Sensory - Touch Development: Difference between revisions

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[[File:Touch receptors in mammalian skin cartoon 01.jpg|thumb|Touch receptors in mammalian skin.{{#pmid:20956378|PMID20956378}}]]  
[[File:Touch receptors in mammalian skin cartoon 01.jpg|thumb|Touch receptors in mammalian skin.{{#pmid:20956378|PMID20956378}}]]  
[[File:Pacinian_corpuscle_histology_01.jpg|thumb|Skin Pacinian corpuscle]]
[[File:Pacinian_corpuscle_histology_01.jpg|thumb|Skin Pacinian corpuscle]]
These notes introduce the development of the sense of touch, part of the somatosensory system. Because of the distribution of the sensory structures within the skin, this topic is generally also covered in [[Integumentary Development|integumentary]] development.
These notes introduce the development of the sense of touch, part of the somatosensory system. Because of the distribution of the sensory structures within the skin, this topic is generally also covered in {{integumentary}} development and neural component is covered in {{peripheral nervous system}} development from {{neural crest}}.




[[Sensory - Touch Development|Touch]]:  [[Sensory - Touch Development#Touch Receptors|Touch Receptors]] | [[Sensory - Touch Development#Touch Pathway|Touch Pathway]] | {{Pacinian corpuscle}} | {{Meissner's corpuscle}} | {{Merkel cell}} | [[Sensory - Touch Development#Sensory Modalities|Sensory Modalities]] | {{neural crest}} | {{neural}} | [[2012_Group_Project_2|Student project]] | {{integumentary}}
{|
 
|-bgcolor="F5FFFA"
| [[Sensory - Touch Development|'''Touch''']]:  [[Sensory - Touch Development#Touch Receptors|touch receptors]] | [[Sensory - Touch Development#Touch Pathway|touch pathway]] | {{Pacinian corpuscle}} | {{Meissner's corpuscle}} | {{Merkel cell}} | [[Sensory - Touch Development#Sensory Modalities|sensory modalities]] | {{neural crest}} | {{neural}} | [[2012_Group_Project_2|Student project]] | {{integumentary}}
|}
<br>
{{Integumentary Links}}
{{Integumentary Links}}
 
<br>
{{Senses Links}}
{{Senses Links}}
== Some Recent Findings ==
== Some Recent Findings ==
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|-bgcolor="F5FAFF"  
|-bgcolor="F5FAFF"  
|
|
* '''A Cascade of Wnt, Eda, and Shh Signaling Is Essential for Touch Dome Merkel Cell Development'''{{#pmid:27414798|PMID27414798}} "In the skin, touch domes develop in tandem with primary hair follicles and contain sensory Merkel cells. We found dermal Wnt signaling and subsequent epidermal Eda/Edar signaling promoted Merkel cell morphogenesis by inducing Shh expression in early follicles. Lineage-specific gene deletions revealed intraepithelial Shh signaling was necessary for Merkel cell specification. Additionally, a Shh signaling agonist was sufficient to rescue Merkel cell differentiation in Edar-deficient skin. ...Although developmentally associated with hair follicles, fate mapping demonstrated Merkel cells primarily originated outside the hair follicle lineage. These findings suggest that touch dome development requires Wnt-dependent mesenchymal signals to establish reciprocal signaling within the developing ectoderm, including Eda signaling to primary hair placodes and ultimately Shh signaling from primary follicles to extrafollicular Merkel cell progenitors." [[Developmental Signals - Sonic hedgehog|Sonic hedgehog]]
* '''{{Notch}} pathway signaling in the skin antagonizes Merkel cell development'''{{#pmid:29241683|PMID29241683}} "Merkel cells are mechanosensitive skin cells derived from the epidermal lineage whose development requires expression of the basic helix-loop-helix transcription factor Atoh1. The genes and pathways involved in regulating Merkel cell development during embryogenesis are poorly understood. Notch pathway signaling antagonizes Atoh1 expression in many developing body regions, so we hypothesized that Notch signaling might inhibit Merkel cell development. We found that conditional, constitutive overexpression of the Notch intracellular domain (NICD) in mouse epidermis significantly decreased Merkel cell numbers in whisker follicles and touch domes of hairy skin. Conversely, conditional deletion of the obligate NICD binding partner RBPj in the epidermis significantly increased Merkel cell numbers in whisker follicles, led to the development of ectopic Merkel cells outside of touch domes in hairy skin epidermis, and altered the distribution of Merkel cells in touch domes. Deletion of the downstream Notch effector gene Hes1 also significantly increased Merkel cell numbers in whisker follicles. Together, these data demonstrate that Notch signaling regulates Merkel cell production and patterning." {{notch}}


* '''Unipotent, Atoh1+ progenitors maintain the Merkel cell population in embryonic and adult mice'''{{#pmid:25624394|PMID25624394}} "Resident progenitor cells in mammalian skin generate new cells as a part of tissue homeostasis. We sought to identify the progenitors of Merkel cells, a unique skin cell type that plays critical roles in mechanosensation. We found that some Atoh1-expressing cells in the hairy skin and whisker follicles are mitotically active at embryonic and postnatal ages. Genetic fate-mapping revealed that these Atoh1-expressing cells give rise solely to Merkel cells. Furthermore, selective ablation of Atoh1(+) skin cells in adult mice led to a permanent reduction in Merkel cell numbers, demonstrating that other stem cell populations are incapable of producing Merkel cells. These data identify a novel, unipotent progenitor population in the skin that gives rise to Merkel cells both during development and adulthood."
* '''The development of human digital Meissner's and Pacinian corpuscles'''{{#pmid:29842990|PMID29842990}} "Development of Pacinian corpuscles starts at 13 weeks {{GA}}, and it is completed at 4 months of life, although their basic structure and immunohistochemical characteristics are reached at 36 weeks {{GA}}. During development, around the axon, a complex network of S100 positive Schwann-related processes is progressively compacted to form the inner core, while the surrounding mesenchyme is organized and forms the outer core and the capsule. Meissner's corpuscles start to develop at 22 weeks {{GA}} and complete their typical morphology and immunohistochemical profile at 8 months of life. In developing Meissner's corpuscles, the axons establish complex relationships with the epidermis and are progressively covered by Schwann-like cells until they complete the mature arrangement late in postnatal life. The present results demonstrate an asynchronous development of the Meissner's and Pacini's corpuscles and show that there is not a total correlation between morphological and immunohistochemical maturation."


