The Integumentary System
(The Skin)
Anatomy & Physiology I
Chapter 6
The Integumentary System
Integumentary System – consists of the skin and
its accessory organs
◦ hair, nails, and cutaneous glands
most visible system and more attention paid to
this organ system
skin is the most vulnerable organ
◦ exposed to radiation, trauma, infection, and injurious
chemicals
dermatology – study and medical treatment of
the integumentary system
inspection of the skin, hair, and nails is significant
part of a physical exam
Skin and Subcutaneous Tissue
the body’s largest and heaviest organ
◦ 15% of body weight
consists of two layers:
◦ epidermis – stratified squamous epithelium
◦ dermis – connective tissue layer
hypodermis – another connective tissue layer below
the dermis
thick skin – on palms and sole, and corresponding
surfaces on fingers and toes
◦ has sweat glands, but no hair follicles or sebaceous (oil)
glands
thin skin – covers rest of the body
◦ possesses hair follicles, sebaceous glands and sweat glands
Cross section of the skin.
Epidermis
epidermis – surface portion of the skin
keratinized stratified squamous epithelium
◦ dead cells at the surface packed with tough
protein – keratin
◦ lacks blood vessels; depends on the diffusion of
nutrients from underlying connective tissue
Stratum basale – deepest layer of epidermis
Stratum corneum – superficial layer of
epidermis
Cells of Epidermis
five types of cells of the epidermis
◦ stem cells - undifferentiated cells that give rise to
keratinocytes
in deepest layer of epidermis (stratum basale)
◦ keratinocytes - synthesize keratin
great majority of epidermal cells
◦ Melanocytes - synthesize pigment melanin that shields DNA
from ultraviolet radiation
occur only in stratum basale
◦ tactile (merkel) cells - touch receptor cells associated with
dermal nerve fibers
in basal layer of epidermis
◦ dendritic (langerhans) cells - macrophages originating in bone marrow
that guard against pathogens that penetrate the skin
Life History of Keratinocytes
keratinocytes are produced deep in the epidermis
by stem cells in stratum basale
mitosis requires an abundant supply of oxygen and
nutrients
◦ deep cells acquire from blood vessels in nearby dermis
newly formed keratinocytes push the older ones
toward the surface
in 30 - 40 days a keratinocyte makes its way to the
skin surface and flakes off
◦ slower in old age
◦ faster in skin injured or stressed
calluses or corns – thick accumulations of dead keratinocytes on
the hands or feet
Cell Types and Layers of the of the Epidermis
Sweat pore
Stratum corneum
Stratum lucidum
Stratum granulosum
Exfoliating
keratinocytes
Dead keratinocytes
Sweat duct
Living keratinocytes
Stratum spinosum
Dendritic cell
Tactile cell
Melanocyte
Stem cell
Stratum basale
Dermal papilla
Tactile nerve fiber
Dermis
Dermal blood vessels
Epidermal Water Barrier
epidermal water barrier - forms between stratum
granulosum and stratum spinosum
consists of:
◦ lipids secreted by keratinocytes
◦ tight junctions between keratinocytes
critical to retaining water in the body and
preventing dehydration
cells above the water barrier quickly die
◦ barrier cuts them off from nutrients below
◦ dead cells exfoliate (dander)
◦ dandruff – clumps of dander stuck together by sebum (oil)
Dermis
dermis – connective tissue layer beneath the
epidermis
composed mainly of collagen with elastic fibers,
reticular fibers
well supplied with blood vessels, sweat glands,
sebaceous glands, and nerve endings
hair follicles and nail roots are embedded in dermis
smooth muscle (piloerector muscles) associated
with hair follicles
◦ contract in response to stimuli, such as cold, fear, and
touch – goose bumps
Dermis
dermal papillae – upward fingerlike extensions of the
dermis
◦ friction ridges on fingertips that leave fingerprints
The dermis has two layers:
◦ papillary layer (superficial) – thin layer of areolar
tissue; rich in small blood vessels
◦ reticular layer – deeper and much thicker layer
of dermis
consists of dense, irregular connective tissue
stretch marks – tears in the collagen fibers caused
by stretching of the skin due to pregnancy or obesity
Structure of the Dermis
Papillary layer of dermis
Reticular layer of dermis
Subcutaneous Layer: Hypodermis
(superficial fascia)
NOT a layer of skin
binds skin to underlying tissues
Adipose and areolar tissue
pads body
Highly vascular
◦ drugs introduced by injection quickly
absorbed
subcutaneous fat
◦ energy reservoir; thermal insulation
◦ 8% thicker in women
Nerves and nerve endings
Accessory Structures of the Skin
Some structures of the integumentary system
protect the skin and have some more generalized
functions as well
