Integumentary System Flashcards
What are the types of cells in the skin
- Keratinocytes (epidermal cells)
- Merkel cells (tactile cells)
- Langerhans cells (macrophages that presents antigens)
- Melanocytes (derived from neural crest cells)
Dermis - what does it contain
Papillary dermis that is loosely packed
Then we have reticular dermis that is densely packed and finally we have hypodermis which has subcutaneous fat
Histology of the skin
On the top we have stratum corneum, the keratin layer.
Below we have papillary dermis and then we have the reticular dermis (that creates the waves)
What are the layers of epidermis
Starting from the top
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum (have extensive desmosomes)
- Stratum basale
In the thickness stratum corneum is much thicker
Excessive skin shedding - what is the condition called and what is the biochemical basis of it
Psoriasis
The underlying infiltrating immune cells release cytokines that signals the keratinocytes to proliferate more quickly, reducing the time of the cell cycle.
The blood vessels thicken to provide with the extra nutrients for increased cell activity.
Silver white flaky layer is created which are just a bunch of dead cells on the top of skin
Facts about Psoriasis (there are 4)
Disease of the epidermal-dermal layer:
- Persistant hyperplasia of keratinocytes due to increased proliferation
- Neutrophils migrate to the dermis, forming abscess when they die. (or microabscess).
- Lymphocytes are the ones below the dermis secreting cytokines
- Also there are nuclei displayed in the now thickened stratum corneum
How are the fingerprints formed
The dermal papillae that come out to the surface of the skin gives us our unique fingerprints
What do we need to know about the keratin that is being expressed in the different layers of the dermis by the keratinocytes
The keratin changes as the cells move along from the basale layer to the spinosum and to granulosum to lucidum and then finally to Stratus corneum
What compound is secreted to aggregate keratin
Filaggrin
What layer of cells secrete the keratin aggregate
Granulosum
Where does the fat comes from in the top of the skin
Lamellar bodies
What does the fat do
Envelopes the keratin in structures called cell envelopes
What is the structure of the cell envelope
Lipid is on the outside, cell envelope molecules and then comes the aggregated keratin on the inside surface of the cell envelope
One of the molecules of envelope and how it is cross linked
Loricrin (one of the envelope molecules) is cross linked by transglutaminase K (TGK)
Mutation associated with TGK
there are 2
One of them results in scaled fish like skin called Lamellar ichthyosis (there is a mutation is TGK)
The other one is Dermatitis herpetiformis (antibodies directed to TGK, IgA)
Types of cells in the epidermis
- Melanocytes: derived from neural crest cells, they make melanin and put this melanin in adjacent cells (so not all cells with melanin are melanocytes)
- Merkel cells: these are also derived from neural crest cells, they are tactile mechanoreceptors
- Langerhan cells are the macrophages of the skin. They do antigen recognition and phagocytosis
How is melanin made
Made in melanocytes, they make premelanome which then matures into melanosome and is then released and taken in by keratinocytes.
Biochemical details of the production of melanin
Made from oxidation of tyrosine to dihydroxyphenylalanine. This then becomes melanin
What are the spines in the spinosum layer made of? what do they represent?
Desmosomes
What are the 2 major types of pemphigus
- Pemphigus vulgaris (autoantibodies to desmogleins 3)
- Pemphigus foliaceous (autoantibodies to demoglein 1)
There’s another type called the mucocutaneous which have antobodies to 1 and 3 both.
What is the gradient of DG1 and DG3
DG 1 is high on the surface, reduces towards the basal layer and DG3 is high on the basale layer, reduced towards the surface.
What is a factor in mucous membrane
DG1 is not really a factor in mucous membrane, DG3 is present, in the same gradient form
PF and PV, where do they split
PF on the top, PV on the bottom
What is the structure involving hair
- External root sheath is continuous with the stratum basale.
- Bunch of stem cells that are keratinocyte in the bugle
- Internal Root Sheath surround the hair shaft
- Dermal papillae are a reservoir of stem cells
