Structure and function of skin Flashcards
What are the functions of epithelia cells?
- secretion
- absorption
- transport in and out
- protective barrier
- selective barrier
- strength and support
What is the epidermis?
- avascular epithelium layer of skin
- stratified squamous keratinised epithelium
- undergoes proliferation
- synthesises keratin for
What is the function of keratin?
- adheres cells together
- forms a protective layer
How do keratins attach in epithelial cells?
keratin proteins inside epithelial cells attach to proteins called desmosomes on the surface
What is the structure of the dermis?
- vascular - blood vessels, lymphatics, cutaneous nerves
- tough (leather)
- collagen and elastic fibres not replaced with age
What is the structure of the hypodermis?
- superficial fascia - varies in thickness
- blood vessels, nerves and lymphatics
- fatty tissue - adipose tissue
- skin ligaments, loose skin or taut skin implication in scarring and incisions
Wha is cell proliferation?
process that results in an increase in the number of cells
What are the dangers of burns?
loss of skin barrier function
- fluid loss
- infection
What are the functions of the skin?
> homeostasis - temp regulation, internal homeostasis (water, electrolytes), metabolic (fit D, fat store)
sensory information - sensation (pain, temp), psychosocial signals (visual, chemicals)
protection - melanin (UV), keratin (chemicals, water, mechanical), immune (organisms)
What are the layers of the epidermis?
> S. corneum - waterproof, dead cells, organised keratin layers, cornfield
S. lucidum - specialised cell death program, few nuclei
S. granulosum - keratin aggregation
S. Spinosum - keratin filaments formed, linkage via desmosomes
S. Basale - cell division
What does cornfield mean?
process by which squamous epithelial cells develop into tough protective layers or structures (such as hair, hooves) and the outer layer of skin - final stage of keratinisation
What is the interface of the epidermis with the dermis?
stratum basale
- hemidesmosomes (junctions) anchor basal cells to basal lamina
- dermis anchored to basal lamina by collagen VII (epidermis binds to dermis)
What causes dystrophic epidermolysis bullosa?
a mutation in collagen VII
(interface of basal lamina with dermis - causes blistering
What is filaggrin?
a protein that binds keratin fibres in epithelial cells - maintains optimal skin barrier
- precursor profilaggrin - formed from it during terminal differentiation of epithelial cells
- inhibits water loss
- main component of keratohyaline granules in the S.granulosum
What causes most cases of eczema and other keratinisation disorders?
mutations such as reduced filaggrin expression (eczema)
What are melanocytes?
found in the basal layer of the epidermis
synthesis and release melanin
What is melanin?
brown pigment
synthesised and released by melanocytes
- amount varys between races and individuals
- absorbs UV-B
- prevents DNA damage to underlying cells of hypodermis
What are the functions of melanin?
- amount varys between races and individuals
- absorbs UV-B
- prevents DNA damage to underlying cells of hypodermis - lower incidence of skin cancer in individuals with more melanin
What is melanoma?
tumour of melanocytes (melanin forming cells)
Where are melanocytes derived from?
neural crest cells that originate near the developing nervous system and spread into the embryo - mesodermal
What are Langerhans cells?
antigen producing cells of the skin
- contain Birbeck granules
- present in all layers of epidermis - but mainly stratum spinosum
- activated in skin but migrate tp lymph nodes
- express langerin which helps degrade virus (such as HIV) in specialised endoscopes called Birbeck granules
Where are Langerhans cells found?
in all layers of epidermis - but mainly in the stratum spinosum
How do Langerhans cells work?
express lantern which degrades virus
- in special endoscopes called Birbeck granules
- activated in the epidermis then migrate to the lymph nodes
What are dendritic cells?
antigen presenting immune cells
