Detailed examination of the Herpes Simplex Virus (HSV) types 1 and 2, focusing on the pathogenesis, reactivation, and clinical presentations (cold sores, genital herpes).
Overview of Varicella-Zoster Virus (VZV), discussing chickenpox and shingles, as well as complications like post-herpetic neu...
Routes of virus entry:
- Skin is the major route
- Viruses can get into our system through scratches, insect bites and
wounds etc.
- Viruses can get in through other routes such as via eyes by entering the
conjunctiva, respiratory route by breathing the virus in, or by the oral
route via entering the mouth.
- Viruses that enter the respiratory tract can often causes disease in the
skin.
The skin as an organ:
• Largest organ of the body - area of - 2m2
• Constantly sheds dead cells
• Protects us from microbes including viruses
Three major layers of the skin
1. Subcutaneous layer (bottom layer) - fatty tissue
2. Dermis (dermal layer) - contains blood vessels, glands (e.g. sweat
gland, oil gland), hair follicles etc.
3. Epidermis (top layer) - exposed to the environment
The epidermis:
Keratinised stratified squamous epithelium
Made up of keratinocytes which produce large amounts of keratin and this
gives skin its structure.
There is basal layer at the bottom, under normal circumstances it is the only
layer that contains cells that goes under cell division. Once the cell have
divided, the cells move up through the layers of the skin, As the cells start to
move up they start to become more and more specialised through
differentiation. When they come to the top layer, they start to get flat and
produce more keratin. The dead keratinocytes are shredded off.
Skin can be grown in lab and they are really good models for studying skin
themselves, cell differentiation and skin viral infections.
At the bottom of the epidermis, new skin cells are forming. When the cells
are ready, they start moving toward the top of your epidermis. This trip takes
about 2 weeks to 4 months. As newer cells continue to move up, older cells
near the top die and rise to the surface of your skin.
How do viruses get into the skin?
Viruses can get from outside of the skin and into the skin, this is known as
primary infection. They can also get into the skin from bloody vessels and
this is known as secondary infection.
• Viruses do not infect intact skin - the keratinised layer prevents access
• Outer layer is dead, so any virus that lands on skin cannot replicate
• Virus enter skin through cuts and micro abrasions (which may not be
visible)
Infection from outside:
A micro skin trauma can reach from top layer all the way down to the basal
layer of the epidermis. Virus can gain access to our skin cells and the internal
system via entering through the cut and infecting internal system.
Viruses of the skin Page 1
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