Integumentary System Development: Difference between revisions
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* '''merkel cell''' - An epidermal-derived cell in touch-sensitive area of the epidermis and mediate mechanotransduction in the skin. Previously thought to be neural crest in origin, but recently shown to arise from the embryonic epithelium. The cells are named after Friedrich Sigmund Merkel, a German anatomist who was the first to describe them in 1875. (More? [[2009_Lecture_18|Lecture - Integumentary Development]] | [http://www.ncbi.nlm.nih.gov/pubmed/19786578 PMID19786578] | [http://www.ncbi.nlm.nih.gov/pubmed/3782861 PMID3782861]) | |||
* '''melanin''' - (Greek, ''melanos'' = black) The pigment produced by [[M#melanocyte|melanocytes]] that provides photoprotection, preventing cellular DNA damage, and colouring of the cells that secret and absorb the pigment. | |||
*''' melanoblast''' - (Greek, ''melanos'' = black) The [[N#neural crest|neural crest]] precursor cell that differentiates to form [[M#melanocyte|melanocytes]] located in the skin and other tissues that produces [[M#melanin|melanin]]. (More? [[Neural Crest Development]] | [[Integumentary Development]]) | |||
* '''melanocyte''' - (Greek, ''melanos'' = black) A pigmented cell, [[N#neural crest|neural crest]] in origin, differentiating from [[M#melanoblast|melanoblasts]] located in the skin and other tissues that produces [[M#melanin|melanin]]. The melanocytes within the integument (skin) transfer melanin to keratinocytes to give skin colour and to the hair follicle to give hair colour. Melanocytes are also located within "non-cutaneous" tissues in the eye (for eye colour), [[H#harderian gland|harderian gland]] and inner ear. This is the cell type that proliferates in the cancer melanoma. (More? [[Neural Crest Development]] | [[Integumentary Development]]) | |||
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Revision as of 20:50, 30 September 2010
Introduction
The integumentary system covers the surface of the embryo (skin) and its specialized skin structures including hair, nails, sweat glands, mammary glands and teeth. As a system it has contributions from all embryonic layers.
The skin provides a barrier between ourselves and our environment, it also contains specializations in different regions including hair, nails, glands and sensory receptors.
The two major tissue organizations of epithelial (ectoderm, epidermis) and mesenchyme (mesoderm connective tissue, dermis and hypodermis) are shown within skin. In addition, we have aslo extensive populating by melanocytes (neural crest) and sensory nerve endings.
It remains today as possibly the first epithelial specialization from which other epithelial specializations arose that are now located inside the body.
Ectoderm forms the surface epidermis and the associated glands. Mesoderm forms the underlying connective tissue of dermis and hypodermis. Neural crest cells also migrate into the forming epidermis and the skin is also populated by specialized sensory endings.
System Links: Introduction | Cardiovascular | Coelomic Cavity | Endocrine | Gastrointestinal Tract | Genital | Head | Immune | Integumentary | Musculoskeletal | Neural | Neural Crest | Placenta | Renal | Respiratory | Sensory | Birth |
Some Recent Findings
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Textbooks
- Human Embryology (2nd ed.) Larson Chapter 14 p443-455
- The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud Chapter 20: P513-529
- Before We Are Born (5th ed.) Moore and Persaud Chapter 21: P481-496
- Essentials of Human Embryology Larson Chapter 14: P303-315
- Human Embryology, Fitzgerald and Fitzgerald
- Color Atlas of Clinical Embryology Moore Persaud and Shiota Chapter 15: p231-236
Objectives
- Understand the differentiation of the epidermis and dermis.
- Understand the formation of hair and nails.
- Understand the formation of sweat glands, mammary glands.
- Understand the formation of teeth.
Development Overview
Ectoderm and Mesoderm Origin
4 weeks
- simple ectoderm epithelium over mesenchyme.
1-3 months
- ectoderm- germinative (basal) cell repeated division of generates stratified epithelium.
- mesoderm- differentiates into connective tissue and blood vessels.
