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Chapter 6: Integumentary System
6.1 Introduction
Why is skin considered to be an organ?
What makes up the integumentary system?
Integumentary System
Skin (cutaneous membrane)
Skin derivatives
Sweat glands
Oil glands
Hair
Nails
6.2 Skin and its Tissues
Skin is also know as a cutaneous membrane
How is the skin vital in maintaining homeostasis?
Skin has 2 layers Epidermis: most superficial; thin; stratified
squamous epithelial tissue; keratinized
Dermis: deep to epidermis; thicker; loose and dense connective tissue; contains appendages (hair, glands, blood vessels, nerves, etc)
Subcutaneous layer or hypodermis – lies deep to dermis; consists mostly of loose adipose connective tissue
Skin Structure
Figure 4.3
Epidermis – composed of keratinized stratified squamous epithelium. Structure: Principle Cell types and layers
Keratinocytes – makes up 90%, arranged in 4 to 5 layers, produce:
Keratin: tough, fibrous, waterproof protein
Lamellar granules: repel water
Melanocytes – 8%, produces pigment melanin, have long slender projections that transfer melanin to keratinocytes
Melanin: brown/black pigment, absorbs UV light
Langerhans cells – aid in immune response; easily damaged by UV light
Merkel cells – contact sensory neuron, aid in sensation
A Closer look at the Epidermis
Epidermal Cell layers (deepest to most superficial)
Stratum basale (deepest or base layer) – attached to basement membrane, contains most of the melanocytes, has cuboidal or columnar cells, mitosis.
Stratum spinosum (spiny layer) – 8-10 layers of irregular shaped keratinocytes, become flattened
Stratum granulosum (granular layer) – 3 - 5 layers of flat keratinocytes, undergoing cell death
Stratum lucidum (clear layer) – dead cells w/ lots of keratin; only in thick skin of finger tips, palms and feet
Stratum corneum (most superficial, horny layer) – 25 to 30 layers of flattened dead cells containing keratin, continuously shed and replaced by cells from deeper strata
What is Keratinization?
Melanin
Pigment (melanin) produced by melanocytes
Melanocytes are mostly in the stratum basale
Color is yellow to brown to black
Amount of melanin produced depends upon genetics and exposure to sunlight
Normal Skin Color Determinants
Melanin
Yellow, brown, or black pigments
Carotene
Orange-yellow pigment from some vegetables
Hemoglobin
Red coloring from blood cells in dermal capillaries
Oxygen content determines the extent of red coloring
Functions of epidermis
Protection (damage, UV rays, etc)
Growth / Repair (regeneration)
Immune response
Sensation
Water-repellent & sealant
Epidermal growth and repair
Regeneration time for skin is about 35 days
Shortened regeneration time results in increased thickness of stratum corneum making a callus (thick skin)
Dermis: deep to the epidermis
Structure of Dermis
Much thicker than epidermis has 2 portions:
Papillary Dermis (Superficial part of dermis): Loose areolar connective tissue
Dermal Papillae: finger-like projections indenting epidermis; increase surface area
Contain capillaries
Contain corpuscles of touch (Meissner corpuscles)
Reticular Dermis (Deep part of dermis): dense connective tissue
Contains hair follicles, nerves, blood vessels, sebaceous (oil) glands, & sudoriferous (sweat) glands
A Closer look at the Dermis
Functions of the Dermis
Sensitivity
Strength / support
Stretchable / elasticity
Flexibility
Dermal growth & repair
Dermis does not continually shed and regenerate like epidermis
If this layer is damaged, the fibroblasts form a dense mass of connective fibers forming a scar
Extreme stretching may produce small tears causing striae or stretch marks
Skin Structure
Subcutaneous tissue (hypodermis) is deep to dermis
Not part of the skin
Anchors skin to underlying organs
Composed mostly of adipose tissue
Sebaceous (oil) glands
Secretes oil (sebum), keeps hair & skin soft/pliable, prevents water loss from skin
Located in dermis, except for palms & soles
Aids in formation of pimples & black heads
2 types of Sudoriferous (sweat) glands
Eccrine glands –.
