Lecture - Integumentary Development: Difference between revisions

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Possibly the first epithelial tissue specialization from which arose other epithelial specializations now located inside the body. The external skin associated structures have many different roles and functions. This system is also an excellent model for distribution or "pattern" and adult stem cells.
Possibly the first epithelial tissue specialization from which arose other epithelial specializations now located inside the body. The external skin associated structures have many different roles and functions. This system is also an excellent model for distribution or "pattern" and adult stem cells.
[[Media:ANAT2341_2017_Lecture_16_-_Integumentary_System_.pdf|'''Integumentary Lecture PDF''']]
<center></center>
Shown below on this page is for only background information for this topic.


==Textbooks==
==Textbooks==
===Embryology===
{| class="wikitable mw-collapsible mw-collapsed"
{| border='0px'
! colspan=2|References &nbsp;
|-
|-
| [[File:Logo.png|80px]]
| width=100px|{{Embryo logocitation}}
| Hill, M.A. (2012) <i>UNSW Embryology</i> (12<sup>th</sup> ed.). Sydney:UNSW.
| {{Integumentary Links}}
{{Integumentary Links}} | [[2010_Lecture_22|2010 Lecture]]
|}


 
[[Media:2015ANAT2341_Lecture_14_-_Beverdam-Integumentary Development.pdf|2015 Integumentary Lecture Slides PDF]] | [[Media:ANAT2341_Lecture_4_-_Beverdam_-_Integumentary_System.pdf|2014 PDF]] | [[2010_Lecture_22|2010 Lecture]]
===The Developing Human: Clinically Oriented Embryology===
|-
{|
| [[File:The Developing Human, 10th edn.jpg|90px]]
| {{MPT2015APAcitation}} (links available to UNSW students)
*  [http://ebookcentral.proquest.com.wwwproxy1.library.unsw.edu.au/lib/unsw/reader.action?docID=2074364&ppg=578 Integumentary System]
|-
|-
| [[File:The Developing Human, 9th edn.jpg|90px]]
| [[File:Larsen's human embryology 5th ed.jpg|90px]]
| '''Citation:''' The Developing Human: clinically oriented embryology 9<sup>th</sup> ed. Keith L. Moore, T.V.N. Persaud, Mark G. Torchia. Philadelphia, PA: Saunders, 2011. (links available to UNSW students)
| {{SBBF2015APAcitation}}
* [http://er.library.unsw.edu.au/er/cgi-bin/eraccess.cgi?url=http://www.mdconsult.com/books/page.do?eid=4-u1.0-B978-1-4377-2002-0..00019-9&isbn=978-1-4377-2002-0&uniqId=330028653-2#4-u1.0-B978-1-4377-2002-0..00019-9 Chapter 19 – Integumentary System]
The following chapter links only work with a  UNSW Library connection.
 
* [http://ebookcentral.proquest.com.wwwproxy1.library.unsw.edu.au/lib/unsw/reader.action?docID=2074524&ppg=173 Development of the Skin and Its Derivatives]
|}
 
===Larsen's Human Embryology===
{| border='0px'
|-
|-
| [[File:Larsen's human embryology 4th edn.jpg|90px]]
| '''Links:''' [[Embryology Textbooks]]
| '''Citation:''' Larsen's human embryology 4th ed. Schoenwolf, Gary C; Larsen, William J, (William James). Philadelphia, PA : Elsevier/Churchill Livingstone, c2009. (links available to UNSW students)
* [http://er.library.unsw.edu.au/er/cgi-bin/eraccess.cgi?url=http://www.mdconsult.com/books/linkTo?type=bookPage&isbn=978-0-443-06811-9&eid=4-u1.0-B978-0-443-06811-9..10007-7 Chapter 7 - Development of the Skin and Its Derivatives]
|}
|}
:'''Links:''' [[Embryology Textbooks]]


