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INTEGUMENTARY SYSTEM
Bio 137 Anatomy & Physiology I
Organ System
• Groups of closely related organs that work together to
perform similar functions
• For each organ system studied, know:
• What are the organs that compose the system?
• What are the functions of the system?
Structures of the Integumentary System
• Organ:
• Skin
• Accessory Structures
• Hair
• Sweat Glands
• Sebaceous Glands
• Nails
Skin
• Also called the Cutaneous Membrane
• The largest human organ by weight & surface
area
• 22 ft2
• 4.5-5kg (16% of body weight)
• Thickness varies by location: eyelids vs. heels of feet
Structure of the Skin
• Composed of 2 layers
1. Epidermis – epithelial tissue
2. Dermis – connective tissue
• Subcutaneous (SubQ) layer below dermis
• Adipose and areolar connective tissue
• We lose almost a kg of skin epithelium a year that
becomes a major part of household “dust”.
Structures of the Skin
Integumentary System Functions
• Protection
• Immunity
• Regulation of body
temperature
• Excretion
• Sensory reception
• Synthesis of vitamin D
• Blood reservoir
The Epidermis
• Types of skin:
• Thin (hairy) skin covers all body regions except the palms, palmar
surfaces of digits, and soles.
• Thick (hairless)
skin covers the
palms, palmar
surfaces of
digits, and
soles.
Epidermis
• Keratinized Stratified Squamous Epithelium
• Avascular
• Usually very thin, 0.07mm-0.12mm
• Outermost cells are keratinized and dead
• These cells are sloughed off as new cells below mature and move
up
Cells of the Epidermis
• The epidermis contains
four major types of cells:
• Keratinocytes
• Melanocytes
• Langerhans cells
• Merkel cells
Cells of The Epidermis
• Keratinocytes (90% of the cells)
• Produce keratin - a tough fibrous protein that provides protection.
• Melanocytes
• Produce the pigment melanin that protects against damage by
ultraviolet radiation.
• Langerhans cells
• Macrophages that originated in the red bone marrow.
• Involved in the immune responses.
• Merkel cells (least numerous)
• Function in the sensation of touch along with the other adjacent
tactile discs (receptors).
Epidermis
• Keratinized stratified squamous epithelium
• 5 distinct layers of the epidermis in thick skin (4 in
thin)
Outermost
• Stratum corneum
• Stratum lucidum
• Stratum granulosum
• Stratum spinosum
• Stratum basale
Deepest
Epidermal Layers
• Stratum corneum – Oldest, outermost layer
• 25-50 layers of dead keratinocytes, filled with keratin
• Continuously shed
• Constant friction can stimulate the cell
production in this layer and produces a
callus
• Stratum lucidum - Only in thick skin
of soles and palms
• 4-6 layers of dead keratinocytes
• Stratum granulosum - non-dividing 3rd layer
• 3-5 layers of keratinocytes undergoing apoptosis (cell
death)
• Barrier between metabolically active and dead cells
Epidermal Layers
• Stratum spinosum
• Multilayered keratinocytes
• Stratum basale – deepest
layer
• Contains melanocytes and a
single row of cuboidal
keratinocytes undergoing
mitosis
• Skin stem cells (Youngest layer
of cells) produces all other
epidermal layers
The Epidermis
Five Epidermal Layers
epidermis
dermis
granulosum
corneum
spinosum
basale
lucidum
16
Growth of the Epidermis
• Keratinization
• Process where new cells in the stratum basale move up in
epidermal layers and accumulate more and more keratin
protein
• Takes about 4-6 weeks
Melanin Distribution
• Melanin Pigment is produced by melanocytes in the
stratum basale
• Eumelanin (brown to black)
• Pheomelanin (yellow to red)
• Same # of melanocytes in individuals BUT different
amounts of melanin produced by these cells
•
• Melanin production affected by our DNA, sunlight,
chemicals and drugs
Skin Color is due to accumulation of
melanin within melanocytes
The Epidermis
• Skin Pigments
• Freckles are clusters of concentrated melanin triggered
by exposure to sunlight.
