developmet of integumentary system (special embryology)
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INTEGUMENTARY SYSTEM
SKINDr.Sherif Fahmy
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
Dr.Sherif Fahmy
DEVELOPMENT OF HAIR
Dr.Sherif Fahmy
-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
Dr.Sherif Fahmy
Congenital anomalies of skin and hair• 1- Ichthyosis: excessive
keratinization.• 2- Atrichia: no hair• 3- Hypertrichosis: excessive hair.
Dr.Sherif Fahmy
DEVELOPMENT OF MAMMARY GLAND
Dr.Sherif Fahmy
-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
Dr.Sherif Fahmy
Congenital anomalies
• 1- Polythelia: Extra nipple.• 2- Polymastia: accesory breast.• 3- Inverted nipple.
Dr.Sherif Fahmy