The document summarizes the development of the integumentary system. It states that the skin and its derivatives like hair, nails, sweat glands, and mammary glands develop from both the surface ectoderm and underlying mesoderm. It describes the development process of each structure in detail. For example, it notes that the epidermis forms from the surface ectoderm and develops four layers by the end of the fourth month, while the dermis develops from the mesoderm and forms dermal papillae containing blood vessels and sensory receptors in the third and fourth months. The document also lists several pigmentary, hair, and gland disorders as examples of conditions related to integumentary system development.

1. Development of integumentary system
By Dr Piyush

2. INTRODUCTION
Skin with all its derivatives compose
integumentary system.
Derivatives of skin:
Hair
Nail
Sweat gland
Sebaceous gland
Mammary gland

4. Development of Skin
Dual origin
Epidermis: from surface ectoderm
Dermis: from underlying mesoderm

5. Development of epidermis
Before 2nd month embryo covered by single
layer of ectodermal cells
At begining of 2nd month it divides and
forms periderm or epitrichium
Proliferation continues
By the end of 4th month epidermis acquires
its definitive arrangement of 4 layers.

8. After the completion of various strata of
epidermis periderm shed off
The exfoliated cells+secretion of sebaceous
gland form a pasty substance “Vernix
Caseosa”
By 3rd month melanoblasts have migrated to
basal layer of epidermis
Synthesize melanin pigment in melanosomes.

10. As melanosomes accumulate, they are
transported down dendritic processes of
melanocytes.
Melanosomes transferred intercellularly
to keratinocytes of the skin and hair bulb.
Pigmentation of the skin and hair is thus
acquired.

13. Development of dermis
Also called Corium
Origin from 3 sources
1. Lateral plate mesoderm: Dermis in the limbs
and body wall
2. Paraxial mesoderm: Dermis in the back
3. Neural crest: Dermis in face and neck

17. In 3rd &4th month dermal papilla form
Each papilla has a loop of capillary plexus
and sensory receptors

18. Applied
Pigmentary disorders
Albinism
Vitiligo
Piebaldism
Wardenburg syndrome
Fingerprinting
Ichthyosis and Harlequin foetus

19. Albinism Vitiligo

20. wardenburg syndromepiebaldism

21. Fingerprinting and dermatoglyphics

22. herlequin foetusIchthyosis

23. Development of hair
Solid epidermal proliferations from the
germinative layer penetrates the underlying
dermis.
At their terminal ends, hair buds invaginate.
The invaginations, the hair papillae, are rapidly
filled with mesoderm in which vessels and nerve
endings develop.

25. Central cells of the hair buds become spindle
shaped and keratinized, forming the hair shaft,
Whereas peripheral cells become cuboidal,
giving rise to the epithelial hair sheath
Dermal root sheath is formed by the
surrounding mesenchyme.
A small smooth muscle (arrector pilli), also
derived from mesenchyme, is usually attached to
the dermal root sheath.

26. Proliferation of epithelial cells at the base of the
shaft pushes the hair upward,
By the end of the 3rd month, the first hairs
appear on the surface in the región of the
eyebrow and upper lip.
The first hair that appears, lanugo hair, is shed
at about the time of birth and is later replaced
by coarser hairs arising from new hair follicles.

28. Applied
HypertrichosisAtrichosis

29. Development of sebaceous gland
The epithelial wall of the hair follicle usually shows
a small bud penetrating the surround ing mesoderm
Cells from these buds form the sebaceous glands.
Cells from the central región of the gland
degenerate, forming a fat-like substance (sebum)
secreted into the hair follicle, and from there, they
reach the skin.

31. Whole cell from wall degenerate
to form sebum so gland is
Holocrine
Some gland directly open on skin
e.g. skin of nose, labia minora,
glans penis and tarsal gland of
eyelid.
Absent on palms and soles
Secretory activity controlled by
sex hormones; no nervous
control.

32. Applied
Sebaceous hyperplasia
Sebaceous cyst
Acne

34. Development of nails
Epidermis thicken at tip of digit called nail field
They migrate to dorsal side of digit
Grow proximally and form nail root
Nail fields limited by nail folds (invagination of
epidermis)
Nails grow from Proximal nail fold

36. Nail is basically the continuation of stratum lucidum of
proximal nail fold.
Initially nail covered by stratum corneum but it
disappears except at lunule where it is called
eponychium
Epidermal thickening below the free border of nail
called hyponychium

37. Applied
koilonychia paronychia

38. anonychia congenita

39. Development of sweat glands
Solid ectodermal downgrowth in dermis
deeper ends coilled
Coiled solid growth now canalised to form gland
and its duct
Gland has outer flattened myoepithelial cells and
inner cuboidal cells.

40. 2 types
Eccrine / Merocrine: throughout body except lips ,
glans and labia minora
Primary function thermoregulatioon
Apocrine: limited distribution at hairy parts face, axillae,
and pubic región.
Specialised apocrine gland: ceruminous gland, mammary
glands
All sweat glands innervated by post ganglionic
sympathetic neurons

43. Applied

44. hidraadenitis suppurativa
chromohidrosis
Bromohidrosis

45. Development of mammary glands
Mammary glands are modified sweat glands
In 7 wk embryo: A bilateral bands of thickened
epidermis extends from root of forelimb to the
region of hindlimb
Major part disappear and only a small part in
thoracic region

47. Penetrates underlying mesenchyme
forms 16 to 24 sprouts, which in turn give rise to small,
solid buds.
Epithelial sprouts are canalized and form the
lactiferous ducts
Initially, the lactiferous ducts open into a small
epithelial pit.
Shortly after birth, this pit is transformed into the
nipple by proliferation of the underlying mesenchyme.

49. At birth, lactiferous ducts have no alveoli
and therefore no secretory apparatus.
At puberty, increased concentrations of
estrogen and progesterone stimulate
branching from the ducts to form alveoli
and secretory cells.

50. Applied
amastia athelia

52. Thank you