The anatomy of the skin consists of three main layers - the epidermis, dermis and subcutaneous fat. The epidermis contains five layers and produces keratinocytes, melanocytes, Merkel cells and Langerhans cells. The dermis lies underneath and contains collagen, elastin and ground substance. It is divided into the papillary and reticular layers. Skin appendages include hair follicles, sebaceous and eccrine glands. The skin has blood and lymphatic vessels, nerves and muscles like the arrector pili. Skin thickness and structure varies in different areas and changes with ageing.

1. Presented by -
Dr. Surbhi Abrol
Anatomy Of Skin

2. Introduction
• Largest organ of the human body
• 15% of TBW (70 kg person skin weighs approximately 13 kg)
• Surface area aprox. 2 m2
• Covers the entire external surface of the body, including
external auditory meatus, lateral aspect of the tympanic
membrane , vestibule of the nose. continuous with the mucosae
of the alimentary , respiratory and urogenital tracts, and fuses
with the conjunctiva at the margins of the eyelids, and with the
lining of the lacrimal canaliculi at the lacrimal puncta.
• Thickness of the skin ranges from 1.5 to 5.0 mm & depends on
its location.

3. Functions
• Protection against microorganisms, dehydration,
ultraviolet light, and mechanical damage; first physical
barrier against the external environment.
• Sensation of pain, temperature, touch, and deep pressure
starts with the skin.
• Mobility: The skin allows smooth movement of the body.
• Endocrine activity: The skin initiates the biochemical
processes involved in Vitamin D production .

4. • Exocrine activity: This occurs by the release of water, urea,
and ammonia. Skin secretes products like sebum, sweat,
and pheromones and exerts important immunologic
functions by secreting bioactive substances such as
cytokines.
• Immunity development against pathogens.
• Regulation of Temperature : conserving or releasing heat
and helps maintain the body’s water and homeostatic
balance.

5. The anatomy of the skin is composed of
A. Three main skin layers
1. Epidermis
2. Dermis
3. Subcutaneous fat
B. Three Skin Appendages
1. Hair
2. Hair follicles
3. Glands

6. Anatomical layers of skin

7. Epidermis
• Stratified squamous epithelium
• Derived from ectoderm
• The outermost layer of skin, provides a waterproof barrier and contributes to
skin tone.

8. The epidermis is further divided into five layers on thick skin
1. Stratum basale
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidum
5. Stratum corneum

9. Stratum Germinativum (Basal layer)
• Deepest layer of epidermis contain columnar shaped
keratinocytes, melanocytes.
• It is the site of epidermal cellular proliferation.
• Basement membrane zone (BMZ)
• Downward projections of the epidermis(rete pegs)
• Stem cells are found within the basal layer.

10. Stratum Spinosum
• Contains polygonal cells
• Abundant eosinophilic cytoplasm.
• Connected to each other by desmosomes providing tensile
strength and cohesion.
• Cytoplasm - ck1 and ck10
• As the spinous cells migrate superficially and differentiate into
granular cells, they become larger and flatter.

11. Stratum Granulosum
• One to four cells thick
• Keratohyalin granule-histidine-rich, sulphur-poor protein
profilaggrin-modified to filaggrin as the cell reaches the stratum
corneum.
• The lamellar granules release their hydrophobic
glycophospholipid
• Granular layer and the cornified layer-glycophospholipids-
important component of the permeability barrier of the epidermis.

12. Stratum Lucidium
Only present in Glabrous skin
• Ultrastructurally-compact keratin filaments and
resemble the incompletely keratinized cells
• occasionally seen in the innermost part of the cornified
layer of thin skin.

13. Stratum Corneum
• Contains non-viable keratinised cells shed as dead skin.
• It is the final product of epidermal differentiation
• It consists of closely packed layers of flattened polyhedral corneocytes
• Production of epidermal keratinocytes in the basal layer is matched by
the loss of corneocytes from the cornified layer
• Turnover Rate approx. 30 days.

