not show a growth trend which were not the same as the whole skin, such as the cheek, thigh and costal. |
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