Skin Flashcards
What type of epithelia is found in the epidermis?
Stratified squamous keratinized epithelium
How does thick skin differ from thin skin?
- Thicker epidermal layer
- Found only on the soles of feet and palms of hands
- Hairless
- Has merocrine sweat glands
- Has a 5th layer called the stratum lucidum, a thin, translucent layer
What are keratinocytes?
- Predominant cell type in the epidermis
- Arise from the s. basale and migrate towards the surface
- Undergo keratinization
How is cellular turnover affected in psoriasis?
Can be as rapid as 1 week due to accelerated keratinocyte cell cycling, leading to thockening of the epidermis and accelrated keratinization and desquamation.
What are warts?
Benign epithelial growths caused by papilloma viral infection of keratinocytes
What type of cancer affects the s. basale layer?
Basal cell carcinomas - most common skin cancer
What type of cancer arises from the s. spinosum layer?
Squamous cell carcinomas - 2nd most common
In the s. spinosum, keratinocytes begin to produce ____ ____ on their free ribosomes, which consist of ____ ____ ____. Membrane-bound ____ ____ containing pro-barrier lipids begin to form on the RER.
Keratohyalin granules; intermediate filament-associated proteins; lamellar granules
Cells in the ____ layer first begin to undergo keratinization.
S. Granulosum
The epidermal water barrier is formed when ____ ____ release their lipid contents via exocytosis into the intercellular space.
Lamellar granules
Keratinized cells are shed or “desquamated” from the s.corneum when ____ degrade.
Desmosomes
What are Merkel cells?
- Mechanosensitive touch receptors in the s. basale
- Basal surface of cell associates with afferent nerve ending from the dermis
- Release neuroactive chemicals that stimulate afferent nerve endings
- Most abundant in fingertips
What are Langherhan’s cells?
- Also called dendritic cells
- Found in s. spinosum
- Are the immune cells/APCs of the skin; derived from monocyte-macrophage lineage
What are melanocytes?
- Found in s. basale
- Produce melanin in membrane-bound melanosomes
- Donate melanosomes to keratinocytes for protection against UV radiation
- More melanocytes in areas exposed to the sun
How does melanin provide protection?
Takes a supranuclear position in the cell so that pigment shields the nuclei of keratinocytes from UV radiation
What is malignant melanoma?
- Rare but most dangerous form of skin cancer
- Invades the underlying dermis, and metastasizes by lymph and blood
True or False:
The ratio of melanocytes : keratinocytes varies between races.
False - the activity varies between races
What are three examples of adaptive changes to melanocyte activity?
- Genetically determined forms of melanin (pheomelanin vs eumelanin)
- Rate of melanin production - higher in darker-skinned people
- Rate of lysosomal degradation of melanin - slower in darker-skinned people
____ ____ decreases with age, resulting in paler skin and hair.
Melanocyte population
____ results from autoimmune destruction of melanocytes in symmettrical patches.
Vitiligo
What features increase the surface area between the epidermis and the dermis?
Epidermal ridges and dermal papillae
What creates fingerprints?
- Dermal ridges
- Only present in thick skin
The greater the surface area of the dermal-epidermal interface, the greater the…
Three things
- # of hemidesmosomes (ie. adhesion b/w epidermis and BM to resist friction)
- Gas, nutrient, and metabolite exchange b/w avascular epidermis and dermis
- Population of dividing cells in the germinal layer, and thus the # of keratinocytes being produced
All of these are important in thick skin
What are the two layers of the dermis?
- Papillary layer - consists of loose areolar CT, more cellular, richly vascularized, rich in collagen type I and III
- Reticular layer - consists of dense irregular CT; thicker, less cellular, rich in collagen type I
Label the following diagram, A through D.
A: Subcutaneous plexus - in hypodermis
B: Cutaneous plexus - at dermal-subcutaneous junction
C: Subpapillary plexus - at the papillary-reticular junction
D: Capillary loops - in the dermal papillae, which serve the dermal-epidermal interface
Anastomoses in the ____ plexus control blood flow into the ____ plexus and change to regulate temperature.
Cutaneous; subpapillary
What are the different components of a hair follicle?
- Sebaceous glands - produce sebum to lubricate hair and skin
- Arrector pili - smooth muscle that contracts for a) thermoregulation and b) to compress the sebaceous glands and promote secretion
- Follicular bulge - epidermal stem cells that sustain growth of hair and sebaceous glands
- Hair bulb - germinative cells that give rise to the hair matrix (ie. the hair and its inner covering)
- Melanocytes - within the matrix, supply keratinocytes with melanin
- Dermal papilla - highly vascularized “peg” of loose CT that nourishes the matrix
What are the two types of hair?
- Vellus hairs - fine, pale hair over most of body
- Terminal hairs - coarse, dark hair
Terminal follicles can be converted to vellus follicles, and vice versa, by…
Androgens
What happens to follicles in androgenetic alopecia (male-pattern baldness)?
Terminal hair follicles on the head are converted to vellus follicles in a well-characterized pattern.
What are the three phases of the hair cycle?
- Anagen - active growth takes place
- Catagen - involution of the hair and follicle towards skin surface
- Telogen - resting phase where hair is shed
A hair follicle with its sebaceous gland and arrector pili muscle is called a…
Pilosebaceous unit
What occurs in acne vulgaris?
- Chronic inflammation of pilosebaceous unit
- Hypersecretion of sebum and accelerate keratinization results in a blocked follicle
- Anaerobic bacteria flourish, creating a localized inflammatory response
What are apocrine glands?
- Found in the axillae, areolae, and groin
- Become active at puberty
- Open into hair follicles superficial to sebaceous glands
- They are stimulated by emotions
- No clear function in humans
What are eccrine glands?
- Also called merocrine glands
- Widely distributed, including hands and feet
- Not associated with follicles; ducts open onto skin surface
- Function in thermoregulation and limited excretion
- Reabsorb sodium as fluid moves along duct; thus sweat is salty
What are mammary glands?
- Modified apocrine sweat glands
- Develop along milk lines in the embryo
- The parenchyma is derived from the epithelia and is supported by surrounding CT stroma
Each mammary glands consists of how many lobes?
15-25
Each lobe in a mammary gland consists of…
Numerous lobules, connected to a lactiferous duct system by an extralobular terminal duct
Lactiferous ducts form ____ before opening independently at the nipple.
Lactiferous sinuses
What changes happen to the breasts during puberty?
- Nipples and areolae enlarge
- Sebaceous follicles in the areola enlarge to form Montgomery’s tubercles
- Lactiferous ducts expand
- Adipose tissue accumulates
- Dense CT septa, called suspensory/Cooper’s ligaments, develop to support the weight of the breast
A lobule and its extralobular terminal duct is called a…
Terminal duct lobular unit (TDLU)
During pregnancy, terminal ductules develop into…
Secretory acini
Breast enlargement in the premenstrual period is caused by…
Edema in the loose CT lobular stroma
Breast milk expulsion is caused by…
Myoepithelial cells and SM fibres contracting around the lactiferous ducts and sinuses
Lobar carcinomas arise from…
The terminal ductules
