The skin has two origins - the epidermis develops from surface ectoderm while the dermis develops from mesoderm. Melanocytes invade the epidermis from the neural crest at the third month. Hair develops as epidermal proliferation penetrates the dermis, with the terminal end invaginated by mesoderm forming blood vessels and nerves. Proliferation of hair follicle cells forms sebaceous glands. At birth, the skin is covered in a whitish paste called vernix caseosa formed from secretions that protects the skin. Congenital skin and hair anomalies include ichthyosis, atrichia, and hypertrichosis. The mammary gland develops from a mammary line

1. INTEGUMENTARY SYSTEM
SKIN
Dr.Sherif Fahmy

2. SKIN
• It has double origin:
–Epidermis: from surface ectoderm which
proliferates starting from 5th
week till 5th
month forming 4 layers.
–Dermis: is developed from mesoderm of
the somites (dermatome) and from lateral
plate mesoderm. It forms papillary layer
which is rich with nerves and blood vessels.
- At 3rd
month, epidermis is invaded by
melanocytes from neural crest.Dr.Sherif Fahmy

3. Dr.Sherif Fahmy

4. DEVELOPMENT OF HAIR
Dr.Sherif Fahmy

5. -Epidermal proliferation, that penetrate the
dermis.
-Terminal end is invaginated by mesoderm that
form blood vessel and nerve.
-Proliferation of cells of hair follicle form
sebaceous glands.
-At birth skin is covered by whitish paste (vernix
caseosa) which is formed from secretion of
sebaceous glands, degenerated epithelial cells
and hair.
-Vernix caseosa protects the skin. Dr.Sherif Fahmy

6. Dr.Sherif Fahmy

7. Congenital anomalies of skin and hair
• 1- Ichthyosis: excessive
keratinization.
• 2- Atrichia: no hair
• 3- Hypertrichosis: excessive hair.
Dr.Sherif Fahmy

8. DEVELOPMENT OF
MAMMARY GLAND
Dr.Sherif Fahmy

9. -Mammary line is formed (at 7th
week) by
thickened ectoderm that extends from upper limb
to lower limb.
-Most of mammary line disappears except in
thoracic region.
-Cells proliferates and branch to penetrate the
deeper tissue then it becomes canalized to form
duct.
-Each duct opens on the surface through a pit.
After birth pits become everted and protrude to
form nipple
-Maturation is completed at puberty.
Dr.Sherif Fahmy

10. Dr.Sherif Fahmy

11. Congenital anomalies
• 1- Polythelia: Extra nipple.
• 2- Polymastia: accesory breast.
• 3- Inverted nipple.
Dr.Sherif Fahmy