WEEK 4 - INTEGUMENTARY Flashcards
Skin
- Largest and heaviest organ
- Replaced every 7 years
What are the 3 major region of the skin?
1) Epidermis: above / upon dermis, outer
2) Dermis: middle
3) Hypodermis: below / under dermis, deepest
What is epidermis?
- Stratified squamous epithelium
- 5 cell types and 4 cell layers (5 on palms and soles of foot)
- Replaced every 2-4 weeks
- Avascular (diffusion)
What are stem cells in the epidermis?
- Undifferentiated.
- Generates keratinocytes
What are keratinocytes in the epidermis?
- Main cell
- Produce fibrous protein KERATIN (double-helix), structure, flexibility, water resistance
What are dendritic cells in the epidermis?
- Phagocytic, activate immune system (800 per mm2)
- Damaged by ultraviolet light (UV)
What are tactile cells or disc in the epidermis?
Touch receptors in association with dermal sensory nerve endings
What are melanocytes in the epidermis?
- Produce MELANIN (pigment)
- Long extensions (spider-like)
- Transfers melanin (exocytosis) to keratinocytes (endocytosis)
- Protects nucleus DNA from UV light (melanoma
Stratum Basale
- Simple cuboidal epithelium
- Attached to dermis (via basement membrane)
- Stem cells undergo cell division (Mitosis)
- Generate new keratinocytes.
- Accelerated with injury and mechanical stress
Stratum Spinosum
- Stratified epithelium
- Keratinocytes linked by desmosomes
- KERATIN fibres (cytoskeleton) linked to desmosomes
Stratum Granulosum
- 3-5 layers of keratinocytes
- Organelles degenerate, cells flatten and die
- Accumulate granules that secrete a Protein that binds keratin filaments together
Glycolipid that waterproofs against water loss and gain (and nutrient diffusion)
Stratum Lucidum
- Few rows of DEAD keratinocytes superficial to stratum granulosum
- Where friction present. Fingertips, palms and soles
Stratum Corneum
- Outermost. 5 to 50 layers of very keratinized DEAD cells
- Dead cells (shed 18 kg / year, dust)
Thickness in the epidermis
- Thin epidermis covers most of the body (0.08 mm, plastic sandwich bag)
- Thicker epidermis on palms and soles (0.5 mm, paper towel)
What is dermis?
- Holds body together
- Thicker than epidermis (0.2 to 6 mm)
- Strong, flexible connective tissue, mostly collagen (triple-helix)
- Vascular
What are nursing actions for dermis?
Transdermal drugs:
- Absorbed through skin
- Lipid-soluble
Thermoregulation:
- Vasoconstriction (warming)
- Vasodilation (cooling)
- Sweating
What is thermoregulation?
- Body’s thermostat in hypothalamus (brain)
- Hypothalamus receives input from:
- Peripheral thermoreceptors (skin)
- Central thermoreceptors (hypothalamus)
- Initiates, heat-loss or -promoting mechanisms
What are the 2 layers of dermis?
- Papillary layer
- Reticular (net-like) layer
What is the papillary layer?
- Loose connective tissue
- Collagen, elastic fibers = Spaces for blood vessels, nerves
- Dermal papillae project into epidermis
- Interlock = strong bond (blister) - Increase surface area for grip and sites for
- Tactile (Meissner) corpuscles (light pressure receptors).
- Free nerve endings (temperature, itching etc.). Lips and genitals
What is the reticular layer?
- Dense irregular connective tissue
- 80% of skin thickness
- Fibroblasts, Macrophages, Lamellated corpuscles (deep pressure receptors)
- Collagen and elastin fibers in parallel bundles
- Bundles orientated to resist multi-directional stresses (cleavage / tension lines)
- Cut / tear parallel to cleavage line = better healing, less scarring
What is hypodermis (subcutaneous)?
- Loose connective tissue with adipocytes (50% of bodies fat)
- Collagen fibres interwoven with those of dermis
- Binds skin to underlying muscle
- Shock absorber, insulator, energy source
What are nursing actions related to hypodermis?
Subcutaneous (SC) injections
▪ Adipose. Vascular
▪ Constant turnover
▪ No pain receptors
