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167 Cards in this Set
- Front
- Back
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The skin is composed of several kinds of
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tissues
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Skin is
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a protective covering that prevents many harmful substances from entering the body
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Skin also
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retards water loss & helps regulate body temperature.
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Skin houses
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sensory receptors & contains immune system cells
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Skin synthesizes
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vitamin D & excretes a small amount of waste products
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The two distinct layers of skin are
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epidermis & dermis
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The outer layer is called the
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epidermis
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The epidermis is composed of
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stratified squamous epithelium
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The inner layer is called
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dermis
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The dermis is made up of
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connective tissues, muscle tissue, nervous tissue,& blood
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A basement membrane separates
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the two skin layers
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The subcutaneous layer is beneath
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the dermis
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The subcutaneous layer is composed of
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loose connective tissues & adipose
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No sharp boundary separates the dermis & subcutaneous layer because
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the fibers of the dermis are continuous with the fibers of the subcutaneous layer
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The adipose tissue of the subcutaneous layer
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insulates the body
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The subcutaneous layer also contains
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major blood vessels that supply the skin |
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The epidermis lacks
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blood vessels
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The deepest layer of the epidermis is called the
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stratum basale
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The stratum basale is nourished by
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blood vessels in the dermis
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Cells of the stratum basale can divide & grow because
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they are nourished so well
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When new cells enlarge they
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push old epidermal cells away from the dermis toward the surface of skin
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The farther the cells are moved
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the poorer their nutrient supply becomes & eventually they die
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Older skin cells are called
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keratinocytes
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Keratinocytes
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are held together with desmosomes
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Keratinization is the accumulation of
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keratin in epidermal cells which hardens the epidermis
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As a result of keratinization many layers of tough, tightly packed cells
accumulate in the
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epidermis
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The outermost layer of the epidermis is called the
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stratum corneum
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The epidermis is thickest on
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palms of the hand & the soles of the feet
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Most areas of epidermis have ___ layers
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2
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The four layers starting with the deepest are
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stratum basale, stratum spinosum, stratum germinativum, & stratum corneum
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An additional layer called ______ is in thickened skin of the palms & soles
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stratum lucidum
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In healthy skin, production of epidermal cells is balanced with loss of dead cells from the
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stratum corneum
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The rate of cell division increases where
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the skin is frequently rubbed or pressed
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Calluses are a thickening of the
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stratum corneum
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Corns are
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keratinized conical masses on the toes
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Specialized cells in the epidermis called ______ produce melanin
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melanocytes
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Melanin provides
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skin color & absorbs UV radiation
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Melanocytes lie in the
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stratum basale & in the underlying connective tissues of the dermis
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The extensions of melanocytes transfer melanin granules to epidermal cells by a process called
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cytocrine secretion
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The boundary between the dermis & epidermis is uneven because
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the epidermis projects inward & the dermis has papillae between the ridges of the epidermis
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Fingerprints form from
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the undulations of the dermis & epidermis at the distal end of the palmar surface of a finger
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The dermis binds
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the epidermis to the underlying tissues
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The dermis is largely composed of
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irregular dense connective tissue that includes tough collagenous fibers & elastic fibers in a gel like ground substance
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The dermis also contains smooth muscles that
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can wrinkle the skin of the scrotum.
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Some smooth muscle of the skin is associated with
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hair follicles
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In the face, skeletal muscles are anchored to
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the dermis
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Nerve cell processes are scattered throughout the
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dermis
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Pacinian corpuscles are stimulated by
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heavy pressure
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Meissner’s corpuscles are stimulated by
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light touch.