== Objectives ==
== Objectives ==
Line 48: Line 50:
Skin structure cartoon
Skin structure cartoon
|}
|}
==Skin Origins==
[[File:Stage 13 image 078.jpg|thumb|Embryo epidermis (Stage 13)]]
[[File:Human-_Stage_22_integument_02.jpg|thumb|300px|Human Embryo (Week 8, [[Carnegie_stage_22|Stage 22]]) Integument]]
Skin is our largest organ, providing a protective layer between us and our environment
* '''Ectoderm''' forms the surface epidermis and the associated glands.
* '''Mesoderm''' forms the underlying connective tissue of dermis and hypodermis.
* '''Neural crest''' cells also migrate into the forming epidermis and the skin is also populated by specialized sensory endings.
* epithelia/mesenchyme (ectoderm/mesoderm) interaction an inductive manner (see lecture on kidney)
* 2 main types of histological skin - thin (most of body) thick (soles of feet and hands) based on ectoderm, not the thickest skin including dermis (top of back)
===Regional Specializations===
* skin has different structures associated with different regions of the body
* nails, hail, glands, teeth, eyelashes, eyebrow
== Development Overview ==
[[File:Stage 22 image 208.jpg|thumb|Human embryo cornea and eyelid (Stage 22, week 8)]]
'''4 weeks'''
* simple ectoderm epithelium over mesenchyme.
'''1-3 months'''
* ectoderm - germinative (basal) cell repeated division of generates stratified epithelium.
* mesoderm - somite dermatome spreads out under the epithelium, differentiates into connective tissue and blood vessels.
'''4 months'''
* basal cell - proliferation generates folds in basement membrane.
* neural crest cells - (melanocytes) migrate into epithelium. These are the pigment cell of the skin.
* embryonic connective tissue- differentiates into dermis, a loose connective tissue (ct) layer over a dense ct layer. Beneath the dense ct layer is another loose ct layer that will form the subcutaneous layer.
* Ectoderm contributes to nails, hair follicles and glands.
* Nails form as thickening of ectoderm epidermis at the tips of fingers and toes. These form germinative cells of nail field.
* Cords of these cells extend into mesoderm forming epithelial columns. These form hair follocles, sebaceous and sweat glands.
'''5 months'''
* Hair growth initiated at base of cord, lateral outgrowths form associated sebaceous glands.
* Other cords elongate and coil to form sweat glands.
* Cords in mammary region branch as they elongate to form mammary glands. These glands will complete development in females at puberty. Functional maturity only occurs in late pregnancy.
[[File:Fetal_integumentary_histology_01.jpg]]
'''Fetal human integumentary histology'''<ref name="PMID19701759"><pubmed>19701759</pubmed>| [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2799629 PMC2799629] | [http://www.springerlink.com/content/lv415257322x8247/fulltext.html Arch Dermatol Res]</ref> (Weeks in figure are from LMP)
==Epidermis==
Electron Micrographs of the Developing Human Epidermis<ref><pubmed>2413039</pubmed>| [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2113922 PMC2113922]</ref>
{|
| [[File:Human embryo skin 8-9 week EGA.jpg|300px]]
8-9 week EGA
| [[File:Human embryo skin 9-11 week EGA.jpg|300px]]
9-11 week EGA
| [[File:Human embryo skin 24 week EGA.jpg|250px]]
24 week EGA
|}
[[File:Adult epidermis histology 01.jpg|thumb|Adult epidermis histology]]
* '''week 4-5''' - early skin is a single ectodermal layer, stratum germinativum basal layer. (periderm cells are replaced continuously until 21 weeks)
* '''week 11''' - forms intermediate layer.
* '''week 19-21''' - periderm then lost replaced by stratum corneum, keratinization and disqualification.
* week 10 epidermial ridges are formed by proliferation.
[[File:Human_embryo_skin_8-9_week_EGA_desmosomes.jpg|300px]]
Human embryo skin desmosomes (8-9 week GA)
==Neural crest cells==
[[File:Melanoblast migration.png|thumb|Melanoblast migration]]
* Neural crest cells migrate into skin (late embryonic) form melanoblasts
* day 40-50 differentiate into then melanocytes - form pigment granules
* different content of melanin (Greek, ''melas'' = "black") accounts for differet skin colour
Melanoblast Migration - [[Quicktime_Movie_-_Mouse_Melanoblast_Migration|Quicktime]] | [[Movie_-_Mouse_Melanoblast_Migration|Flash]]
==Dermis==
[[File:Fingerprint.jpg|thumb|Dermal pattern fingerprint]]
* lateral plate mesodermal in origin
* forms connective tissue
* afferent nerves influence dermal ridge formation
==Blood Vessels==
* lateral plate mesodermal in origin
* week 5 - blood vessels form in mesenchyme
* form capillary beds, extensive remodelling with development
==Skin Dermatomes==
[[File:Dermatomes.png|thumb|Dermatomes]]
* pattern of skin innervation
* area supplied by single spinal nerve
* motor and sensory DRG
* cutaneous nerve area
==Keratin==
* large family of intermediate filament protein, 17+ isoforms
* skin disease associated with mutations in keratin genes
==Cornification==
A form of '''cell death''' that occurs in the adult skin epithelium and occurs in the upper layers (granular layer and stratum corneum). Cornified envelope is the formation or ‘keratinization’ is specific of the skin to create a barrier function, exclusive to the upper layers (granular layer and stratum corneum).
* Elimination of cytosolic organelles
* Modifications of plasma membrane
* Accumulation of lipids in keratohyalin granules in stratum granulosum
* Extrusion of lipids in the extracellular space
* Desquamation (loss of corneocytes) by protease activation
:'''Links:''' [http://php.med.unsw.edu.au/cellbiology/index.php?title=Cell_Death_1 Cell Biology - Cell Death]
== Development of Glands ==
[[File:Newborn - vernix caseosa.jpg|thumb|Newborn - vernix caseosa]]
* 2 main types - sebaceous and sweat