* '''Embryonic maturation of epidermal Merkel cells is controlled by a redundant transcription factor network'''{{#pmid:25468937|PMID25468937}} "Merkel cell-neurite complexes are located in touch-sensitive areas of the mammalian skin and are involved in recognition of the texture and shape of objects. Merkel cells are essential for these tactile discriminations, as they generate action potentials in response to touch stimuli and induce the firing of innervating afferent nerves. It has been shown that Merkel cells originate from epidermal stem cells, but the cellular and molecular mechanisms of their development are largely unknown. In this study, we analyzed Merkel cell differentiation during development and found that it is a temporally regulated maturation process characterized by a sequential activation of Merkel cell-specific genes. We uncovered key transcription factors controlling this process and showed that the transcription factor Atoh1 is required for initial Merkel cell specification. The subsequent maturation steps of Merkel cell differentiation are controlled by cooperative function of the transcription factors Sox2 and Isl1, which physically interact and work to sustain Atoh1 expression"
* '''Tree of Vater-Pacinian corpuscles in the human finger and thumb: a comparison between the late fetal stage and old age'''{{#pmid:28653179|PMID28653179}} "Using histological sections of 12 hands from 12 human fetuses at 20-34 weeks of gestation (150-290 mm) and 14 fingers (index and small) from seven donated cadavers of elderly individuals (aged 78-95 years), we compared the features of Vater-Pacinian corpuscles between these two stages of life. Corpuscles with thin, tightly packed lamellae appeared to undergo a change to thick, loosely packed lamellae at 23-32 weeks. The typical fetal corpuscle had two parts: (1) a rod-like proximal part (0.2-0.6 mm in length) extending along the proximodistal axis of the finger, and (2) a distal end (0.1 mm) after acute bending of the proximal part. Corpuscles were associated with palmar digital nerves in the fingers, but were also present along the dorsal nerves in the thumb. A flower bouquet- or tree-like arrangement including 5-10 corpuscles extended to the dermis of the skin along a perforating artery. Serial sections of the thumb and fifth finger revealed approximately 80-180 corpuscles in the distal phalangeal segment. In elderly individuals, the corpuscles were distributed along the palmar digital nerve, but (1) their density was much lower than in fetuses and (2) a bouquet- or tree-like arrangement was rarely seen. In the distal segment, there were fewer than 40 adult corpuscles, being 0.2-0.5 mm thick and 1.0-2.5 mm long. Wavy or coiled corpuscles were evident. Because of the considerable differences in the distribution and number of corpuscles between the fetus and adult, they appear to undergo considerable depletion with age, especially along thin, superficial nerve branches."


* '''Wetness perception across body sites'''{{#pmid:22710006|PMID22710006}} "Human skin is innervated with a variety of receptors serving somatosensation and includes the sensory sub-modalities of touch, temperature, pain and itch. The density and type of receptors differ across the body surface, and there are various body-map representations in the brain. The perceptions of skin sensations outside of the specified sub-modalities, e.g. wetness or greasiness, are described as 'touch blends' and are learned. ...The perception of wetness is generated from the coincident activation of tactile and thermal receptors. The perception of wetness did not, however, differ significantly across body sites and there were no significant interactions between wetness level and body site."
* '''Developmental changes in the perception of visuotactile simultaneity'''{{#pmid:29783043|PMID29783043}} "A simultaneity judgment (SJ) task was used to measure the developmental trajectory of visuotactile simultaneity perception in children (aged 7, 9, 11, and 13 years) and adults. Participants were presented with a visual flash in the center of a computer monitor and a tap on their right index finger (located 20° below the flash) with 13 possible stimulus onset asynchronies (SOAs). ...In summary, the perception of visuotactile simultaneity is not fully mature until 11 years of age. The protracted development of visuotactile simultaneity perception may be related to the need for crossmodal recalibration as the body grows and to the developmental improvements in the ability to optimally integrate visual and tactile signals."


* '''A Shift in Sensory Processing that Enables the Developing Human Brain to Discriminate Touch from Pain'''{{#pmid:21906948|PMID21906948}} "When and how infants begin to discriminate noxious from innocuous stimuli is a fundamental question in neuroscience. However, little is known about the development of the necessary cortical somatosensory functional prerequisites in the intact human brain. ... The results suggest that specific neural circuits necessary for discrimination between touch and nociception emerge from 35-37 weeks gestation in the human brain."
* '''A Cascade of Wnt, Eda, and Shh Signaling Is Essential for Touch Dome Merkel Cell Development'''{{#pmid:27414798|PMID27414798}} "In the skin, touch domes develop in tandem with primary hair follicles and contain sensory Merkel cells. We found dermal Wnt signaling and subsequent epidermal Eda/Edar signaling promoted Merkel cell morphogenesis by inducing Shh expression in early follicles. Lineage-specific gene deletions revealed intraepithelial Shh signaling was necessary for Merkel cell specification. Additionally, a Shh signaling agonist was sufficient to rescue Merkel cell differentiation in Edar-deficient skin. ...Although developmentally associated with hair follicles, fate mapping demonstrated Merkel cells primarily originated outside the hair follicle lineage. These findings suggest that touch dome development requires Wnt-dependent mesenchymal signals to establish reciprocal signaling within the developing ectoderm, including Eda signaling to primary hair placodes and ultimately Shh signaling from primary follicles to extrafollicular Merkel cell progenitors." {{sonic hedgehog}}