• Moles are benign localized overgrowth of melanocytes
• Malignant melanoma is a cancer of melanocytes.
Skin Conditions
• Production of epidermal cells closely balances loss of
dead cells
• If skin is rubbed regularly rate of mitosis increases
• Calluses and corns
• Psoriasis - chronic skin disease
• Cells divide seven times more frequently
• Shed prematurely: 7-10 days
• Make abnormal keratin: flaky, silvery scales at skin surface
• Effective treatments: suppressing cell division
The Epidermis
• Skin Pigment Disorders
• Vitiligo – The partial or complete loss of melanocytes in the
skin.
• Irregular white spots in skin
• Possible autoimmune disorder
• Albinism is the inherited inability to produce melanin.
• Characterized by the complete or partial absence of pigment in the
skin, hair, and eyes due to a defect of an enzyme involved in the
production of melanin.
Aging
• With age, there is an increased susceptibility to
pathological conditions
• Decubitus ulcer
The Dermis
• Connective tissue containing collagen and elastic
fibers
• 1mm - 2mm thick
• Contains:
• Blood vessels, nerves, Hair follicles and glands are
embedded here
• Functions: Binds epidermis to underlying tissues &
nourishes epidermis, great tensile strength
2 Layers of Dermis
1. Papillary Layer – thin uppermost layer
• Thin collagen fibers with elastic fibers
• Dermal papillae - Responsible for a person’s fingerprint
• Sensory receptors for touch (Meissner’s corpuscles)
2. Reticular Layer – attached to SubQ
• Thick Collagen fibers with elastic fibers
• Abundant capillary networks
• Hair follicles, glands, vessels & nerves here
• Tears or excessive stretching in this region cause stretch marks
The Dermis
Subcutaneous Layer
• Also called the hypodermis
• Contains adipose tissue, blood vessels, nerves &
Pacinian Corpuscles
• Attaches skin to underlying tissue
subQ
Sensory Receptors for Touch
The skin contains different types of sensory receptors to differentiate
between the different tactile (“touch”) sensations.
• Light touch, pressure, vibration, itch and tickle
• Meissner’s Corpuscles
• Light touch receptors
• Located in dermal
papillae of papillary layer
• Abundant in hairless
portions of skin
• Lips, fingertips, palms, soles,
nipples, external genitalia
• Pacinian Corpuscles
• Deep pressure receptors
• Located deep in dermis
and/or subcutaneous layer
• Found in deeper dermal
tissues of hands, feet, penis,
clitoris, urethra, breasts,
tendons and ligaments
Figure 12.01
Accessory Structures of the Skin
Hair
• Hair is present on most skin surfaces except the palms,
anterior surfaces of fingers, and the soles of the feet.
• It is composed of dead, keratinized epidermal cells.
• Genetics determines thickness and distribution.
• Functions in touch sensations,
protects the body against
the harmful effects of the
sun and against heat loss.
Hair
• Hair develops from epithelial cells at the base of a hair
follicle deep in the dermis
• Hair shaft – superficial portion above skin surface
• Hair follicle – below the level of the skin
• Hair root – penetrates deep
in dermis
• Color is due to melanin
production from stratum basale
Nails
• Nails are composed of hard, keratinized epidermal cells
located over the dorsal surfaces of the ends of fingers
and toes.
• Nail structures include:
• Free edge
• Transparent nail body (plate)
with a whitish lunula at its base
• Nail root embedded in a fold of skin
• Functions:
• Manipulation
• Protection
Nails
Skin Glands
• Recall from Chapter 4 that glands are epithelial
cells that secrete a substance.
• Sebaceous (oil) glands are connected to hair
follicles.