* both ectodermal in origin
* form as ingrowth of ectoderm into the mesoderm
===Sebaceous===
* associated with hair development
** except plans penis and labia minora
* these glands secrete vernix
===Sweat Glands===
* mostly eccrine some apocrine
* apocrine in axilla, pubic and nipple regions
** see also mammary gland development
===Vernix Caseosa===
* (Latin,  ''vernix caseosa'' = varnish , cheese-like) (Dunglison Dictionary of Medical Sciences, 1846)
* covers fetal skin - secretion from '''sebaceous glands'''
** consists of water (81%), lipid (9%), and proteins (10%)
* possibly unique to human development
* protects skin from extraembryonic fluids amnion, urine
* slippery and helps with parturition
* transition from intrauterine to neonatal extra-uterine life
* suggested to have many different roles
==Mammary Glands==
[[File:Bailey356.jpg|Fetal mammary gland (16 cm CRL)]]
[[File:Mammary anatomy.jpg|thumb|Mammary anatomy]]
* week 6 epidermis downgrowth into dermis, '''modified sweat glands'''
** epithelia/mesenchyme inductive interaction, mesenchyme forms connective tissue and fat
* mammary ridges - mammary bud formation, pair of ventral regions axilla to inguinal
** pectoral regions generate breasts
* buds branch to form lactiferous ducts, only main duct formed at birth
* mammary pit - forms fetal period
* areola - depressed region at gland, proliferation of connective tissue postnatally
* prior to puberty male and female glands the same
===Puberty===
* sex hormone estrogen stimulate growth, full development approx 20 years
* growth also influenced by other hormones - progereterone, prolactin, corticoids, growth hormone
* mainly fat and connective tissue deposition
===Pregnancy===
* raised estrogens and progesterone stimulate gland development
* hemispherical shape due to fat deposition
* lactation supports development
===Breast cancer===
* In 1994, two breast cancer susceptibility genes were identified: BRCA1 on chromosome 17 BRCA2 on chromosome 13
* When an individual carries a mutation in either BRCA1 or BRCA2, they are at an increased risk of being diagnosed with breast or ovarian cancer at some point in their lives. Normal function of these genes was to participate in repairing radiation-induced breaks in double-stranded DNA. It is though that mutations in BRCA1 or BRCA2 might disable this mechanism, leading to more errors in DNA replication and ultimately to cancerous growth.
Breast Cancer Detection - reduce mortality is through early detection (general screening of the population for BRCA1 and BRCA2 is not yet recommended). New strategies to find anti-cancer drugs are constantly being developed. The latest, called 'synthetic lethal screening' looks for new drug targets in organisms such as yeast and fruit flies. In the same way that studies in yeast recently helped to identify the functions of BRCA1 and BRCA2, it is thought that drugs that work in more primative organisms will also be applicable to humans.
:'''Links:''' [[Integumentary_System_-_Mammary_Gland_Development|Mammary Gland Development]]
== Hair Development ==
[[File:Hair development stages.png|thumb|Hair development stages]]
Hair formation, or follicle development, is an example of two distinct developmental processes: epithelio-mesenchymal interactions and pattern formation. The differentiated hair follicle will eventually contain 20 or more different cell types. Melanocytes, which provide the hair colour, have a neural crest origin, and with ageing their numbers decline leading to whitening (grey) of the hair process.
Hair follicle development in humans begins as an epithelial-mesenchymal interaction at week 9 - 12. This initial lanugo hair is replaced in the late fetal or early neonate by vellus and terminal hairs. A second round of development occurs during puberty under the influence of steroidal hormones (More? Puberty).
* Before birth we have embryonic hair that has an imporant role in binding the skins waxy protective coating against our watery environment.
* After birth we have early postnatal hair that is gradually replaced by the mature form.
* At puberty we have a second round of hair formation under endocrine regulation by sex hormones.
* The hair follicle is also a site for stem cells, allowing replacement of the follicle.
===Hair Follicle===
[[File:Hair follicle cell development.png|thumb|Hair follicle cell development]]
* follicle forms in stratum germinativum of epidermis
* '''hair bud''' then hair bulb forms hair
* mesenchyme forms hair papilla
* germinal matrix cells become keratinized to form hair shaft
* week 12 - lanugo hair (Latin, ''lana'' = wool) - first hair formed replaced postnatally, role in binding vernix to skin
* arrector pili muscle - develop in mesenchyme and form the muscles that move hair.
* hair colour - melanocytes (neural crest) produce melanin which influences hair colour.
* Puberty - coarse hair in pubis and axilla in both male and female (in males also on face and other body regions chest, etc)
===Fetal Hair===
* Month 5 - hair appears on the head and beginning of vernix caseosa deposition.
* Month 6 - body is covered by fine hairs (lanugo) and the deposit of vernix caseosa is considerable. Skin papilla are developed and the free border of the nail projects from the corium of the dermis.
* Month 8 - skin now completely coated with vernix caseosa, and the lanugo begins to disappear. Skin is also pink in colour and subcutaneous fat being deposited (hypodermis layer).
* Month 9 - lanugo has largely disappeared from the trunk.
=== Lanugo Hair ===
* From about the third month lanugo hair (Latin, ''lana'' = wool) hiar is initially formed and it has a role in binding vernix to skin.
