Skin and Appendages Flashcards
what are the two principle layers of the skin?
- epidermis
- dermis
epidermis layer composition
- outermost (surface) layer of skin
- composed of 30-50 layers of stratified keratinized squamous epithelium (mostly keratinocytes)
dermis layer composition
- deep to epidermis
- composed of CT (fibroblasts, collagen and elastic fibers)
what are all the layers of the skin?
- epidermis
- dermis
- hypodermis
hypodermis layer composition
- located beneath the skin
- composed of loose CT (areolar) and adipose tissue
- anchors skin loosely to underlying muscle
- acts as a shock absorber and insulator of fat
what are the functions of the skin?
- protection
- excretion
- synthesis
- communication
- absorption
- thermoregulation
- sensation
what is the hypodermis also called?
-subcutaneous tissue
protection function types
- physical barrier
- chemical barrier
- biological barrier
physical barrier protection function
- impermeable to water-soluble substances (due to keratin)
- prevents dehydration
chemical barrier protection function
- acidity skin secretions retards bacterial growth
- melanin protects against UV light
biological barrier protection function
-langerhans cells and macrophages engulf foreign material and bacteria
thermoregulation function
- body temperature is regulated through activity of sweat glands and changes in the diameter of blood vessels
- hair and adipose tissue also acts as insulators
absorption function
- lipid soluble substances
- steroids
- plant resins, organic solvents and heavy metals
what are some types of lipid soluble substances?
-vitamin A, D, E, K
excretion function
- urea, ammonia and uric acid are excreted in sweat
- salts (NaCl) are also lost, especially with excessive sweating
synthesis function
-exposure to sunlight aids in the production of Vitamin D
sensation function
-contains receptors for touch, pain, and temperature, etc
communication function
-various emotions are expressed through color changes and secretions
what are the layers of the epidermis?
- stratum germinativum
- stratum spinosum
- stratum granulosum
- stratum lucidum
- stratum corneum
epidermis stratum germinativum layer special characteristics
- deepest layer
- single layer of cells
- undergo mitosis and gradually move to the surface
epidermis stratum spinosum layer special characteristics
- several layer of squamous like cells
- “prickle cells”
- attacked and spine-like processes
- keratin synthesis begins
epidermis stratum granulosum layer special characteristics
- cells contain dark glands
- abundant keratin
- cells begin to die (bc no active metabolism)
epidermis stratum lucidum layer special characteristics
- “clear layer”
- cells appear empty
- only found in thick skin
epidermis stratum corneum special characteristics
- artificial layer
- dead, scale-like keratinized cells
dermis location
-deep to the epidermis
dermis composition
- CT (elastin and collagen fibers)
- macrophages
- mast cells
- nerve fibers
- blood vessels
- sweat glands
- hair follicles
- sebaceous glands
which components of the dermis help with the stability of the skin?
- connective tissue
- blood vessels
epidermis composition
-keratinized stratified squamous epithelium
what are the layers of the dermis?
- papillary layer
- reticular layer
papillary layer components
- dermal papilla
- friction ridges
papillary layer location
- most superficial
- just below epidermis
dermis papillary layer dermal papilla layer special characteristics
-projections of dermis towards surface layer
dermis papillary layer friction ridges layer special characteristics
- elevations on epidermal surface (cause by CT of dermis)
- distinct pattern (“finger prints”) genetically determined
- help in grasping objects (identification)
dermis reticular layer special characteristics
- deep layer of dense, regular CT
- contains many elastin and collagenous fibers
- provides skin tone, strength, and resiliency
dermis functions
- serves as an attachment for the epidermis, provides supporting hase
- contains a dense network of blood vessels for diffusion of nutrients to epidermis
- plays a role in thermoregulation (due to hair glands)
what are the other characteristics of skin?
- skin color
- skin tone
what causes skin color?
-the presence of three pigments
skin color pigments
- melatonin
- carotene
- hemoglobin
melanin pigment special characteristics
- produced by metactyes in epidermis
- yellow-brown-black pigment which protects again UV light damage
carotene pigment special characteristics
- yellow-orange pigment
- rich in vitamin A
hemoglobin pigment special characteristics
- iron-containing pigment in red blood cells
- -> transports oxygen
skin tone special characteristics
-refers to strength and resiliency of skin caused by elastic and collagenous CT fibers located in the dermis
appendages of the skin location
-derived embryologically from the epidermis
types of appendages of the skin
- nails
- hair
- sebaceous glands
- sweat glands
- mammary glands
nails special characteristics
- a modification of the stratum corneum of epidermis
- composed of thick plates called keratin
- cover distal ends of fingers and toes and function to protect them
- root of nail is embedded in the skin and is covered by the cuticle (or eponychium)
- the free edge of the nail is attached to the epidermis by the quick (or hypochium)
hair location
- aka pilli
- originate in the epidermis and are embedded in the dermis
- hair projects above the skin to cover the surface of the body
hair function
- protection: shields body from UV light and physical trauma and limits heat loss
- sensory reception
hair structure components
- root
- hair
- shaft
hair root
-location of active, multiplying epithelial cells from which hair growth occur
hair follicle
-tube that surrounds the root and extends into the dermis
shaft
- portion of hair that projects above the skin’s surface
- composed of dead, keratinized cells
other characteristics of hair components
- color
- arrector pili muscles
hair color characteristics
-primarily due to different proportions of melanin
what does gray hair result from?
-results from a decreased production of melanin and air bubbles in the hair shaft
arrector pili muscle characteristics
- smooth muscles attached to the hair follicle
- regulated by the autonomic nervous system
- when they contract they put pressure on the sebaceous glands causing the release of sebum
- their contraction causes the hair to stand “on end”(goosebumps)
types of glands in the skin
- sebaceous glands
- sweat glands
- mammary glands
sebaceous gland structure
-holocrine glands: rupture to release their contents
sebaceous gland location
- all over body except palms of hands and soles of feet
- very numerous along the base of the hair
sebaceous gland function
- produces sebum
- secretion is stimulated by hormones
what is sebum?
-an oily substance which lubricates the hair shaft
what is the anatomical name for sweat glands?
-sudoriferous
sweat gland structure
-coiled, tubular exocrine glands
sweat gland location
- body of gland located in the dermis
- coiled duct extends to surface of skin to release secretions through a pore
sweat gland function
- important for thermoregulation
- excretion of waste products (urea)
- protection by preventing growth of microorganisms
types of classifications of sweat glands
- merocrine glands
- apocrine glands
merocrine glands special characteristics
- most numerous
- produces sweat consisting mostly of water, salt, and waste products such as urea
- regulated by the ANS
what does the root “-crine” mean?
sweat
apocrine glands special characteristics
- located only in axillary and anogenital regions of the body
- secretes sweat and lipoproteins which produce odors when acted upon by bacteria
- generally begin to function during puberty (bc linked to hormones)
mammary glands special characteristics
- exocrine glands (bc they secrete their product through a duct)
- considered a accessory reproductive organ