*''' Identification of epidermal progenitors for the Merkel cell lineage'''{{#pmid:21041368|PMID21041368}} "Epithelial stem cells in adult mammalian skin are known to maintain epidermal, follicular and sebaceous lineages during homeostasis. Recently, Merkel cell mechanoreceptors were identified as a fourth lineage derived from the proliferative layer of murine skin epithelium; however, the location of the stem or progenitor population for Merkel cells remains unknown. Here, we have identified a previously undescribed population of epidermal progenitors that reside in the touch domes of hairy skin, termed touch dome progenitor cells (TDPCs)."
|}
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{| class="wikitable mw-collapsible mw-collapsed"
{| class="wikitable mw-collapsible mw-collapsed"
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<pubmed limit=5>Touch Development</pubmed>
<pubmed limit=5>Touch Development</pubmed>
|}
{| class="wikitable mw-collapsible mw-collapsed"
! Older papers &nbsp;
|-
| {{Older papers}}
* '''Unipotent, Atoh1+ progenitors maintain the Merkel cell population in embryonic and adult mice'''{{#pmid:25624394|PMID25624394}} "Resident progenitor cells in mammalian skin generate new cells as a part of tissue homeostasis. We sought to identify the progenitors of Merkel cells, a unique skin cell type that plays critical roles in mechanosensation. We found that some Atoh1-expressing cells in the hairy skin and whisker follicles are mitotically active at embryonic and postnatal ages. Genetic fate-mapping revealed that these Atoh1-expressing cells give rise solely to Merkel cells. Furthermore, selective ablation of Atoh1(+) skin cells in adult mice led to a permanent reduction in Merkel cell numbers, demonstrating that other stem cell populations are incapable of producing Merkel cells. These data identify a novel, unipotent progenitor population in the skin that gives rise to Merkel cells both during development and adulthood."
* '''Embryonic maturation of epidermal Merkel cells is controlled by a redundant transcription factor network'''{{#pmid:25468937|PMID25468937}} "Merkel cell-neurite complexes are located in touch-sensitive areas of the mammalian skin and are involved in recognition of the texture and shape of objects. Merkel cells are essential for these tactile discriminations, as they generate action potentials in response to touch stimuli and induce the firing of innervating afferent nerves. It has been shown that Merkel cells originate from epidermal stem cells, but the cellular and molecular mechanisms of their development are largely unknown. In this study, we analyzed Merkel cell differentiation during development and found that it is a temporally regulated maturation process characterized by a sequential activation of Merkel cell-specific genes. We uncovered key transcription factors controlling this process and showed that the transcription factor Atoh1 is required for initial Merkel cell specification. The subsequent maturation steps of Merkel cell differentiation are controlled by cooperative function of the transcription factors Sox2 and Isl1, which physically interact and work to sustain Atoh1 expression"
* '''Wetness perception across body sites'''{{#pmid:22710006|PMID22710006}} "Human skin is innervated with a variety of receptors serving somatosensation and includes the sensory sub-modalities of touch, temperature, pain and itch. The density and type of receptors differ across the body surface, and there are various body-map representations in the brain. The perceptions of skin sensations outside of the specified sub-modalities, e.g. wetness or greasiness, are described as 'touch blends' and are learned. ...The perception of wetness is generated from the coincident activation of tactile and thermal receptors. The perception of wetness did not, however, differ significantly across body sites and there were no significant interactions between wetness level and body site."
* '''A Shift in Sensory Processing that Enables the Developing Human Brain to Discriminate Touch from Pain'''{{#pmid:21906948|PMID21906948}} "When and how infants begin to discriminate noxious from innocuous stimuli is a fundamental question in neuroscience. However, little is known about the development of the necessary cortical somatosensory functional prerequisites in the intact human brain. ... The results suggest that specific neural circuits necessary for discrimination between touch and nociception emerge from 35-37 weeks gestation in the human brain."
*''' Identification of epidermal progenitors for the Merkel cell lineage'''{{#pmid:21041368|PMID21041368}} "Epithelial stem cells in adult mammalian skin are known to maintain epidermal, follicular and sebaceous lineages during homeostasis. Recently, Merkel cell mechanoreceptors were identified as a fourth lineage derived from the proliferative layer of murine skin epithelium; however, the location of the stem or progenitor population for Merkel cells remains unknown. Here, we have identified a previously undescribed population of epidermal progenitors that reside in the touch domes of hairy skin, termed touch dome progenitor cells (TDPCs)."
|}
|}
==Historic People==
==Historic People==
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==Pacinian Corpuscle==
==Pacinian Corpuscle==
These receptors are lamellar vibration receptors that produce rapidly adapting responses. They are located in the subcutaneous tissue, deeper in interosseous membranes, and also mesenteries of the gut.  The inner core cells form from Schwann cells extending from the nerve terminal.
These receptors are lamellar vibration receptors that produce rapidly adapting responses. They are located in the subcutaneous tissue, deeper in interosseous membranes, and also mesenteries of the gut.  The inner core cells form from Schwann cells extending from the nerve terminal.
A recent study in developing human digits,{{#pmid:29842990|PMID29842990}} show appearance at 11 weeks (13 weeks {{GA}}), and  completed at 4 months of life. Both basic structure and immunohistochemical characteristics were reached at 36 weeks {{GA}}. The Schwann cell processes progressively compact to form the inner core, while the surrounding mesenchyme is organised to form the outer core component and the capsule.


[[File:Pacinian corpuscle histology 01.jpg|600px]]
[[File:Pacinian corpuscle histology 01.jpg|600px]]
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==Meissner's Corpuscle==
==Meissner's Corpuscle==
Located in glabrous skin the mechanoreceptor lies between the dermal papillae for sensitivity to light touch. They are rapidly adaptive elongated receptors formed by a connective tissue capsule that formed by several lamellae of Schwann cells enclosing one or more afferent nerve fibres. The sensory corpuscle is a stack of discoid components of flattened axon terminals sandwiched between Schwann cell lamellae covered with a connective tissue capsule linked to the basal aspect of the epidermis by dermal collagen fibers.{{#pmid:14724379|PMID14724379}}
{{Meissner's corpuscle}}s are mechanoreceptors located in glabrous skin within the dermal papillae for sensitivity to light touch. They are rapidly adaptive elongated receptors consisting of a connective tissue capsule containing several lamellae of {{Schwann cell}}s enclosing one or more afferent nerve fibres. The sensory corpuscle is a stack of discoid components of flattened axon terminals sandwiched between Schwann cell lamellae covered with a connective tissue capsule linked to the basal aspect of the epidermis by dermal collagen fibers.{{#pmid:14724379|PMID14724379}}  
 
A recent study in developing human digits,{{#pmid:29842990|PMID29842990}} show appearance at 20 weeks (22 weeks {{GA}} and complete their typical morphology and immunohistochemical profile at 8 months of life.


