13. Integumentary Sytem Flashcards
Integumentary consists of
Skin (epidermis and dermis)
Subcutaneous tissue (hypodermis)
Appendages (glands, hair, nails)
What is skin?
Largest organ of the body
Varies in thickness across body regions
Composed of 2 layers: epidermis and dermis
Holds a variety of appendages important for its function
Functions of skin
Protection
Temperature regulation
Excretion
Vitamin D production
Sensory reception
How does skin regulate temperature
Capillaries and sweat glands regulate heat loss
How does skin excrete waste
Excrete urea, salts, and water through sweat
How does skin produce vitamin D
Cells use UV radiation to synthesize vitamin D
Characteristics of the epidermis
Superficial layer of skin
Consists of keratinized stratified squamous epithelium
Primary cell type= keratinocytes
Dead cells rub off and are replaced
There are thick and thin skin
What are the surface cells of the epidermis
Dead keratinocytes full of protective protein, keratin
What are keratinocytes?
Produce keratin, primary cell type of epidermis
Number of layers of thick and thin skin
Thick: 5 layers ( hands & feet)
Thin: 4 layers
Layers of the epidermis
Stratum basale, stratum spinosum, stratum granulosum, stratum corneum, and stratum lucidum (only in thick skin)
Characteristics of stratum basale
Deepest layer, attached to dermis
Single row of stem cells undergoing mitosis
Includes tactile epithelial cells (Merkel cells) and melanocytes
What are tactile epithelial cells (Merkel cells)
Cells attached to nerve ending in stratum basale for touch sensation
What are melanocytes
Produce melanin and gives skin color
Absorbed by keratinocytes, protect from radiation
Characteristics of stratum spinosum
Several cell layers thick
Mitosis occurs but less that basal layer
Cells contain thick bundles of intermediate filaments with pre-keratin to resist tension
Include dendritic cells
What are dendritic cells?
Part of immune system for recognizing foreign proteins
Characteristics of stratum granulosum
1-5 flat cell layers
Cells contain pre-keratin and granules (i.e. granular layer)
Cells far from nutrients supplied by capillaries in dermis, organelles start to breakdown
What are granules
Help form keratin
Produce glycolipids to help prevent water loss
Characteristics of stratum corneum
External layer, many cells thick
Consists of dead keratinocytes, filled with keratin
Protects deeper layers from abrasions
Waterproof from glycolipids between cells
Cells are shed continuously
Characteristics of stratum lucidum
Only in thick skin
Between stratum granulosum and stratum corneum
Few rows of flat, dead keratinocytes
Cells identical to bottom of stratum corneum
Characteristics of dermis
Deep layer of the skin
Made of connective tissue that resists tension in all directions and is vascular & innervated
Same as hide used to make leather
2 layers: papillary dermis and reticular dermis
Characteristics of papillary dermis
Superficial layer of dermis
Mostly areolar connective tissue
Contains projections into epidermis (dermal papillae)
Larger dermal ridges create ridges of the epidermis on palms and soles of feet (e.g., fingerprints)
What to dermal papillae do
Increase surface area for exchange of materials with epidermis
Characteristics of reticular dermis
Deepest layer of dermis
Dense irregular connective tissue
Dense network of collagen and elastic fibers give strength and stretching properties
Has rich supply of nerves and vessels
What do dermal vessels do?
Blood vessels supply nutrients and regulate temperature
When hot, dermal vessels open to allow for cooling (become flush)
What pigments are involved in skin color
Melanin, carotene, hemoglobin
Characteristics of melanin
Primary pigment of skin
Range from yellow to black
Generally, differences in amount and type if melanin causes variation in skin color
Characteristics of skin color
Melanin is primary pigment
Skin colors track geography
Dark skin provides protection against UV radiation near equator
Lighter skin evolved away from the equator (UV rays promote vitamin D synthesis for calcium absorption)
Characteristics of carotene
Yellow-orange pigment
Obtained in diet, too much can cause skin to turn orange (carotenemia)
Accumulate in stratum corneum
Characteristics of hemoglobin in skin color
Protein in red blood cells
Causes reddish hue in light color skin with little melanin
Sun tanning and burns
Skin darkens with exposure to UV radiation for protection
Melanocytes respond to UV radiation by increasing production of melanin
Too much UV radiation = sun burn (damage to epidermis resulting in inflammatory response: redness, swelling, pain)
Characteristics of subcutaneous tissue
Deep to the dermis, not part of the skin
Called the hypodermis or superficial fascia
Composed of loose areolar connective tissue and adipose connective tissue
Functions of subcutaneous tissue
Fat storage
Insulation
Anchor skin to underlying structures with moveability
What are skin appendages
Derivatives of the epidermis but extend into dermis
Fingernails, hair, sebaceous glands, sweat glands
Characteristics of fingernails
Composed of dead, keratinized cells (similar to hoofs or claws)
Nail plate with a foot embedded in skin
Proximal end (nail matrix) continuously growing part of nail
Characteristics of hair
For protection and touch sensation
Long keratinized filaments with pigment from melanocytes of hair follicle (graying due to decreased melanin production)
Hair types
Vellum hair: fine, short hairs all over body
Terminal hair: long, thicker hair (scalp, armpits, pubic region)
Characteristics of hair follicles
Tubular invagination of epidermis from which hair grows
Extends down into dermis
Bulb wrapped by nerve endings- great touch receptors
Arrector pili (smooth muscle in dermis) attach to hair follicle and erect hair with goosebumps
Characteristics of sebaceous glands
Oil glands of skin (produce sebum)
Cover entire body except palms and soles
Associated with hair follicles
Functions of sebaceous glands
Softens, lubricates skin and hair
Collects dirt and kills bacteria
Slow water loss
Types of sweat glands
Eccrine glands, apocrine glands, ceruminous glands, mammary glands
Characteristics of eccrine glands
More numerous, many on palms, soles, and forehead
Glands in dermis of skin
Sweat released through pores in epidermis
Helps with temperature regulation
Characteristics of apocrine glands
Found in armpit, anal, and genital areas
Ducts open into hair follicles
Secretions considered pheromones, involved with sexual signaling
Start function at puberty
Characteristics of ceruminous glands
Line external ear canal
Produce wax (cerumen) in the ear canal
Characteristics of mammary glands
Modified to secrete milk
Part of integumentary system but important part of female reproduction
