Ch. 5 Integumentary Flashcards
3 layers of skin
epidermis, dermis, subcutaneous (hypodermis)
Epidermis
- most superficial layer
- consists of epithelial tissue
- prevents water loss
- protects against abrasion and UV light
Cells of epidermis
keratinocytes and melanocytes
keratinocytes
- produce a protein mixture called keratin (makes cells more durable)
- all cells in all layers are these
melanocytes
contribute to skin color
keratinization
cells moving from the deeper epidermal layers to the surface and change shape and chemical composition
Epidermal strata
the many layers of cells in the epidermis (different regions)
Stratum basale (germinativum)
- single layer of cuboidal or columnar cells
- layer of epidermis that all cells arise from (basement membrane)
- attach to dermis by desmosomes
- mitosis happens, daughter cells get pushed upwards
Stratum spinosum
- consist of daughter cells from basale
- cells are still alive
- keratin fibers accumulate and are stockpiled
- lamellar bodies accumulate
Lamellar body (SS)
vesicles filled with triglycerides and other lipids
Stratum granulosum
- cells begin to flatten out and die
- lamellar bodies release lipids or fats and oils (cause the water proofing of skin)
Stratum lucidum
- not much difference between here and granulosum
- not present in all areas of the body
- cells are dead and appear transparent
Stratum corneum
- most superficial stratum of epidermis
- 2 to 3 dozens dead cells thick
- cells begin to shed due to non-working desmosomes
Keratohylin granules
- cross linking protein
- more of this, the tougher the cell
Thick skin
- has all 5 epithelial strata
- ie. palms of hands and soles of feet
Thin skin
- stratum lucidum is usually absent
- covers the rest of the body
Skin color
melanin, melanocytes, and melanosomes
Melanin
- the group of pigments primarily responsible for skin, hair, and eye color
- absorbs UV radiation (ie. tanning)
Melanocytes
- irregularly shaped cells that produce melanin
- does not produce new epidermal cells
- extend into the stratum spinosum
Melanosomes
- transport vesicles that are filled with melanin
- cells in stratum spinosum phagocytize a portion of the melanocyte that contains melanin which contains color
Production on melanin
-enzyme tyrosinase convert the aa tyrosine to dopaquinone (which can convert to a variety of active pigments, melanin being most common)
Dermis
-connective tissue containing fibroblasts, a few adipocytes and macrophage
Macrophage
first line of defense against foreign substances
Reticular layer of dermis
- deep
- dense irregular connective tissue that contain collagen elastic fibers
- main layer of dermis
Paillary layer of dermis
-contain dermal papillae that interdigitates with epidermis
Dermal papillae
- dermal extensions into epidermis
- finger prints are derived from this
- blood vessels extend into the living portions of the epidermis though this
Cleavage lines in dermis
tension lines
-elastic and collagen fibers that are oriented more in some directions than in others
Accessory structures
hair, glands, nails
Hair
is dense and covers most of the body
lanugo
delicate, unpigmented hair that is in place by the 5th or 6th month of fetal development
Terminal hairs
- long, coarse and pigmented hairs
- replace lanugo of scalp, eyelids and brows
- are in place at time of birth
Vellus hairs
- short, fine unpigmented hair
- replace lanugo on the rest of the body
Anatomy of hair
- root: below skin surface
- bulb: base of hair root
- shaft: above skin surface
Medulla
- central axis of the hair
- consists of 2 or 3 layers of cells containing soft keratin
Cortex
- forms the bulk of the hair
- consists of cells containing hard keratin
Cuticle
- -a single layer of cells that contain hard keratin
- covers the cortex
Hair follicle
housed in the dermis, but it is epidermal tissue
-consists of dermal root sheath, epithelial root sheath, matrix, hair papilla
Dermal root sheath
covering of hair follicle
Epithelial root sheath
divided into internal and external parts
- internal: next to the cuticle
external: inbetween internal and root sheath
Matrix
- growth zone (produces hair)
- undifferentiated epithelial cells
Hair papilla
- where dermis of skin project into hair bulb
- contains blood vessels that provide nourshiment
Glands
sebaceous, sweat, ceruminous, mammary
Sebaceous glands
- located in the dermis
- simple or compound aveolar glands
- produce sebum
Sebum
hair lubercation; oily white substance rich in lipids
Sweat glands
eccrine or apocrine
Eccrine sweat
- liqid sweat
- collects tissue fluid from the dermis
- active transport to collect Na+ and Cl+ ions and put them back into dermal tissue, solution reaches surface and is considered hypoosmotic sweat
Apocrine sweat
- housed in the sub q
- scent glands
Ceruminous gland
- modified eccrine sweat glands that are located in the ear canal
- produce cerumen
Cerumen
- earwax
- composed of the combined secretions of ceruminous glands and sebaceous glands