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Hair is present on all skin surfaces except
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the palms, soles, lips, nipples, & parts of external reproductive organs
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A hair follicle is
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a group of epidermal cell at the base of a tubelike depression in the dermis of skin
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A follicle extends
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from the surface of skin into the dermis
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The hair root is
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the portion of hair embedded in skin
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The hair papilla is
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a projection of connective tissue at the end of the hair follicle. It contains blood vessels
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The hair shaft
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is the portion of hair that extends from the surface of skin
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A hair is composed of
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dead epidermal cells
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Baldness results when
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hairs fall out & are not replaced
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Genes determine hair color by
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directing the type & amount of pigment that epidermal melanocytes produce
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Dark hair has more _____ than blond hair
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melanin
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White hair of people with albinism lack
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melanin
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Red hair contains
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an iron pigment called trichosiderin
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Hairs appear gray from
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a mix of pigmented & unpigmented cells
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An arrector pili muscle is
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a band of smooth muscle & attaches to hair follicles
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Goose bumps are
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produced when arrector pili muscles contract
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Nails are
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protective coverings on the ends of fingers & toes
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Each nail consists of
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a nail plate that overlies a surface of skin called the nail bed
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The lunula of a nail is
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the whitish, thickened, half moon shaped region at the base of a nail plate with the most active growth
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Sebaceous glands contain
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groups of specialized epithelial cells & are associated with hair follicles
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Sebaceous glands are
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holocrine glands
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Sebaceous glands
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their cells produce sebum
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Sebum
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is a mixture of fatty material & cellular debris
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Sebum is secreted
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into hair follicles & helps keep hair & skin soft, pliable & waterproof
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Sebaceous glands are not found
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on palms & soles
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Sebaceous glands open
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directly onto the surface of the skin in some regions, such as, the lips, corners of the mouth, & parts of the external reproductive organs
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Sweat glands are also called
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sudoriferous glands
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Each sweat gland consists of
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a tiny tube in the dermis or superficial subcutaneous layer
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The most numerous sweat glands are
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eccrine glands
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Eccrine glands respond to
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body temperature elevated by environmental heat or exercise
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Eccrine glands are common
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on the forehead, neck, & back
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A pore
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is the opening of a sweat gland duct
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Sweat contains
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water, wastes, & salts.
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Apocrine glands become active
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at puberty
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Apocrine glands can wet
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certain areas of skin when a person is nervous or stressed
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Apocrine glands are most numerous
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in the axillary regions, groin, & around the nipples
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Ceruminous glands are located in
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the external ear canal
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Ceruminous glands function to
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secrete ear wax
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Mammary glands
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secrete milk
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Regulation of body temperature is important because
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even slight shifts can disrupt the rates of metabolic reactions
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A normal temperature of deeper body parts remains close to
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37oC.
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Heat is a product of
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cellular metabolism
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When body temperature rises above the set point
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nerve impulses stimulate structures in the skin & other organs to release heat
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During physical activity
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active muscles release heat, which the blood carries away
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When warmed blood reaches the hypothalamus
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muscles in the walls of dermal blood vessels relax
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As dermal blood vessels dilate
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heat escapes to the outside world
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Skin reddens because
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dermal blood vessels are dilated
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The primary means of body heat loss is
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radiation
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Radiation
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is the spread of infrared heat from warm surfaces to cooler surroundings
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Conduction
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is the movement of heat into molecules of cooler objects
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Convection
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is the continuous circulation of air over a warm surface
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Evaporation
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is the change of a liquid to a gas
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When sweat evaporates
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it carries heat away from the skin surface
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When body temperature falls below the set point
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muscles of dermal blood vessels constrict which decreases the flow of blood through the skin
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When body temperature falls
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sweat glands become inactive
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When body temperature continues to fall
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small groups of muscles contract rhythmically to produce shivering
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Hyperthermia
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is a rise in body temperature
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If air temperature is high
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heat loss by radiation is less effective
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Hypothermia
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is a low body temperature
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Hypothermia can result from
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prolonged exposure to cold or as part of an illness
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Hypothermia can lead to
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mental confusion, lethargy, & loss of consciousness
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People at a higher risk for developing hypothermia
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elderly, very thin individuals, homeless & the very young
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All people have about the same number of
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melanocytes in their skin
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Differences in skin color result from
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the differences in the amount of melanin melanocytes produce
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The more melanin produced
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the darker the skin
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The distribution & size of pigment granules within melanocytes
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also influence skin color.
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Environmental factors such as
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sunlight, ultraviolet light from sunlamps, & X rays affect skin color
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Tans fade
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as pigmented epidermal cells become keratinized & wear away.
