9.14:
Sensory Functions of the Skin
The skin has several exteroceptors to detect external stimuli such as the blowing wind, changing temperature, or pain.
Upon detecting the stimuli, the receptors initiate a nerve impulse that travels to the brain to generate an appropriate response. These cutaneous receptors can be either non-encapsulated or encapsulated nerve endings.
For instance, the hair follicle receptors in the dermis relay the presence of a crawling insect because of hair movement. If the insect bites, the damage to the epidermis excites the pain-sensing nociceptors.
Located in the basal epidermis, the non-encapsulated Merkel discs transmit information about the texture and shape of an object held.
The encapsulated Meissner's corpuscles in the dermal papillae respond to light touch generating the nerve impulse.
Lower into the dermis, the encapsulated Ruffini endings perceive warmth and detect skin stretching.
The Pacinian corpuscles, located deeper into the dermis, efficiently transduce information about a deep touch and vibration.
9.14:
Sensory Functions of the Skin
The skin is the largest organ of the human body and plays a crucial role in our sensory perception. It contains a vast network of sensory receptors that contribute to the skin's protective function by perceiving physical, biological, and environmental cues and generating relevant responses.
There are two main categories of receptors on the skin: capsulated and non-capsulated. The non-capsulated ones are mainly the pain receptors. The capsulated ones can be further categorized based on the nature of the stimuli they perceive, such as mechanoreceptors and thermoreceptors.
We take our hands away while touching a boiling liquid. We remove our hands because the thermoreceptors make us aware that extreme temperatures can harm our tissues. We can feel an ant crawling on the skin, allowing us to flick it before it bites. The hair follicles on the skin can feel the movement. The hair root plexus at the base of the hair follicle transmits information regarding the presence of the ant to either the brain or spinal cord to act against the ant.
The general sense of touch, known as somatosensation, can be separated into light pressure, deep pressure, vibration, itch, pain, temperature, or hair movement based on the type of mechanoreceptors that perceive these touch sensations. Other senses include temperature perception by thermoreceptors and pain perception by nociceptors.
The epidermis, dermis, and hypodermis have specialized sensory receptors. These receptors are nerve structures that detect stimuli like touch, temperature and pain. The sensory receptors are densely concentrated on the tips of the fingers, which are extremely sensitive to touch, especially the Meissner corpuscle (tactile corpuscle) that responds to light touch and the Pacinian corpuscle (lamellated corpuscle) that senses vibration. Merkel cells scattered in the stratum basale are also touch receptors. In addition to these specialized receptors, sensory nerves are connected to each hair follicle, pain and temperature receptors are scattered throughout the skin, and motor nerves innervate the arrector pili muscles and glands. This rich innervation helps us sense our environment and react accordingly.
This text is adapted from Openstax, Anatomy and Physiology 2e, Section 4.1: Sensory perceptions.