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The Integumentary System
Chapter 5
Functions of the Integumentary System
Protection – chemical, physical, and mechanical barrier
Body temperature regulation is accomplished by:
o Dilation (cooling) and constriction (warming) of
dermal vessels
o Increasing sweat gland secretions to cool the body
Cutaneous sensation – exoreceptors sense touch and
pain
Metabolic functions – synthesis of vitamin D in dermal
blood vessels
Blood reservoir – skin blood vessels store up to 5% of
the body’s blood volume
Excretion – limited amounts of nitrogenous wastes are
eliminated from the body in sweat
Skin (Integument)
Consists of three major regions
o Epidermis – outermost superficial region
o Dermis – middle region
o Hypodermis (superficial fascia) – deepest region
Back to dermis
Back to Accessory
Skin (Integument)
Back to dermis
Epidermis
Outer portion of skin exposed to the external environment & functions in protection
Composed of keratinized stratified squamous epithelium
Cell types
o Keratinocytes – produce the fibrous protein keratin
o Melanocytes – produce the brown pigment melanin
o Langerhans’ cells –epidermal macrophages
o Merkel cells –touch
receptors associated with
sensory nerve endings
Layers of the Epidermis:
Stratum Granulosum
Basale (Basal
Spinosum
(Prickly
– Layer)
(Granular
Layer)Layer)
o Thin;
Deepest
Cells
three
contain
epidermal
to weblike
five cell
layer
system
layers
firmly
inofwhich
attached
intermediate
drastic
to the
changes
filaments
dermis inattached
keratinocyte
to
desmosomes
appearance
o Consists of a single row of the youngest keratinocytes
o Keratohyaline
and
lamellated
granules
accumulate
ingerminativum
the
of this layer
Melanin
granules
and
Langerhans’
cells
are stratum
abundant
in cells
this layer
Cells undergo
rapid
division,
alternate
name
Keratinized – skin on body
suface
Nonkeratinized – moist
skin In mouth
Thick skin – palms and
soles
Thick skin – palms and
soles
Layers of the Epidermis (cont.)
Stratum Corneum
Lucidum -(Clear
-(HornyLayer)
Layer)
o Thin,
Outermost
transparent
layer ofband
keratinized
superficial
cells
to the stratum granulosum
o Accounts
Consists of
forathree
few rows
quarters
of flat,
of dead
the epidermal
keratinocytes
thickness
o Present
onlyinclude:
in thick skin
Functions
 Waterproofing
 Protection from abrasion and penetration
 Rendering the body relatively insensitive to biological, chemical,
and physical assaults
Layers of the Dermis:
Dermis mainly connective tissue (pink collagen); binds epidermis to underlying
Hypodermis
tissues
o Subcutaneous layer deep to the skin
Papillary layer – note the capillaries and nerve endings in the dermal papillae
o Composed of adipose and areolar connective tissue
o
Areolar connective tissue with collagen and elastic fibers
Reticular layer- irregular dense connective tissue which contains hair follicles,
glands, blood vessels, arrector pili muscle, nerve fibers and nerve receptors.
o Accounts for approximately 80% of the thickness of the skin
Pacinian corpuscles
o Collagen fibers in this layer add strength and resiliency to skin
o Elastin fibers provide stretch-recoil properties
Accessory Organs of the Skin
Epidermal Derivatives – note the basal layer around the following structures:
Sweat Glands - prevent overheating of the body; secrete cerumen and milk
o Eccrine sweat glands – found in palms, soles of the feet, and forehead
o Apocrine sweat glands – found in axillary and anogenital areas
o Ceruminous glands – modified apocrine in ear canal that secrete cerumen
o Mammary glands – specialized sweat glands that secrete milk
Sebaceous Glands
o Simple alveolar glands found all over the body
o Soften skin when stimulated by hormones
o Secrete an oily secretion called sebum
Nail -Scalelike modification of the epidermis on the distal, dorsal
surface of fingers and toes
Details health
Accessory Organs of the Skin (cont.)