Apocrine glands –
Glands
Appendages of the Skin
Sebaceous glands
Produce oil
Lubricant for skin
Prevents brittle hair
Kills bacteria
Most have ducts that empty into hair follicles; others open directly onto skin surface
Glands are activated at puberty
Appendages of the Skin
Figure 4.6a
Appendages of the Skin
Sudoriferous (sweat) glands
Produce sweat
Widely distributed in skin
Two types
Eccrine
Open via duct to pore on skin surface
most common; secretes sweat, eliminates wastes, maintains core temp
Apocrine
Ducts empty into hair follicles
activated during puberty, located in armpit, groin, beard.
Appendages of the Skin
Figure 4.6b
Sweat and Its Function
Composition Mostly water
Salts and vitamin C
Some metabolic waste
Fatty acids and proteins (apocrine only)
Function Helps dissipate excess heat
Excretes waste products
Acidic nature inhibits bacteria growth
Odor is from associated bacteria
Appendages of the Skin
Ceruminous glands
Located in ear canal
Produces ear wax (cerumen)
Too much wax can cause a blockage of ear canal, loss of hearing
Appendages of the Skin
Hair follicles – composed of epithelial cells, distributed all over body except for palms, anterior side of fingers, soles, genitalia, and lips
Dermal and epidermal sheath surround hair root
Genetics and hormones determine thickness and distribution of hair
Hair is also important for protection and reproduction
Melanocytes provide pigment for hair color
Arrector pili muscle
Smooth muscle
Pulls hairs upright when cold or frightened (goose bumps)
Appendages of the Skin
Figure 4.7c
Appendages of the Skin
Hair anatomy
Central medulla
Cortex surrounds medulla
Cuticle on outside of cortex
Most heavily keratinized
Figure 4.7b
Appendages of the Skin
Figure 4.7a
Appendages of the Skin
Figure 4.8
Appendages of the Skin
Nails – Plates of tightly packed, hard, keratinized cells of epidermis
Very protective of ends of fingers; aids in grasping and manipulating small objects; scratching
Stratum basale extends beneath the nail bed
Responsible for growth
Lack of pigment makes them colorless
Appendages of the Skin
Nails can indicate health issues
Bluish nail beds may indicate circulation issue
White nail bed or oval depressions can indicate anemia
Pigmented spot (not injury) can indicate melanoma
Horizontal furrows may indicate period of illness or malnutrition
Disorders of heart, liver, or lungs may cause extreme curvature of nails
Red streaks in nails may be traced to RA, uclers, or hypertension
Nails: Figure 6.4
Free edge – extends past end of finger
Nail plate / body – visible part of nail
Nail root – sides and bottom of nail in groove, hidden by cuticle
Nail bed – skin surface that is covered by nail plate
Cuticle – skin around bottom of nail (stratum corneum)
Lunula – half-moon shaped white area at base of nail; the most active growing region
average growth is 0.5 to 1 mm per week
Appendages of the Skin
Figure 4.9
Skin Functions
Table 4.1 (1 of 2)
Skin Functions
Table 4.1 (2 of 2)
Overall Functions of the Integumentary System
Regulation of body temperatures
Sensitivity
Excretion and absorption
Vitamin D synthesis
Protection
Barrier to microorganisms
Barrier to chemical hazards
Reduces injury to underlying structures
Prevents dehydration
Protects (via melanin) excessive UV exposure
Surface film – protective barrier over skin’s surface; (like wax on your car)
6.4 Regulation of Body Temp.
How does your skin aid in regulating body temperature?
What portion of the brain controls the set point for body temperature?
Differentiate between hypothermia and hyperthermia. Discuss the consequences of each.
6.5 Healing of Wounds
What is inflammation? Is it normal or abnormal and why?
Differentiate between the healing processes of a superficial wound and a deeper wound. Which one would result in a scar?
