Chapter 5- Integumentary System Flashcards
What are the two layers of the skin
- Epidermis
2. Dermis
Epidermis
unvascularized outermost portion of the skin, gets nutrients from diffusion from blood vessels in the dermis
What type of tissue makes up the epidermis
Stratified squamous epithelial tissue
Dermis
Vascularized, has nervous supply, makes up most of integument by mass
What type of tissue makes up the dermis
dense connective tissue
Hypodermis
Composed mostly of adipose tissue. Located below the dermis but superficial to the tough connective tissue wrapping (fascia) of the skeletal muscles
Functions of the hypodermis (4)
- Storage- easy to access energy source for the body
- Protection/shock absorption- prevents physical trauma to internal organs
- Insulation- prevents excessive heat loss
- Anchor- holds skin to underlying skeletal muscle tissue- is still flexible
Keratinocytes
produce keratin, the fibrous protein that helps give the epidermis its protective properties
How are keratinocytes linked
Linked by desmosomes (with some tight junctions) to hinder movement of water between cells
How do keratinocytes reproduce
Reproduce mitotically in stratum basale in response to epidermal growth factor, and from the bottom up- keratinocytes are dead once they approach the skin surface
Persistent friction to the epidermis causes
callus formation, a thickening of the epidermis to prevent excessive skin cell loss. Millions of cells are lost each day- you get a new epidermis every 25-45 days
Keratinocyte function
give the epidermis its protective qualities (tough and dry)
Where are melanocytes located in the epidermis
stratum basale
Melanosomes
Melanin producing organelle in the melanocytes
What happens to melanin after it’s produced by the melanosomes
Melanin is transferred to the keratinocytes and migrates to the superficial side of the keratinocyte to form a pigment shield that protects the nucleus and the nuclear DNA from the damaging effects of UV light. Melanin does not remain in the melanocytes
Dendritic cells (Langerhans cells)
Move to epidermis from bone marrow
Active macrophages- this activates the immune system
Located in the epidermis
Tactile cells (Merkel cells)
Present in epidermal-dermal junction
Associated with sensory nerve endings, resulting in sensory receptor function for 2 types of touch
What types of touch are detected by the tactile cells (2)
- Light touch
2. Vibration
What types of cells are located in the epidermis (4)
- Keratinocytes
- Melanocytes
- Dendritic cells
- Tactile cells
Layers of the epidermis (5)
- Stratum basale
- Stratum spinosum
- Stratum granulosum
- Stratum lucidum
- Stratum corneum
Stratum basale
innermost/deepest epidermal layer
Single layer of stem cells attached to dermis- the many mitotic nuclei in this layer suggests rapid cell division
Cell composition of the stratum basale
Mostly keratinocytes, 10-25% of cells are melanocytes
What happens in the stratum basale when cells divide
Reproduces from the bottom up. When cells divide, When cells divide, one daughter cell is pushed into the cell layer above to begin to specialize into a mature keratinocyte. The other remains in the stratum basale to make sure the layer is replenished
Stratum spinosum
Second deepest (spiny layer) due to spiny extensions of its keratinocytes, several cell layers thick. Contains pre-keratin- thick bundles of filaments that resist tension are are anchored to the desmosomes