Introduction
Mammalian Skin: The Basics The first line of defence between the outside world and inside an animal is the skin. It is an effective barrier against physical, chemical and pathogenic assault (1). However, the skin is not only a barrier but a sensory organ enabling animals to sense the surrounding environment, provoking appropriate responses for animal survival. There are two main types of skin; thin skin (hairy), which makes up nearly all the skin on the body, and glabrous skin (hairless), found is exclusively in areas like the paw and rhinarium (naked nose tip). Unspecialised thin mammalian skin is comprised of multiple layers, all with specific functions. The epidermis is the outermost skin layer. It has a highly active …show more content…
This valuable information provokes involuntary (physiological) or voluntary (behavioural) actions over a wide range of temperatures (8) (9). It is crucial for animal survival allowing escape response against noxious heat and cold, or attraction responses towards preferable temperatures (8). Interestingly, recent thermal studies have shown that glabrous skin in dogs can be as cold at 0.5°C without the animal showing signs of discomfort (10). Therefore, mammalian thermosensitivity and limits for noxious temperatures cannot be generalised. The sensory cells which respond to temperature as well as pain, pressure and touch are distributed throughout the epidermal and dermal layers of the skin. The transduction of these stimuli primarily relies on unique somatorysensory neurons which reside in the trigeminal and dorsal root ganglia and have axonal processes that extend into the outer layers of skin (8). The sensory neurons use dendrites to gather information relating to their environment, the detected information is then transduced via axons to the brain to be processed. The epidermis and dermis are penetrated throughout by free nerve endings of Aδ and C fibres. Aδ-fibres typically exhibit medium-sized cell bodies, thinly myelinated axons and intermediate conduction velocities (9). C-fibres on the other hand exhibit small cell bodies, no myelin sheath and slow conduction velocities (9). Both types of fibres aid in thermotransduction (9). Specific thermosensitive channels are believed to be associated with these free nerve endings, working in concert to orchestrate an appropriate response over a wide range of temperatures (8). Once thermally stimulated the thermosensitive channels cause depolarisation of the free sensory nerve endings, generating action potentials, which travel from the periphery to the central nervous system (CNS) eliciting a
Mammalian Skin: The Basics The first line of defence between the outside world and inside an animal is the skin. It is an effective barrier against physical, chemical and pathogenic assault (1). However, the skin is not only a barrier but a sensory organ enabling animals to sense the surrounding environment, provoking appropriate responses for animal survival. There are two main types of skin; thin skin (hairy), which makes up nearly all the skin on the body, and glabrous skin (hairless), found is exclusively in areas like the paw and rhinarium (naked nose tip). Unspecialised thin mammalian skin is comprised of multiple layers, all with specific functions. The epidermis is the outermost skin layer. It has a highly active …show more content…
This valuable information provokes involuntary (physiological) or voluntary (behavioural) actions over a wide range of temperatures (8) (9). It is crucial for animal survival allowing escape response against noxious heat and cold, or attraction responses towards preferable temperatures (8). Interestingly, recent thermal studies have shown that glabrous skin in dogs can be as cold at 0.5°C without the animal showing signs of discomfort (10). Therefore, mammalian thermosensitivity and limits for noxious temperatures cannot be generalised. The sensory cells which respond to temperature as well as pain, pressure and touch are distributed throughout the epidermal and dermal layers of the skin. The transduction of these stimuli primarily relies on unique somatorysensory neurons which reside in the trigeminal and dorsal root ganglia and have axonal processes that extend into the outer layers of skin (8). The sensory neurons use dendrites to gather information relating to their environment, the detected information is then transduced via axons to the brain to be processed. The epidermis and dermis are penetrated throughout by free nerve endings of Aδ and C fibres. Aδ-fibres typically exhibit medium-sized cell bodies, thinly myelinated axons and intermediate conduction velocities (9). C-fibres on the other hand exhibit small cell bodies, no myelin sheath and slow conduction velocities (9). Both types of fibres aid in thermotransduction (9). Specific thermosensitive channels are believed to be associated with these free nerve endings, working in concert to orchestrate an appropriate response over a wide range of temperatures (8). Once thermally stimulated the thermosensitive channels cause depolarisation of the free sensory nerve endings, generating action potentials, which travel from the periphery to the central nervous system (CNS) eliciting a