ANATOMY AND
PHYSIOLOGY OF THE
SKIN
• Dr Tampaki Ekaterini Christina, Plastic and Reconstructive Surgeon
• Dr Filippou Dimitrios, Assistant Professor- General Surgeon
• Dr Sinou Natalia, PhD candidate
What is Skin?
■ Skin = Integument
■ The body’s largest organ contributing to one
sixth of the total body weight.
■ Covers 20 square feet in area (adult)
■ Three primary layers:
Epidermis
Dermis
Subcutaneous tissue: adipose tissue beneath
dermis.
■ Deep (muscular) fascia: thick fascia between
subcutaneous tissue and underlying muscles.
■ Skin appendages: Hair, nails, sweat glands,
sebaceous glands.
Epidermis
■ The outmost/top layer of the skin (protective layer)
■ Has an average thickness of 0.1mm (15-100 cell
layers)
■ Avascular (no blood vessels)
■ Made up of stratified squamous keratinizing epithelium
■ Divided into five sub layers:
Stratum corneum
Stratum lucidum
Stratum granulosum
Stratum spinosum
Stratum basale
Four (thin skin) versus five (thick skin) areas
of epidermis comes in.
Epidermal Layer
■ Contains four distinct layers of cells:
Keratinocytes – produce keratin
Melanocytes – pigment producing cells
Same number in all skin colors
Size and activity greater in darker skin (skin color
based on the amount produced)
Cells in dark skin more compact therefore skin more
resistant to injury
Merkel Cells – they let you feel light touch
Langerhan Cells – are part of the immune system
■ The external layer is almost completely replaced every
three to four weeks (continually shedding and reviewing)
Epidermis: Stratum Corneum
■ Avascular
■ Made up of mature keratinocytes
■ Multilayer (up to 20 cell layers matured or
keratinized): keratinized squamous epithelium
■ Function
Fights infections
Protects against : chemical damage, wear and tear,
dehydration. Barrier to environment and prevents
transepidermal water loss:
Dressing adhesives can strip stratum corneum
and cause transepidermal water loss
Involved in formation of an acid mantle:
Makes skin less permeable to water.
Protects skin from microorganism invasion.
Epidermis
Statum Lucidum Stratum Granulosum
■ Lucid = clear. Appears cleared on
histological slides.
■ The second layer of the epidermis can
only be found in areas of your body where
the skin is thicker
■ Granular layer
Palms of the hands
Comprised of mature keratinocytes
Soles of the foot containing granules in their
cytoplasm.
No nuclei: in this layer the
keratinocytes lose their organelles
including their nuclei and then they
die.
Epidermis
Stratum Spinosum Stratum Basale
■ The cells here are attached to the base
■ Desmosomes membrane below the hemidesmosomes
■ Spiney ■ Cells both devide and grow in this layer
■ Antigen presenting dendritic cells: ■ Keratinocytes originate from this layer
Langerhans cells (most abundant in this
layer, although they can be found in other ■ Contains melanocytes – produce pigmen
layers) gives skin, hair, eyes their color.
Acid Mantle
■ Damage to the skin increases it’s pH and risk of infection
■ Diseases/conditions associated with increased skin pH:
Eczema
Dermatitis
Dry skin
Diabetes
Chronic renal failure
CVD
■ Urine, stool, perspiration on the skin increases it’s pH
Dermis
■ Immediately below the basement membrane
of the epidermis (nourishes, supports,
sustains the epidermis)
Fibroblasts, collagen, macrophages,
mast cells
■ Largest portion of the skin
■ Composed of two layers:
Papillary Dermis -- Stratum Papillare
(superficial):
Reticular (deep):
Blood vessels
Collagen fibers
Connective tissue
Dermal Layer
■ Made up of blood (vessel plexus) and lymph
vessels, nerves, sweat and sebaceous glands and
hair roots
■ Often referred to as true skin
■ Functions:
Provides tensile strength, mechanical support
and protection to the underlying muscles,
bones, and organs
Regulates temperature
Senses the environment
Papillary Dermis- Stratum Reticular Dermis –
Papillosum Stratum Reticulare
■ Is composed of thicker connective
tissue which surrounds:
The hair follicles of the skin
Sweat glands
Sebaqeous glands
■ The papillae increase the surface
area for the transfer of nutrients and Nerves
oxygen to the epidermis. Blood vessel plexus
■ It is made up of loose connective ■ Contains fibroblasts, collagen
tissue – areolar connective tissue (strength and resistance) and elastic
fibers
Dermal
Appendages
■ Includes:
Hair follicles
Sebaceous and sweat glands
(lubricate, control pH, temperature)
Fingernails and toe nails
■ Originates in dermis and protrude into the
epidermis
■ Contribute epithelial cells for
reepithelialization
Dermis: Illustrations of a tactile Meissner corpuscle. A tactile corpuscle (corpuscu
tactus) such as the Meissners corpuscles facilitate the sensorial capabilities of
skin such as light touch, low frequency vibration.