Skin Homeostatic Imbalances
Infections
Athlete’s foot (tinea pedis)
Caused by fungal infection
Itchy, red, peeling condition of skin between the toes
Boils and carbuncles
Caused by bacterial infection
Common on dorsal neck, inflammation of hair follicles and sebaceous glands.
Cold sores
Caused by virus (herpes simplex) – activated by stress, fever, illness, and UV Radiation
Small fluid-filled blisters that itch and sting
Homeostatic Imbalances
Skin Homeostatic Imbalances
Infections and allergies
Contact dermatitis
Exposures cause allergic reaction
Itching, redness, and swelling of skin – progressing to blistering
Impetigo
Caused by bacterial infection
Pink, water-filled, raised lesions (nose and mouth) that develop a yellow crust and eventually rupture
Psoriasis
Cause is unknown
Triggered by trauma, infection, stress
Overproduction of skin cells, reddened epidermal lesions covered with dry, silvery scales that itch, burn, crack and sometimes bleed.
Skin Homeostatic Imbalances
Figure 4.10
Skin Homeostatic Imbalances
Burns
Tissue damage and cell death caused by heat, electricity, UV radiation, or chemicals
Associated dangers
Dehydration
Electrolyte imbalance
Circulatory shock
Rule of Nines
Way to determine the extent of burns
Body is divided into 11 areas for quick estimation
Each area represents about 9% of total body surface area
Rule of Nines
Figure 4.11a
Severity of Burns First-degree burns
Only epidermis is damaged
Skin is red and swollen
Second-degree burns
Epidermis and upper dermis are damaged (partial-thickness burn)
Skin is red with blisters
Third-degree burns
Destroys entire skin layer (full-thickness burn)
Burn is gray-white or black
Severity of Burns
Figure 4.11b
Critical Burns
Burns are considered critical if
Over 25% of body has second-degree burns
Over 10% of the body has third-degree burns
There are third-degree burns of the face, hands, or feet
Skin Cancer
Cancer—abnormal cell mass
Classified two ways
Benign
Does not spread (encapsulated)
Malignant
Metastasized (moves) to other parts of the body
Skin cancer is the most common type of cancer
Skin Cancer Types
Basal cell carcinoma
Least malignant – 99% cure in which lesion is removed surgically
Most common type – Sun Exposure
Arises from stratum basale – cells are altered so that they cannot form keratin
They invade dermis and subcutaneous tissue
Symptoms: shiny, dome-shaped nodule that later develop a central ulcer with a “pearly” beaded edge.
Skin Cancer Types
Figure 4.12a
Basal Cell Carcinoma
Skin Cancer Types
Squamous cell carcinoma
Metastasizes to lymph nodes if not removed
Early removal allows a good chance of cure
Believed to be sun-induced
Arises from stratum spinosum
Symptoms: lesion, scaly, reddened papule (small, rounded elevation), that gradually forms a shallow ulcer with a firm, raised border.
Grows rapidly and metastasizes to adjacent lymph nodes if not removed
If caught early and removed surgically or by radiation – the cure rate is good.
Squamos Cell Carcinoma
Skin Cancer Types
Figure 4.12b
Skin Cancer Types
Malignant melanoma
Most deadly of skin cancers
Cancer of melanocytes
Metastasizes rapidly to lymph and blood vessels
Detection uses ABCD rule
Cause: Genetics, accumulated damage to DNA in skin cells
Symptoms: arise as a spreading brown to black patch that metastasizes rapidly to surrounding lymph and blood vessels
Chance of survival is 50%
Accounts for 5% of skin cancers
Skin Cancer Types
Figure 4.12c
Malignant Melanoma
ABCD Rule A = Asymmetry
Two sides of pigmented mole do not match
B = Border irregularity
Borders of mole are not smooth
C = Color
Different colors in pigmented area
D = Diameter
Spot is larger then 6 mm in diameter
E = Elevation/Evolves
Spot is elevated or changes over time
