The integument Flashcards
What is the function of the integument?
Protection, sensation/excretion, thermoregulation, synthesis of vitamin D
What are the 5 layers of the epidermis?
Stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale
What composes the epidermis of the skin?
keratinocytes, melanocytes, Merkel Cells, Langerhans cells
What is the difference between thick and thin epidermis?
Thick is found on the palms and soles and will have the lucidum layer while thin skin only has 4 layers
Describe the stratum basale and what layer is it?
Most deep layer of the skin- single layer of keratinocytes, mitotically active, cubodial/columar cells, contains melanin, bound apically by desmosomes and basally by hemidesmosomes
Describe the stratum spinosum and what layer is it?
The layer above the basale and next most deep- several layers thick, contains polyhedral keratinocytes with spiny processes, layer thickens with pressure
Describe the stratum granulosum and what layer is it?
The layer above the spinosum and the next most deep- Thickest non-keratinized layer- keratinocytes contain keratohyalin granules- irregularly shaped and variable in size
Describe the stratum corneum and what layer is it?
The most superficial layer- anucleated cells that have no organelles, filled with keratin, plasma membrane coated with EC layer of lipids to form a water barrier
Describe the stratum lucidum and what layer is it?
Only present in thick skin and will be found deep to the corneum- typically will be poorly stained- also has no organelles or nucleus
What are keratinocytes?
Produce keratin- participate in the water barrier
What do the basal cells do in kertinization?
They synthesis intermediate filaments for keratin, group them into bundles
What are tonofibrils?
bundles of intermediate keratin filaments produced by the basal layer of the epidermis
What do the spinous cells do in the keratinization process?
keratin synthesis continues, keratohyalin granules and glycolipid containing lamellar bodies begin to form
What do the granular cells do in the keratinization process?
they discharge the lamellar bodies to create water barrier, keratohyalin granules with filaggrin present- filaggrin will promote further tonofibrils
What promote the loss of organelles and the aggregation of keratin in the cell?
The change in pH of the cell to a more acidic pH
What are melanocytes?
They are neural crest derived cells that are scattered through out the stratum basale- they produce melanin and transfer it to the keratinocytes to protect from Uv radiation- there is one melanocyte for about 36 keratinocytes
What is the mechanism of production of melanin?
Oxidation of tyrosine into DOPA by tyrosinase. DOPA is then polymerized into melanin
Tyrosinase is an enzyme that does what and works in reaction to what?
It aids in the production of melanin by oxidizing tyrosine to DOPA- it is stimulated by UV radiation
What is the process through which keratinocytes get their melanin?
The reaction occurs in premelanosomes then as more is made they travel to the cell process and become melanosomes- they are then transferred to keratinocytes via phagocytosis
What are Langerhans cells?
The are antigen presenting cells that provide defense against pathogens- Antigen is phagocytized then presented on the outside of the cell which will then migrate to nearby lymph node-
where are the Langerhan cells located and what do they look like under staining?
They are in the stratum spinosum and have pale cytoplasm with long processes
What are Merkel Cells?
They have cutaneous sensation, they are associated with a nerve ending
Where are Merkel Cells found?
In the stratum basale
What is the Dermal-epidermal junction?
The boundary is uneven to ensure that there is no shearing of the skin, fingerlike dermal papillae project into the dermis that are complemented by epidermal ridges. hemidesmosomes provide tight interface and there are focal adhesions
