







Skin (integument)
o Consists of three major regions
 Epidermis- superficial region
 Dermis- middle region
 Hypodermis- (superficial fascia) deepest region
Epidermis
o Keratinized- protein (stratified squamos)
o Cell of epidermis
 Keratinocytes
 Melanocytes
 10-25% of cells in lower epidermis
 Produce pigment melanin
o Epidermal dendritic- cells macrophages that help activate
immune system.
o Tactile (merkel) cell- touch receptors
Layers of the epidermis: Stratum Basale (basal layer)
o Deepest epidermal layer firmly attached to the dermis
o Single row of stem cells
o Also called stratum germinativum cells undergo rapid division
o Journey form basal layer to surface
 Take 25-45 days
Layers of epidermis: stratum spinousum (prickly layer)
o Cells contain a weblike system of intermediate prekeratin
filaments attached to desmosomes
o Abundant melanin granules and dendritic cell
Layers of epidermis: stratum granulosum (granular layer)
o Thin, three to five cell layers in which the cells flatten
o Keratohyline and lamellate granules accumulate
Layers of epidermis: stratum lucidum (clear layer)
o In thick skin
o Thin, transparent band superficial to the stratum granuiosum
o Few row of flat, dead keratinocytes
Layers of epidermis: stratum corneum (horny layer)
o 20-30 rows of dead, flat, keratinized membranous sacs
o Three-quarters of the epidermal thickness
o Function:
 Protects from abrasion and penetration
 Waterproofs
 Barrier against biological, chemical and physical assaults
Dermis
o Strong, flexible connective tissue
o Cells include fibrolasts, macrophages, and occasionally most cells
and white blood cells
o Two layers:







 Papillary
 Recticular
Layers of Dermis: Papillary
o Papillar layer
 Areolar connective tissue with collagen and elastic fibers
and blood vessels
o Cermal papillae contain:
 Capillary loops
 Meissner’s corpuscles
 Free nerve endings
Layers of Dermis: Reticular
o Reticular layer
 80% of the thickness of dermis
 Collagen fibers provide strength and resiliency
 Elastic fibers provide stretch- recoil properties
Skin Marketing: Friction ridges
o Epidermal ridges lies atop deeper dermal papillary ridges to form
friction fridges of finger prints
Skin Marking: Cleavage lines
o Collagen fibers arranged in bundles form cleavage (tensions)
lines
o Incisions made parallel to cleavage lines heal more readily
Skin color
o Three pigments contribute to skin color:
 Melanin
 Yellow to redish- brown black
 Freckles and melanin mole
 Produce in melanocytes- keratinocyte “pigment shields”
 Accumulation of melanin
 Carotene
 Yellow to orange; palms and soles
 Hemoglobin
 Pinkish hue of cell
Appendages of the skin
o Derivatives of the epidermis
 Sweat gland
 Oil glands
 Hairs and hair follicles
 Nails
o Sweat Gland
o Aprocrine and eccrine
Eccrine- palms, soles, and forehead
o 99% water, NaCl, VC, antibiotic
o Ducts connect to pores











o Function in thermo regulation
Aprocrine- avilary and anogenital area
o Sebum- sweat and fatty substances and proteins
o Ducts connect to hair follicles
o Functional from puberty on wad
Specialized procrine
o Ceruminous gland- external ear canal secrete cerement
o Mammary glands
Sebaceous (oil) gland
o Widely distributed
o Most develop from hair follicles
o Become active at puberty
Sebum
o Oily holocrine secretion
o Bacterial
o Softens hair and skin
Hair
o Functions:
 Alertin the body to presence of insects on the skin
 Guarding the scalp against physical trauma, heat loss, and
sunlight
Distribution
o Entire surface except palms, soles, lips, nipples, and portion of
external genitalia
o Consists of head keratinized cells
o Contains hard keratin, more durable than soft keratin of skin
o Hair pigments: melanin (yellow, rust brown, black, gray)
 Gray/white hair: decreased melanin production, increased
air bubbles in shaft
Hair follicles
o Extends from the epidermal surface into dermis
o Two-layered wall: outer connective tissue root sheath
o Hair bulb: expended
Hair follicle receptor (root hair plexus)
o Sensory nerve ending
o Stimulate by bending hair
Arrector pili
o Smooth muscle attach
o “goosebumps”
Types of hair
o Vellus- pale, fine body hair of children and adult females
o Terminal- coarse, long hair of eyebrows, scalp, axillaries, and
pubic regions (and face and neck of males)
Hair growth




o Growth phase (weeks to years) followed by regressive stage and
resting phase (1-3month)
o Growth phase varies (6-10 years in scalp, 3-4 months in
eyebrows)
Hair thinning and baldness
o Genetically determined and sex influenced condition
o Male pattern baldness is caused by follicular response to DHT
Structure of nails
o Scale like modification of the epidermis on the distal dorsal
surface of fingers and toes (DHT testrosome)
Integumary system:
o Protection- 3 types barrier
 Chemical:
 Low pH (acid mantle) and releasing defensins
retard bacterial activity
 Physical/Mechanical
 Keratin and glycolipids brock most water and watersoluble substances
 Limited penetration of skin by lipid-soluble
substances, plant oleoresins (poison ivy)
 Biological
 Dendritic cells, macrophages, and DNA
o Body temperature regulation
 500 ml/day of routine insensible perspiration (at normal
body temperature)
 At elevated temperature, dilation of dermal vessels and
increased sweat gland
o Cutaneous sensation
 Temp, touch, pain
o Metabolic functions
 Synthesis of vitamin D precursor and collagen
o Blood reservoir- up to 5% of body’s blood volume
o Excretion- nitrogenous wastes and salt in sweat
Skin cancer:
o Most skin tumors are benign (do not metastasize)
o Risk factor
 Over exposure to UV radiation
 Irritation to skin
o Some skin lotions contain enzymes in liposome’s that con fix
damaged DNA
o Three major types:
 Basal cell carcinoma
 Least (most common)
 Surgical excision- successful 99%


Squamos cell carcinoma
 Second most common
 High success rate
 Kerintinocytes
 Radian therapy
Melonoma
 Most dangerous
 Treat by wide surgical excision by immunotherapy
 Melanocyte
 Resistant to chemotherapy