Ch. 5.2-5.4 Skin Color, Sunlight, & EFG Flashcards
Carotene
- orange-yellow pigmant that accumulates in epidermal cells.
- Most apprent in stratum corneum of light-skinned individuals
- Also in fatty tissues of deep dermis and subcutaneous layer
- Can be converted to Vitamin A
Melanocytes
- Located in stratum basale, between or deep to epithelial cells
- Convert tyrosine into melanin
- Package it into melanolsomes - intracellular vesicles - and transferred into keratinocytes
- In dark skinned, transfer also occurs in stratum ganulosum - pigmentation thus more persistant
- Melanocytes: basal cells between 1:4 - 1:20 and same across individuals. Only activity differs.
- Synthesis peaks 10 days after sun exposure

Freckles
areas with irregular borders with normal melanocytes that have higher synthetic actvity

Lentigos
Have regular borders and contain abnormal melanocytes
senile lentigos (liver spots)
variably pigmented areas that develop on sun-exposed skin of older individuals
UV Radiation
Stimulates epidermal production of compounds for calcium ion homeostatis
UVA: least harmful
UVB:
UVC: germicide; most harmful. Highest frequency. Cannot pass intact ozone.
hemoglobin
pigment in red blood cells
Jaundice
Liver cannot excrete bile; yellowish pigment accumulates in body fluids. Skin and whites of eyes can turn yellow in advanced stages.
Melanocyte-stimulating hormone
Tumors affecting pituitary gland. Hormome causes darkening of the skin (hyperpigmentation)
Addison’s disease
pituitary gland secretes large quantities of adrenocorticotropic hormone (ACTH), similar to MSH

Vitiligo
Individuals lose melanocytes, causing white spots. Tied to thyroid gland disorders; possible mAbs attacking melanocytes.

cholecalciferol
Vitamin D3
epidermal cells in stratum basale convert a steroid into this.
calcitrol
Hormone produced by the kidneys.
The liver converts cholecalciferol into an intermediate product used by the kidneys to synthesize this hormone.
Essential for the normal absorption of calcium and phosphorus in the small intestines.
Rickets
Caused by a lack of cholecalciferol (Vitamin D3). Inadequate calcium and phosphorus absorption in the small intestine leads to inadequate bone growth and maintenance in children.

Epidermal growth factor (EFG)
- Peptide. Affects epidermis, and other epithelia.
- Used to stimulate epithelial growth/tissue culture (epidermal burn sheets)
- Produced by salivary glands and glands of duodenum
- Promote division of basal cells in stratum basale and stratum spinosum
- Accelerates the production of keratin in differentiating keratinocytes
- Stimulates epidermal development and repair
- Stimulates synthetic activity & gland secretion
Moles & Warts
Benign tumors of the skin
actinic keratosis
a scaly area on sun-damaged skin. An indication that sun damage has occured. Not a sign of skin cancer.
basal cell carcinoma
- A cancer that originates in stratum basale
- most common
- Least malignant
- Sun exposure and genetic

Squamous cell carcinoma
- Restricted to areas of sun-exposed skin
- Metastasis seldom occurs
- Involves keratinocytes of stratum spinosum

malignant melanoma
- cancerous melanocytes grow rapidly and metastasize in lymphatic system.
ABCD Rule
To identify a malginant melanoma:
A - asymmetry
B - border (irregular or notched)
C - color (mottled, with combination of tones)
D - diameter (more than 5mm ~eraser pencil).
