ANATOMY and PHYSIOLOGY
for
DEBRIDEMENT
Professor Donald G. MacLellan
Executive Director
Health Education & Management Innovations
Structures of the Skin
EPIDERMIS
4 MAIN CELL TYPES:
Keratinocytes - main cell type; arranged in 5
layers; perpetually being generated
Melanocytes - melanin production; brown skin
colour
Merkel Cells - mechanoreceptor function
Langerhan’s cells – immune function
Stratum Germinativum
• Deepest layer, in contact with dermis
• Single layer of cells
• Only layer of epidermis capable of
cell division
• Contain melanocytes
Melanocytes
• Capable of producing the brown
pigment, melanin
• Melanin can absorb energy from
ultraviolet (UV) light
• UV light contains high energy
photons that can damage DNA –
mutations
• Melanin can prevent damage to DNA,
helps to prevent skin cancer
Stratum Spinosum
• Several layers thick
• Cells of this layer begin to produce
keratin
• Keratin is a water-insoluble protein
that protects the body from water
Stratum Granulosum
• Multilayer and cells become
compressed
• Keratin crystallizes into granules
within the cytoplasm
• Cells are metabolically dead
Stratum Lucidum
• Clear layer of cells
• Only present in thick skin
• Cells nothing more than a bag of
keratin
Dermis
1.
2. Protection
- physical abrasion
- dehydration
- ultraviolet radiation
3. Sensation
- touch
- vibration
- pain
- temperature
4. Excretion
5. Immunity/ Resistance
6. Blood Reservoir
- 8 to10 % in a resting adult
7. Synthesis of vitamin D
- UV light
- aids absorption of calcium
Dermis
Papillary layer:
– 1/5 of dermis – loose areolar
connective tissue
– Highly vascular
– Dermal papillae - fingerprints
Dermis
Reticular layer:
– Dense irregular connective tissue
– Sebaceous (oil) glands
– Hair follicles
– Ducts of sudoriferous (sweat)
glands
– Meissner’s and Pacinian corpuscles
Hypodermis
• Attaches the reticular layer to the
underlying organs
• Loose connective tissue and adipose
tissue
• Major blood vessels
Accessory organs or
epidermal derivatives
Hair:
– Epidermal growths - for protection
– 100,000 hairs on head
– 100 hairs fall out daily
– Sebaceous glands, arrector pili
muscle, and hair root plexus
(touch)
– Hair growth and replacement have
a cyclical pattern
Nails:
• Plates of highly packed, keratinized
cells
• Protection, scratching & manipulation
• Formed by cells in nail bed called the
matrix (in area of lunula)
• Growth 1 mm / week
• Eponychium - cuticle
DEFINITIONS
Endocrine - ?
Exocrine - ?
Merocrine - secrete into vesicles & release at cell surface
Apocrine - lose part of membrane with secretion
Holocrine – cell lysed with secretion
Skin Glands
Sebaceous (oil) glands:
– Holocrine glands
– Sebum is typically secreted into a
hair follicle or occasionally onto
the body surface.
– Moistens hair and waterproofs skin
– It also is quite bactericidal.
– Lanolin is sheep sebum
Merocrine Sweat
Glands
• More numerous than apocrine sweat glands.
• Especially prominent on the palms, soles,
and forehead.
• Simple, coiled, tubular glands.
• Duct empties into a funnel-shaped pore at
the skin surface.
• Major function of merocrine sweating is to
cool the body – thermoregulation.
Merocrine Sweat Glands
• Merocrine sweat is a
dilute watery solution of
some salts (including
NaCl), vitamin C,
antibodies, small amounts
of nitrogenous wastes
(urea, uric acid, and
ammonia) and lactic acid.
• pH of sweat is 4-6
creating a film on the
body known as the acid
mantle which is
bacteriostatic
Apocrine Sweat
Glands
• Found primarily in the axillary, pubic,
and anal regions of the body.
– Also found in the facial region in
men only.
• Larger than merocrine sweat glands.
• Ducts empty into hair follicles.
• Apocrine sweat is thicker than
merocrine sweat since it contains
more lipids and proteins.
• When it’s degraded by epidermal
bacteria, foul odours can be
produced.
Apocrine Sweat Glands
• Become active at puberty.
• Secrete sweat during times of pain, stress, and
sexual activity.
• May (??) have a possible pheromone-like
function.
• Play no role in thermoregulation.
Remember: Glands are derivatives of epithelial tissue.
So even though many reside in the dermis, they are not
made from connective tissue.
Sensory Innervation of the Skin
Physiology of Aged Skin
Functional Decrement:
- Epidermal turnover
- Barrier function/ chemical clearance
- Inflammatory response
- Mechanical protection
Nervous System
A Dermatome is an
area of skin
associated with a
pair of dorsal roots
from the spine