"Skin" - what is it, definition of the term
In rats and mice, the integument is a multilayered organ consisting of a keratinized outer epithelium, a dermal layer of collagenous connective tissue, and associated structures such as hair follicles, sebaceous and sweat glands, and a dense network of sensory nerve endings; it functions as a protective barrier, regulates temperature, prevents fluid loss, and provides a surface for sensory perception.
Detailed information
The outer protective covering of rodents such as rats and mice consists of a multilayered structure that safeguards internal organs, regulates temperature, and provides sensory input. The primary components include:
- Epidermis – a stratified squamous layer composed of keratinocytes; it forms the most superficial barrier and undergoes continuous renewal.
- Dermis – a connective‑tissue matrix rich in collagen and elastin fibers; it houses blood vessels, lymphatics, nerves, and appendages.
- Subcutaneous tissue – a layer of loose connective tissue and adipocytes that insulates and stores energy reserves.
In both species, the epidermis displays a relatively thin cornified layer, but the rat’s epidermal thickness exceeds that of the mouse, reflecting differences in habitat exposure. The dermal composition shows a higher density of hair follicles in mice, whereas rats possess larger, more widely spaced follicles accompanied by prominent sebaceous glands.
Key physiological aspects:
- Barrier function – the cornified envelope prevents water loss and blocks pathogen entry; lipid-rich intercellular matrices reinforce impermeability.
- Thermoregulation – vasodilation and vasoconstriction within the dermal vasculature adjust heat dissipation; subcutaneous fat contributes to insulation.
- Sensory reception – mechanoreceptors (e.g., Merkel cells, Pacinian corpuscles) embedded in the dermis detect tactile stimuli, crucial for navigation and foraging.
- Healing capacity – rodents exhibit rapid epithelial migration and robust fibroblast activity, enabling swift closure of wounds.
Microscopic examination reveals that rat epidermal cells possess larger nuclei and a more pronounced stratum granulosum compared with mice, where the stratum spinosum is relatively thicker. Immunohistochemical studies show higher expression of keratin 14 in mouse epidermis, indicating a distinct pattern of differentiation.
Overall, the cutaneous covering of these rodents reflects adaptations to their size, ecological niche, and metabolic demands, with measurable variations in layer thickness, follicular density, and cellular composition that influence protection, sensory perception, and regenerative efficiency.