* Hair grows over the entire body at the same rate, so the hairs are the same length, and is shed abut 4 weeks before birth. Premature infants can still be covered with these hairs.
=== Neonatal Hair ===
[[File:Neonate hair.jpg|thumb|Neonate hair]]
Newborn infants have two types of hair:
* '''Vellus Hairs''' - short hairs, only a centimetre or two long, and contain little or no pigment, follicles that produce them do not have sebaceous glands and never produce any other kind of hairs
* '''Terminal Hairs''' - long hairs that grow on the head and in many people on the body, arms and legs, produced by follicles with sebaceous glands, the hairs in these follicles gradually become thinner and shorter until they look like vellus hairs
=== Hair Follicle Phases ===
There are several phases of hair follicle growth.
* '''Anagen Phase''' - active phase
* '''Catagen Phase''' - apoptosis-driven involution, end of active growing phase of the life cycle of the hair, between growing phase (anagen) and resting stage (telogen).
* '''Telogen Phase''' - hair follicle resting phase of hair growth cycle.
=== Puberty Hair Development ===
The appearance of pubic hair occurs along with ther secondary sexual characteristics (also Tanner staged) and is under endocrine control.
* Estrogens- (1 beta-estradiol, E2) involved in skin physiology and are potent hair growth modulators.
* Testosterone- Face, trunk and extremities increases hair follicle anagen phase (active) and increases also hair growth rate, thickness, medullation and pigmentation. Effects due to high hormone levels and target organ conversion to 5 alpha-dihydrotestosterone. Pubic hair develops even in absence of 5 alpha-reductase effect.
{| class="prettytable"
| &nbsp;&nbsp;'''Tanner Stage'''
| &nbsp;&nbsp;'''Pubic Hair Development'''
|-
| &nbsp;&nbsp;1
| &nbsp;&nbsp;None
|-
| &nbsp;&nbsp;2
| &nbsp;&nbsp;Few darker hairs along labia or at base of penis
|-
| &nbsp;&nbsp;3
| &nbsp;&nbsp;Curly pigmented hairs across pubes
|-
| &nbsp;&nbsp;4
| &nbsp;&nbsp;Small adult configuration
|-
| &nbsp;&nbsp;5
| &nbsp;&nbsp;Adult configuration with spread onto inner thighs
|-
| &nbsp;&nbsp;6
| &nbsp;&nbsp;Adult configuration with spread to linea alba
|}
Table based upon the  [http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=endocrin&part=A972&rendertype=box&id=A1059 Tanner stages] of secondary sexual development.<ref>Tanner JM. '''Growth at Adolescence.''' 2nd ed. Oxford: Blackwell Scientific, 1962.</ref>
:'''Links:''' [[Integumentary_System_-_Hair_Development|Hair Development]]
== Nail Development ==
[[File:Neonatal_nail.jpg|thumb|Neonatal nail]]
* Forelimb before hindlimb - week 10 fingernails, week 14 toe nails
* nail field - appears at tip and migrates to dorsal surface
* thickened epidermis -  surrounding cells form nail fold
* keratinization of proximal nail fold forms nail plate
Nails reach Digit Tip
* week 32 fingernails
* week 36 toenails
** nail growth indicator of prematurity
Nail Terms
* nail plate - visible part of the nail
* nail bed - skin beneath the nail plate
* cuticle -  tissue that overlaps the plate and rims the base of the nail
* nail folds -  skin folds that frame and support the nail on three sides
* lunula -  half-moon at the base of the nail
* matrix - hidden part of the nail unit under the cuticle
:'''Links:''' [[Integumentary_System_-_Nail_Development|Nail Development]] | [http://www.med.unc.edu/embryo_images/unit-mslimb/mslimb_htms/mslimb026.htm Embryo Images - Human (day 64) primary nail fields]
==Teeth==
[[File:Fetal_head_lateral.jpg|thumb|Fetal Head (12 weeks) lateral]]
[[File:Deciduous teeth.jpg|thumb|Deciduous teeth]]
[[File:Permanent teeth.jpg|thumb|Permanent teeth]]
[[File:Bailey252.jpg|400px]]
Section of developing tooth from a 3 months human fetus
* integumentary system specialization by epitheilal/mesenchymal interactions in development and develops with a major contribution from the neural crest.
** ectoderm of the first pharyngeal arch and neural crest, ectomesenchymal cells.
* week 6 - odontogenesis begins, tooth bud
* 4 morphological stages describing the early tooth development: bud, cap, bell, and terminal differentiation
* 2 sets of teeth: 20 deciduous teeth, 32 permanent teeth
* differential rates of growth, shed at different times over 20 year period
* ectoderm, mesoderm and neural crest mesenchyme contribute
* inductive influence of neural crest with overlying ectoderm
* tooth growth occurs in ossifying jaws 
'''odontoblasts'''
* neural crest-derived mesenchymal cells which differentiate under the influence of the enamel epithelium. Cells secrete predentin, calcifies to form dentin.
'''ameloblasts'''
* inner enamel epithelium forms pre-ameloblasts differentiate and produce enamel
'''periodontal ligament'''
* tooth is not anchored directly onto its bony socket (alveolar bone) but held in place by the periodontal ligament (PDL), a specialized connective tissue structure that surrounds the tooth root coating of cementum.
* ligament also act as; a shock absorber, transmitter of chewing forces (from tooth to bone), sensory information (heat, cold, pressure and pain).
** collagen fiber bundles within the ligament are called "Sharpey's fibres".
=== Teeth Postnatal ===
Deciduous teeth
* '''6 - 24 months''' - erupt from gums by pushing toward surface
* '''2 years''' - all deciduous teeth present
Permanent teeth
* 6 years until early adult
* tooth bud lie in gums beneath deciduous teeth
* osteoclasts resorb deciduous teeth roots
* growth affects face shape
:'''Links:''' [[Integumentary_System_-_Tooth_Development|Tooth Development]]
==Molecular==
* Role of homeobox genes in the patterning, specification, and differentiation of ectodermal appendages in mammals. Duverger O, Morasso MI. J Cell Physiol. 2008 Aug;216(2):337-46. Review. [http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=18459147 PMCID: 18459147] | [http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2561923&rendertype=figure&id=F1 Figure 1 Key steps in the development of three major ectodermal appendages]