Hair Follicle
o Root
Filamentous
sheath extending
strands of from
deadthe
keratinized
epidermal
cells
surface
produced
into the
by dermis
hair follicles
o Deep
Contains
endhard
is expanded
keratin which
forming
is tougher
a hair bulb
more durable than soft keratin of skin
A knot of sensory
nerve endings
(root hair
plexus)
ooPigmented
by melanocytes
at the base
of the
hair wraps around each hair bulb
o Made up of the shaft
projecting from the skin, and
the root embedded in the skin
o Consists of a core called the
medulla, a cortex, and an
outermost cuticle
More on Hair
Functions of hair include:
o Helping to maintain warmth
o Alerting the body to presence of insects on skin
o Guarding the scalp against physical trauma,
heat loss, and sunlight
Hair is distributed over entire skin surface except
o Palms, soles, and lips
o Nipples and portions of the external genitalia
Types of Hair
o Vellus – pale, fine body hair found in children and the adult female
o Terminal – coarse, long hair of eyebrows, scalp, axillary, & pubic regions
Hair Thinning and Baldness
o Alopecia – hair thinning in both sexes
o True, or frank, baldness
 Genetically determined and sex-influenced condition
 Male pattern baldness – caused by follicular response to DHT
(dihydrotestosterone)
Skin Cancer
Most skin tumors are benign and do not metastasize
Crucial risk factor for nonmelanoma skin cancers is disabling of the p53 gene
The three major types of skin cancer are:
o Basal cell carcinoma
 Least malignant and most common skin cancer
 Stratum basale cells proliferate and invade dermis and hypodermis
 Slow growing and do not often metastasize
 Can be cured by surgical excision in 99% of the cases
o Squamous cell carcinoma
 Arises from keratinocytes of stratum spinosum
 Arise most often on scalp, ears, and lower lip
 Grows rapidly and metastasizes if not removed
 Treated by radiation therapy or removed surgically
o Melanoma (next page)
Melanoma
Melanoma - Cancer of melanocytes is
the most dangerous type of skin cancer
because it is:
o Highly metastatic
o Resistant to chemotherapy
Melanomas have the following characteristics (ABCD rule)
o A: Asymmetry; the two sides of the pigmented area do not match
o B: Border is irregular and exhibits indentations
o C: Color (pigmented area) is black, brown, tan, and sometimes red or blue
o D: Diameter is larger than 6 mm (size of a pencil eraser)
Treated by wide surgical excision accompanied by immunotherapy
Chance of survival is poor if the lesion is over 4 mm thick
Burns
First-degree – only the epidermis is damaged
o Symptoms include localized redness, swelling,
and pain
Second-degree – epidermis and upper
regions of dermis are damaged
o Symptoms mimic first degree burns,
but blisters also appear
Third-degree – entire thickness of the skin is
damaged
o Burned area appears gray-white, cherry red, or
black; there is no initial edema or pain
Rule of Nines - Estimates the severity of burns
o Burns considered critical if:
 Over 25% of the body has second-degree burns
 Over 10% of the body has third-degree burns
 There are third-degree burns on face, hands, or feet
Lund and Browder
Developmental Aspects of the Integument
Fetal
o Epidermis develops from ectoderm
o Dermis and hypodermis develop from mesoderm
o Lanugo – downy coat of delicate hairs covering the fetus
o Vernix caseosa – substance produced by sebaceous glands that protects
the skin of the fetus in the amnion
Adolescent to Adult
o Skin and hair become oilier and acne may appear
o Skin shows effects of cumulative environmental assaults around age 30
o Scaling and dermatitis become more common
Old Age
o Epidermal replacement of cells slows and skin becomes thinner
o Skin becomes dry and itchy
o Subcutaneous fat layer diminishes, leading to intolerance of cold
o Decreased elasticity and loss of subcutaneous tissue leads to wrinkles
o Decreased numbers of melanocytes and Langerhans’ cells increase the risk
of skin cancer
Homeostatic Imbalances of
the Skin
o Stretch marks, blisters, calluses, bed
sores (Decubitus Ulcers)
Erythema, pallor, jaundice,
cyanosis, black and blue marks
Acne Vulgaris
o most common skin disorder
o sebum and epithelial cells clog glands
o produces whiteheads and blackheads
(comedones)
o anaerobic bacteria trigger inflammation
(pimple)
o largely hormonally induced
o androgens stimulate sebum production
o treatments include antibiotics, topical creams,
birth control pills
Terms - intradermal injection; hypodermic
(subcutaneous injection; intramuscular injection)