11-Dev. Integumentary system lecture.ppt
- 2. The Integumentary System The Integumentary System
- 3. The Integumentary System The Integumentary System Consists of skin & Consists of skin & Its derivatives: Its derivatives: Sweat glands Sweat glands Sebaceous glands Sebaceous glands Arrector pili Arrector pili muscles muscles Nails Nails Hair Hair Mammary glands Mammary glands
- 4. Development of Skin Development of Skin Skin consists of Skin consists of two layers two layers that are that are derived from two different germ layers derived from two different germ layers Epidermis Epidermis, superficial epithelial tissue , superficial epithelial tissue derived from derived from surface ectoderm surface ectoderm Dermis Dermis, deeper layer of connective , deeper layer of connective tissue derived from the tissue derived from the mesoderm mesoderm
- 5. Epidermis Epidermis In the In the 4-5th week 4-5th week, the skin of , the skin of the embryo consists of simple the embryo consists of simple cuboidal epithelium….the cuboidal epithelium….the surface ectoderm surface ectoderm By the By the 7th week 7th week, the surface , the surface ectodermal cells proliferate and ectodermal cells proliferate and form a layer of squamous form a layer of squamous epithelium, the epithelium, the periderm periderm (epitichium) and a (epitichium) and a basal basal germinative layer. germinative layer. During During 1 1st st & 2 & 2nd nd trimesters trimesters, , epidermal growth occurs in epidermal growth occurs in stages, which result in an stages, which result in an increase in epidermal thickness increase in epidermal thickness
- 6. Periderm Periderm The peridermal cells The peridermal cells continually undergo continually undergo keratinization and keratinization and desquamation and are desquamation and are replaced by cells arising from replaced by cells arising from the the basal layer basal layer The exfoliated cells form part The exfoliated cells form part of the white greasy substance, of the white greasy substance, the the vernix caseosa vernix caseosa, that , that covers the body of the fetus covers the body of the fetus Replacement of peridermal Replacement of peridermal cells continue untill about the cells continue untill about the 21 21st st week week, thereafter the , thereafter the periderm disappears and the periderm disappears and the stratum corneum stratum corneum forms forms
- 7. Basal Germinative Layer Basal Germinative Layer This layer becomes the This layer becomes the stratum germinativum stratum germinativum of the epidermis of the epidermis It proliferates and the It proliferates and the new cells are displaced new cells are displaced into the layers into the layers superficial to it. superficial to it. By By 11 11th th week week, an , an intermediate layer intermediate layer, , containing several cell containing several cell layers, is interposed layers, is interposed between the basal cells between the basal cells and the periderm. and the periderm.
- 8. Basal Germinative Layer cont’d Basal Germinative Layer cont’d Proliferation of stratum Proliferation of stratum germinativum also forms germinativum also forms epidermal ridges epidermal ridges which which extend into the developing extend into the developing dermis. dermis. These ridges begin to These ridges begin to appear in embryo of appear in embryo of 10 10 weeks weeks and are permenantly and are permenantly established by the established by the 17 17th th week week. . These ridges produce These ridges produce grooves on the surface of grooves on the surface of palms of the hand and soles palms of the hand and soles of the feet including digits of the feet including digits
- 9. Melanoblasts & Melanocytes Melanoblasts & Melanocytes During the early fetal During the early fetal period the epidermis is period the epidermis is invaded by invaded by melanoblasts melanoblasts, , cells of the neural crest cells of the neural crest origin. origin. Melanoblasts move to Melanoblasts move to dermoepidermal junction dermoepidermal junction and differentiate into and differentiate into melanocytes melanocytes The melanocytes have The melanocytes have several long processes. several long processes.
- 10. Melanoblasts & Melanocytes cont’d Melanoblasts & Melanocytes cont’d The The cell bodies cell bodies of of melanocytes are melanocytes are confined to the confined to the basal basal layers layers of the of the epidermis, and their epidermis, and their processes extend processes extend between the between the epidermal cells epidermal cells The melanocytes begin The melanocytes begin producing producing melanin melanin before birth before birth and and distribute it to the distribute it to the epidermal cells epidermal cells
- 11. At birth all At birth all layers of the layers of the adult epidermis adult epidermis are present are present
- 12. Dermis Dermis The The dermis dermis is derived from is derived from the mesenchyme underlying the mesenchyme underlying the surface ectoderm the surface ectoderm This mesenchyme is derived This mesenchyme is derived from the: from the: Somatic layer of the lateral Somatic layer of the lateral mesoderm mesoderm (most of it) (most of it) Dermatomes of the Dermatomes of the somites somites (some) (some). . By By 11 11th th week week, the mesenchymal , the mesenchymal cells begin to produce cells begin to produce collagenous and elastic collagenous and elastic connective tissue fibers connective tissue fibers
- 13. Dermal Papillae Dermal Papillae As the epidermal As the epidermal ridges are formed, the ridges are formed, the dermis projects dermis projects upward into the upward into the epidermis and forms epidermis and forms the the dermal papillae dermal papillae Capillary loops and Capillary loops and sensory nerve endings sensory nerve endings develop in these develop in these papillae papillae DP DP
- 14. Hair Hair Begin to develop during Begin to develop during the the 3rd month 3rd month, but they do , but they do not become visible until not become visible until the the 20 20th th week week Begins as an epidermal Begins as an epidermal proliferation, the proliferation, the hair bud hair bud, , into the underlying dermis. into the underlying dermis. The deepest part of the The deepest part of the hair bud becomes cup- hair bud becomes cup- shaped, forming a shaped, forming a hair hair bulb bulb The hair bulb gets The hair bulb gets invaginated by invaginated by mesenchymal mesenchymal hair papilla hair papilla
- 15. Hair cont’d Hair cont’d The The central central epithelial cells of epithelial cells of the hair bulb give rise to the the hair bulb give rise to the shaft of the shaft of the hair, hair, that grows that grows through the epidermis and through the epidermis and protrudes above the surface protrudes above the surface of the skin of the skin The The peripheral peripheral cells of the cells of the hair bulb form the hair bulb form the epithelial epithelial root sheath root sheath. . The cells of the epithelial The cells of the epithelial root sheath proliferate to root sheath proliferate to form a form a sebaceous gland sebaceous gland bud bud. .
