Integument Flashcards
Functions of the skin
Protective - keratin synthesis, haris, sebum
Sensory - specialized nerve ending
Thermoregulation - sweat glands, control of blood flow
Metabolic - vit D synthesis, ion balance
Immunilogical - Langerhan’s cells, wandering lymphocytes
Integument Layers
1) Epidermis
- stratified squamous keratinizing epithelium
- keratinocytes
- avascular
2) Dermis
- connective tissue layer
- contains specialized glands, hairs, sensory receptors
3) Hypodermis*
- subcutaneous (=superficial fascia)
- adipocytes
- contains specialized glands, hairs, sensory receptors
Thick Skin vs. Thin Skin
Four layers of the epidermis
1) Stratum Corneum
2) Stratum Granulosum
3) Stratum Spinosum
4) Stratum Basale (Germinativum)
Stem cells are located…
… at the top of dermal papilae, on top of the basal lamina
They migrate down and differentiate; the differentiating cells then push up
Turnover takes 15-30 days
Hemidesmosomes
- epithelial cell-matrix adhesion
- links keratin intermediate filaments to basal lamina
- comprised of:
- transmembrane: integrins, collagen XVII (BP180)
- peripheral proteins: plectin, BP230
- visually similar to half-desmosomes
*Antibodies against Collagen XVII causes blistering, Bullous pemphigoid
Bullous pemphigoid
An autoimmune disorder resulting from production of autoantibodies against collagen XVII (BP180) or BP230, which disrupts hemidesmosomes connecting epithelial cells to connective tissue (lamina lucida of basal lamina)
Stratum basale
Single cell layer on the basal lamina, connected by hemidesmosomes to lamina lucide, has stem cells sitting at the top of dermal papilae
Turnover takes 15-30 days
Also contains melanocytes and merkel cells
Stratum Spinosum
aka “prickle cell layer” (remnants of desmosomes form prickles around cells during staining)
thickest living layer
Contains desmosomes, made of demoglein and desmocollin attached to keratin IFs
Desmosomes
Aka Macula adherens
Made of desmoglein and desmocollin, attached through cell membrane to cytoplasmic plaque and keratin IFs
Diagnostic dark staining of plaque
Desmoglein are the target for auto-antibodies in Pemphigus
and a serine protease relased during Staphylococcus aureus infections causing impetigo
Pemphigus
Auto-immune disease in which auto-antibodies target desmogleins of desmosomes in cell, causing blistering
Impetigo
results from Staphylococcus aureus infection which releases a serine protease which targets demogleins of desmosomes –> causes blistering and is highly contageous
Friction blister
break in the stratum spinosum that fills with edema from plasma of dermal cells
If it is clear, there is no blood, the split is in the epidermis
If it contains blood, the split would be deeper, in the dermis, where there are blood vessels
Stratum granulosum
4-5 cell thick later, containing dark staining karatohylaine granules, has degenerating nucleus (specialized form of apoptosis)
karatohylaine granules contain:
- filaggrin
- loricrin
- trichohyalin
Stratum corneum
top layer of dead cells packed with keratin (the abundance of protein makes this layer quite eosinophilic)
Although they are dead cells, they still have desmosomes
Lipid loss can result in: dehydration and/or infection
Melanocytes
melanin pigment producing cells found in stratum basale
- neural crest derivative
- lie superficial to BL
- constant #’s between races
- synthesize tyrosinase (unique*), which converts tyrosine to DOPA which is converted into melanin
- pigment “donation”
- malinin formation is within melanosomes, creates caps between nuclei and radiation
Melanin
synthesized in pre-melanosomes by tyrosinase (from melanocytes) converting tyrosine to DOPA which becomes melanin
Two types:
- eumelanin
- phaeomelanin (red heads)
- less effective at blocking UV rays
- weaker antioxidant
- thus risk of melanoma/skin cancer is higher
- permits vitamin D synthesis under low light conditions
Langerhan’s Cell
important in immunosurveillance, found in stratum spinosum
- antigen presentation
- no desmosomes, few IF
- derived from bone marrow
Merkel Cells
mechanoreceptors part of the stratum basale
Basal outfoldings
of the plasma membrane
Function to increase surface area for attachment to underlying CT
Hairs
keratinized epithelial structures, epidermal derivatives
Associated structures:
- sebaceous glands
- pilosebaceous unit
- apocrine glands
- arrector pili muscle
Glands of the Skin
- Eccrine (merocrine)
- Apocrine
- Sebaceous
Eccrine sweat glands
Characteristics:
- simple, coiled tubular gland
- thermoregulation
- salt balance
- has myoepithelial cells
- ducts modify the secretion
Cystic fibrosis sweat glands
Apocrine sweat glands
Characteristics:
- simple, coiled tubular gland
- apocrine (or merocrine) secretion
- product is stored
- ducts do not modify the secretion
- restricted distribution
- develop at puberty
- activated by stress, sexual stimulation
Sebaceous glands
Characteristics:
- acinar morphology
- holocrine secretion
- secrete oily substance (sebum)
- usually associated w/hairs
- may exist without hairs
Non-encapsulated sensory nerve endings
Free-nerve endings
- thermoreceptors
- mechanoreceptors
- nociceptors (pain)
- extend to stratum Gr.
Merkel cells
- slow-adapting mechanoreceptors
Encapsulated nerve endings
Meisser’s corpuscle
- rapidly-adapting mechanoreceptors
- high density = discriminatory (Braille)
- dermal papilla
Pacinian corpuscles
- rapidly-adapting mechanoreceptors (vibrations)
- up to 2mm in length
- hypodermis
Study contents of each layer (no question)
Keratinocyte
Major cell type of the epidermis, found in all layers, but largley in stratum spinosum
ID the cell type
Melanocyte
ID the arrow and the asterisk
Arrow is pointing to an eccrine sweat gland
Eccrine sweat glands are surrounding by myoepithelial cells, basket cells
Asterisk is the dermal papillae
Study (no question)
