Functions of the skin:
- maintains homeostasis
- protective covering
- prevents water loss
- regulates body temperature
What do skin cells do?
Help produce Vitamin D needed for normal bone and tooth development
Layers of the skin:
1. Epidermis
2. Dermis
3. Subcutaneous layer (hypodermis)
Describe the epidermis.
- Lacks blood vessels (avascular)
- Thickest on palms and soles (0.8-1.4mm)
- Rests on basement membrane
- Replaced every 35 days
1st layer of epidermis
Stratum corneum
2nd layer of epidermis
Stratum lucidum (only in thick skin – palms, soles)
3rd layer of epidermis
Stratum granulosum
4th layer of epidermis
Stratum spinosum
5th layer of epidermis
Stratum basale
Epidermis: Genetic factors
- Varying amounts of melanin
- Varying size of melanin granules
- Albinos lack melanin
Epidermis: Physiological factors
- Dilation of dermal blood vessels
- Constriction of dermal blood vessels
- Accumulation of carotene
- Jaundice
Epidermis: Environmental factors
- Sunlight
- UV light from sunlamps
- X-rays
Describe the dermis.
- On average 1.0-2.0mm thick
- Made up of irregular dense connective tissue
- Contains muscle cells (arrector pili)
Layer to the dermis: Papillary layer
- Thin
- Superficial
- Includes dermal papillae
Layer to the dermis: Reticular layer
80% of dermis
Describe the Subcutaneous/Hypodermis Layer.
- Composed of loose connective tissue and adipose (fat) tissue
- Insulates
- Major blood vessels present
Describe hair follicles
- Dead epidermal cells
- Extends into dermis
- Contains melanin
- Arrector pili muscles are attached to every hair
3 parts to hair follicles:
1. Hair shaft (above the skin)
2. Hair root (below the skin)
3. Hair papilla (base of root)
Nail part: Nail plate
hard outer covering
Nail part: Nail bed
under the plate; vascular
Nail part: Lunula
half moon structure at the base mitotic division/growth
Sebaceous Glands
- Usually associated with hair follicles
- Classified at holocrine glands
- Secrete sebum (oil) for moisturizing
- Absent on palms and soles
Sweat Glands/Sudoiferous Glands
- Widespread in the skin
- Originates deep in the dermis or hypodermis
Eccrine glands
- most numerous
- respond to elevated body temps
- found on head, neck, and back
Apocrine glands
- respond to emotional stress
- become active at puberty
- found in axillary region and groin
- associated with hair follicles
- develop a scent (skin bacteria)
Sweat gland: Ceruminous glands
- External ear canal
- Secrete ear wax
Sweat gland: Mammary glands
Secrete milk
Regulation of Body Temperature
vitally important because even slight shifts can disrupt metabolic reactions.
Hyperthermia
abnormally high body temperature
Hypothermia
abnormally low body temperature
Healing of Wounds and Burns
- Inflammation is a normal response to injury or stress.
- Blood vessels in affected tissues dilate and become more permeable, allowing fluids to leak into the damaged tissues.
Inflamed skin may become:
- Reddened
- Swollen
- Warm
- Painful
First degree burn
superficial, partial-thickness
Second degree burn
deep, partial-thickness
Third degree burn
full-thickness
- Autograft
- Homograft
- Various skin substitutes