Studies in the histology of bovine skin

Nisbet, Annie Myfanwy (1956) Studies in the histology of bovine skin. PhD thesis, University of Glasgow.

Abstract

In the first part of the thesis an account is given of studies on the structure of bovine sweat glands and their relation to sweat gland homologues is discussed. These glands in both Bos taurus and Bos indicus are of apocrine type. They are short sac-like structures and are lined by a layer of secreting epithelial cells enclosed within a layer of spindle shaped myoepithelial cells. They were compared with the large coiled sweat glands found in the skin of the concave surface of the bovine ear and also with bovine and human ceruminous glands. Structurally all the glands have a similar structure but lipids occur only in the human ceruminous glands. It has been suggested by Russian workers that the development of bovine mammary glands, which are sweat gland homologues, may be correlated with that of the sweat glands in the ears of cows, and some of these workers have claimed that there is a highly significant correlation between the milk yield and the number of sweat glands in the pinna of the ear. This claim was investigated for Ayrshire cattle and no such correlation was found. The second part of the thesis deals with the types of blood vessel present in bovine skin and the pattern of their arrangement. Using skin perfused with Indian ink the distribution of blood vessels was studied. It was found that in bovine skin three plexuses of blood vessels lie in planes parallel to the surface. The first lies just deep to the dermis, the second at a level between the sweat glands and sebaceous glands, and the third between the second plexus and the epidermis. Venae comites were observed to occur in all three plexuses. The blood supply to the bovine apocrine glands was found to be poor compared with that to the human eccrine coiled sweat glands. Using skin perfused with haematoxylin to stain the blood vessels preferentially it was found that arteriovenous anastomoses occur in the skin of the forehead, cheek, and ear and in the perichondrium of the ear. They were not observed in the skin of the trunk. In the third part of the thesis an account of an investigation of the structure of the bovine muzzle is given. It was found that the secretion which usually keeps the surface of the muzzle moist is produced by multilobular tubulo-acinous glands which lie in the dermis. Their secretion contains mucin. The arrangement of the blood vessels differs from that found in the hairy part of the integument, and arteric-venous anastomoses occur in the dermis between the glands and the epidermis large numbers of sensory nerve endings occur in the muzzle. In the epidermis some nerve fibres end freely and some in menisci while in the dermis some end in organised endings and others in relation to blood vessels. The arterio-venous anastomoses have a great number of nerve fibres in their walls. The possible importance of all the findings mentioned above is discussed, with special regard to the part which the skin plays in the dissipation of heat. The following conclusions are reached, 1. Although it is apparent from recent studies that the sweating response of Bos indicus is greater than that of Bos taurus, the difference in function cannot be ascribed to any difference in the epithelial cells and myoepithelial coat of their sweat glands. 2. The structural and histochemical similarity between the sweat glands and sebaceous glands of the general skin surface and the glands of the external auditory meatus indicates that a mixed secretion similar to cerumen is produced all over the body surface of cattle, 5. The venae comites present in bovine skin, by allowing cooling of arterial blood before it reaches the skin surface, limit the amount of heat which may be lost to the environment when the environmental temperature is lower than body temperature. 4. Since the number of capillaries found in the third plexus of blood vessels in the skin is directly proportional to the number of hairs, a coat with a large number of fine, short hairs and consequently with a relatively poor insulation combined with a large capillary surface area, will allow maximum loss of heat. 5. The arterio-venous anastomoses in the ear may be responsible for a sudden increp.se in the temperature of the ear which has been shown to occur when the environmental temperature reaches 180G. 6. The muzzle may be used by the animal in the selection of fodder, since it is well-supplied with nerve endings of various types that may serve as pressure, heat and, indirectly, humidity receptors.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Advisers: J D Findley; H SD Garven
• Keywords: Animal sciences, Histology
• Date of Award: 1956
• Depositing User: Enlighten Team
• Unique ID: glathesis:1956-72693
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 11 Jun 2019 11:06
• Last Modified: 11 Jun 2019 11:06
• URI: https://theses.gla.ac.uk/id/eprint/72693