- 16. Hair cont’d Hair cont’d Surrounding Surrounding mesenchymal cells mesenchymal cells differentiate into differentiate into dermal root sheath dermal root sheath. . The The arrector pili arrector pili muscle muscle differentiates differentiates from the surrounding from the surrounding mesenchyme mesenchyme Melanoblasts Melanoblasts migrate into the hair migrate into the hair bulb and differentiate bulb and differentiate into melanocytes into melanocytes
- 17. Hair cont’d Hair cont’d Hairs are first recognizable in the Hairs are first recognizable in the region of region of eyebrows, upper lip and eyebrows, upper lip and chin chin The first set of hairs that appear are The first set of hairs that appear are fine and colorless and are called fine and colorless and are called ‘lanugo’ ‘lanugo’ hair hair Lanugo hair are replaced during the Lanugo hair are replaced during the perinatal period perinatal period by coarser hair by coarser hair
- 18. Sweat Glands Sweat Glands Develop at about Develop at about 20 weeks 20 weeks as solid growth of as solid growth of epidermal cells epidermal cells into the into the underlying dermis underlying dermis Its terminal part Its terminal part coils coils and and forms the forms the body of the body of the gland gland The The central cells central cells degenerate to form the degenerate to form the lumen of the gland lumen of the gland The The peripheral cells peripheral cells differentiate into differentiate into secretory secretory cells cells and and contractile contractile myoepithelial cells myoepithelial cells
- 19. Vernix Caseosa Vernix Caseosa Vernix caseosa Vernix caseosa, is the waxy , is the waxy or cheesy white substance or cheesy white substance found coating the skin of the found coating the skin of the newborn. newborn. The vernix is secreted by the The vernix is secreted by the sebaceous glands around the sebaceous glands around the 20th week of gestation 20th week of gestation It is composed of: It is composed of: Sebum Sebum (the secretion of (the secretion of the sebaceous glands) the sebaceous glands) Desquamated epithelial Desquamated epithelial cells cells Fetal hair (lanugo hair) Fetal hair (lanugo hair) It protects the baby's skin It protects the baby's skin from dehydation and from from dehydation and from constant exposure to the constant exposure to the amniotic fluid. amniotic fluid.
- 20. Nails Nails Begin to develop at about Begin to develop at about 10th week 10th week of gestation, as of gestation, as thickened areas of the thickened areas of the epidermis at the epidermis at the tips of the tips of the digits. digits. Later, these nail fields Later, these nail fields extend to the extend to the dorsal surface dorsal surface and become surrounded by and become surrounded by the the nail folds nail folds. . Cells from the Cells from the proximal nail proximal nail fold fold grow over the nail field grow over the nail field and form and form keratinized nail keratinized nail plate plate, the primordium of , the primordium of the nail. the nail.
- 21. The M The Mammary ammary Glands Glands Begin to develop Begin to develop during the during the 6th week 6th week as as thickened strips of the thickened strips of the ectoderm ectoderm ( (mammary mammary ridges ridges) that extend ) that extend from the axillary to the from the axillary to the inguinal regions. inguinal regions. They They regress regress in most in most locations locations except in the except in the area of the pectoral area of the pectoral muscle muscle, where they , where they proliferate. proliferate.
- 22. The M The Mammary ammary Glands cont’d Glands cont’d The downgrowth of The downgrowth of epithelial tissue epithelial tissue continues to proliferate continues to proliferate into 16 to 24 solid into 16 to 24 solid outbuddings which give outbuddings which give rise to the rise to the lactiferous lactiferous ducts. ducts. Fibrous connective Fibrous connective tissue and fat of the tissue and fat of the mammary gland mammary gland develop from the develop from the surrounding surrounding mesenchyme. mesenchyme. The lactiferous ducts at The lactiferous ducts at first open into a small first open into a small mammary mammary pit pit. .
- 23. Postnatal Development Postnatal Development A. A. Newborn Newborn (nipple is (nipple is inverted) inverted) B. B. Child Child (nipple elevates (nipple elevates to form the usual to form the usual nipple) nipple) C. C. Puberty Puberty (breast (breast enlarges due to enlarges due to development of the development of the mammary glands) & mammary glands) & deposition of fat deposition of fat D. D. Late puberty Late puberty E. E. Young adult Young adult F. F. Pregnant female Pregnant female
- 24. Anomalies Anomalies Gynecomastia Gynecomastia Polythelia Polythelia Inverted nipples Inverted nipples