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1. Development of Skin
Handout for Medical Students
Prepared by: Melaku Geletu (M.Sc. in Anatomy)

2. Development of Skin
• Epidermis is derived from surface ectoderm
• Dermis is derived from mesodermal
mesenchyme

4. Epidermis
• Primordium of the epidermis is
a layer of surface ectodermal
cells
• These cells proliferate and
form:
– Periderm—a layer of squamous
epithelium
– A basal (germinative) layer

5. Epidermis
• Peridermal cells
– Continually undergo keratinization and
desquamation
– Replaced by cells arising from the basal layer
– Form part of the white greasy substance-vernix
caseosa

6. Epidermis
• Vernix caseosa
– Covers the fetal skin
– It contains epidermal cells, lanugo hair and sebum
– Protects the developing skin from constant
exposure to amniotic fluid
– It also facilitates birth of the fetus

7. Epidermis
• Basal layer becomes stratum
germinativum
• Stratum germinativum
– Produces new cells
– By 11 weeks, cells from it forms
an intermediate layer
– Epidermal ridges also forms.

8. Epidermis
• The type of pattern of epidermal ridges that
develops is determined genetically
• Abnormal chromosome complements affect
its development patterns
– E.g. Down syndrome

9. Epidermis
• Periderm disappears and the stratum
corneum forms at 21st
week

10. Epidermis
• Neural crest cells migrate into the developing
dermis and differentiate into melanoblasts
• Later melanoblasts migrate to the
dermo-epidermal junction and differentiate
into melanocytes
– This differentiation involves the formation of
pigment granules

11. Epidermis
• Melanin
– Begins to be produced and distributed before birth
by melanocytes
– Its amount increases in response to ultraviolet light
– Its relative content is responsible for different skin
colors
– Pigment formation can be observed prenatally in
epidermis

12. Epidermis
• Development of epidermis need inductive
interactions of dermis
• Skin is classified as thick or thin based on the
thickness of the epidermis

13. Dermis
• It develops from mesenchyme, which is derived from
the mesoderm
• Origin of the mesenchyme for the development of
dermis:
– Most from somatic layer of lateral mesoderm
– Some from dermatomes of the somites

14. Dermis
• Dermal ridges
– Formed by the projection of dermis into the
epidermis
– Capillary loops develop in some of it
– Sensory nerve endings form in others

15. Anomalies of the skin
Congenital Ectodermal Dysplasia
• A group of hereditary disorders involving
tissues that are ectodermal in origin
• Teeth are completely or partially absent
• Often the hairs, nails, and skin are also
severely affected

16. Anomalies of the skin
Ectrodactyly-Ectodermal Dysplasia-Clefting Syndrome
• It is a congenital skin condition that is inherited as an
autosomal dominant trait
• It involves both ectodermal and mesodermal tissues
• Consists of ectodermal dysplasia

17. Anomalies of the skin
Ectrodactyly-Ectodermal Dysplasia-Clefting Syndrome
• Associated with:
– Hypopigmentation of skin and hair
– Scanty hair and eyebrows
– Absence of eyelashes
– Nail dystrophy
– Hypodontia and microdontia
– Cleft lip and palate