[[File:Meissner_corpuscle_02.jpg|thumb|Meissner's corpuscle]]
[[File:Meissner_corpuscle_02.jpg|thumb|Meissner's corpuscle]]
[[File:Meissner corpuscle 01.jpg|600px]]
[[File:Meissner corpuscle 01.jpg|600px]]


Meissner's corpuscles are located throughout the skin and are seen concentrated in regions of high touch (finger tips, lips, genital regions).
Meissner's corpuscles are located throughout the skin and are seen concentrated in regions of high touch (finger tips, lips, genital regions). There is evidence that these receptors are concentrated in the fingertips of primates and may be associated with the evolution of manipulative abilities of the hands.{{#pmid:26053332|PMID26053332}}
 
===Structure===
Coiled spring-like structures, composed of stacked, disk-like lamellar cells with lamellae orientation usually parallel to the skin surface.
 
* lamellar cells - Schwann cell-derived with peripherally displaced nuclei in a fibroblastic capsule incomplete at the apex. 
* sensory neurites - course through the lamellae, not visible by {{HE}}.
 


==Merkel Cell==
==Merkel Cell==
Merkel cells occur in many species including reptiles, fish, and mammals. Merkel cell complexes mediate slowly adapting type I (SAI) responses, which are characterized by an irregular firing pattern during sustained pressure.  Merkel cells arise in the embryo{{#pmid:25468937|PMID25468937}} and in the adult{{#pmid:25624394|PMID25624394}} from an epidermal progenitor cell population. These cells express the transcription factor Atoh1 and when differentiated are post-mitotic. Merkel cells can be organised into specialised clustered structure known as a "touch dome" associated with primary hair follicles.
 
Merkel cells develop from epidermal progenitor population differentiation in the embryo, and also during their replacement postnatally.{{#pmid:19786578|PMID19786578}} They form a long-lived cell population within the skin with both a sensory and a neuroendocrine functions.
 
 
Merkel cells occur in many species including reptiles, fish, and mammals. Merkel cell complexes mediate slowly adapting type I (SAI) responses, which are characterized by an irregular firing pattern during sustained pressure.  Merkel cells arise in the embryo{{#pmid:25468937|PMID25468937}} and in the adult{{#pmid:25624394|PMID25624394}} from an epidermal progenitor cell population.{{#pmid:19782676|PMID19782676}} These cells express the transcription factor Atoh1 and when differentiated are post-mitotic. Merkel cells can be organised into specialised clustered structure known as a "touch dome" associated with primary hair follicles.


[[File:Integumentary touch dome model 01.jpg|500px]]
[[File:Integumentary touch dome model 01.jpg|500px]]


A molecular signalling cascade from Wnt, Eda, and Shh is required for touch dome Merkel cell development.{{#pmid:27414798|PMID27414798}} Keratin 8 (K8) and Keratin 18 (K18) are Merkel cell markers identified in late fetal and adult skin.
A molecular signalling cascade from Wnt, Eda, and Shh is required for touch dome Merkel cell development.{{#pmid:27414798|PMID27414798}} Keratin 8 (K8) and Keratin 18 (K18) are Merkel cell markers identified in late fetal and adult skin.
The {{Notch}} signaling pathway has been shown to antagonize Atoh1 expression that is required for Merkel cell development in the skin. {{#pmid:29241683|PMID29241683}}


   
   
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* '''Merkel cell carcinoma''' (MCC) PMID 12007193
* '''Merkel cell carcinoma''' (MCC) PMID 12007193
==Historic==
The fine structure of Meissner's touch corpuscles of human fingers.{{#pmid:13691669|PMID13691669}}
:"The principal part of Meissner's corpuscle is made up of flattened laminar cells stretching across the corpuscle in irregular layers. The perinuclear cytoplasm of these cells contains numerous small mitochondria, a sparse granular endoplasmic reticulum, and a large number of small vesicles. Nerve fibers enter the side or base of the corpuscle, lose their myelin sheaths, and follow a meandering course between the laminar cell plates. The nerve endings enter into a close appositional relationship with the flattened portions of the laminar cells. In some areas the apposed axolemma and cell membranes are slightly thickened with small vesicles located along the cell membrane or on both surfaces. These regions are interpreted as synapses. The most prominent feature of the nerve endings is an extraordinary accumulation of small mitochondria which vary in size and internal density. The nerve endings also contain vacuoles, groups of dense concentric membranes, and small dense vesicles of irregular distribution. The laminar cells are separated from one another by a dense intercellular substance of uniform thickness which also envelops the entire corpuscle. This material contains randomly oriented collagen fibers and fine fibrils bound together by a dense material at nodal points recurring at regular intervals of approximately 120 mmicro. These findings are discussed in relation to the problems of the function of Meissner's corpuscle, neural material loss and replacement, and the presence of synapses."


== References ==
== References ==
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===Reviews===
===Reviews===
{{#pmid:30085522}}
{{#pmid:27702783}}
{{#pmid:27702783}}
{{#pmid:27457037}}


{{#pmid:25480024}}
{{#pmid:25480024}}
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{{#pmid:20956378}}
{{#pmid:20956378}}
{{#pmid:13691669}}
===Articles===
===Articles===
{{#pmid:25471886}}
{{#pmid:25471886}}
===Books===
===Books===
'''Neurobiology of Sensation and Reward.''' Gottfried JA, editor. Boca Raton (FL): CRC Press; 2011. [http://www.ncbi.nlm.nih.gov/books/NBK92803 Chapter 7 - Touch]
'''Neurobiology of Sensation and Reward.''' Gottfried JA, editor. Boca Raton (FL): CRC Press; 2011. [http://www.ncbi.nlm.nih.gov/books/NBK92803 Chapter 7 - Touch]
PMID 22593916
PMID 22593916

Latest revision as of 11:47, 19 November 2019

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Introduction

Touch receptors in mammalian skin.[1]
Skin Pacinian corpuscle

These notes introduce the development of the sense of touch, part of the somatosensory system. Because of the distribution of the sensory structures within the skin, this topic is generally also covered in integumentary development and neural component is covered in peripheral nervous system development from neural crest.