== Abnormalities ==
The list below represents only a selection of associated abnormalities.
===Skin===
*  '''Ehlers-Danlos Syndrome''' - (EDS I and EDS II)  loose-jointedness and fragile, bruisable skin that heals with peculiar scars. The syndrome is caused by mutation in the collagen gene. Infants are born prematurely due to premature rupture of fetal membranes.
* '''Epidermolysis Bullosa Simplex''' - autosomal dominant disease of keratin, generating skin fagility and non-scarring blisters of the skin caused by little or no trauma. Four clinical subtypes: 1. EBS - Weber-Cockayne - mild blistering of the hands and feet 2. EBS - Koebner, 3. EBS - mottled pigmentation, 4. EBS - Dowling-Meara - generalized blistering which can be fatal.
* '''Autosomal Recessive Congenital Ichthyosis''' - an excessive keratinization disorder.
* '''Cutis Aplasia''' - congenital absence of the skin, particularly on the scalp, larger defects may extend to the dura or meninges. Generally isolated lesions, but can also be associated with a variety of other genetic disorders. Heals as a flat scar or keloid lump.
* '''Incontinentia Pigmenti''' - X-linked dominant disorder with most but not all cases affecting females. The skin changes follow characteristic four stages. In the neonatal period the first stage is noted with blisters often preceded or accompanied by erythema. These involve any part of the body but usually not the face. They do not cross the midline. These lesions are best seen in the second photograph in the groin and suprapubic region. The lesions follow a linear distribution in the limbs and circumferentially around the trunk. Crops of lesions may occur over a period of weeks to few months. During that stage, peripheral eosinophilia may be noted. The second stage follows and is characterised by hyperkeratosis or verrucous changes. At times the 2 stages occur simultaneously as noted in the first and third photograph. The third stage is that of hyperpigmentation typically appearing as streaks or whorls. It may be present throughout childhood. The fourth stage seen in teenage or adults is that of pale or atrophic streaks.
* '''Haemangiomas''' - relatively common (10% of infants), more common more common in preterm infants and girls. Initially present neonatally as a small "spot" or blanched vascular area which grows over the next 6 months before gradually involuting, usually over the next few years.
===Breast ===
* occurs in 1% of female population
* '''polymastia''' - extra breast
* '''polytheli''' - extra nipple, supernumerary nipple (relatively common in males)
===Hair===
* '''androgenetic alopecia''' - male- and female-pattern hair loss.
* '''telogen effluvium''' - alteration of the normal hair cycle, due to many different stress stimuli (severe stress, chemotherapy, childbirth, major surgery, severe chronic illness, rarely occurance in vaccination)
* '''alopecia areata''' - autoimmune disease, form antibodies against some hair follicles, distinct circular pattern of hair loss.
===Nail===
* '''Congenital hyponychia''' or '''anonychia''' - (hyponychium is the thickened epidermis beneath the free distal end of the digit) fingernails and toenails are absent without significant bone anomalies.
** '''Total anonychia congenita''' -  all absent, is a rare condition and may have an autosomal dominant inheritance patternis a rare condition, potentially autosomal dominant inheritance.
* '''Nail-patella syndrome''' - small, poorly developed nails and kneecaps, autosomal dominant inheritance.
* '''Ectodermal dysplasias''' - group of syndromes all deriving from abnormalities of the ectodermal structures.
* Brachydactylies
===Teeth===
* '''adontia''' - total lack of tooth development.
* '''amelogenesis imperfecta''' - abnormal tooth enamel formation (AMELX, ENAM, KLK4, MMP20).
* '''dentinogenesis imperfecta''' - discoloured teeth with an opalescent sheen, dentin does not support enamel (dentin sialophosphoprotein mutation)
* '''dens evaginatus''' - dental anomaly mainly affecting premolars in people of Mongolian origin.
* '''hypodontia''' - lack of development of one or more teeth.
* '''hypohidrotic ectodermal dysplasia''' - maldevelopment of one or more ectodermal-derived tissues.
* '''microdontia''' - small teeth.
==Links==
* Teeth -  [http://bite-it.helsinki.fi/ University of Helsinki - Gene Expression in Tooth] | [http://www.ada.org/public/topics/tooth.asp American Dental Association Overview - Tooth] |  [http://www.simplestepsdental.com/SS/ihtSS/r.WSIHW000/st.31843/t.31886/pr.3.html Columbia University Medical Centre - Illustrations: How a Tooth Decays] |  [http://www.merck.com/mmhe/sec08/ch114/ch114a.html Merck - Tooth disorders] | [http://kidshealth.org/parent/pregnancy_newborn/common/teething.html Nemours Foundation - Teething Tots]
* Neonatal Dermatology - [http://www.adhb.govt.nz/newborn/TeachingResources/Dermatology/Dermatology.htm NZ National Women's Health]
* Dermatology Image Atlas - [http://dermatlas.med.jhmi.edu/derm/ DermAtlas]
==References==
<references/>
* Before We Are Born (5th ed.) Moore and Persaud Chapter 21: P481-496
* Essentials of Human Embryology Larson Chapter 14: P303-315
* Color Atlas of Clinical Embryology Moore Persaud and Shiota Chapter 15: p231-236
* [http://www.nature.com/milestones/skinbio/index.html Nature - Milestones in Cutaneous Biology] "highlights groundbreaking advances in cutaneous biology over the past 100 years."
* [http://www.ijdb.ehu.es/04023contents.htm International Journal Developmental Biology 2004 - Skin Development special issue]


