Ap integumentary Flashcards
Epidermis function
The epidermis is composed of layers (strata) of keratinocytes
Thick skin = five layers (palms of hands, soles of feet) Thin skin = four layers (everywhere else)
- Provides mechanical protection
- Prevents fluid loss
- Keeps microorganisms from invading the body
- 4 cell types
- 4 or 5 layers
layers of epidermis
Keratinocytes
- 90% of cells in the skin
- Originate in the S. basale and differentiate as they progress upwards.
- Differentiated cells produce keratin
- Tightly connected by specialized gap junctions called desmosomes
- Growth is controlled at least in part by epidermal growth factor (EGF)
Langerhans Cells
- Specialized macrophages
- Arise from bone marrow, migrate to epidermis (s. spinosum / s. granulosum)
- Recognize antigens and present them to lymphocytes for destruction
Merkel Cells
- Present at the epidermal – dermal junction
- Associated with a sensory nerve fiber
- Functions in touch reception
Melanocytes
- Present in the S. basale
- Synthesize a reddish-brown biochrome, melanin, and dispense it to keratinocytes through their dendrites
- Melanin: dispersed screen against the potentially harmful ultraviolet rays of the sun
Skin color depends on
–Amount of melanin produced by melanocytes
- Blood supply
- Freckles and pigmented moles are local accumulations of melanin
Disorders of melanocytes
Vitiligo:
- Occurs when melanocytes die or stop producing melanin
- Autoimmune condition
Albinism:
- Inherited genetic disorder with mutation in genes involved in melanin production
- Vision problems
•Describe the location and explain the purpose of mitosis in the epidermis.
Dermis
Dermal Organization
•Papillary layer
–Contains blood vessels, lymphatics, sensory nerves of epidermis
•Reticular layer
–Contains network of collagen and elastic fibers to resist tension
Papillary layer
Loose connective tissue
Highly vascular
Most sensory receptors for cutaneous senses are found here
Free nerve endings – for heat, cold, itch and pain
Encapsulated nerve endings like Meissner’s corpuscles (tactile corpuscle) for touch and pressure
Epidermal Ridges
•Interacts with the epidermis, forming “ridges” and “valleys”
thumb print
Reticular layer
About 80% of the dermis
Dense connective tissue with collagen and elastin
Also vascular
Lamellated corpuscle senses vibration / pressure touch
Stretch marks
- Caused by excessive stretching of the reticular layer
- Patterns of collagen and elastic fibers form lines of cleavage
The Subcutaneous Layer
hypodermis
- Stabilizes skins position against underlying organs and tissues
- Known as subcutaneous tissue or superficial fascia
•
•Consists of
–Lose connective tissue (WBC, mast cell)
–Adipose tissue