| Skin and Eye Infections |
Skin and Eye
Infections
- There are three major regions of the
skin, epidermis, dermis and hypodermis.
Each of the three regions have a distinctive
structure and function.
- Infective agents favor specific regions
of the skin and exploit those regions.
- Learn to regard the great diversity of
visual symptoms associated with different
pathogens.
- Epidermis has 5 layers of cells, each
layer forming a �stratum�. The layers of
the epidermis include: Stratum Corneum,
Stratum Lucidum, Stratum Granulosum and
Stratum Spinosum.
- Dermis has two distinct layers:
- Papillary layer with bumps called
papillae
- Reticular layer under the papillae layer
- Blood vessels in the dermis do not enter
the epidermis. Nutrients and wastes of the
epidermis move by diffusion between the
layers. The papillae increase the contact
surface area between the epidermis and
dermis this enhances adhesion between the
layers as well as diffusion of nutrients and
wastes.
- Hypodermis Structure: Lies under the
dermis, is not part of the skin, connects
the skin to underlying tissues and stores
energy.
- Sweat and sebaceous glands are the two
primary glands of the skin. Both glands
create their secretions within the dermis
then dump them onto the surface of the
skin. The skins surface is typically
covered with salt that is left aft sweat
evaporates and sebum. Sebum is an oily
lipid secreted by sebaceous glands in the
dermis. Chemicals in sweat and sebum are
antimicrobial
- Although the sweat is formed in the
deepest coiled portion of the sweat gland,
the tube that lead to the surface of the
skin actively refines the concentrations of
ions and that will ultimately reach the
surface. In the case of cystic fibrosis,
the function of ion channels has been
altered and therefore also the concentration
of ions that appear in the sweat.
- There are four nerve sensors in the
skin. Of which only one is located in the
epidermis and is called the merkel cell.
- Bacterial Infections Described: Acne,
Rocky Mountain Spotted Fever, Impetigo,
Necrotizing Fasciitis (Flesh Eating
Bacteria), Cat Scratch Fever, Cutaneous
Anthrax, and Pseudomonas.
- Viral Infections of the Skin:
Poxviruses, Herpes, Warts, Rubella, Rubeola,
Chicken Pox, Shingles and Varicella-zoster.
- Fungal infections of the skin are
categorized by the regions of the body they
infect. The categories of Mycoses:
Superficial, Cutaneous, Subcutaneious and
Systemic (affecting internal organ systems).
- The Protozoa infection, Leishmaniasis is
profiled as an example of this type of
infection.
- Basic Eye Structure:
- The cornea is the first structure
crossed as light enters the eye; it offers
the greatest degree of bending of the light.
Next the light passes through the iris which
through the motions of two muscles, a
sphincter and a dilator, controls the amount
of light that enters the eye. Next the light
passes through the lens of the eye which
controls the fine focusing of the eye.
Interesting, when the focusing muscles of
the lens relax, the eye focuses on close
objects. The light exits the lens, transits
the clear jelly-like vitreous humor to
strike the optically active retina where the
energy of the photons will be converted into
neural signals. The neural signals are
conducted to the brain via the optic nerve
(CN II). The sclera is very tough fibrous
exterior structure which is the site of
attachment for all of the muscles that move
the eye. One can imagine that the sclera is
pretty special, because it must not change
shape when the muscle attached to it move
the eye.
- Aqueous humor is produced in the
posterior compartment and drained away by
the canal of Schlemm in the anterior
compartment. Blockage of this canal cause
blindness. Excessive pressure from the
aqueous humor damages the tissues. This is
called glaucoma. It is a very serious
condition !!!
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