4 months
- Basal cell - proliferation generates folds in basement membrane.
- Neural crest cells - melanoblasts migrate into epithelium. These are the future melanocyte pigment cell of the skin.
- Embryonic connective tissue- differentiates into dermis, a loose ct layer over a dense ct layer. Beneath the dense ct layer is another loose ct layer that will form the subcutaneous layer.
- Ectoderm contributes to nails, hair follictles and glands.
- Nails form as thickening of ectoderm epidermis at the tips of fingers and toes. These form germinative cells of nail field.
- Cords of these cells extend into mesoderm forming epithelial columns. These form hair follocles, sebaceous and sweat glands.
5 months
- Hair growth initiated at base of cord, lateral outgrowths form associated sebaceous glands.
- Other cords elongate and coil to form sweat glands.
- Cords in mammary region branch as they elongate to form mammary glands. These glands will complete development in females at puberty. Functional maturity only occurs in late pregnancy.
Adult Epidermal Stem Cells
The following information is from a recent study on mouse skin using a single cell labelling system with longitudinal tracing and confocal imaging.[2]
Organization of the epidermis. Hair follicles contain stem cells located in the bulge (b, green), with the potential to generate lower hair follicle (lf), sebaceous gland (sg, orange) upper follicle (uf) and interfollicular epidermis (IFE, beige). The schematic shows the organization of keratinocytes in the IFE, as proposed by the stem/TA cell hypothesis. The basal layer comprises stem cells (S, blue), transit amplifying cells (TA, dark green), and post-mitotic basal cells (red), which migrate out of the basal layer as they differentiate (arrows).
Projected Z-stack confocal images of IFE wholemounts from AhcreERT R26EYFP/wt mice viewed from the basal surface at the times shown following induction. Yellow, EYFP; blue, DAPI nuclear stain. Scale bar, 20 microns.
Reprinted by permission from Macmillan Publishers Ltd: Nature. 2007 Mar 8;446(7132):185-9, copyright (2007)
Adult epidermal stem cells[2] "According to the current model of adult epidermal homeostasis, skin tissue is maintained by two discrete populations of progenitor cells. ...Here we show that clone-size distributions are consistent with a new model of homeostasis involving only one type of progenitor cell. These cells are found to undergo both symmetric and asymmetric division at rates that ensure epidermal homeostasis."
Links: MRC - Phil Jones Laboratory
References
Reviews
Articles
Search PubMed
Search April 2010 "Integumentary Development" - All (86) Review (9) Free Full Text (18)
Search Pubmed: Integumentary Development | Skin Development | Hair Development | Tooth Development
Additional Images
Terms
- merkel cell - An epidermal-derived cell in touch-sensitive area of the epidermis and mediate mechanotransduction in the skin. Previously thought to be neural crest in origin, but recently shown to arise from the embryonic epithelium. The cells are named after Friedrich Sigmund Merkel, a German anatomist who was the first to describe them in 1875. (More? Lecture - Integumentary Development | PMID19786578 | PMID3782861)
- melanin - (Greek, melanos = black) The pigment produced by melanocytes that provides photoprotection, preventing cellular DNA damage, and colouring of the cells that secret and absorb the pigment.
- melanoblast - (Greek, melanos = black) The neural crest precursor cell that differentiates to form melanocytes located in the skin and other tissues that produces melanin. (More? Neural Crest Development | Integumentary Development)
- melanocyte - (Greek, melanos = black) A pigmented cell, neural crest in origin, differentiating from melanoblasts located in the skin and other tissues that produces melanin. The melanocytes within the integument (skin) transfer melanin to keratinocytes to give skin colour and to the hair follicle to give hair colour. Melanocytes are also located within "non-cutaneous" tissues in the eye (for eye colour), harderian gland and inner ear. This is the cell type that proliferates in the cancer melanoma. (More? Neural Crest Development | Integumentary Development)
Glossary Links
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Cite this page: Hill, M.A. (2024, March 28) Embryology Integumentary System Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Integumentary_System_Development
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G