===Online Textbooks===
===Online Textbooks===
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* '''Blue Histology''' [http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Integumentary/Integum.htm Integumentary System]
* '''Blue Histology''' [http://www.lab.anhb.uwa.edu.au/mb140/CorePages/Integumentary/Integum.htm Integumentary System]


==Terms==
==External Links==
{{External Links}}


'''dermal papilla''' - the extensions of the dermis into the epidermis.
* Teeth - [http://bite-it.helsinki.fi/ University of Helsinki - Gene Expression in Tooth] | [http://www.ada.org/public/topics/tooth.asp American Dental Association Overview - Tooth] |  [http://www.simplestepsdental.com/SS/ihtSS/r.WSIHW000/st.31843/t.31886/pr.3.html Columbia University Medical Centre - Illustrations: How a Tooth Decays] |  [http://www.merck.com/mmhe/sec08/ch114/ch114a.html Merck - Tooth disorders] | [http://kidshealth.org/parent/pregnancy_newborn/common/teething.html Nemours Foundation - Teething Tots]


'''dermatoglyphic patterns''' - (Greek, ''derma'' = "skin", ''glyph'' = "carving") fingers, palms, toes, and soles skin patterns.
* Neonatal Dermatology - [http://www.adhb.govt.nz/newborn/TeachingResources/Dermatology/Dermatology.htm NZ National Women's Health]
* Dermatology Image Atlas - [http://dermatlas.med.jhmi.edu/derm/ DermAtlas]


'''epidermal growth factor receptor''' - expressed on cells in the epidermis basal layer, signaling stimulates both epidermal growth and wound healing and also mediates an inhibition of differentiation.
<pubmed>18459147</pubmed>| [http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=2561923&rendertype=figure&id=F1 Figure 1 Key steps in the development of three major ectodermal appendages]


'''rete ridge''' -  the extensions of the epidermis into the dermis. These epidermal surface thickenings extend downward between underlying connective tissue dermal papillae. This is also the site of initial eccrine gland differentiation.


==Terms==
{{Integumentary terms}}


[[Category:Science-Undergraduate]]
[[Category:Science-Undergraduate]]
[[Category:Integumentary]] [[Category:Hair]]
[[Category:Integumentary]] [[Category:Hair]]


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Revision as of 10:32, 11 September 2018

Introduction

Adult skin histology showing epidermis, dermis and hypodermis as well as specializations, such as hair follicles and sweat glands

The skin provides a barrier between ourselves and our environment (temperature, water, UV), and contains specializations in different regions including hair, nails, teeth, glands and sensory receptors. In other species there are also specializations of beaks, scales and feathers.

The two major tissue organizations of epithelial (ectoderm, epidermis) and mesenchyme (mesoderm connective tissue, dermis and hypodermis) are shown within skin. In addition, we have also have extensive populating by melanocytes (neural crest) and sensory nerve endings.

Possibly the first epithelial tissue specialization from which arose other epithelial specializations now located inside the body. The external skin associated structures have many different roles and functions. This system is also an excellent model for distribution or "pattern" and adult stem cells.


Integumentary Lecture PDF



Shown below on this page is for only background information for this topic.

Textbooks

References  
UNSW Embryology logo
Hill, M.A. (2020). UNSW Embryology (20th ed.) Retrieved March 28, 2024, from https://embryology.med.unsw.edu.au
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

2015 Integumentary Lecture Slides PDF | 2014 PDF | 2010 Lecture

The Developing Human, 10th edn.jpg Moore, K.L., Persaud, T.V.N. & Torchia, M.G. (2015). The developing human: clinically oriented embryology (10th ed.). Philadelphia: Saunders. (links available to UNSW students)
Larsen's human embryology 5th ed.jpg Schoenwolf, G.C., Bleyl, S.B., Brauer, P.R., Francis-West, P.H. & Philippa H. (2015). Larsen's human embryology (5th ed.). New York; Edinburgh: Churchill Livingstone.

The following chapter links only work with a UNSW Library connection.

Links: Embryology Textbooks

Objectives

  • Understand the embryonic origin and differentiation of the epidermis and dermis.
  • Understand the formation of hair and nails.
  • Understand the formation of sweat glands, mammary glands.
  • Understand the formation of teeth.
  • Brief understanding of associated abnormalities.
Skin structure cartoon.jpg

Skin structure cartoon

Online Textbooks

External Links

External Links Notice - The dynamic nature of the internet may mean that some of these listed links may no longer function. If the link no longer works search the web with the link text or name. Links to any external commercial sites are provided for information purposes only and should never be considered an endorsement. UNSW Embryology is provided as an educational resource with no clinical information or commercial affiliation.

