Chapter 6 - Skin Flashcards
The Integumentary System is made up by…?
(hair, nails, glands,
sensory receptors)
the Skin is…?
- Largest organ by weight
- Composed of several tissue types
- Also called the cutaneous membrane
The skin contains what 2 layers?
epithelial tissue overlying connective tissue
Epidermis
Outer Layer of skin, composed of stratified squamous epithelium
Basement membrane between epidermis and dermis
Dermis
Inner Layer of skin, thicker than epidermis
Connective tissue, with collagenous and elastic fibers,
muscle, blood, nervous tissue
Subcutaneous layer (hypodermis):
- Beneath dermis; insulating layer
- Areolar and adipose connective tissue.
- Not considered part of the skin
- Contains blood vessels that supply skin
Epidermis, more info
- Stratified squamous epithelium
- Lacks blood vessels
- Deepest layer, stratum basale, nourished by blood vessels in dermis
- As cells grow, they migrate toward free surface, away from nutrient supply
- As they migrate, older cells, keratinocytes, begin to flatten and die
- Thickest on palms and soles (0.8 through 1.4 mm)
- Most of body has thinner epidermis, 0.07 through 0.12 mm
Keratinization
Process of hardening, dehydration, and keratin accumulation
that occurs in epidermal cells as they migrate outward
Keratin
Tough, fibrous, waterproof protein made and stored in the cells
* As cells reach outer surface, become tightly packed, develop desmosomes,
form outermost layer, stratum corneum
stratum corneum cells are…?
eventually shed from skin surface
What is the Function of the Epidermis?
protects against water loss, harmful chemicals, mechanical injury,
pathogens
What are the Special Cells of the Epidermis?
Dendritic (Langerhans) Cells:
Tactile (Merkel) Cells:
Melanocytes:
Dendritic (Langerhans) Cells:
- Found in the stratum spinosum
- Phagocytes; protect skin and underlying tissues from infection
Tactile (Merkel) Cells:
- Found in stratum basale
- Along with sensory nerve endings, for Tactile Discs in dermis
- Act as sensory receptors for light touch
Melanocytes
- Found in stratum basale
- Produce the pigment melanin
- Absorbs UV light from sunlight and provides skin color
- Melanin is distributed to keratinocytes, to protect from UV
radiation (DNA damage, fibroblast damage, skin cancer)
Skin color results mainly from…?
Melanin Pigment
What are other Factors affecting Skin Color?
Hereditary Factors and Albinism
Hereditary Factors
- All people have same number of melanocytes, but vary in
amount of melanin produced (this is under genetic control) - Varying distribution and size of melanin granules
Albinism
inherited mutation in melanin genes; lack
melanin
Environmental Factors to Skin Color
Sunlight, UV light from sunlamps, and X-Rays
Physiological Factors
- Oxygenation in blood of dermal blood vessels: pinkish,
cyanosis - Vasodilation/vasoconstriction of dermal blood vessels
- Accumulation of carotene pigment from diet
- Jaundice
Dermis
- Inner layer of skin
- Average of 1 to 2 mm thick
- Contains projections called dermal papillae between epidermal
ridges - Binds epidermis to underlying tissues
- Connective tissue layer, containing muscle fibers, nerve cell
processes - Dermal blood vessels supply nutrients to all skin cells
- Contains hair follicles, sweat and sebaceous glands
- Contains sensory receptors: Lamellated (Pacinian) corpuscles
for pressure, Tactile (Meissner’s) corpuscles for light touch
The dermis consists of 2 layers which are…?
Papillary and Reticular layer
Papillary layer:
- Superficial layer
- Areolar connective tissue
- Thinner of the 2 layers
- Location of dermal papillae, which form fingerprints
Reticular layer:
- Deeper layer
- Dense irregular connective tissue
- Thicker of 2 layers
Accessory structures of the skin originate from the…?
Epidermis, extend into Dermis or Hypodermis
Accessory structures of the skin include…?
- Hair follicles
- Nails
- Skin glands (sweat and sebaceous)
If accessory structures remain intact, injured/burned dermis
can regenerate
Nails
protective coverings on ends of fingers and toes
What are the 3 parts of a nail? CHECK THIS IN THE POWERPOINT
- Nail plate (body): Visible portion, keratinized cells, overlies nail
bed - Nail bed: Surface of skin, under nail plate
- Nail matrix: Active growth region, not visible, at proximal end of
nail bed
Lunula
Pale, half-moon-shaped region that lies over nail matrix;
nail matrix conceals deeper blood vessels
Cuticle
Fold at proximal end of nail; part of stratum corneum that
extends slightly over nail
Hair is present on all surfaces of skin except…?
palms, soles, lips, nipples,
parts of external reproductive organs
Hair follicle:
Tube-like depression of epidermal cells from which hair
develops; extends into dermis or the subcutaneous layer
Parts of Hair
Hair Root, Hair Bulb, Hair Shaft, Hair Papilla, Arrector pili Muscle
Hair Root
Extends from skin surface to dermis or hypodermis
Hair Bulb
Deepest part of hair root; contains dividing cells of hair matrix
Hair Shaft
Portion of hair that extend beyond skin surface; composed
of dead, epidermal cells
Hair Papilla
contains blood vessels to nourish hair
Hair color is due to type and amount of melanin
Arrector pili muscle:
Attached to hair follicle; contracts in response to
cold or fear, and causes goosebumps
Sebaceous Glands:
- Holocrine glands
- Usually associated with hair follicles
- Produce sebum, which consists of fatty material and
cellular debris - Sebum keeps hair and skin soft and waterproof
- Excess sebum can result in acne
- Absent on palms and sole
Sweat (Sudoriferous) Glands:
- Widespread in skin
- Originate in deeper dermis or hypodermis as ball-shaped coils
What are the types of Sweat Glands?