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When blood is well oxygenated
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the blood pigment hemoglobin is bright red & the skin of light complexioned people appears pink
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When blood oxygen concentration is low
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hemoglobin is dark red & the skin appears bluish
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If dermal blood vessels are dilated
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more blood enters skin & skin appears pinkish or reddish
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If dermal blood vessels are constricted
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more blood enters the dermis,
reddening the skin of a light complexioned person
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Carotene
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is a yellow orange pigment found in certain vegetables
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Carotene can
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give skin a yellowish color
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Inflammation is a normal response
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to injury or stress
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During inflammation
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blood vessels dilate & become more permeable
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Inflamed skin may become
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reddened, swollen, warm, & painful to the touch
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The dilated blood vessels provide
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the tissues with more nutrients & oxygen, which aids healing
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The specific events of healing depend on
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the nature & extent of the injury
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If a break in the skin is shallow
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epithelial cells are stimulated to divide more rapidly than normal
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If a cut extends into the dermis or subcutaneous layer
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blood vessels break & the escaping blood forms a clot
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A clot consists mainly of
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fibrin, plasma, blood cells, & platelets
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A scab is
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a blood clot & dried fluids
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Fibroblasts migrate
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into the injured area & begin forming new collagenous fibers that bind the edges of the wound together
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Connective tissue matrix releases
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growth factors that stimulate certain cells to divide & regenerate damaged tissues
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As healing continues
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blood vessels extend into the area beneath the scab
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Phagocytic cells
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remove dead cells & other debris
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A scar results when
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the wound is extensive
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A granulation consists of
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a branch of a blood vessel, & a cluster of collagen secreting fibroblasts
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A first degree burn
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is one that only affects the epidermis
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A second degree burn is that affects
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a part of the dermis & epidermis
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Blisters appear in
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second degree burns
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The healing of second degree burns depends on
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accessory structures of the skin that survive the burn
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A third degree burn
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is one that destroys the epidermis, dermis, & the accessory structures
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In a third degree burn
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the skin becomes dry & leathery
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If a third degree burn is extensive
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treatment may involve removing a thin layer of skin from an unburned region of the body & transplanting it to the injured area
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An autograft is
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a graft from the same person
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A homograft
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is a graft from a cadaver |
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Skin substitutes include
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amniotic membranes, membranes of silicone, polyurethane or nylon
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The treatment of a burn patient requires
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estimating the extent of the body’s surface that is affected
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To estimate, physicians use
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the rule of nines
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This rule divides the skin’s surface into
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11 areas of 9% each
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Aging skin affects
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appearance, temperature regulation & vitamin D production
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Age spots or liver spots are
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patches of pigments
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The aging dermis becomes
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reduced as synthesis of the connective tissue proteins collagen & elastin slows
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Wrinkling & sagging skin result from
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the shrinking of the dermis & loss of fat from the subcutaneous layer
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Skin becomes drier because
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sebaceous glands produce less oil
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Slowed melanin production causes
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gray or white hair
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Nail growth is impaired because
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the blood supply to the nail beds is diminished
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Sensitivity to pain & pressure ______ with age
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diminishes
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An older person is less able to tolerate ______ because the sweat glands & hair follicle shrink
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heat
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With age the number of dermal blood vessels
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decrease
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Vitamin D
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is necessary for bone tissue to absorb calcium
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Stratum granulosum |
3. the keratinocytes are still on the move, by this point they have kertahyalin granulesStratum spinosum: the keratinocytes migrating up, they have nice oval nucleiStratum basale: Single layer of proliferating columnar keratinocytes, melanocytes (pigmented cells) and Merkel cells (mechanoreceptors) also live here |
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Stratum corneum |
1. The outmost layer, made of dead keratinocytes with a layer of protein around them (they have undergone keratinization) |
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Stratum lucidum |
2. Also dead keratinocytes (there is no real distinction here other than that the poor keratinocytes have died but have not finished the keratinization process) |
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Stratum basale |
5. Single layer of proliferating columnar keratinocytes, melanocytes (pigmented cells) and Merkel cells (mechanoreceptors) also live here |
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Stratum spinosum |
4. the keratinocytes migrating up, they have nice oval nuclei |
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Whats your mnemonic device for the layers of the skin? |
Come, lets get sun burned |
