Skin Flashcards
Chapter 10
1
Q
Skin intro
A
- largest organ of body
- cutaneous membrane
- 2 layers: epidermis (superficial epithelial layer) and dermis (deep vascular connective tissue layer)
2
Q
Thin skin
A
Covers most of body surface, except palms of hands and soles of feet
3
Q
Thick skin
A
Does not contain hair
- soles of feet and palms of hands
- friction ridges form fingerprints
4
Q
Epidermis intro
A
- most superficial layer
- composed of keratinocytes, melanocytes, dendrite cells, and tactile epithelial cells (merkel cells)
5
Q
Keratinocytes
A
- 90%+ of cell
- eventually become filled with keratin (tough fibrous tissue)
- keratin protects epidermis from mechanical and shearing forces
- once the keratinocytes have migrated to the outer most layer and flattened out, they are called corneocytes
6
Q
Melanocytes
A
- in stratum basale
- make granules of pigment (melanin)
- melanocytes do not migrate
- melanin granules are transported to adjacent keratinocytes
- melanin migrates around nucleus to “shield” DNA from UV radiation by reducing the amount of UV that can penetrate into deeper layers of skin
7
Q
Dendrite cells
A
Langerhans cells
- branched cells that play a role in the immune response
8
Q
Tactile or Merkel cells
A
- located in deepest layer of the epidermis near sensory nerve endings
- serve as light touch receptors
9
Q
Epidermis cell layers
A
- 5 layers
- stratum corneum - stratum lucidum - stratum granulosum - stratum spinosum - stratum basale
10
Q
Stratum basale
A
- base layer
- stratum germinativum: attached to basement membrane via rete pegs (downward projections into the papilary dermis)
- 1 layer of columnar cells
- some of these cells are stem cells that divide to produce new keratinocytes
11
Q
Stratum spinosum
A
- spiny layer (when dead on a slide)
- cells arranged in 8-10 layers of irregularly shaped cells
- cells are rich in RNA making them well equipped to initiate the protein synthesis required for production of keratin
12
Q
Stratum granulosum
A
- granular layer 3-5 layers thick
- keratinocytes begin keratin formation
- cell start degeneration getting further away from blood supply
- cells are filled with keratohyalin granules - required for keratin synthesis
13
Q
Stratum lucidum
A
- clear layer
- layer only present in thick skin
- few layers thic of flattened, dead keratinocytes
14
Q
Stratum corneum
A
- horny layer
- most superficial layer
- 15-30 cell layers thick
- composed of very thin squamos cells, which at the skin surface are dead and continually being shed and replaced
- dead cells filled with keratin (barrier area)
15
Q
Epidermal growth and repair
A
Regeneration time refers to time required for keratinocytes to form in the stratum basale and migrate to the skin surface -35 days (4-6 weeks)
- shortened turnover time will increase the thickness of the stratum corneum and may result in callus formation
16
Q
Dermoepidermal junction
A
Basement membrane
- contains polysaccharide gel that glues the two layers together (between rete pegs and papillary dermis)
- resists shear forces
- creates partial barrier to some large molecules
17
Q
Dermis
A
- true skin: much thicker than epidermis and lies beneath it
- gives strength to skin
- provides protection against mechanical injury and compression
- serves as a reservoir area for storage of water and electrolytes
- contains many nerves and nerve endings
- highly vascularized
18
Q
Papillary layer
A
- composed of dermal papillae that project into the epidermis and transfer nutrients and molecules to avascular epidermis
- composed of fine collagenous and elastic fibers - dense irregular connective tissue
- forms a unique pattern that gives an individual fingerprints
- makes up <20% of the dermis
19
Q
Reticular layer
A
- contains dense, interlacing white collagenous fibers and elastic fibers to make the skin tough yet stretchable; dense irregular CT
- contains many different sensory receptors and nerve endings
- provides attachment site for skeletal muscle of the face and scalp
20
Q
Dermal growth and repair
A
- dermis does not continually shed and regenerate itself like the epidermis
- during wound healing, the fibroblasts begin forming an unusually dense mass of new connective fibers
- if the epidermis is damaged, it will simply re-epithialize. If dermal damage is present a scar may form
- tension/cleavage lines - patterns formed by the collagenous fibers of the reticular layer of the dermis; also called langer’s lines
21
Q
Hypodermis
A
Subcuatneous loayer or superficial fascia
- not part of the skin - accessory structure
- lies deep to the dermis
- functions to anchor skin to underlying tissues (muscles), energy source, thermoregulation
- mostly loose fibrous and adipose tissue
22
Q
Skin color
A
- determined by pigment concentration and genetics
- melanin granules produced by tyrosine and tyrosinase
- UV exposure increases activity of tyrosinase
- albinism: lack/decreased function of tyrosinase
23
Q
Functions of skin (7)
A
- Protection
- Sensation
- Flexibility
- Excretion
- Hormone (vitamin D) production
- Immunity
- Homeostasis of body temp
24
Q
- Protection
A
- protects underlying tissues against invasion by microorganisms, chemical hazards, and mechanical trauma
- provides protection against dehydration caused by loss of fluid
- protects us from the harmful effect of overexposure to UV light
25
1. Protection (acid)
- epidermis is slightly acidic pH5
- acid mantle of skin
- acidic pH prevents bacteria present on skin form becoming pathogenic
- important to maintain acid mantle of skin
26
2. Sensation
- skin acts as a sophisticated sense organ covering the entire body surface
- receptors permit us to detect pressure, touch, temperature, pain and other general sensations
- allows the body to respond to changes occurring in both the external and internal environments
27
3. Flexibility
- skin is supple and elastic (elastin fibers)
| - permits change in body contour without injury
28
4. Excretion
- regulates the volume and chemical content of sweat
| - influences the total fluid volume of the body as well as amounts of certain waste products
29
5. Hormone production
Vitamin D
- exposure of skin to UV light converts a cholesterol molecule in the dermal blood supply to a vitamin D precursor
- blood transports (hormone) precursor to liver and kidneys, where vitamin D is produced
- excessive sunscreen use may decrease/prevent the synthesis of vitamin D
30
6. Immunity
- important defensive cells that destroy pathogenic microorganisms are found in the skin and play an important role in immunity
- langerhans cells - macrophages
- langerhans/dendritic cells trigger helpful immune reaction by working with helper T cells
31
7. Homeostasis of body temperature
- to maintain homeostasis of body temp, heat production must equal heat loss
- skin plays a critical role in this process through various processes: heat production, heat loss, evaporation, radiation, conduction, and convection
32
Evaporation
- constitutes one method by which heat is lost from the body
| - heat energy must be expended to evaporate any fluid
33
Heat production and loss
- by metabolism of foods in skeletal muscles and liver
- chief determinant of heat production is the amount of muscular work being performed
- approx 80% of heat loss occurs through the skin; remaining 20% occurs through the mucosa of the respiratory, digestive, and urinary tracts
- heat loss occurs through vasodilation
34
Homeostatic regulation of heat loss
- heat loss by the skin is controlled by a negative feedback loop
- receptors in the hypothalamus monitor the body’s internal temperature
- if body temperature is increased, the hypothalamus sends a nervous signal to the sweat glands and blood vessels fo the skin
- the hypothalamus continues to send signals until the body’s temperature returns to normal
35
Rule of nines
```
Head: 9%
UE x2: 9%
Trunk: 18%
Back: 18%
LE x2: 18%
1%
```