14. KERATINOCYTES
• Columnar to cuboidal in shape, with large nuclei and prominent nucleoli
• Cytoplasm contains melanosomes and keratin filament
• Mostly keratin 5 (K5) and keratin 14 (K14)

15. • Melanin pigment-producing cells derived from the neural crest
Ratio of melanocytes to basal cells ranges from 1 : 4 on the cheek
to 1 : 10 on the limbs.
Epidermis and its appendages, oral epithelium, some mucous
membranes, uveal tract(choroid coat) of the eyeball, parts of
the middle and internal ear, and in the pial and arachnoid
meninges, principally over the ventrolateral surfaces of the
medulla oblongata
Single melanocyte may be in functional contact via its dendritic
processes with up to 30 keratinocytes.
MELANOCYTES

16. This partly explains why people with less pigmentation are at greater risk
for development of cutaneous malignant neoplasms, such as basal cell
carcinoma, squamous cell carcinoma, and melanoma.
Melanocytes in basal layer (arrows) project stellate,
dendritic processes to surrounding keratinocytes in
basal and spinous layers (epidermal melanin unit).
Note umbrella-like distribution of melanin pigment
over keratinocyte nuclei.

17. Merkel cells
• Neuroendocrine sensory receptors
• Neural crest Mechanoreceptors
• Derived from ectoderm
• It undergo malignant transformation

18. Langerhans Cells
• APCS for the immune system suprabasal
• Bone marrow derived.
• Langerhans cells are characterized by dendritic processes
• Electron microscopy, contains small racket-shaped structures
known as Birbeck or Langerhans cell granules
• The number of Langerhans cells decreases after ultraviolet
irradiation.
• This results in a diminished capacity for immune surveillance, which may play a role in cutaneous carcinogenesis. The number of Langerhans cells also decreases with age.8

19. DERMIS
• Makes most of skin thickness.
• Derived from mesoderm
• Contains connective tissue, hair follicles, blood vessels,
lymphatic vessels, and sweat glands.
• There are two layers in the dermis.
• Papillary dermis: superficial, fine collagen fibres, type III
collagen.
• Reticular dermis: deeper, coarser collagen fibres, type I collagen.

21. The structures within the dermis are most commonly produced and secreted by
fibroblasts.
These include:
• Collagen: standard ratio of type 1: type 3 is 5:1. There are 5 different types
of collagen. There is increased collagen III in ageing skin.
• Elastin: as the name suggests, it provides skin elasticity.
• "Ground Substance"/Glycosaminoglycans: hyaluronic acid, dermatan
sulphate, chondroitin sulphate.
• Other cells include fibroblasts and mast cells.

22. Papillary Dermis
• It provides mechanical anchorage
• Metabolic support and trophic maintenance
• Sensory nerve endings and blood vessels
• Superficial surface of the dermis -rete ridges-rete pegs- dermal–epidermal junction

23. Reticular layer
• Collagen fibres are thicker than those in the papillary layer
• They form a strong but deformable three-dimensional lattice with
variable number of elastic fibres.
• Skin lines- owing to local mechanical forces on dermis due to
predominant parallel orientation of the collagen fibres.

24. Skin Appendages
Their name originates from the fact that they develop as ingrowths of
the epidermis into the dermis.
Hair Follicles
• Arises from the epidermis and dermis of the skin.
• Drainage from sebaceous glands via the contraction of arrector pili
muscles.
• It contains an inner root (from epidermis) and an outer root (from
dermis).

25. • Hair is composed of medulla, cortex and outer cuticle.
• 2 types of hair: fine vellus and coarse terminal hairs.
• They undergo a growth (anagen - most common), regressing
(catagen - least common) and resting (telogen) phase.

26. • There are three main glands in the skin: eccrine, apocrine and
sebaceous
• Eccrine: odourless sweat glands in most locations in the body
• Apocrine: odour sweat glands, mainly found in the axilla and groin.
• Sebaceous: sebum-producing holocrine glands that drain in
pilosebaceous units in hair-bearing skin and directly onto the skin
in labia minor and penis
• Appendages include Meissner's corpuscle (light touch), Pacinian
corpuscle (vibration, deep pressure), Bulb of Krause (cold
temperature), Ruffini ending (hot temperature).
Glands

28. • Deep Vessels: arteries such as the aorta or common carotids etc
• Fasciocutaneous vessels: travel across the fascia directly to the
skin
• Musculocutaneous vessels: travel in the muscle and indirectly
provided perforators to the skin.
• Plexuses: there are a series of fascial, subcutaneous and dermal
plexuses.

