Page 342 - Veterinary Histology of Domestic Mammals and Birds, 5th Edition

Common integument 15

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(integumentum commune)

The common integument constitutes the external surface undergo transformation to form skin glands (sweat and
of the body. It protects the animal from the environment sebaceous glands). In specific locations, further modifica-
while also presenting a large surface area over which tion of apocrine sweat glands gives rise to the mammary
interactions with the exterior can occur. These roles are glands. These specialisations of the epidermis are accom-
supported by other sensory and regulatory organs; in this panied by structural changes in the deeper layers of the
capacity, the nervous system (via sensory organs) and the skin (Figure 15.1).
immune system (via innate and adaptive immune cell pop- The structure of the skin varies with species and with
ulations) are significant components of the skin. body region. Various factors (e.g. external mechanical or
The common integument has numerous functions. It thermal insult) bring about adaptations in skin thickness,
forms a protective barrier against mechanical, thermal, hair cover or the number and distribution of skin glands.
chemical and biological influences and prevents dehy- The epidermis is thin in regions with a thick hair coat,
dration. By means of its well-developed vascular supply, becoming thicker in areas in which hair is sparse or absent.
the common integument contributes to thermo- and
hydroregulation. Skin glands have multiple functions that Structure of the skin
are under autonomic control. Fat deposits in the subcu- While it performs a diverse range of functions, and exhib-
taneous tissue serve as energy stores and participate in its regional structural modifications, the basic structure of
thermoregulation and mechanical cushioning. As indi- the common integument is consistent, comprising the fol-
cated above, the skin also serves as a sensory organ and as lowing layers:
an immunoprotective layer.
The external layer of the skin, the epidermis, incor- · cutis:
porates several modifications. Epithelial cells differentiate − epidermis (epithelial layer),
through various stages into hair or, with extensive kerati- − dermis (corium) and
nisation, into the cornified layer of the hoof, nail, claw · subcutis (tela subcutanea).
and horn. In the deeper layers of the skin, epithelial cells

15.1 Scanning electron microscope image of the layers of the skin (cut surface) (pig; x30).

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