Skin histology Flashcards
What typical percentage of body weight is skin?
15-20%
What is the main component of epidermis?
Stratified squamous keratinized epithelium - keratinocytes
What are the two general classification of cells in the epidermis?
Keratinocytes
Non-keratinocytes
What are the 4 types of keratinocytes?
Stratum corneum
Stratum granulosum
Stratum spinosum
Stratum basale
What are the 3 types of non-keratinocytes?
Melanocytes
Langerhans’ Cells
Merkel’s cells
What is the subdivision of stratum corneum and where is it found?
Stratum lucidum found in thick skin
About how long is total epidermal turnover?
47 days
What are the characteristics of stratum basale?
Hemidesmosomes to underlying CT
Mitotically active
Desmosomes to eachother
What are the characteristics of stratum spinosum and another name?
Several layers, larger
Attached by desmosomes at end of cytoplasmic processes
Also called prickle cells
What are the characteristics of stratum granulosum?
Flattened
Keratohyalin granules - precursors to filaggrin
Lamellar bodies - epidermal water barrier
What are the characteristics of stratum corneum?
Most superficial
no nuclei
Entirely filled with keratin
What is the function of filaggrin in skin?
Binds and condenses keratin
Protection against entry of foreign environmental substances
What are the characteristics of melanocytes?
Scattered in stratum basale
Round with long processes
No desmosomes
What is the function of melanocytes?
Pigment producing with tyrosinase enzyme
Form melanosomes with melanin
To keratinocytes by pigment donation
What does melanin form in keratinocytes?
Supranuclear cap shading DNA against UV radiation
What causes albinism?
Absence of tyrosinase enzyme
What are the characteristics of Langerhans’ cells?
From monocyte precursors
Mostly in stratum spinosum
No desmosomes
Immune component of skin barrier
Pale in light microscope
Cytoplasmic processes
What are the characteristics of Merkel’s cells?
In stratum basale
Associated with afferent nerve fiber
Sensitive mechanoreceptor
Where would you see more Merkel’s cells in the body?
Fingertips and other sensitive skin
What are the two general layers of the dermis?
Papillary layer
Reticular layer
What are the characteristics of the papillary layer?
Loose CT with type I and III collagen
Type VII collagen into basal lamina binding dermis and epidermis
What are the characteristics of the reticular layer?
Dense irregular CT - mainly type I collagen
Thicker - more fibers
Network of elastic fibers
What is the structure of hair?
Elongated keratinized structures
What are the two general skin glands?
Sebaceous
Sweat
What are the two types of sweat glands?
Eccrine
Apocrine
What type of secretion is done by sebaceous glands?
Holocrine secretion
What is the function of sebum?
Coats hair shaft and skin surface
Makes hair less brittle and skin more supple
Under hormonal control
What causes acne?
Obstructed sebaceous glands
What type of secretion is sweating?
Merocrine
How is sweat discharged?
Myoepithelial cells contract
What is the function of eccrine glands?
Evaporation of sweat lowers body temp
What does sweat contain?
Water, sodium, and chloride
Smaller quantities of other ions, urea, and small metabolites
Where are apocrine glands mostly found?
Axillary and perineal regions
How do apocrine glands compare to eccrine?
Larger lumen
Start after puberty
What creates odor of sweat from apocrine glands?
Odorless secretion metabolized by bacteria
What are two modified apocrine glands?
In external ear canal - produce cerumen
In eyelids - glands of Moll
What are the 6 sensory nerve receptors in skin?
Epidermal free endings
Merkel’s corpuscles
Pacinian corpuscles
Krause’s end bulb
Meissner’s corpuscles
Ruffini’s corpuscles
What sensory nerve fibers are encapsulated in skin?
Pacinian corpuscle
Krause’s end bulb
Meissner’s corpuscle
Ruffini’s corpuscle
What is the function of Merkel’s corpuscles?
Disc receptors for afferent myelinated nerve fiber
What is the location of Pacinian corpuscle?
Deep dermis and hypodermis
What is the function of Krause’s end bulb?
Cold receptor
Where is Meissner’s corpuscle located?
Papilla of dermis
Where is the location of Ruffini’s corpuscle?
Deep dermis