Touch: touch receptors | touch pathway | pacinian corpuscle | Meissner's corpuscle | Merkel cell | sensory modalities | neural crest | neural | Student project | integumentary


Integumentary Links: integumentary | Lecture | hair | tooth | nail | integumentary gland | mammary gland | vernix caseosa | melanocyte | touch | Eyelid | outer ear | Histology | integumentary abnormalities | Category:Integumentary
Hair Links  
Hair Links: Overview | Lanugo | Neonatal | Vellus | Terminal | Hair Follicle | Follicle Phases | Stem Cells | Molecular | Pattern | Puberty | Histology | Hair Colour | Arrector Pili Muscle | Hair Loss | Integumentary
Touch Links  
Touch Links: Touch Receptors | Touch Pathway | Pacinian Corpuscle | Meissner's Corpuscle | Merkel Cell | Sensory Modalities | Neural Crest Development | Neural System Development | Student project | Integumentary | Sensory System
Historic Embryology - Integumentary  
1906 Papillary ridges | 1910 Manual of Human Embryology | 1914 Integumentary | 1923 Head Subcutaneous Plexus | 1921 Text-Book of Embryology | 1924 Developmental Anatomy | 1941 Skin Sensory | Historic Disclaimer
Tinycc  
http://tiny.cc/Integument_Development


Senses Links: Introduction | placode | Hearing and Balance hearing | balance | vision | smell | taste | touch | Stage 22 | Category:Sensory

Some Recent Findings

  • Notch pathway signaling in the skin antagonizes Merkel cell development[2] "Merkel cells are mechanosensitive skin cells derived from the epidermal lineage whose development requires expression of the basic helix-loop-helix transcription factor Atoh1. The genes and pathways involved in regulating Merkel cell development during embryogenesis are poorly understood. Notch pathway signaling antagonizes Atoh1 expression in many developing body regions, so we hypothesized that Notch signaling might inhibit Merkel cell development. We found that conditional, constitutive overexpression of the Notch intracellular domain (NICD) in mouse epidermis significantly decreased Merkel cell numbers in whisker follicles and touch domes of hairy skin. Conversely, conditional deletion of the obligate NICD binding partner RBPj in the epidermis significantly increased Merkel cell numbers in whisker follicles, led to the development of ectopic Merkel cells outside of touch domes in hairy skin epidermis, and altered the distribution of Merkel cells in touch domes. Deletion of the downstream Notch effector gene Hes1 also significantly increased Merkel cell numbers in whisker follicles. Together, these data demonstrate that Notch signaling regulates Merkel cell production and patterning." Notch
  • The development of human digital Meissner's and Pacinian corpuscles[3] "Development of Pacinian corpuscles starts at 13 weeks GA, and it is completed at 4 months of life, although their basic structure and immunohistochemical characteristics are reached at 36 weeks GA. During development, around the axon, a complex network of S100 positive Schwann-related processes is progressively compacted to form the inner core, while the surrounding mesenchyme is organized and forms the outer core and the capsule. Meissner's corpuscles start to develop at 22 weeks GA and complete their typical morphology and immunohistochemical profile at 8 months of life. In developing Meissner's corpuscles, the axons establish complex relationships with the epidermis and are progressively covered by Schwann-like cells until they complete the mature arrangement late in postnatal life. The present results demonstrate an asynchronous development of the Meissner's and Pacini's corpuscles and show that there is not a total correlation between morphological and immunohistochemical maturation."
  • Tree of Vater-Pacinian corpuscles in the human finger and thumb: a comparison between the late fetal stage and old age[4] "Using histological sections of 12 hands from 12 human fetuses at 20-34 weeks of gestation (150-290 mm) and 14 fingers (index and small) from seven donated cadavers of elderly individuals (aged 78-95 years), we compared the features of Vater-Pacinian corpuscles between these two stages of life. Corpuscles with thin, tightly packed lamellae appeared to undergo a change to thick, loosely packed lamellae at 23-32 weeks. The typical fetal corpuscle had two parts: (1) a rod-like proximal part (0.2-0.6 mm in length) extending along the proximodistal axis of the finger, and (2) a distal end (0.1 mm) after acute bending of the proximal part. Corpuscles were associated with palmar digital nerves in the fingers, but were also present along the dorsal nerves in the thumb. A flower bouquet- or tree-like arrangement including 5-10 corpuscles extended to the dermis of the skin along a perforating artery. Serial sections of the thumb and fifth finger revealed approximately 80-180 corpuscles in the distal phalangeal segment. In elderly individuals, the corpuscles were distributed along the palmar digital nerve, but (1) their density was much lower than in fetuses and (2) a bouquet- or tree-like arrangement was rarely seen. In the distal segment, there were fewer than 40 adult corpuscles, being 0.2-0.5 mm thick and 1.0-2.5 mm long. Wavy or coiled corpuscles were evident. Because of the considerable differences in the distribution and number of corpuscles between the fetus and adult, they appear to undergo considerable depletion with age, especially along thin, superficial nerve branches."
  • Developmental changes in the perception of visuotactile simultaneity[5] "A simultaneity judgment (SJ) task was used to measure the developmental trajectory of visuotactile simultaneity perception in children (aged 7, 9, 11, and 13 years) and adults. Participants were presented with a visual flash in the center of a computer monitor and a tap on their right index finger (located 20° below the flash) with 13 possible stimulus onset asynchronies (SOAs). ...In summary, the perception of visuotactile simultaneity is not fully mature until 11 years of age. The protracted development of visuotactile simultaneity perception may be related to the need for crossmodal recalibration as the body grows and to the developmental improvements in the ability to optimally integrate visual and tactile signals."
  • A Cascade of Wnt, Eda, and Shh Signaling Is Essential for Touch Dome Merkel Cell Development[6] "In the skin, touch domes develop in tandem with primary hair follicles and contain sensory Merkel cells. We found dermal Wnt signaling and subsequent epidermal Eda/Edar signaling promoted Merkel cell morphogenesis by inducing Shh expression in early follicles. Lineage-specific gene deletions revealed intraepithelial Shh signaling was necessary for Merkel cell specification. Additionally, a Shh signaling agonist was sufficient to rescue Merkel cell differentiation in Edar-deficient skin. ...Although developmentally associated with hair follicles, fate mapping demonstrated Merkel cells primarily originated outside the hair follicle lineage. These findings suggest that touch dome development requires Wnt-dependent mesenchymal signals to establish reciprocal signaling within the developing ectoderm, including Eda signaling to primary hair placodes and ultimately Shh signaling from primary follicles to extrafollicular Merkel cell progenitors." sonic hedgehog
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Search term: Touch Development

<pubmed limit=5>Touch Development</pubmed>

Older papers  
These papers originally appeared in the Some Recent Findings table, but as that list grew in length have now been shuffled down to this collapsible table.