- Ilustration of free nerve endings, hair follicles, sweat glands, sebaqueous glands.
Subcutaneous Tissue
■ Adipose or hypodermis layer
■ Innermost layer of the skin, various thickness
■ It is composed of:
adipose tissue (energy storage, shock absorption).
The thicker the adipose layer, the poorer the blood
supply through it.
blood vessels (thermoregulation), subcutaneous
vascular plexus. loose connective tissue
nerve tissue (cutaneous nerves): provide sensory
skin innervation – sensory receptors. Ex. lamellar
corpuscles = Pacinian corpuscles detect pressure
and high frequency vibrations.
Fascia: separates the subcutis from the underlying muscle. It is a thin lay
of fibrous connective tissue, protects the muscles and helps reduce
friction.
Muscle layer: contains intramuscular arteries and veins.
Function of Skin
Six primary functions:
■ Temperature regulation
■ A sensory organ for pain, temperature, and
touch
■ Eliminates waste
■ A protective barrier between internal organs
and the external environment
■ Synthesis of Vitamin D
■ Social interaction
Temperature Regulation
■ Thermoregulation accomplished through combined function of nerves, glands, and
blood vessels
■ When skin exposed to cold:
Blood vessels constrict and blood flow reduced to skin
Body temperature falls
Body conserves heat
■ When skin exposed to heat:
Blood vessels dilate and blood flow increased to skin
Body temperature rises
Sweat production increases allowing body to cool
Sensation
■ Nerve endings in skin sense:
Pain
Pressure
Temperature
■ Nerve fibers (which originate in nerve roots in the spine),
supply the skin, (Dermatomes)
■ Loss or reduction in sensation increases risk for injury
■ Tactile corpuscles (corpusculum tactus) such as the
Meissner corpuscles facilitate the sensorial capabilities
of the skin such as light touch, low frequency vibration
and other sensations.
■ Lamellar corpuscles such as the Pacinian corpuscles
detect pressure and high frequency vibrations.
Waste Elimination
■ Excretes:
Waste products
Electrolytes
Water
Average adult looses 500mL water through skin per day
■ 2 million skin pores release water and body waste to air
Vitamin D
Synthesis
■ Vitamin D assists in mineralization of
bones and teeth
■ Vitamin D that is synthesized in skin
is transferred to other parts of body
Skin Barrier
■ Barrier to:
Trauma
Bacterial invasion
Excessive loss of fluids and protein
■ Also protects tissues and underlying structures
from injury
■ Skin pigmentation protects against UV radiation
Factors that may impair skin Integrity
• Dryness
• Age
• Nutrition
• Hydration
• Environment
The Aging Process
■ Biological age does not correlate with
chronological age
■ The rate at which we age is dependent on:
Our genes
Our environment
How we look after our bodies
Aging Skin
■ 20% decrease in dermal thickness leads
to thinning of the skin
■ Epidermal-dermal papillae become
flattened, increasing susceptibility to
friction and shear
■ Loss of penetrability to substances in the
environment – irritants more readily
absorbed
■ Elastin fibers are lost – skin less elastic
Skin and the effects of aging
• Dermis atrophies:
• Slows wound contraction
• Increases risk of
dehiscence
• Diminished dermis vascularity
• Subcutaneous fat atrophies
(most noticeable in face, backs of
hands and shins)
• Collagen in the skin reduces
(collagen fibers become
compressed)
Skin Aging
• Blood vessels become
thinner and more fragile
causing small hemorrhages
called senile purpura
• Reduction in sweat glands
and sebum resulting in
decreased skin hydration (dry,
itchy, inelastic skin)
Examples of skin conditions
■ Basal cell carcinoma: Arises from the stratum basale of the epidermis
■ Squamous cell carcinoma: Involves the squamous cells of the stratum spinosum
■ Melanoma: Type of malignant skin cancer that involves melanocytes
■ Naevi = moles , congenital or acquired that are caused by a benign overgrowth of melanocyte
■ Psoriasis: Autoimmune condition causing pink scaly plaques all over the body. Treatmen
phototherapy, immunosuppresants, topical agents and alternative therapies.
■ Eczema: atopic dermatitis. A dry inflammation of the skin. It has been linked to asthma an
hay fever. Treatment: Steroid creams and moisturizers.
Most common skin cancers – Surgical
treatment
■ MELANOMA
■ SCC
■ BCC
Questions
Thank you