Eccrine (merocrine) glands:
Apocrine sweat glands:
Specialized sweat glands:
Eccrine (merocrine) glands:
- Most numerous, consist mainly of water, some salts, wastes
- Respond to elevated body temperature
- Open to body surface through pores
Apocrine sweat glands:
- Axillary and groin areas; open into hair follicles
- Called apocrine, but secrete by exocytosis
- Respond to emotions, pain
Specialized sweat glands:
- Ceruminous glands—ear wax
- Mammary glands—milk
Skin is…?
Versatile and vital for Homeostasis
What are the functions of the Skin?
Protective Barrier, Sensation, Excretion, Protection of Vitamin D, Regulation of Body Temperature
Protective barrier:
Protects against harmful substances,
UV radiation, microorganisms, water loss
Sensation
Contains sensory receptors for touch, pressure, temperature changes, pain
Excretion
of some wastes
Production of Vitamin D
Starts in skin; when produced and activated, helps with calcium absorption
Regulation of Body Temperature
Helps cool body by
sweating and blood flow changes
What are the methods of Heat Loss through the Skin?
Radiation, Conduction, Convection, and Evaporation
Radiation
Primary method, infrared heat rays travel from
warmer skin to cooler environment
Conduction
Heat moves from warmer skin to cooler
objects it is in contact with
Convection
Heat loss from skin into circulating air
currents
Evaporation
Heat is lost through sweat as it evaporates,
and carries heat away from the skin
When body temperature rises, what happens…?
- Thermoreceptors signal hypothalamus
- Vasodilation of dermal blood vessels
- Vasoconstriction of deep blood vessels
- Sweat glands are activated
When body temperature falls, what happens…?
- Thermoreceptors signal hypothalamus
- Vasoconstriction of dermal blood vessels
- Vasodilation of deep blood vessels
- Sweat glands are inactive
- Muscles contract involuntarily (shivering)
Hyperthermia
abnormally high body temperature
* Can occur on hot, humid day, when sweat cannot evaporate
* When air temperature is high, radiation is less effective
* Body may gain heat from hotter air
* Skin becomes dry, person gets weak, dizzy, nauseous, with
headache, rapid pulse
Hypothermia
abnormally low body temperature
* Can result from prolonged exposure to cold, or illness
* Shivering is involuntary skeletal muscle contraction, caused by
hypothalamus
* Progresses to confusion, lethargy, loss of reflexes and
consciousness
* Without treatment, organs shut down
Inflammation
- A normal response to injury or stress
- Body’s attempt to restrict spread of infection
- Blood vessels in affected tissues dilate and become more
permeable, allowing fluids to leak into the damaged
tissues
Inflamed skin may become:
- Reddened
- Swollen
- Warm
- Painful
A Shallow Cut results in…?
Shallow cuts only affects the epidermis, results in
epidermal cells along its margin dividing more rapidly than usual,
to fill gap
A Deep Cut results in…?
reaching dermis or subcutaneous layer, results in
blood vessels breaking
Released blood forms a…?
Clot
What is the full process with a Deep Cut?
- Clot consists of fibrin, blood cells, and platelets
- Clot and dried tissue fluid form scab
- Epithelial cells reproduce, fill in the wound
- Fibroblasts secrete collagen fibers to bind wound together
- Growth factors stimulate new tissue formation
- Phagocytic cells remove dead cells and debris, scab sloughs off
- Excess collagenous fibers may form elevated mass called a
scar
Burns are classified by…?
extent of tissue damage
Superficial, partial-thickness (first degree) burn:
- Injures only epidermis, as in sunburn; redness, heat,
inflammation - Healing takes days to weeks, no scarring
Deep, partial-thickness (second degree) burn:
- Destroys epidermis and some dermis, as in burn from hot liquid
- May blister, healing varies with severity of burn and stem cell
survival - Stem cells in hair follicles and glands can help regenerate skin
- Usually recovers completely, no scarring
Full-thickness (third degree) burn:
- Destroys epidermis, dermis, accessory structures
- Results from prolonged exposure to heat, flames, hot
liquids - Some healing from margins
- Often requires skin graft, skin substitutes
Rule of Nines:
- Divides body surface into regions of 9% or multiples of 9
- Used to estimate extent of injured body surface from a
burn for treatment - From this estimate, plans to replace fluids, electrolytes,
and skin can be figured
Life-Span Changes
- Cell cycle slows, skin becomes scaly, age spots appear
- Epidermis and dermis become thinner
- Loss of fat in subcutaneous layer; person feels cold
- Wrinkling, sagging of skin occur
- Sebaceous glands secrete less oil; skin becomes dry
- Melanin production slows; hair whitens
- Hair thins
- Number of hair follicles decreases
- Nail growth becomes impaired
- Sensory receptors decline
- Body temperature regulation becomes less effective
- Diminished ability to produce Vitamin D
