Development of the skin and its derivatives

Development of the skin and its derivatives Resources: http://php.med.unsw.edu.au/embryology/ Larsen s Human Embryology The Developing Human: Clinically Oriented Embryology Dr Annemiek Beverdam School of Medical Sciences, UNSW Wallace Wurth Building Room 234 A.Beverdam@unsw.edu.au

Lecture overview Skin function and anatomy Skin origins Development of the overlying epidermis Development of epidermal appendages: Hair follicles Glands Nails Teeth Development of melanocytes Development of the Dermis Resources: http://php.med.unsw.edu.au/embryology/ Larsen s Human Embryology The Developing Human: Clinically Oriented Embryology Dr Annemiek Beverdam School of Medical Sciences, UNSW Wallace Wurth Building Room 234 A.Beverdam@unsw.edu.au

Skin Function and Anatomy Largest organ of our body Protects inner body from outside world (pathogens, water, sun) ThermoregulaMon Diverse: thick vs thin skin, scalp skin vs face skin, etc Consists of: - Overlying epidermis - Epidermal appendages: - Hair follicles, - Glands: sebaceous, sweat, apocrine, mammary - Nails - Teeth - Melanocytes - Dermis - Hypodermis

Skin origins Trilaminar embryo Ectoderm (Neural crest) brain, spinal cord, eyes, peripheral nervous system epidermis of skin and associated structures, melanocytes, cranial connective tissues (dermis) Mesoderm musculo-skeletal system limbs connective tissue of skin and organs urogenital system, heart, blood cells Endoderm epithelial linings of gastrointestinal and respiratory tracts

Ectoderm Overlying epidermis, epidermal appendages, nerve endings

Neural Crest Melanocytes

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Embryonic development: Page 342 S.F. Gilbert Developmental Biology 5th edimon

Epidermal development Surface ectoderm Skin/Interfollicular epidermis: stramfied squamous epithelium Appendages: Hair follicles Glands (sebaceous, sweat, apocrine, mammary, lacrimal, salivary) Nails Teeth

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Epidermal Appendages - Hair follicles, - Glands: sebaceous, sweat, apocrine, mammary, salivary, lacrimal - Nails - Teeth Share common developmental mechanisms

Hair follicle development and cycling Epidermal appendage Involved in thermoregulation/sun protection Month 2-4: Onset hair follicle development Hair follicles develop first in cranial region Month 5: most hair follicles present 5,000,000 hair follicles

Hair follicle development Hair germ Hair peg Bulbous hair peg Invasion of dermis cells

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Telogen: rest Anagen: growth Catagen: regression Postnatal hair follicle cycling

Epidermal gland development Epidermal appendages Sebaceous glands: sebrum/vernix Sweat glands Apocrine glands ( smelly glands) Mammary glands Salivary glands Lacrimal glands

Epidermal gland development Epidermal appendages Sebaceous glands: develop from hair follicle (4 weeks +) Sweat glands: develop from basal layer IFE (20 weeks+) Apocrine glands: develop in association with HFs, most lost late in fetal dev.

4 weeks: Mammary gland development Epidermal appendage

Nails

Nail development Ectoderm Week 10: epidermal thickening, nail field Week 11: nail anlagen moves proximally, nail folds, proximal hair fold: formamon of formamve zone h`p://discovery.lifemapsc.com/library/review- of- medical- embryology/chapter- 75- development- of- the- nails

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Teeth

Tooth development Ectoderm/cranial neural crest derived mesenchyme &%-'&3#,&%M%# :&&)#cn##,&%<-3#3-'(%-# 8P61-J&,#"(,=&6# :&&)#an# 5&6&%01G'&# 02%,&%6-M2%# L;0)&"#-%,#/1-"J&7#9-<;"&#T&%&M06#?]]A# :&&)#dn# 5&6&%01G'&# (%+-,&6#F-6&# <22<1#F;,N#!&%<-3#J-J(33-# :&&)#[AN# RJ(<1&3(-3#0&336N## $'&32F3-6<6N#&%-'&3# # 5&6&%01G'-3#0&336N## Q,2%<2F3-6<6N#,&%M%# #

Week 6: dental lamina forms Tooth development Week 7-8: formamon of tooth buds: Bud stage Week 8: formamon of dental papilla: Cap and Bell Stage

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Melanocytes

Melanocyte development Neural crest R"%42"67#R_J#O&33#>&6#?][]#

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Melanocyte development Neural crest *&42"&#6<"-MY0-M2%# Q%6&<#6<"-MY0-M2%# *;3F2;6#1-("#J&=6# $%-=&%# 5-<"(_# S-("#4233(03&#*;3=&#!f(-%Pg-2;01&7# H(='&%<#O&33#5&3-%2'-#>&6#?][?#

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Dermis development Somitic mesoderm Somatic lateral plate mesoderm Cranial neural crest derived mesenchyme

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Lecture overview Skin Skin origins Development of the overlying epidermis Development of epidermal appendages: Hair follicles Glands Mammary glands Nails Teeth Development of Melanocytes Development of the Dermis Resources: http://php.med.unsw.edu.au/embryology/ Larsen s Human Embryology The Developing Human: Clinically Oriented Embryology Dr Annemiek Beverdam School of Medical Sciences, UNSW Wallace Wurth Building Room 234 A.Beverdam@unsw.edu.au