Page 349 - Veterinary Histology of Domestic Mammals and Birds, 5th Edition

Common integument (integumentum commune) 331

subjected to mechanical stress (e.g. digital pads), the fatty
VetBooks.ir tissue is divided into compartments by connective tissue
septa, increasing its resilience. The subcutis incorporates
local striated muscle tissue that serves to tauten the skin.

Skin glands (glandulae cutis)
The glands of the skin are divided into two types (Table
15.1). Embryologically, both are considered derivatives of
the epidermis. The types of glands, and their features and
functions, are as follows:

· sweat glands (glandulae sudoriferi):
− exocrine, extra-epithelial,
− tubular, simple or branched,
− single layer of secretory cells, apocrine or
merocrine,
− participate in thermoregulation, serve as scent
glands, occur in modified forms (e.g. glands of
the nasolabial plane, glands of the anal sacs), 15.12 Coiled tubular sweat glands in a foot pad (cat).
· sebaceous glands (glandulae sebaceae): Haematoxylin and eosin stain (x40).
− exocrine, extra-epithelial,
− alveolar, simple or compound, Apocrine glands, the most numerous type of sweat
− secretion formed by mass of cells, holocrine and gland in domestic mammals, are associated with hair
− produce sebum, which forms the bulk of the epi- follicles (Figure 15.15). Their secretory product encloses
dermal surface lipid layer. components of the apical cytoplasm and incorporates
scents that are specific to the individual animal of origin.
The secretory portion is coiled and the duct opens into
Sweat glands (glandulae sudoriferi) the hair follicle.
Sweat glands are exocrine, extra-epithelial, tubular (some- Merocrine glands occur less frequently in domestic
times saccular) glands (Figure 15.12). Their secretory product mammalian species and are limited to hairless areas such
is released by the apocrine or merocrine (eccrine) modes. as the foot pads of carnivores. They are unbranched coiled

Table 15.1 Structural differences between sweat and sebaceous glands.

Gland Structure Location Mode of secretion Special features
Sweat glands Exocrine, Distributed across Apocrine secretion Contribute to
(glandulae extra-epithelial, the entire skin directly into the thermoregulation and
sudoriferi) tubular, single surface, apocrine hair follicle, eccrine excretion of soluble
layer of secretory type usually (merocrine) secretion waste products, source
cells closely associated directly onto the skin of species-specific scents
with hair follicles surface; secretion including pheromonones
comprises proteolytic (apocrine type)
enzymes, electrolytes,
water and albuminoid
substances
Sebaceous Exocrine, Closely associated Holocrine secretion; Occur independently of
glands extra-epithelial, with the external sebum, composed of hair in some locations
(glandulae alveolar, mass root sheath of various fats and oils (e.g. eyelids [Meibomian
sebaceae) of cells gives hair follicles glands], on the penis
rise to secretory and in the external
product acoustic meatus);
increase suppleness and
reduce dehydration of
the skin; secretion has
antibacterial properties

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