29. Lymphatics
• An extensive lymphatic framework runs alongside many of the skin’s blood
vessels
• Particularly those attached to the venous end of the capillary networks

30. Nerves
• Meissner receptors detect light touch.
• Pacinian corpuscles perceive deep pressure and vibrational changes.
• Ruffini endings detect deep pressure and stretching of the skin’s
collagen fibers.
• Free nerve endings located in the epidermis respond to pain, light
touch, and temperature variations.
• Merkel receptors associated with the Merkel cell respond to
sustained light touch induction over the skin

31. • Dermatomes are areas of skin mainly supplied by a single
spinal nerve
• Eight cervical nerves contribute to the dermatomes (except for
C1),
• 12 thoracic nerves, five lumbar nerves, and five sacral nerves.
• Each of these nerves relays sensation (including pain) from a
particular region of the skin to the brain.

32. Muscles
• Arrector pili muscles, the smallest skeletal muscles of the body,
are found in all areas of the skin that contain hair follicles.
• Tiny muscular structures control the positioning of hairs and the
activity of sebaceous glands in response to environmental
induction, such as heat and abrasion.
• The arrector pili muscles contract and raise the hairs under
conditions of stress when the sympathetic nervous system is
activated
• They also perform this action in response to cold, "goosebumps."

33. Physiological variants
• Thick skin is present on the palms and soles, where there is
marked keratinization and the stratum lucidum layer.
• Thinner skin is present on eyelids, axillae, genitals, and the
mucosal surfaces exposed to the external environment, such
as oral mucosa, vaginal canal, and other selected internal body
surfaces.

34. Ageing Skin Anatomy

35. Pointers during Skin examination
• Individuals with fair skin, light hair, and blue eyes may develop
postoperative scars that remain pink for an extended period.
• Persons with dark skin, hair, and eyes may develop scars that remain
pigmented for a prolonged period after surgery.
• An assessment of previous scars and keloids should be made.
• Individuals with hyperelastic skin features are characterized by
hyperextensibility of the joints (elbows, wrists, and knees), anterior
hooding of the navel, and lax skin.

36. • Higher risk for development of wide scars, permanent railroad tracking
suture marks, hypertrophic scars, and prolonged erythema of the scars
lasting up to 1 year, eventually resulting in a porcelain-colored white scar
• Patients with common skin conditions, such as atopic dermatitis,
psoriasis, and unusually dry skin, may have high counts of staphylococcal
organisms on their skin and thereby increased risk of wound infections

37. Surgical considerations
Surgical incisions are usually made along the relaxed skin tension lines to improve
healing and reduce scarring, especially in cosmetic surgical procedures
They closely match the alignment of bundles of collagen fibers within the dermis.
surface of the skin and its deeper structures show various linear markings, seen as
grooves, raised areas and preferred directions of stretching
1. Surface pattern lines, tension lines and skin creases
2. Wrinkle lines
3. Flexure joint lines
4. Papillary ridges
5. Relaxed skin tension lines
6. Lines of langer and kraissl
7. Blaschkos lines

38. • Department web library- presentation by Dr. R.K sir
• Anatomy of skin plastic surgery key Marcus L. Frohm, Alison B. Durham, Christopher K. Bichakjian and
Timothy M. Johnson
• Anatomy, Skin (Integument) Lopez -Ojeda W, Pandey A, Alhajj M, et al.
• Maranduca MA, Branisteanu D, Serban DN, Branisteanu DC, Stoleriu G, Manolache N, Serban IL.
Synthesis and physiological implications of melanic pigments. Oncol Lett. 2019 May;17(5):4183-4187.
[PMC free article] [PubMed)
• Parikh UM, Mentz J, Collier I, Davis MJ, Abu-Ghname A, Colchado D, Short WD, King A, Buchanan EP,
Balaji S. Strategies to Minimize Surgical Scarring: Translation of Lessons Learned from Bedside to Bench
and Back. Adv Wound Care (New Rochelle). 2022 Jun;11(6):311-329. [PubMed]
References

39. Ageing is a fact of life.
Looking your age is not.
- Dr. Howard Murad.
Thank You!