wk 9- the skin Flashcards
what is the largest organ of the body?
skin
what layers make up the skin? 2
the most superificial layer is the epidermis and
the thicker, deeper layer, the dermis
what is the epidermis comprised of?
containing keratinized and stratified squares epithelium. It has four to five layers of epithelial cells (keratinocytes, melanocytes, dendritic cells, tactile cells) depending on if it is thick or thin skin. the epidermis is avascular.
(new cells migrate form basal layer to the apical surface and slough off over time)
what is the dermal layer comprised of?
contains extensive capillary beds, lymphatic vessels, nerve cells as well as accessory structures like hair follicles, sebaceous glands, sudoriferous glands.
within the skin there are 2 types of structures
the cutaneous membrane
accessory structures
desquamation is?
shedding or sloughing off of keratinized dead skin
what is below the dermis layer?
superficial fascia (hypodermis/subcutaneous layer)
connects the skin to underlying fascia of bones and muscles. not a true layer of skin however
consists of well-vasuclarised, loose, areolar connective tissue and adipose tissue which functions as a mode of fat storage and provides insulation and cushioning for the skin.
dermis has how many layers / strata? and what are they?
2 layers of connective tissue
papillary layer- thin, superficial layer comprised of areolar connective tissue which forms dermal papillae to connect to the superficial epidermal layer
reticular layer- comprises of 80% of dermis and is comprised of dense fibrous connective tissue
what % of total body mass does the skin have?
16
what surface area does the skin have
approx 2 square metres
what are keratinocytes in epidermis layer?
the most abundant cell type in the skin. these cells produce the protein keratin and continuously slough off as they become superficial from basal to apical layer.
what are melanocytes in the epidermis?
the pigment producing cells of the skin. located in the stratum basale and protect against UV damage
what are dendritic cells in the epidermis?
are phagocytic immune cells located throughout the layers of the skin and are responsible for engulfing debris and infectious agents
what are tactile Markel cells?
the sensory cells of the skin, that detect pressure, temperature and vibration
what is the difference between thick and thin skin?
thick skin is located on anatomical areas subjected to abrasion and herring forces (palms of hands, soles of feet and is comprised of 5 strata (lacks hair and sebaceous glands)
think skin lacks a stratum lucidum and is only 4 strata.
skin color and the types of pigments
melanin - brown pigment (melanocytes)
carotene- orange pigment
hemoglobin- red pigment
what is the relationship between pigmentation and location?
concentration of melanin is increased in populations living close to the equator for protective purposes against UV-DNA damage (reasons for reduced skin cancer rates in darker skin)
what are dermal modifications and what do they form? what are examples
include friction ridges, cleavage lines, flexure lines which provide individual identity and enhanced flexibility to the skin
- fingerprinting- friction ridges
- surgical incsions- cleavage lines
- movement - flexure lines
locations of needle injection 4
intradermal- penetrate epidermis and deposit contents into dermal layers
intravenous- penetrate epidermis and dermis and deposit contents into a blood vessel (vein) in dermal layer
subcutaneous- penetrate epidermis and dermis and deposit content into the superficial fascia layer
intramuscular- penetrate the epidermis and dermis and superficial fascia and deposit contentions in the muscle layer below.
hair- what is it comprised of, what are its functions over the body in specific areas and where is it absent?
hair is comprised of filamentous strands and dead keratinized cells (hard keratin and is pigmented by melanocytes)
scalp- reduces heat loss, sun damage and trauma
eyelashes- shield eyes against matter and objects
nose hairs- filter air to remove matter
body hair- sensory information, temp control
absent from thick skin.
nails what are they made of and their function?
hard keratin
function is to protect the digits and add to dexterity
sweat glands function
produce 2 main secretions
1. perspiration (eccrine glands)- offloading excess sodium chloride and thermoregulate via evaporation
2. pheromones (apocrine glands)
sebaceous glands function
produce sebum - secreted into hair follicle to act as lubricant and provide antimicrobial activity (disrupt the skin barrier)
absent in think skin
functions of integumentary system 6
-physical barrier for protection against external agents
- temperature regulation by the rich vasculature of dermis where vasodilation or constriction can position blood vessels superficially or deep to retain or lose heat and perspiration/evaporation.
-blood reservoir for shunting to critical organs
-excretion of excess sodium chloride
-cutaneous sensation gives feedback from thermoreceptors (hot cold) and mechanoreceptors (pressure)and nociceptors (pain)
-metabolic functions such as vitamin D absorption
