Cutaneous mechano-receptors and
their mechanism of action.
Presented by: Dr. Mahesh
– sensory receptor that responds to mechanical
pressure or distortion.
• Normally there are four main types in glabrous
– Pacinian corpuscles,
– Meissner's corpuscles,
– Merkel's discs, and
– Ruffini endings.
• The nerve networks of skin contains
somatosensory and sympathetic autonomic
• The sensory fibres alone (free nerve ending)
or in conjunction with specialized structures
(corpuscular receptors) functions as receptor
of touch, pain, temperature, itch and
• Receptors are particularly dense in hairless
areas such as the areola, labia, and glans
• Sympathetic motor fibers are codistributed
with the sensory nerves in the dermis until
they branch to innervate
• the sweat glands,
• vascular smooth muscle,
• the arrector pili muscle of hair follicles, and
• Sebaceous glands.
• In glabrous (hairless) skin, there are four
principal types of mechanoreceptors, each
shaped according to its function.
• The tactile corpuscles (meissner) respond to
light touch, and adapt rapidly to changes in
texture (vibrations around 50 Hz).
• The bulbous corpuscles (ruffini) detect tension
deep in the skin and fascia.
• The Merkel nerve endings detect sustained
• The lamellar corpuscles(pacinian) in the skin
and fascia detect rapid vibrations (of about
• Receptors in hair follicles sense when
a hair changes position. Indeed, the most
sensitive mechanoreceptors in humans are
the follicular receptors for the hair cells in
the cochlea of the inner ear; these
receptors transduce sound for the brain.
• Mechanoreceiving free nerve endings detect
touch, pressure, and stretching.
• Cutaneous mechanoreceptors provide the senses
of touch, pressure, vibration, proprioception and
others. They are located in the skin, like
other cutaneous receptors.
• They are all innervated byAβ fibers, except the
mechanorecepting free nerve endings, which are
innervated by Aδ fibers.
• Cutaneous mechanoreceptors can be categorized
by morphology, by what kind of sensation they
perceive, and by the rate of adaptation.
Furthermore, each has a different receptive field.
• Slowly adapting: Slowly adapting
mechanoreceptors include Merkel and Ruffini
corpuscle end-organs, and some free nerve
– Slowly adapting type I mechanoreceptors have
multiple Merkel corpuscle end-organs.
– Slowly adapting type II mechanoreceptors have
single Ruffini corpuscle end-organs.
• Intermediate adapting: Some free nerve
endings are intermediate adapting.
• Rapidly adapting: Rapidly adapting
mechanoreceptors include Meissner corpuscle
end-organs, Pacinian corpuscle endorgans, hair follicle receptors and some free
– Rapidly adapting type I mechanoreceptors
have multiple Meissner corpuscle endorgans.
• Rapidly adapting type II mechanoreceptors
(usually called Pacinian) have single Pacinian
Mechanism of action
• Ability of mechanoceptors to detect
mechanical cues relies on the presence of
mechano-transducer channels on sensory
• They rapidly transform mechanical forces into
electric signals and depolarise the receptive
• This local depolarization, called the receptor
potential, can generate action potentials that
propogate towards CNS.
• The afferent neurons transmit messages
through synapses in the dorsal column nuclei,
where second-order neurons send the signal
to the thalamus and synapse with third-order
neurons in the ventrobasal complex.
• The third-order neurons then send the signal
to the somatosensory cortex
• 2 pathways
ion & touch
• Lies in the deep dermis and subcutaneous
• Characteristic lamellar and capsular
• Perineural capsule is organised into 30 or
more concentric layer of cells and fibrous
• The middle subcapsular zone is composed of
collagen and fibroblasts.
• The inner core consists of Schwann cellderived hemilamellae.
• Pacinian corpuscles serve as rapidly adapting
mechanoreceptors:responds briefly to
beginning and end of stimuli.
• Detects pressure changes esp.to vibrational
•Highly concentrated in
areas sensitive to light
tongue, soles, genitals
and inner core
located in the
• Meissner's corpuscles are elongated or ovoid
• located in the dermal papillae of digital skin
and oriented vertically toward the epidermal
• One to six axons enter the corpuscle, ramify
extensively, and terminate in bulboid endings
that are surrounded by lamellae.
•Slow adaption because of rigid structure.
•Sustainable response – 30 min. in humans
•Irregular firing in sustained.
•Large receptive field.
•Small, sharp pressure: fast firing rate.
•Large, flat pressure: slow rate
•Located in hairless skin and in hair follices.
•Not in skin surrounding follicle.
• Free nerve endings are also associated with
individual Merkel cells.
• Merkel cell-nerve complexes also known as:
• touch domes,
• hederiform endings,
• Iggo's capsule,
• Pinbus corpuscles,
• In palmoplantar skin, these complexes are found
at the site where the eccrine sweat duct
penetrates a glandular epidermal papilla
Free nerve endings
• Free nerve endings include the penicillate and
papillary nerve fibres.
• Most widespread and important sensory
receptors of the body.
• Particularly found In papillary dermis.
• rapidly adapting receptors that function in the
perception of touch, temperature, pain, and
• In haired skin: Because of overlapping
innervations, discrimination tends to be
• In non-haired skin: project individually
without overlapping distribution.
• Found at the orifice of the follicle.
• thought to be particularly receptive to cold