• They secrete an oily substance called
sebum which does 2 important things:
• Prevents dehydration of hair
and skin
• Inhibits growth of certain bacteria
Eccrine Sweat Glands
• Most numerous
• Secrete a water solution (600ml/day) that cools the body
• Secretion is water, salts and wastes (urea/uric acid); no odor
• Respond to elevated temperature & emotional stress
• Function throughout life
• Common and widely distributed throughout skin
• Forehead
• Neck
• Back
Apocrine Sweat Glands
• Secretion empties into a hair follicle
• Located mainly in the SubQ layer
• Not involved in thermoregulation
• Function from puberty on
• Secretion is water, salts, wastes and cellular debris that is
metabolized by bacteria = ODOR
• Most abundant Locations:
• Axillary region (Armpit)
• Groin
Skin Glands
• Ceruminous glands are modified sweat
glands located in the ear canal.
• Along with nearby sebaceous glands, they are
involved in producing a waxy secretion called
cerumen (earwax) which provides a sticky
barrier that prevents entry of foreign bodies into
the ear canal.
Integumentary System Functions
• Protection
• Regulation of body temperature
• Excretion
• Sensory reception
• Immunity
• Synthesis of vitamin D
• Blood reservoir
Integumentary System Functions
• Protection
• Moisture loss
• Injury
• Microorganisms
• Chemicals
• The skin is the 1st line of defense in
the immune system!!!
Regulation of Body Temperature
• Involves sweat glands
• Shivering
• This is the diagram we covered on the very first
day of class!
Sensory Reception
• Meissner’s Corpuscles
• Light Touch receptors
• Located in dermal papillae
• Pacinian Corpuscles
• Deep Pressure receptors
• Located deep in dermis or subcutaneous layer
Integumentary System Functions
• Immunity
• Langerhan Cells
• Specialized immune cells that reside in the epidermis
• Interact with T cells in immune responses
• Acidic pH of perspiration retards microbe growth
Integumentary System Functions
• Synthesis of Vitamin D:
• Requires sunlight
• Needed for bone development, growth and remodeling
• Promotes absorption of calcium and phosphorous from
the small intenstine
Sunlight
• Cholesterol → Provitamin D → Vitamin D
(In skin)
Integumentary System Functions
• Blood reservoir:
• 10% of our blood vessels are located in
dermis
Wound Healing
• Two kinds of wound-healing processes can occur,
depending on the depth of the injury.
• Epidermal wound healing occurs following superficial
wounds that affect only the epidermis.
• Deep wound healing occurs when an injury extends to
the dermis and subcutaneous layer.
• Loss of some function and development of scar tissue usually
occurs.
Wound Healing
Wound Healing
• Inflammation is a normal response to injury, especially
if deep
• Blood vessels dilate and become leaky
• Skin becomes reddened, swollen, warm
• This provides tissues with more nutrients and oxygen
which aids in healing
• Also allows for WBC to enter tissue and prevent
infection
• Macrophages remove foreign material and begin
tissue repair
Wound Healing
Burns
• A burn is tissue damage caused by excessive
heat, electricity, radioactivity, or corrosive
chemicals that denature (break down) the proteins
in the skin cells.
• Burns destroy some of the skin's important contributions
to homeostasis—protection against microbial invasion
and desiccation, and thermoregulation.
• Burns are graded according to their severity.
Burns
• A first-degree burn involves only the epidermis
• It is characterized by mild pain and erythema (redness)
but no blisters and skin functions remain intact.
• Mild sunburn, redness but no blisters
• Heals in a few days to 2 weeks
Burns
• A second-degree burn destroys the epidermis
and part of the dermis - some skin functions are
lost.
• Redness, blister formation, edema, and pain result.
• Heals in 3-4 weeks
Burns
• A third-degree burn is a full-thickness burn
(destroys the epidermis, dermis, and subcutaneous
layer).
• Most skin functions are lost, and the region is numb
because sensory nerve endings have been destroyed.
• May be treated by skin grafting
Rule of Nines