development of the skin and its derivatives · 2014-08-22 · skin function and anatomy skin...

Development of the skin and its derivatives

Dr Annemiek Beverdam – School of Medical Sciences, UNSW Wallace Wurth Building Room 234 – [email protected]

Resources: http://php.med.unsw.edu.au/embryology/

Larsen’s Human Embryology The Developing Human: Clinically Oriented Embryology

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




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

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

Skin origins

Ectoderm Overlying epidermis, epidermal appendages,

nerve endings

Neural Crest Melanocytes

Mesoderm Dermis, Hypodermis

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S.F. Gilbert Developmental Biology 5th ediMon

Embryonic development:

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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StraMfied skin/IFE

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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

Hair follicle development

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Postnatal hair follicle cycling

Telogen: rest Anagen: growth Catagen: regression

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.

Mammary gland development Epidermal appendage

4 weeks:

Nail development Ectoderm

Week 10: epidermal thickening, nail field

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Week 11: nail anlagen moves proximally, nail folds, proximal hair fold: formaMon of formaMve zone

Nail development Ectoderm

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Tooth development Ectoderm/cranial neural crest derived mesenchyme

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Tooth development Week 6: dental lamina forms

Week 7-‐8: formaMon of tooth buds: Bud stage

Week 8: formaMon of dental papilla: Cap and Bell Stage

Tooth development H"('-"G#<&&<1#

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Melanocytes

Melanocyte development Neural crest

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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




development of the skin and its derivatives · 2014-08-22 · skin function and anatomy skin...

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