See also the Discussion Page for other references listed by year and References on this current page.

  • Unipotent, Atoh1+ progenitors maintain the Merkel cell population in embryonic and adult mice[7] "Resident progenitor cells in mammalian skin generate new cells as a part of tissue homeostasis. We sought to identify the progenitors of Merkel cells, a unique skin cell type that plays critical roles in mechanosensation. We found that some Atoh1-expressing cells in the hairy skin and whisker follicles are mitotically active at embryonic and postnatal ages. Genetic fate-mapping revealed that these Atoh1-expressing cells give rise solely to Merkel cells. Furthermore, selective ablation of Atoh1(+) skin cells in adult mice led to a permanent reduction in Merkel cell numbers, demonstrating that other stem cell populations are incapable of producing Merkel cells. These data identify a novel, unipotent progenitor population in the skin that gives rise to Merkel cells both during development and adulthood."
  • Embryonic maturation of epidermal Merkel cells is controlled by a redundant transcription factor network[8] "Merkel cell-neurite complexes are located in touch-sensitive areas of the mammalian skin and are involved in recognition of the texture and shape of objects. Merkel cells are essential for these tactile discriminations, as they generate action potentials in response to touch stimuli and induce the firing of innervating afferent nerves. It has been shown that Merkel cells originate from epidermal stem cells, but the cellular and molecular mechanisms of their development are largely unknown. In this study, we analyzed Merkel cell differentiation during development and found that it is a temporally regulated maturation process characterized by a sequential activation of Merkel cell-specific genes. We uncovered key transcription factors controlling this process and showed that the transcription factor Atoh1 is required for initial Merkel cell specification. The subsequent maturation steps of Merkel cell differentiation are controlled by cooperative function of the transcription factors Sox2 and Isl1, which physically interact and work to sustain Atoh1 expression"
  • Wetness perception across body sites[9] "Human skin is innervated with a variety of receptors serving somatosensation and includes the sensory sub-modalities of touch, temperature, pain and itch. The density and type of receptors differ across the body surface, and there are various body-map representations in the brain. The perceptions of skin sensations outside of the specified sub-modalities, e.g. wetness or greasiness, are described as 'touch blends' and are learned. ...The perception of wetness is generated from the coincident activation of tactile and thermal receptors. The perception of wetness did not, however, differ significantly across body sites and there were no significant interactions between wetness level and body site."
  • A Shift in Sensory Processing that Enables the Developing Human Brain to Discriminate Touch from Pain[10] "When and how infants begin to discriminate noxious from innocuous stimuli is a fundamental question in neuroscience. However, little is known about the development of the necessary cortical somatosensory functional prerequisites in the intact human brain. ... The results suggest that specific neural circuits necessary for discrimination between touch and nociception emerge from 35-37 weeks gestation in the human brain."
  • Identification of epidermal progenitors for the Merkel cell lineage[11] "Epithelial stem cells in adult mammalian skin are known to maintain epidermal, follicular and sebaceous lineages during homeostasis. Recently, Merkel cell mechanoreceptors were identified as a fourth lineage derived from the proliferative layer of murine skin epithelium; however, the location of the stem or progenitor population for Merkel cells remains unknown. Here, we have identified a previously undescribed population of epidermal progenitors that reside in the touch domes of hairy skin, termed touch dome progenitor cells (TDPCs)."

Historic People

Friedrich Sigmund Merkel
Friedrich Sigmund Merkel (1845-1919)
  • Georg Meissner - (1829-1905) German histologist, physiologist and anatomist. Beiträge zur Anatomie und Physiologie der Haut. (Contributions to the anatomy and physiology of the skin.) Leipzig, 1853.
  • Friedrich Sigmund Merkel- (1845-1919) German anatomist and histologist, the name "Merckel cell" was based upon his first full description of touch cells (Tastzellen) and named by Robert Bonnet (1851–1921). Referred to these cells as Tastzellen or "touch cells" but this proposed function has been controversial as it has been hard to prove.
  • Filippo Pacini - (1812-1883) Italian anatomist, published in 1840, and the name "Pacini's corpuscles" was proposed in 1844 by Henle and also by Kölliker.
  • Angelo Ruffini (1864-1929) Italian histologist and embryologist, the name "Ruffini corpuscles" was based upon his first description of skin mechanoreceptors.

Touch Receptors

Dermatomes the surface map of segmental spinal nerve innervation of the skin surface.

Touch receptors in mammalian skin cartoon.jpg

Touch receptors in mammalian skin and the neural encoding of reception.[1]

Touch Pathway

Pacinian Corpuscle

These receptors are lamellar vibration receptors that produce rapidly adapting responses. They are located in the subcutaneous tissue, deeper in interosseous membranes, and also mesenteries of the gut. The inner core cells form from Schwann cells extending from the nerve terminal.

A recent study in developing human digits,[3] show appearance at 11 weeks (13 weeks GA), and completed at 4 months of life. Both basic structure and immunohistochemical characteristics were reached at 36 weeks GA. The Schwann cell processes progressively compact to form the inner core, while the surrounding mesenchyme is organised to form the outer core component and the capsule.


Pacinian corpuscle histology 01.jpg

Meissner's Corpuscle

Meissner's corpuscles are mechanoreceptors located in glabrous skin within the dermal papillae for sensitivity to light touch. They are rapidly adaptive elongated receptors consisting of a connective tissue capsule containing several lamellae of Schwann cells enclosing one or more afferent nerve fibres. The sensory corpuscle is a stack of discoid components of flattened axon terminals sandwiched between Schwann cell lamellae covered with a connective tissue capsule linked to the basal aspect of the epidermis by dermal collagen fibers.[12]

A recent study in developing human digits,[3] show appearance at 20 weeks (22 weeks GA and complete their typical morphology and immunohistochemical profile at 8 months of life.

