Chapter 6 - skin/appendages Flashcards
What is the body’s largest organ?
Skin
What is the Integumentary System?
Describes the skin and its appendages (hair, nails, and skin, glands)
Two primary layers of the skin?
Epidermis and dermis
Where is the hypodermis?
underneath the dermis
What is thin skin?
Thin skin, covers most of the body’s surfaces (1-3 mm thick);
What is thick skin?
thick skin, coveres soles and palms (4-5 mm thick)
What is the epidermis cell types?
keratinocytes, melanocytes, epidermal dendritic cells, and tactile epithelial cells
What is keratinocytes?
fully keratinized, element of the outer skin, 90% of all cells present
What are melanocytes?
pigment producing cells; contributes to skin color and filter ultraviolet (UV) light, 5% of total
What are epidermal dendrite cells?
branched antigen-presenting cells; play a role in immune response (also called langerhans cells)
What are tactile epithelial cells(merkel cells)?
attach to sensory nerve endings to form “light touch” recepetors
What are the skin layers of the epidermis?
stratum basale (base layer), stratum spinosum (spiny layer), stratum granulosum (granular layer), stratum lucidum (clear layer), and stratum corneum (horny layer)
Stratum basale layer (base layer):
single layer of columnar cells; only these cells go through mitosis and then migrate through the other layers until they shed
Stratum spinosum (spiny layer):
cells arrange in 8-10 layers with desmosomes that pull cells into spiny shapes; rich in RNA– can initiate protein synthesis required for production of keratin
Stratum granulosum (granular layer):
cells arrange into 2-4 layers and fill with keratin granules; high levels of lysosomal enzymes
Stratum lucidum (clear level):
cells filled with keratin precursor called “eleidin”; absent in thin skin
Stratum corneum (horny layer):
most superficial layer; dead cells filled with keratin (barrier area)
Turnover or regeneration time in Epidermal growth and repair:
Turnover or regeneration time refers to time required for epidermal cells to form in the stratum basale and migrate to the skin surface - approximately 35 days.
What regulates epidermal growth and repair?
epidermal growth factor
What is dermoepidermal junction?
a basement membrane with unique fibrous elements and a polysaccharide gel “glue” the epidermis to the dermis below. The junction is a partial barrier to the passage of some cells and large molecules
What is the dermis responsible for?
gives strength to the skin, serves as a reservoir storage area for water and electrocytes, plays a critical role in temperature regulation
Layers of dermis?
papillary layer and reticular layer
What is the papillary layer?
contains fine collagenous and elastic fibres and the dermoepidermal junction, unique pattern that gives individuals fingerprints, composed of dermal papilae that prpject into the epidermis
What is the dermal growth and repair?
the dermis does not continually sged and regenerate itself as does the epidermis
What is the hypodermis?
also called the subcutaneous layer or superficial fascia; forms connective between skin (dermis) and other structures, NOT PART OF THE SKIN
Melanin basic determinants?
quantity, type and distribution of melanin
Types of melanin?
Eumelanin (dark brown, almost black) and pheomelanin (reddish, orange)
Melanin formed from tyrosnie by melanocytes:
melanocytes release melanin into packets called meanosomes and melanosomes are ingested by surrounding keratinocytes and form a cap over the nucleus
What is Albinism?
congenital absence of melanin
What is melanin:
skin color
Other pigments:
beta-carotene, hemoglobin, bile pigment
Beta-carotene is:
group of yellowish pigment from food, can also contribute to skin color
Hemoglobins are:
color changes also can occur as a result of changes in blood flow; redder skin colour when blood flow to the skin increases, cyanosis is when bluish color caused by darkening of hemoglobin when it looses oxygen & gains carbon dioxide, bruising can cause a rainbow of different colors inn the skin
What is lanugo?
fine and soft hair present before birth
What is papilla?
clusters of capilaries under germinal matrix
What is root?
part of hair embedded in follicle in dermis
What is shaft?
visible part of hair
What is medulla in hair?
inner core of hair
What is the cortex?
outer portion of hair
Color of hair:
results in different amounts, distribution, types of melanin in cortex of hair
Growth of hair:
growth and rest periods alternate; hair on head averages 5 inches per year
Sebaceous glands:
glands that attach to and secrete sebum (skin oil) into follicle
Nails consist of?
epidermal cells converted to hard keratin
Nail body is?
visible part of each nail
Nail root is?
part of nail in groove hidden by folded skin (CUTICLES)
Nail lunula is:
moon shaped white area nearest root
Nail bed is?
layer of epithelium under nail body, contains abundant blood vessels
Growth of nail?
nail grows by mitosis od cells in stratum basale beneath the lunula; 0.5mm/wk or 1inch/yr
What are the sweat glands in the skin?
Eccrine glands and apocrine glands
What is the eccrine gland?
most numerous and quite small, distributed over total body surfaces with a few exceptions
What is the eccrine glands function?
secretes perspiration or sweat; eliminates wastes and help maintain a constant core temperature
What is the aporine gland?
located deep in subcutaneous layer, begins to function at puberty, around axilla, aeola of breastm and around anus
Skin glands are?
sebaceous glands and ceruminous glands
What is the sebaceous gland?
secretes sebum that keeps hair and skin soft and pilant and prevents excessive water loss from skin, increase in adolescence–may lead to formation of pimples and blackheads
What is the cercuminous gland?
modified apocrine sweat glands, protect area from dehydration