<pubmed>18459147</pubmed>| Figure 1 Key steps in the development of three major ectodermal appendages


Terms

Integumentary Terms  
Integumentary Development
  • acrosyringium - coiled intra-epidermal region of the eccrine gland sweat duct.
  • apocrine gland - (sweat gland) proteinaceous secretion associated with hair (axilla, areola, genital and anal regions). Additional glands associated with eyelashes are called the glands of Moll (ciliary gland). (More? image - apocrine secretion)
  • arrector pili muscle - bundle of smooth muscle associated with hair follicle, inserts into the papillary layer of the dermis and attaches to the dermal sheath of the hair follicle. (More? image - arrector pili muscle)
  • Blaschko lines - (lines of Blaschko) may represent pathways of epidermal cell migration and proliferation during development. Specific type of lupus erythematosus shows this distinctive pattern. Named after Alfred Blaschko a German dermatologist who first described the feature in 1901. (More? PMID 21396561 | Historic Terminology)
  • bulb - the hair follicle enlargement located at its deepest end, dividing cells form the hair and the root sheath.
  • café-aut-lait macule - (French, cafe-au-lait = coffee with milk; birthmark) describes the characteristic colour of the skin hyperpigmented patch present at birth (congenital) or appearing in early infancy. Common single feature, multiple are associated with various genetic syndromes including Neurofibromatosis type 1 and 2.
  • corneocytes - terminally differentiated keratinocytes forming the stratum corneum.
  • cutis - alternative term for the epidermis and the dermis layers of the skin.
  • dermal papillae - interdigitation of the dermis with the epidermis.
  • dermatoglyphic patterns - (Greek, derma = "skin", glyph = "carving") fingers, palms, toes, and soles skin patterns.
  • dermis - connective tissue middle layer of the skin, consists of two sublayers (papillary and reticular layers) that do not have a clear boundary. Embryologically derived from the somite dermatome.
  • dermomyotome - Early embryonic dorsolateral half of the somite that will later divide to form both the dermatome and myotome. The dermatome will contribute the dermis and hypodermis of the skin. The myotome will contribute the skeletal muscle of muscoloskeletal system. Development sequence: mesoderm to paraxial mesoderm to somite to "dermomyotome" then dermatome and myotome. (More? Somitogenesis | Musculoskeletal System Development | Integumentary System Development)
  • eccrine gland (Greek, ekkrinein = "secrete"; merocrine glands) sweat glands unique to some primates and used in humans for thermoregulation. Adult body has 2 to 4 million sweat glands with concentrations (700/cm) on the palms of the hand, soles of the feet and forehead. Secretion is timulated by sympathetic nervous system, post-ganglionic cholinergic branch, and other stimuli
  • ephilis - (pl., ephilides; freckle) Clinical term describing a "freckle", that is a small brown or tan mark on the skin. These inherited features result from a copy of variant Melanocortin 1 Receptor (MC1R) gene and are common on fair skinned Celtic children. Melanocytes produce locally more melanin, this can also increase following exposure to ultraviolet radiation in sunlight. (More? Integumentary | Neural Crest | OMIM MC1R)
  • epidermis - Histological term describing the external cellular epithelial layer of the integumentary (skin) covering the entire body. This surface layer of keratinocytes is ectoderm in origin, while the underlying connective tissue layers of dermis and hypodermis are mesoderm in origin. (More? Integumentary Development)
  • epidermal differentiation complex - (EDC) human chromosome (1q2) containing linked 63 genes within four gene families that are molecular markers for stratified epidermis terminal differentiation.
  • epidermal growth factor receptor - expressed on cells in the epidermis basal layer, signaling stimulates both epidermal growth and wound healing and also mediates an inhibition of differentiation.
  • glabrous skin - skin without hair, refers to the palms of hands and soles of feet.
  • hair - (pili) in humans consists of vellus and terminal hairs.
  • holocrine - form of gland secretion where the secretory cells eventually lyse (rupture) and are lost. On the skin, these cells release sebum consisting mainly of lipid. (More? image - holocrine secretion)
  • hypodermis - (subcutis, subcutaneous adipose) a connective tissue ilower layer of the skin that binds it to underlying structures.
  • integumentary - term for the skin and its appendages.
  • involucrin - protein that binds loricrin in the development of the cell envelope protecting corneocytes in the skin.
  • keratinocyte - the main cell type forming the layers of the epidermis, derived from ectoderm.
  • keratohyalin granule - found in the stratum granulosum consist of profilaggrin and loricrin.
  • Langerhans cell - skin dendritic cell (antigen presenting cell) develops initially from fetal liver monocytes and yolk sac macrophages. May, depending on the immunological setting, elicit immunity or tolerance. Named after Paul Langerhans.
