A quantitative study of the blood vessels of the pig's skin and the influence of environmental temperature

Abstract

The vascular supply to the skin of pigs was studied in animals perfused with the dye, monastral fast blue. The arrangement of the blood vessels in control animals was in three plexuses, similar to that in other mammals but with the middle plexus poorly developed.A litter of pigs was divided into two groups at the age of 12 days and one group was raised in a warm room and the other in a cold room. The pigs were killed at age three months when the warm room was 35°C and the cold room 5°C. A quantitative evaluation of the blood supply to the skin of the experimental animals revealed that the pigs from the warm room had more blood vessels in the skin than those raised in the cold; the difference was statistically significant (P < 0.01). In the case of pigs from a second litter reared at 35°C and 20°C, no significant difference in the number of blood vessels was detected.Unlike most domestic animals the hair coat of the pig is sparse and for this reason changes in the blood flow through the skin are likely to be as important in the regulation of heat loss as they are in man. In addition to making physiological measurements of blood flow, however, it is also of importance to know the anatomical arrangement of the skin blood vessels, and to determine the extent to which this arrangement can be modified by long periods of exposure to different ambient temperatures. This information is crucial to a better understanding of the process of adaptation to environmental temperature in the pig, which is already known to involve changes in heat production, in thyroid activity and in behavior (Ingram and Mount, '65; Ingram and Slebodzinski, '65; Baldwin and Ingram, '68).Some information about the vascularity of the pig's skin is already available (Moritz and Henriques, '57), but the species has not been studied from the point of view of heat loss. Moritz and Henriques ('47) studied sections of skin treated with benzidine and emphasized the resemblance to human skin, which is so great in some instances that it is difficult to distinguish between them. In the present study blood vessels were injected with a dye and the skin vessels of pigs living at different en-ANAT. REC., 163: 517-524.vironmental temperatures were compared quantitatively with each other. MATERIALS AND METHODS AnimalsPigs of the English Large White breed, of both sexes, aged 12 weeks were used. In studies of the general distribution of blood vessels the animals were taken from the farm stock and the environmental temperature at which they had been living was not specially controlled. In the studies on acclimatization the temperature at which the animals lived was controlled from 12 days of age. Injection of dyeThe animals were deeply anesthetized with sodium pentabarbitone and the neck region opened to expose the carotid arteries and jugular veins. One glass cannula was then introduced into the carotid artery of one side and another into the contralateral internal jugular vein. The carotid artery was then perfused at a pressure of 120 to 180 mm Hg with a so...

Morphological Changes in Swine Associated with Environmental Temperature

“…Post mortem examination.-The animals were anesthetized and the blood vascular system perfused with a dye. The results of this study have been reported elsewhere (Ingram and Weaver 1969). The thickness of the fat layer on the back was determined and the skull and limb bones were defleshed and prepared for measurement and examination.…”

Temperature regulates limb length in homeotherms by directly modulating cartilage growth

“…However, no study to date has tested this central hypothesis directly. Impairment of bone growth by disruption of blood flow is well-known (13), as are correlations of enhanced blood flow with bone elongation (14) and ear enlargement (15). It is equally well established that cold-induced vasoconstriction shunts blood away from the periphery as a heat-conserving mechanism (1, 9), just as warm temperature enhances heat dissipation via vasodilation (1).…”

Development of arteriovenous anastomoses in the skin of the chicken and the influence of environmental temperature

“…a rats acclimated to an ambient temperature of 6°C had a significantly greater number of blood vessels in the ears than did rats acclimated to 30°C. Ingram and Weaver (1969) reported that pigs reared a t 5°C developed more blood vessels in the skin than did animals reared a t 35°C; in a second experiment, however, Ingram and Weaver (1969) did not observe any difference in skin vascularity between animals at 20 and 35°C.…”

“…It appears that the vascularity of the skin is increased after heat or cold acclimation (Heroux, 1959;Ingram and Weaver, 1969), and there are also some observations that suggest that the number of AVAs is affected. For example, Clark and Clark (1934a) found that ears of rabbits exposed to various thermal stimuli developed more AVAs than did ears kept from such stimulation, and Morris and Bevan (1986) noted that rabbits from Vermont had more AVAs in their ears than did rabbits from warmer California.…”