Meissner's corpuscle

Meissner corpuscle 01.jpg

Meissner's corpuscles are located throughout the skin and are seen concentrated in regions of high touch (finger tips, lips, genital regions). There is evidence that these receptors are concentrated in the fingertips of primates and may be associated with the evolution of manipulative abilities of the hands.[13]

Structure

Coiled spring-like structures, composed of stacked, disk-like lamellar cells with lamellae orientation usually parallel to the skin surface.

  • lamellar cells - Schwann cell-derived with peripherally displaced nuclei in a fibroblastic capsule incomplete at the apex.
  • sensory neurites - course through the lamellae, not visible by (Stain - Haematoxylin Eosin).


Merkel Cell

Merkel cells develop from epidermal progenitor population differentiation in the embryo, and also during their replacement postnatally.[14] They form a long-lived cell population within the skin with both a sensory and a neuroendocrine functions.


Merkel cells occur in many species including reptiles, fish, and mammals. Merkel cell complexes mediate slowly adapting type I (SAI) responses, which are characterized by an irregular firing pattern during sustained pressure. Merkel cells arise in the embryo[8] and in the adult[7] from an epidermal progenitor cell population.[15] These cells express the transcription factor Atoh1 and when differentiated are post-mitotic. Merkel cells can be organised into specialised clustered structure known as a "touch dome" associated with primary hair follicles.

Integumentary touch dome model 01.jpg

A molecular signalling cascade from Wnt, Eda, and Shh is required for touch dome Merkel cell development.[6] Keratin 8 (K8) and Keratin 18 (K18) are Merkel cell markers identified in late fetal and adult skin.

The Notch signaling pathway has been shown to antagonize Atoh1 expression that is required for Merkel cell development in the skin. [2]


Merkel cell EM 01.jpg

Isolated Merkel cell (em)

Merkel cell (Merkel-Ranvier cell) integumentary (skin) receptor cell connected with somatosensory afferents.

Cell characteristics a polylobulated nucleus and numerous typical dense-core granules in a clear cytoplasm.

The name "Merckel cell" was based upon Friedrich Sigmund Merkel (1845 – 1919) a German anatomist and histologist, first description of these touch cells (Tastzellen) and named in his honour by Robert Bonnet (1851–1921).

Scale bar 5 µm (Stain - Osmium)

Integumentary touch dome functions.jpg

Integumentary touch dome suggested functions[16]

The Merkel cell is also a part of the touch dome (TD) apparatus, an innervated structure composed of specialised keratinocytes, and may have additional neuroendocrine and immune roles, as they associate with Langerhans cells (dendritic antigen presenting cells) in the epidermis.[16]


In the adult, abnormalities in Merkel cell development can lead to the rare disease of Merkel cell carcinoma (MCC) associated with sun (UV) exposure.

Sensory Modalities

Thermoreceptors

  • Receptors for heat (warmth) and cold (chill) detection.
    • heat - C-fibres
    • cold - Aδ fibres

Nociceptors

  • Receptors for encoding and processing noxious stimuli.
    • A-δ nociceptors
    • Polymodal C-nociceptors
    • C- mechano-insensitive nociceptors

Abnormalities

  • Merkel cell carcinoma (MCC) PMID 12007193


Historic

The fine structure of Meissner's touch corpuscles of human fingers.[17]

"The principal part of Meissner's corpuscle is made up of flattened laminar cells stretching across the corpuscle in irregular layers. The perinuclear cytoplasm of these cells contains numerous small mitochondria, a sparse granular endoplasmic reticulum, and a large number of small vesicles. Nerve fibers enter the side or base of the corpuscle, lose their myelin sheaths, and follow a meandering course between the laminar cell plates. The nerve endings enter into a close appositional relationship with the flattened portions of the laminar cells. In some areas the apposed axolemma and cell membranes are slightly thickened with small vesicles located along the cell membrane or on both surfaces. These regions are interpreted as synapses. The most prominent feature of the nerve endings is an extraordinary accumulation of small mitochondria which vary in size and internal density. The nerve endings also contain vacuoles, groups of dense concentric membranes, and small dense vesicles of irregular distribution. The laminar cells are separated from one another by a dense intercellular substance of uniform thickness which also envelops the entire corpuscle. This material contains randomly oriented collagen fibers and fine fibrils bound together by a dense material at nodal points recurring at regular intervals of approximately 120 mmicro. These findings are discussed in relation to the problems of the function of Meissner's corpuscle, neural material loss and replacement, and the presence of synapses."

