Ch 6-Integumentary System (Exam 2) Flashcards
What is melanin
Natural substance that gives color to skin, hair, eyes
What does subcutaneous mean
Under the skin
What is the largest organ in the body?
Skin- 15-16% of body weight
What is the top layer of the skin?
Epidermis
What is the epidermis and dermis separated by?
Basement membrane
What is the epidermis nourished by? (Since it is avascular)
Diffusion from capillaries of the papillary layer of the dermis
What is the epidermis composed of
Cells arranged into stratified layers
What are the cells of the epidermis?
-stem cells
-keratinocytes
-melanocytes
-dendritic cells
What are stem cells
-undifferentiated cells that give rise to keratinocytes
-in the deepest layer of the epidermis
What is the deepest layer of the epidermis?
Stratum basale
What are keratinocytes?
Cells of the epidermis that produce keratin (great majority of epidermal cells)
What are melanocytes?
-occur only in the stratum basale
-synthesize pigment melanin that shields DNA from ultraviolet radiation
What are dendritic cells?
Macrophages originating in bone marrow that guard against pathogens
What is the only layer of the epidermis to undergo cell division?
Stratum basale
What are the layers of the epidermis?
(BSGLC)
-Stratum basale
-stratum spinosum
-stratum granulosum (granular layer)
-stratum lucidum (clear layer)
-stratum corneum (horny layer)
Stratum spinosum
made up of multiple layers of cells that are held together by desmosomes
Stratum granulosum (granular layer)
-contains keratohyalin
-contains lysosomal enzymes
-contains granules
-nucleus and other organelles degenerate and cells die
Stratum lucidum (clear layer)
-thin, clear zone. Found only in palms and soles
-dead cells filled with keratin precursor called eleidin
Stratum corneum
-most superficial and consists of cornified cells
-outermost layer of the skin
Layers of the epidermis in order (bottom to top)
1.Stratum basale (deepest layer)
2. Stratum spinosum
3. Stratum granulosum
4. Stratum lucidum
5. Stratum corneum (outermost layer of skin)
How long does it take for epidermal cells to form in the stratum basale and migrate to the skin surface?
30-40 days
What percent of cells in the stratum basale enter mitosis daily?
10%-12%