Lecture 21: Skin Structure and Function Flashcards
What are the 3 layers of skin?
Epidermis
Dermis
Hypodermis
What are the differences of the dermis in men and women?
Men - hypodermis thickest in abdomen and shoulders
Women - hypodermis thickest in hips, thighs, and buttocks
Both thick in palms of hands
What is the location of the hypodermis?
Lowest layer of skin
What are the 3 kinds of substances that hypodermis contain?
Mainly adipose tissue, neurovascular bundles, lymphatic
What kind of tissue is the hypodermis?
Loose connective tissue
What are the 5 functions of the hypodermis?
- Energy store
- Insulator
- Shock absorber
- Connects skin to underlying muscles and bones
- Makes hormones
What is the location of the dermis?
Between epidermis and hypodermis
What is corium?
Dermis
What is the cutis?
Dermis and epidermis
What are the 2 layers of dermis?
Papillary and reticular
What is the papillary?
Upper layer of dermis
What is the reticular?
Lower layer of dermis
What are the 3 functions of the dermis?
- Thermoregulation by hairs and sweat glands
- Sensory
- Gives structure to skin
What is the location of epidermis?
Outermost layer of epithelial cells (keratinocytes)
How many layers of cells is in the epidermis?
4-5
What are the cells held together laterally by?
Adherens junctions
What are the cells held together vertically by?
Desmosomes
What are the 6 functions of the epidermis?
- Prevent water loss
- Prevent entry to bacteria and parasites
- Special cells that present pathogens to immune cells
- Synthesis of keratin
- Prevents underlying tissue loss due to abrasion
- Allows gaseous exchange
What are the 5 layers of the epidermis?
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
What is the stratum corneum?
Outermost corny or horny layer made of squamous dead keratinocytes
What is the stratum lucidum?
Transparent layer under stratum corneum only on palms and soles of feet
What is the stratum granulosum?
Granular layer
What kind of epithelial cells does the stratum granulosum have?
Stratified squamous epithelium
What are the 2 components of the stratum granulosum?
Lamellar granules (filament-associated proteins that assemble keratin fibrils and secrete it)
Tonofibrils (bundles of keratin filaments and keratohyalin granules)
What is the stratum spinosum?
Spinous layer
What kind of epithelial does the stratum spinosum have?
Cuboidal epithelium arranged in 3 layers held together by desmosomes
What is the function of stratum spinosum?
Produce lamellar bodies (keratohyalin factories)
What is the stratum basale?
Basal cell layer
What kind of epithelial cell does the stratum basale have?
Tall columnar epithelial cells
What are the 3 functions of stratum basale?
Renew keratinocytes by cell division
Keratinocytes make keratin filaments
Melanocytes produce melanin
What are keratinocytes?
Synthesize keratin that contribute to the strength of epidermis
What is the normal transit time of a keratinocytes from basal layer to stratum corneum?
28-40 days
What happens in psoriasis?
Transit time of keratinocytes from basal layer to stratum corneum reduced to 2-3 days, so stratum corneum is produced in abundance as silvery scales