References

  1. 1.0 1.1 Lumpkin EA, Marshall KL & Nelson AM. (2010). The cell biology of touch. J. Cell Biol. , 191, 237-48. PMID: 20956378 DOI.
  2. 2.0 2.1 Logan GJ, Wright MC, Kubicki AC & Maricich SM. (2018). Notch pathway signaling in the skin antagonizes Merkel cell development. Dev. Biol. , 434, 207-214. PMID: 29241683 DOI.
  3. 3.0 3.1 3.2 Feito J, García-Suárez O, García-Piqueras J, García-Mesa Y, Pérez-Sánchez A, Suazo I, Cabo R, Suárez-Quintanilla J, Cobo J & Vega JA. (2018). The development of human digital Meissner's and Pacinian corpuscles. Ann. Anat. , 219, 8-24. PMID: 29842990 DOI.
  4. Kobayashi K, Cho KH, Yamamoto M, Mitomo K, Murakami G, Abe H & Abe S. (2018). Tree of Vater-Pacinian corpuscles in the human finger and thumb: a comparison between the late fetal stage and old age. Surg Radiol Anat , 40, 243-257. PMID: 28653179 DOI.
  5. Chen YC, Lewis TL, Shore DI, Spence C & Maurer D. (2018). Developmental changes in the perception of visuotactile simultaneity. J Exp Child Psychol , 173, 304-317. PMID: 29783043 DOI.
  6. 6.0 6.1 Xiao Y, Thoresen DT, Miao L, Williams JS, Wang C, Atit RP, Wong SY & Brownell I. (2016). A Cascade of Wnt, Eda, and Shh Signaling Is Essential for Touch Dome Merkel Cell Development. PLoS Genet. , 12, e1006150. PMID: 27414798 DOI.
  7. 7.0 7.1 Wright MC, Reed-Geaghan EG, Bolock AM, Fujiyama T, Hoshino M & Maricich SM. (2015). Unipotent, Atoh1+ progenitors maintain the Merkel cell population in embryonic and adult mice. J. Cell Biol. , 208, 367-79. PMID: 25624394 DOI.
  8. 8.0 8.1 Perdigoto CN, Bardot ES, Valdes VJ, Santoriello FJ & Ezhkova E. (2014). Embryonic maturation of epidermal Merkel cells is controlled by a redundant transcription factor network. Development , 141, 4690-6. PMID: 25468937 DOI.
  9. Ackerley R, Olausson H, Wessberg J & McGlone F. (2012). Wetness perception across body sites. Neurosci. Lett. , 522, 73-7. PMID: 22710006 DOI.
  10. Fabrizi L, Slater R, Worley A, Meek J, Boyd S, Olhede S & Fitzgerald M. (2011). A shift in sensory processing that enables the developing human brain to discriminate touch from pain. Curr. Biol. , 21, 1552-8. PMID: 21906948 DOI.
  11. Woo SH, Stumpfova M, Jensen UB, Lumpkin EA & Owens DM. (2010). Identification of epidermal progenitors for the Merkel cell lineage. Development , 137, 3965-71. PMID: 21041368 DOI.
  12. Takahashi-Iwanaga H & Shimoda H. (2003). The three-dimensional microanatomy of Meissner corpuscles in monkey palmar skin. J. Neurocytol. , 32, 363-71. PMID: 14724379 DOI.
  13. Verendeev A, Thomas C, McFarlin SC, Hopkins WD, Phillips KA & Sherwood CC. (2015). Comparative analysis of Meissner's corpuscles in the fingertips of primates. J. Anat. , 227, 72-80. PMID: 26053332 DOI.
  14. Van Keymeulen A, Mascre G, Youseff KK, Harel I, Michaux C, De Geest N, Szpalski C, Achouri Y, Bloch W, Hassan BA & Blanpain C. (2009). Epidermal progenitors give rise to Merkel cells during embryonic development and adult homeostasis. J. Cell Biol. , 187, 91-100. PMID: 19786578 DOI.
  15. Morrison KM, Miesegaes GR, Lumpkin EA & Maricich SM. (2009). Mammalian Merkel cells are descended from the epidermal lineage. Dev. Biol. , 336, 76-83. PMID: 19782676 DOI.
  16. 16.0 16.1 Xiao Y, Williams JS & Brownell I. (2014). Merkel cells and touch domes: more than mechanosensory functions?. Exp. Dermatol. , 23, 692-5. PMID: 24862916 DOI.
  17. CAUNA N & ROSS LL. (1960). The fine structure of Meissner's touch corpuscles of human fingers. J Biophys Biochem Cytol , 8, 467-82. PMID: 13691669


Reviews

Piccinin MA & Schwartz J. (2018). Histology, Meissner Corpuscle. , , . PMID: 30085522

Lai HC, Seal RP & Johnson JE. (2016). Making sense out of spinal cord somatosensory development. Development , 143, 3434-3448. PMID: 27702783 DOI.

Verriotis M, Chang P, Fitzgerald M & Fabrizi L. (2016). The development of the nociceptive brain. Neuroscience , 338, 207-219. PMID: 27457037 DOI.

Woo SH, Lumpkin EA & Patapoutian A. (2015). Merkel cells and neurons keep in touch. Trends Cell Biol. , 25, 74-81. PMID: 25480024 DOI.

Zimmerman A, Bai L & Ginty DD. (2014). The gentle touch receptors of mammalian skin. Science , 346, 950-4. PMID: 25414303 DOI.

Jeffry J, Kim S & Chen ZF. (2011). Itch signaling in the nervous system. Physiology (Bethesda) , 26, 286-92. PMID: 21841076 DOI.

Lumpkin EA, Marshall KL & Nelson AM. (2010). The cell biology of touch. J. Cell Biol. , 191, 237-48. PMID: 20956378 DOI.

CAUNA N & ROSS LL. (1960). The fine structure of Meissner's touch corpuscles of human fingers. J Biophys Biochem Cytol , 8, 467-82. PMID: 13691669

Articles

Ranade SS, Woo SH, Dubin AE, Moshourab RA, Wetzel C, Petrus M, Mathur J, Bégay V, Coste B, Mainquist J, Wilson AJ, Francisco AG, Reddy K, Qiu Z, Wood JN, Lewin GR & Patapoutian A. (2014). Piezo2 is the major transducer of mechanical forces for touch sensation in mice. Nature , 516, 121-5. PMID: 25471886 DOI.

Books

Neurobiology of Sensation and Reward. Gottfried JA, editor. Boca Raton (FL): CRC Press; 2011. Chapter 7 - Touch PMID 22593916

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Search Pubmed: Touch Development | touch receptors |

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Terms

Touch Terms  
  • free nerve endings- abundantly innervate the epidermis, include nociceptors and low-threshold C-fibers.
  • glabrous - smooth hairless skin for example the fingertips, palms, and soles.
  • lanceolate endings - rapidly adapting or down hair afferents sensitive light-touch receptors that depend on Neurotrophin-4 for proper development.
  • Meissner’s corpuscles - glabrous skin mechanoreceptor lie between the dermal papillae for sensitivity to light touch. They are rapidly adaptive elongated receptors formed by a connective tissue capsule that formed by several lamellae of Schwann cells enclosing one or more afferent nerve fibres.
  • Merkel cells - (Merkel's disks, Merkel cell–neuron complexes) mediate slowly adapting type I (SAI) responses, which are characterized by an irregular firing pattern during sustained pressure.
  • Pacinian corpuscles- lamellar vibration receptors that produce rapidly adapting responses.
  • Ruffini endings - proposed to mediate stretch-sensitive slowly adapting type II (SAII) responses, unknown developmental pathbwayreceptors.
  • somatosensory - neural sensation associated with pressure (touch), pain, or temperature.
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Cite this page: Hill, M.A. (2024, March 29) Embryology Sensory - Touch Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Sensory_-_Touch_Development

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