Cutaneous Glands
Hair
Nails
Cutaneous Glands
the skin has five types of glands:
• Two types of sudoriferous glands:
―
merocrine (eccrine) sweat glands
―
apocrine sweat glands
• sebaceous glands
• ceruminous glands
• mammary glands
Sweat Glands (Sudoriferous)
merocrine (eccrine) sweat glands
◦ most numerous skin glands
◦ watery perspiration that helps cool the body
apocrine sweat glands
◦ develop at puberty; ducts lead to nearby hair follicles
◦ occur in groin, anal region, axilla, bearded area in mature
males
◦ scent glands that respond to stress and sexual stimulation
◦ produce sweat that is thicker, milky, and contains fatty acids
◦ bromhidrosis - disagreeable body odor produced by
bacterial action on fatty acids
Sweat
potassium ions, urea, lactic acid, ammonia, and some
sodium chloride remain in the sweat, most sodium
chloride reabsorbed by duct
some drugs are also excreted in sweat
on average, 99% water, with pH range of 4 to 6
◦ acid mantle – inhibits bacterial growth
insensible perspiration – 500 ml per day
◦ does not produce visible wetness of skin
diaphoresis – excessive sweating with wetness of the skin
◦ exercise – may lose one liter of sweat per hour
Sebaceous Glands
Produce a variety of secretions
◦ Sebum – oily secretion produced by sebaceous glands
◦ Vernix caseosa - the waxy looking white substance that covers a
newborn baby
◦ Eye lubrication - Sties are formed because of bacterial infection
in the Sebaceous glands of the eye.
short ducts opening into hair follicle
keeps skin and hair from becoming dry,
brittle, and cracked
lanolin – sheep sebum
6-18
Ceruminous Glands
found only in external ear canal
their secretion combines with sebum and dead
epithelial cells to form earwax (cerumen)
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keep eardrum pliable
waterproofs the canal
kills bacteria
makes guard hairs of ear sticky to help block
foreign particles from entering auditory canal
Mammary Glands
Men and women have mammary glands but they are
underdeveloped in men
mammary glands – milk-producing glands that
develop only during pregnancy and lactation
◦ modified apocrine sweat gland
◦ richer secretion released by ducts opening into the nipple
Hair
Composed mainly of keratin and is not living
Hair follicles
Melanocytes
Arrector pili
• Hair is divisible into three zones along its
length
– bulb – a swelling at the base where hair
originates in dermis or hypodermis
• only living hair cells are in or near bulb
– root – the remainder of the hair in the follicle
– shaft – the portion above the skin surface
Portion of skin showing associated glands and hair
Nails
Made of keratin produced by cells that
originate in the outer layer of the epidermis
Nail root
Nail plate
Nail bed
Lunula
Cuticle
Nail structure.
Functions of the Skin
Four major functions
Protection against infection
Protection against dehydration (drying)
Regulation of body temperature
Collection of sensory information
Protection Against Infection
Intact skin forms a primary barrier against
invasion
Interlocking pattern resists penetration
Shedding removes pathogens
Protects against bacterial toxins
Protects against some harmful
environmental chemicals
Protection Against Dehydration
Skin prevents water loss by evaporation
Keratin in the epidermis
Sebum release from the sebaceous glands
Regulation of Body Temperature
Loss of excess heat and protection from
cold are important functions of the skin
Constriction of blood vessels
Dilation of blood vessels
Evaporation of perspiration
Collection of Sensory Information
Skin has many nerve endings and other
special receptors
Free nerve endings
Touch receptors (Meissner corpuscle)
Deep pressure receptors (Pacinian
corpuscle)
Other Activities of the Skin
Absorption of substances such as medications
Excretion
◦ Water
◦ Electrolytes
◦ Wastes
Manufacture of vitamin D
Color
Factors that influence skin color
Amount of pigment in the epidermis
◦ Melanin
◦ Carotene
Quantity of blood circulating in superficial blood vessels
◦ Hemoglobin – pigment that gives blood its color
Composition of substances circulating in blood
◦ Oxygen
Color
Factors that influence skin color
Discoloration
◦ Pallor: pale skin, reduced blood flow
◦ Flushing: redness, as in fever
◦ Cyanosis: bluish color of skin; lack of oxygen in blood
◦ Yellow skin: jaundice, bilirubin in blood; carotenemia
from excessive intake of carrots or other deeply
colored vegetables
Lesions
Any wound or local damage to tissue
Surface lesions
◦ Macule – spot that is not raised or depressed
◦ Papule – solid, raised lesion
◦ Vesicle – fluid filled sac or blister
◦ Pustule – a vesicle filled with pus
Deeper lesions
