Tuesday test Skin3 Flashcards
Major functions of skin (7)?
Mechanical protection
Moisture barrier
Host defense
Thermoregulation
Excretion of salt
Synthesis of vitamin D & regulation of calcium absorption
Sensory organ
How big is skin as an organ?
15-20% of body weight
- 1.5 to 2 square meters of surface area
How thick is skin?
Thickness varies from 1 mm (eyelid) to 5 mm (upper back)
Cornified barrier is composed of __
What important things does it make?
Keratinocytes
Vitamin D production
Cells that protect agains ultraviolet radiation?
Melanin, melanocytes
Cells/structures that help with thermoregulation ?
Sweat glands, blood vessels
Sensory cells and structures?
Sensory dendrites, mechanoreceptors, thermoreceptors,
nociceptors
Leathery barrier is composed of __ and __
Fibroblasts and thick collagen fibers
primary barrier against pathogen access to deeper tissues?
Skin
Mucous membranes role in pathogenesis?
produce mucus (watery mix of the protein mucin and salts) → trap pathogens and can be expelled from the body
The first line of defense in innate immunity are ______, which block pathogen entry into the tissues of the body.
barrier defenses
Two main parts of the skin?
Epidermis (keratinocytes and non-keratinocytes) and dermis (Papillary layer, reticular layer).
CT is between them
Hypodermis isnt technically part of the skin
2 layers of dermis? major difference
Papillary (loose CT) and reticular (dense CT)
Two parts of Hypodermis?
Subcutis
Superficial fascia
I dont know if this is correct!
Name the 5 strata of epidermis
from deepest to superficial
Stratum basale
Stratum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum
Stratum basale - special things?
single cell layer between epidermis and dermis
• Germinative layer = high rate of mitosis - only one doing mitosis
• Keratin filaments form fibrils
What holds Stratum basale together?
Desmosomes
What does stratum spinosum produce?
membrane-coated granules
keratin fibrils
how is stratum spinosum hold together?
What does it contain?
desmosomes
Keratohyalin granules, Keratin fibrils, Membrane-coated granules
Where are keratohyalin granules formed and what is their role?
Stratum granulosum. Hold keratin fibers together → cell stretches like a pancake
Composition of Keratohyalin granules? 3
filaggrin, loricrin, involucrin
what is the layer of the cells we only see in thick skin layer?
Stratum lucidum
describe stratum lucidum
Extensive crosslinking of keratin fibrils, changes cell shape to squamous
What does stratum lucidum do?
Glycolipids (from m-c granules) secreted into extracellular space seal the squamous layers.
Cells of the stratum corneum form ___
Cornified envelope
Difference of thick vs thin skin?
- Named for different thicknesses of epidermis, not for thickness of entire skin.
Thin skin: almost all has hair; 14 days to turnover/replace.
Thick skin: only on palms and soles; hairless; 48 days to turnover.
What are the non-keratinocytes cells? What do they originate from?
Melanocytes - originate from Neural crest cells and Merkel cells - originate from ectodermal basal cells
Main functions of Melanocytes? How do they originate?
Contain pigment melanin -(Oxidation of tyrosine -> DOPA -> melanin), packaged into melanosomes. They are dendritic cells -> cytoplasmic extensions with over 30 keranocytes. bMelanin granules form a shield protecting stratum basale and nuclei from UV rad Originate from Neural crest cells -> migrate to epithelium and located between dermis and epidermis
How do we visualise melanocytes?
Antibody to a protein, active early in melanin synthesis is used. In the basal layer of epithelium
What are Langerhans cells? Where are they located? How does it do its job? How are they attached?
- antigen presenting dendritic cell (derived from a bone marrow macrophages like all monocytes) Located in Stratum spinosum It’s motile and moves within the keratinocytes and bw epithelium and lymph vessels. Migrates regionally to lymph nodes and presents antigens to T cells. Langerhans cells aren’t attached with desmosomes to keratinocytes, but associated with E-cadherins
Merkel cells job?
Slowly adapting mechanoreceptor (pressure) touch in thin skin. Sence of touch
What do Merkel cells contain? How are they attached?
It’s ectodermal, desmosomal attachments to basal layers of epithelial cells Keratin tonofilaments Small granules presumably containing neurotransmitters
What are the sensory innervations of epidermis?
Merkel cells - Tactile -touch to the skin. Unmyelinated nerve ending expands into plate like sensory ending Free nerve endings (Epidermis - Pain, temperature)
What does the dermis contain?
Capillary network, AV shunts, Sensory nerve endings
How do we prevent loosing heat during a cold day?
Blood supply to superficial capillaries is regulated through Shunts (pericapillary sphincter)
What’s the sensory innervation of dermis?
1) Ruffini’s corpuscle (stretching)
2) Meisner’s corpuscle - fine sense of touch (papillary layer, Detects changes in “texture” • Vibrations around 50Hz • Fingertips, lips have increased innervation density (fine touch in thick skin)
Sensory Innervation of Reticular layer? What does it sense?
Pacinian corpuscles
Rapidly adapting – Type II mechanoreceptor – Deep pressure & vibration
At the base of the follicle, the ______ is surrounded by the hair bulb, whose keratinocytes proliferate, take up melanin granules and gain more keratin
dermal papilla (DP)
What does Eccrine Sweat Gland secrete? How?
Reabsorbs sodium and chloride ions from the sweat, plus some of the water.
its continuous production
Eccrine Sweat Gland - what types of cells?
Stratified cuboidal epithelium (two cell layers)
Excretory duct
Excretory duct locations?
Big glands that lead to body odor; restricted to the arm pits, genital and anal regions
What do apocrine sweat glands secrete?
Protein-rich secretion (odorless when secreted but bacteria like it, leading to body odor)
Apocrine sweat gland - how does it secrete sweat?
Duct empties into canal of hair follicle, dont produce continuously
Apocrine sweat gland structural difference?
Coiled tubular gland: lumen is larger than in eccrine sweat glands
Sebaceous glands product? How is it secreted?
Oil (sebum) glands of the skin
Secrete into canal of hair shaft -Holocrine secretion: dying sebaceous gland cells…lots of lipids
How do Sebaceous glands look like?
Branched acinar glands
The acini have no lumens.
Describe wound healing process
Blood vessels clot → leukocytes clean the wound → blood vessels regrow and granulatio tissue forms→ stratum basale is restored → producing more keratinocytes