  • Langer's lines - (skin cleavage lines, cleavage lines) Clinical term for the orientation of reticular dermis collagen bundles causing tensions on skin and subcutaneous tissues. Lines tend to be horizontal in the trunk and neck, and longitudinal in the skin and limbs. (More? PMID 15791423)
  • Meissner corpuscle - sensory structure acting as a rapidly-adapting mechanoreceptor mainly in the dermal papillae of (digital) skin. (More?Touch
  • melanin - (Greek, melanos = black) The pigment produced by melanocytes that provides photoprotection, preventing cellular DNA damage, and colouring of the basal epithelial cells that absorb the pigment.
  • melanodermia - hyperpigmentation causing abnormal darkening (brown/black) of the skin due to excess melanin or by metallic substances. See also the abnormality ceruloderma (blue/grey). (More? PMID 23522626)
  • melanocyte - (Greek, melanos = black) A pigmented cell, neural crest in origin, differentiating from melanoblasts located in the skin and other tissues that produces melanin. The melanocytes within the integument (skin) transfer melanin to keratinocytes to give skin colour and to the hair follicle to give hair colour. Melanocytes are also located within "non-cutaneous" tissues in the eye (for eye colour), harderian gland and inner ear. This is the cell type that proliferates in the cancer melanoma. (More? Neural Crest Development | Integumentary System Development)
  • Merkel cell - An epidermal-derived cell in touch-sensitive area of the epidermis and mediate mechanotransduction in the skin. Previously thought to be neural crest in origin, but recently shown to arise from the embryonic epithelium. The cells are named after Friedrich Sigmund Merkel, a German anatomist who was the first to describe them in 1875. (More? Touch | Lecture - Integumentary Development | PMID 19786578 | PMID 3782861)
  • merocrine gland - (sweat gland, eccrine sweat) simple tubular glands located at the border between the dermis and hypodermis. These glands regulate the body temperature. (More? image - merocrine secretion)
  • nestin - (neuroectodermal stem cell marker) an intermediate filament protein (type VI) expressed in stem cells and transiently during development, and in cells within hair follicles, sebaceous and sweat glands.
  • papillary layer - dermis sublayer that appears less dense and contains more cells lying close beneath the epidermis. (More? image)
  • pilosebaceous unit - term used to describe a hair and its associated structures: hair follicle, arrector pili muscle and sebaceous gland.
  • rete ridge - the extensions of the epidermis into the dermis. These epidermal surface thickenings extend downward between underlying connective tissue dermal papillae. This is also the site of initial eccrine gland differentiation.
  • reticular layer - dermis sublayer that appears denser and contains fewer cells with thick collagen bundles lying beneath the papillary layer parallel to the skin surface. (More? image)
  • root sheath - cell layers that surround the hair.
  • sebaceous gland - holocrine gland associated with both the hair follicle and hairless parts of the skin (lips, cheek oral surface and external genitalia). Embedded in the dermis and are sites of infections (acne).
  • simple - consisting of a single cell layer.
  • terminal hairs - hair seen in obviously hairy parts of the body.
  • thick skin - refers to the skin histology found on the palms of the hand and soles of the feet, does not contain hair. Note that this is used as a histological term not a measurement of overall skin thickness.
  • thin skin - refers to the skin histology found on skin on all body regions, other than palms and soles (thick skin).
  • vellus hairs - fine short hairs only lightly pigmented covering the body.
  • vernix caseosa - (vernix, Latin, "caseosa" = cheese-like) a fetal protective coating consisting of sebum, skin cells and lanugo hair. Forming late in fetal development in a rostra-caudal sequence associated with epithelium differentiation.
  • Voigt's lines - clinical term to describe the skin borders between areas of innervations by specific peripheral cutaneous nerves. (More? Sensory Touch | Historic Terminology)
Other Terms Lists  
Terms Lists: ART | Birth | Bone | Cardiovascular | Cell Division | Endocrine | Gastrointestinal | Genital | Genetic | Head | Hearing | Heart | Immune | Integumentary | Neonatal | Neural | Oocyte | Palate | Placenta | Radiation | Renal | Respiratory | Spermatozoa | Statistics | Tooth | Ultrasound | Vision | Historic | Drugs | Glossary
 2017 ANAT2341 - Timetable | Course Outline | Group Projects | Moodle | Tutorial 1 | Tutorial 2 | Tutorial 3

Labs: 1 Fertility and IVF | 2 ES Cells to Genome Editing | 3 Preimplantation and Early Implantation | 4 Reproductive Technology Revolution | 5 Cardiac and Vascular Development | 6 CRISPR-Cas9 | 7 Somitogenesis and Vertebral Malformation | 8 Organogenesis | 9 Genetic Disorders | 10 Melanocytes | 11 Stem Cells | 12 Group

Lectures: 1 Introduction | 2 Fertilization | 3 Week 1/2 | 4 Week 3 | 5 Ectoderm | 6 Placenta | 7 Mesoderm | 8 Endoderm | 9 Research Technology | 10 Cardiovascular | 11 Respiratory | 12 Neural crest | 13 Head | 14 Musculoskeletal | 15 Limb | 16 Renal | 17 Genital | 18 Endocrine | 19 Sensory | 20 Fetal | 21 Integumentary | 22 Birth | 23 Stem cells | 24 Revision

 Student Projects: 1 Cortex | 2 Kidney | 3 Heart | 4 Eye | 5 Lung | 6 Cerebellum