◦ Excoriation – simple scratch
◦ Laceration – rough; jagged wound formed from tearing
of the skin
◦ Ulcer – sore associated with disintegration and death of
tissue
◦ Fissure – a crack in the skin
Burns
leading cause of accidental death
◦ fires, kitchen spills, sunlight, ionizing radiation, strong acids
or bases, or electrical shock
◦ deaths result primarily from fluid loss, infection and toxic
effects of eschar – burned, dead tissue debridement –
removal of eschar
Categorized by
Depth of damage
◦ Superficial partial-thickness
◦ Deep partial-thickness
◦ Full-thickness
Amount of body surface area (BSA) involved
◦ Rule of nines
◦ Lund and Browder method
Burns
classified according to the depth of tissue involvement
◦ first-degree burns – partial thickness burn - involve only
the epidermis
marked by redness, slight edema, and pain
heal in a few days
most sunburns are first degree burns
◦ second-degree burns – partial thickness burn - involve
the epidermis and part of the dermis
leaves part of the dermis intact
red, tan, or white
two weeks to several months to heal and may leave scars
blistered and very painful
◦ third-degree burn – full thickness burn – the epidermis
and all of the dermis, and often some deeper tissues
(muscles or bones) are destroyed
often require skin grafts
needs fluid replacement and infection control
Degrees of Burn Injuries
Partial-thickness burns
First degree
Second degree
Full-thickness burns
Third degree
Tissue Repair
Wound healing
Occurs only in areas with actively dividing cells
◦ Epithelial tissues
◦ Connective tissues
◦ Minimally in muscle and nervous tissue
Is affected by
◦ Nutrition
◦ Blood supply
◦ Infection
◦ Age
Care of the Skin
Proper nutrition
Adequate circulation
Regular cleansing
◦ Removes dirt and dead skin
◦ Sustains slightly acid environment to inhibit
bacteria
Protection from sunlight
◦ Exposure to UV light causes genetic
mutations in skin that can lead to cancer, and
causes premature aging.
Skin Disorders
Range from superficial to deep-seated
Dermatitis
Inflammation of the skin
Dermatosis is any skin disease
Atopic dermatitis
Psoriasis
Chronic, recurrent overgrowth of
epidermis
Sharply outlined red (erythematous) areas
Flat areas (plaques) covered with silvery
scales
A hereditary pattern sometimes present
Immune disorder may be involved
Skin Cancer
skin cancer – induced by the ultraviolet rays of the
sun
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most often on the head and neck
most common in fair-skinned people and the elderly
the most common form of cancers in the US
one of the easiest to treat
has one of the highest survival rates if detected and
treated early
◦ three types of skin cancer named for the epidermal cells in
which they originate
◦ basal cell carcinoma, squamous cell carcinoma, and
malignant melanoma
Basal Cell Carcinoma
Basal cell carcinoma
- most common type
- least dangerous because it seldom metastasizes
- forms from cells in stratum basale
- lesion is small shiny bump with central depression and beaded
edges
Squamous Cell Carcinoma
Squamous cell carcinoma
- arise from keratinocytes from stratum spinosum
- lesions usually appear on scalp, ears, lower lip, or back of the hand
- have raised, reddened, scaly appearance later forming a concave
ulcer
- chance of recovery good with early detection and surgical removal
- tends to metastasize to lymph nodes and may become lethal
Malignant Melanoma
Malignant melanoma
- skin cancer that arises from melanocytes often in a preexisting mole
- less than 5% of skin cancers, but most deadly form
- treated surgically if caught early
- metastasizes rapidly - unresponsive to chemotherapy - usually fatal
- person with metastatic melanoma lives only 6 months from diagnosis
- 5% - 14% survive 5 years
- greatest risk factor – familial history of malignant melanoma
- high incidence in men, redheads, people who experience severe
sunburn in childhood
Acne and Other Skin Infections
Acne
◦ Sebaceous glands disease
Impetigo
◦ Staphylococcal or streptococcal origin
Viral infections
◦ Herpes simplex virus
◦ Herpes zoster virus (shingles)
◦ Human papillomavirus (HPV) (wart or verruca)
Fungal infections
◦ Tinea or ringworm
Alopecia (Baldness)
Factors that affect baldness
Heredity, aging, and male sex hormones
(male pattern baldness)
Systemic disease
Drugs
Allergy and Other Immune Disorders
Often involve the skin
Allergy—reaction to a substance
Autoimmune disorders—reaction to
one’s own tissues
◦ Pemphigus
◦ Lupus erythematosus
◦ Scleroderma
Pressure Ulcers
Skin lesions that appear where the body
rests on skin that covers bony projections.
Also known as decubitus ulcers or
bedsores
End of Presentation
