The Integumentary System Flashcards
What are the two major parts of the integumentary system?
▪ Cutaneous membrane (skin)
▪ Accessory structures
What are the components of the cutaneous memebrane
– Outer epidermis
▪ Superficial epithelium
– Inner dermis
▪ Connective tissues
What are the accessory structure
– Originate in the dermis
– Extend through the epidermis to skin surface
▪ Hair and hair follicles
▪ Exocrine glands
▪ Nails
What is another name for the subcutaneous layer
hypodermis
Describe the subcutaneous layer
– Loose connective tissue
– Below the dermis
What are the functions of the integumentary system?
– Protection of underlying tissues and organs
– Excretion of salts, water, and organic wastes
– Maintenance of normal body temperature
– Production of melanin
– Production of keratin
– Synthesis of vitamin3D
– Storage of lipids
– Detection of touch, pressure, pain, etc.
– Coordination of the immune response
Describe the main structural features
of the epidermis, and explain the functional significance of each.
- Epidermis
– Stratified squamous epithelium
– Avascular, like all epithelia
– Nutrients and oxygen diffuse from capillaries in the dermis
What are the cells of the epidermis?
– Keratinocytes
▪ The body’s most abundant epithelial cells
▪ Contain large amounts of keratin
What are the two types of skin
Thin skin
▪ Covers most of the body
▪ Has four layers of keratinocytes
– Thick skin
▪ Covers the palms of the hands and soles of the feet
▪ Has five layers of keratinocytes
What are the five strata of keratinocytes in thick skin
– From basement membrane to free surface
▪ Stratum basale
▪ Stratum spinosum
▪ Stratum granulosum
▪ Stratum lucidum
▪ Stratum corneum
Describe the Stratum Basale
– Attached to basement membrane by hemidesmosomes
– Forms a strong bond between epidermis and dermis
– Contains epidermal ridges
▪ Lie next to dermal papillae in dermis
– Has many basal cells, or germinative cells
▪ Stem cells that replace superficial keratinocytes
Describe the specialized structures of stratum basale
– Tactile discs
▪ Tactile (Merkel) cells with sensory nerve endings
▪ Found in hairless skin
▪ Respond to touch
– Melanocytes
▪ Contain the pigment melanin
Describe the Stratum spinosum
The “spiny layer”
– Eight to ten layers of keratinocytes bound by
desmosomes
– Cells appear spiny in histological sections
– Produced by division of cells in stratum basale, some of which continue dividing
– Contains dendritic (Langerhans) cells, which are active in immune response
Describe the stratum granulosum layer
the “granular layer”
– Three to five layers of keratinocytes
– Produced from cells of stratum spinosum
– Most cells stop dividing and produce
▪ Keratin
▪ Keratohyalin
– Forms dense granules
– Promotes cellular dehydration and cross-linking of keratin fibers
– After production of proteins, cells die
Describe the stratum lucidum
The “clear layer”
– Found only in thick skin
– Covers stratum granulosum
Describe the Stratum corneum
—the “horny layer”
– Exposed surface of skin
– Water resistant
– 15 to 30 layers of keratinized cells
▪ Keratinization is the formation of protective layers of cells filled with keratin
– New cells move from stratum basale to stratum corneum in 7 to 10 days
– Exposed cells are shed after two weeks
What are the two ways water is lost from the skin?
– Insensible perspiration
▪ Water diffuses across stratum corneum and
evaporates from skin
▪ 500 mL per day
▪ Rate increases if stratum corneum is damaged (e.g., from burns)
– Sensible perspiration
▪ Water excreted by sweat glands
What is the function of the Epidermal growth factor?
– Promotes division of basal cells
– Accelerates keratin production
– Stimulates epidermal repair
– Stimulates glandular secretion
Describe the structures and functions
of the dermis.
–Located between epidermis and subcutaneous layer
–Anchors epidermal accessory structures (e.g., hair follicles and sweat glands)
–Two components
▪Outer papillary layer
▪Deeper reticular layer
Describe the papillary layer
– Consists of areolar tissue
– Contains capillaries, lymphatic vessels, and sensory neurons
– Named for dermal papillae that project between epidermal ridges
– Becomes inflamed in dermatitis
▪ Caused by infection, radiation, mechanical irritation, or chemicals (e.g., poison ivy)
▪ May produce itching or pain
Describe the reticular layer
– Consists of dense irregular connective tissue
– Contains collagen and elastic fibers
– The dermis contains all cells of connective tissue proper
Explain the dermal strength and elasticity
– Collagen fibers
▪ Very strong, resist stretching
▪ Easily bent or twisted
▪ Limit flexibility to prevent tissue damage
– Elastic fibers
▪ Permit stretching and then recoil to original length
▪ Provide flexibility
– Fibers and water provide flexibility and resilience
▪ Known as skin turgor
Explain tension lines
– Produced by parallel bundles of collagen and elastic fibers in the dermis
– Resist forces applied to skin
– A cut made parallel to a tension line remains shut, heals well
▪ A cut at a right angle pulls open and scars
Describe the dermal blood supply
– Cutaneous plexus
▪ Deep network of arteries along the reticular layer
– Subpapillary plexus
▪ Network of small arteries in papillary layer
▪ Capillaries drain into small veins that lead to larger veins in subcutaneous layer
– Contusion (bruise)
▪ Caused by damage to blood vessels in dermis
Describe the innervation of skin
– Nerve fibers in skin
▪ Control blood flow
▪ Adjust gland secretion rates
▪ Monitor sensory receptors
Sensory receptors respond to
– Light touch—tactile (Meissner) corpuscles, in dermal
papillae
– Deep pressure and vibration—lamellar (Pacinian)
corpuscles, in the reticular layer
Skin color is influenced by two pigments in the epidermis
– Melanin
– Carotene
What is the color of melanin
red-yellow or brown-black pigment
Which cell produce melanin
mealanocytes
Where is melanin stored?
