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Development of the integumentary system

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Notes

Embryology

Organ system development

Cardiovascular system

Development of the cardiovascular system

Fetal circulation

Eyes, ears, nose and throat

Development of the face and palate

Pharyngeal arches, pouches, and clefts

Development of the ear

Development of the eye

Gastrointestinal system

Development of the digestive system and body cavities

Development of the gastrointestinal system

Development of the teeth

Development of the tongue

Integumentary system

Development of the integumentary system

Musculoskeletal system

Development of the axial skeleton

Development of the limbs

Development of the muscular system

Nervous system

Development of the nervous system

Renal system

Development of the renal system

Reproductive system

Development of the reproductive system

Respiratory system

Development of the respiratory system

High Yield Notes

28 pages

Chapter 29 Embryology: Body System Structures DEVELOPMENT OF THE INTEGUMENTARY SYSTEM osms.it/integumentary-system-development DEVELOPMENT OF THE SKIN Epidermis ▪ Derived from single layer of surface ectoderm ▪ In second month: cells divide, forms layer of periderm (AKA epitrichium) ▪ Cells of periderm desquamated during second ½ of prenatal life, form vernix caseosa ▪ Neural crest cells invade epidermis, form melanocytes ▫ Move to keratinocytes in skin, hair bulb ▫ Produce skin, hair pigmentation ▪ Cells in basal layer proliferate, form intermediate zone ▪ By end of fourth month, four layers complete ▫ Basal/germinative layer, spinous layer, granular layer, horny layer ▪ Hair, nails, glands all develop as epidermal proliferations Dermis ▪ Derived from mesenchyme from three sites ▪ Lateral plate mesoderm: produces dermis of limbs, body wall ▪ Paraxial mesoderm: produces dermis of back ▪ Neural crest cells: dermis of neck, face ▪ During third, fourth months, dermis forms many irregular papillary structures (AKA dermal papillae) ▫ Project upward into epidermis ▫ Contain Meissner corpuscles (AKA tactile sensory receptors) Hair ▪ Week 12: hair follicles form from cells of stratum basale ▪ Begins as epidermal proliferation that penetrates into dermis (AKA hair bud) ▪ Hair bud invaginates at terminal end, forming hair papillae ▪ Each hair papilla ﬁlls with mesoderm ▫ Vessels, nerves develop ▪ Cells of hair bud’s center become keratinized, forming hair shaft ▪ Peripheral cells form the epithelial hair sheath ▪ Mesenchyme surrounding hair bud forms dermal root sheath, attached arrector pili muscle ▪ By end of third month, ﬁrst hair appears as lanugo ▫ Begins to shed at term ▪ Sebaceous gland forms from small bud in mesoderm ▫ Secretes sebum Nails ▪ By end of third month, nail ﬁelds form from thickenings at tips of digits ▪ Nail ﬁelds form nail root through migration ▪ Growth proximal, dorsal to each side of digit ▪ Tissue proliferates around each nail ﬁeld, forming shallow depression ▪ Epidermis at nail roots differentiates into ﬁngernails, toenails ▫ Reaches tips by ninth month of development Sweat glands ▪ Eccrine glands ▫ Forms over most of body ▫ Buds arise from germinative layer ▫ Buds grow into dermis ▫ Terminal part coils, forms secretory part of glands ▪ Apocrine glands ▫ Develop during puberty over hairy parts of the body ▫ Arise from epidermal buds that produce OSMOSIS.ORG 247

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