Stored in intracellular vesicles (melanosomes)
▪ Transferred to keratinocytes
▪ Dark-skinned people have large, numerous
melanosomes
What is the color of carotene?
orange-yellow pigment
Where is the carotene found
in orange vegetables
– Accumulates in epidermal cells, deep dermis, and subcutaneous layer
– Can be converted to vitamin A, required for
▪ Maintenance of epithelia
▪ Synthesis of photoreceptor pigments in eye
Describe the illness and skin color
– Jaundice
▪ Buildup of bile produced by liver
▪ Skin and whites of eyes may turn yellow
– Pituitary tumor
▪ Excess MSH increases production of melanin
– Addison’s disease
▪ Causes pituitary gland to release excess ACTH,
which has an effect similar to MSH
– Vitiligo
▪ Loss of melanocytes causing loss of color
Describe the interaction between
sunlight and vitamin D3 production
- Vitamin3D (cholecalciferol)
– Produced by epidermal cells in presence of UV
radiation
– Liver and kidneys together convert vitamin3D into calcitriol
▪ Essential for absorption of calcium and phosphate ions by small intestine
– Insufficient vitamin3D can cause rickets
Hairs cover almost all of the body, except
– Palms of hands, sides of fingers
– Sides and soles of feet, sides of toes
– Lips
– Portions of external genitalia
What is the function of hair
– Protect and insulate
– Guard openings from particles and insects
– Serve as sensory receptors
Describe the hair follicles
– Extend deep into dermis
– Produce nonliving hairs
– Wrapped in a dense connective tissue sheath
– Base is surrounded by sensory nerves (root hair plexus)
– Arrector pili muscle
▪ Involuntary smooth muscle
▪ Contraction causes hairs to stand up
▪ Produces “goose bumps”
What are the regions of the hair?
– Hair root
▪ Portion that anchors it into skin
– Hair shaft
▪ Upper part of the hair
Describe the hair structure
– Medulla
▪ Central core
– Cortex
▪ Intermediate layer
– Cuticle
▪ Surface layer
What are the layers of the follicle?
– Internal root sheath
▪ Surrounds hair root
– External root sheath
▪ Extends from skin surface to hair matrix
– Glassy membrane
▪ Clear layer wrapped in connective tissue sheath
Explain hair production
– Begins at the hair bulb, at base of hair follicle
▪ Surrounds hair papilla—connective tissue
containing capillaries and nerves
▪ At base of hair bulb, epithelial cells form a layer known as hair matrix
– Produces hair
– As cells divide, hair is pushed up and out of skin
Explain Hair production
– Begins at the hair bulb, at base of hair follicle
▪ Surrounds hair papilla—connective tissue
containing capillaries and nerves
▪ At base of hair bulb, epithelial cells form a layer known as hair matrix
– Produces hair
– As cells divide, hair is pushed up and out of skin
What are the types of hair
– Vellus hairs
▪ Soft, fine hairs that cover most of body surface
– Terminal hairs
▪ Heavy, pigmented hairs
▪ On head, eyebrows, and eyelashes
▪ Other parts of body after puberty
What are the types of exocrine glands in the skin?
– Sebaceous glands (oil glands)
▪ Holocrine glands
▪ Discharge lipid secretion (sebum) into hair follicles
– Lubricates and protects hair shaft
– Inhibits growth of bacteria
– Sweat glands
▪ Apocrine sweat glands
▪ Eccrine sweat glands
What are the types of sebaceous glands
– Simple branched alveolar glands
▪ Associated with hair follicles
– Sebaceous follicles
▪ Large sebaceous glands not associated with hair
▪ Discharge sebum directly onto skin surface
▪ Located on face, back, chest, nipples, external
genitalia
Where are apocrine sweat glands found
in armpits, around nipples and in pubic region
Describe the function of the apocrine sweat glands
– Secrete products into hair follicles via merocrine secretion
– Produce sticky, cloudy secretions
▪ Nutrient source for bacteria, which cause odors
– Surrounded by myoepithelial cells
▪ Squeeze secretions out of glands in response to hormonal or nervous signals
Describe the eccrine sweat glands
– Coiled, tubular glands that discharge directly onto skin
surface (sensible perspiration)
– Widely distributed on body surface
▪ Especially on palms and soles
What is the function of the eccrine sweat glands?
▪ Cooling surface of skin to reduce body temperature
▪ Excreting water and electrolytes
▪ Providing protection from environmental hazards
What are the other integumentary glands?
– Mammary glands
▪ Produce milk
– Ceruminous glands
▪ Produce cerumen (earwax)
– Prevents foreign particles from reaching the
eardrum
Describe the nail
– Protect tips of fingers and toes
– Made of dead cells packed with keratin
– Metabolic disorders can change nail structure
▪ Example: pitted nails may result from psoriasis
Describe the stricture of a nail
– Nail body
▪ Visible portion of the nail
▪ Covers the nail bed
– Sides of nails
▪ Lie in lateral nail grooves
▪ Surrounded by lateral nail folds
– Skin beneath the distal free edge of the nail is the
hyponychium (onyx, nail)
