Foundations in Dermatology

epidermis

protection from physical and chemical trauma
1/10th of skin thickness
synthesis of vitamin D
antigen uptake

dermis

papillary layer
reticular layer

sensation, epidermis of skin has no nerves or blood vessels, the dermis provides support for nerve ending and capillaries. The epidermis of the skin is supplied with nutrients from capillaries in the papillary layer of the dermis.

cellular

mostly acellular

melanocytes (MC), keratinocytes (KC), and langerhans cells (LC)

they are mostly clear, with smaller nucleuses than keratinocytes

they specialize in the creation of melanin, or skin pigment.

its production is stimulated by endocrine and paracrine signals at the melanocortin receptor.
It is produced by melanocytes, and packaged into melanosomes. These melanosomes are delivered to keratinocytes (KC), and partially digested by them. This causes melanin to cover the KC nucleus, which will scatter and absorb UV light. This protects the keratinocytes somewhat from the mutagenic effects of UV light.

Asymmetry, Border, Color, Diameter, Elevation

brown-black

reddish-yellow

Both types of melanin have their production stimulated by melanocyte stimulating hormone (MSH, or melanocortin)

Autoimmune disorder where melanocytes (MC) are targeted and destroyed, loss of pigmentation in that area.

They function as part of the immune system
they phagocytize and process low MW antigens, and then migrate out of the epidermis to the closest lymph node. At the lymph node they present the antigen to other immune cells and cause an immune response, such as to poison ivy.

basal layer, or stratum germinativa
spinous layer, or stratum spinosum
granular layer, or stratum granulosum
cornified layer, or stratum corneum

mitosis, cells in this lowermost layer of the epidermis replicatr and then migrate out in order to replace damaged or dead cells.

cells are no longer replicating, and form many desmosomes, attachment to other cells. This causes much of the structural strength of the skin.

in the granular layer, the keratin within the cells aggregates and forms granules. The nuclei of the cells break down, and lipids are extruded, forming one solid layer of keratin and other proteins.

Cells no longer metabolize, flatten into discs (squames), and are eventually lost. The entire process from basal lamina (stratum germinativum) to cornified layer (stratum corneum), takes 3-4 weeks.

Sebacious glands break down the entire sebocyte, which releases the sebum to the lumen of the hair follicle. Replicating cells at the perimeter replace the cells that are broken down.

plaque psoriasis- hyperproliferation of keratinocytes, which don't complete maturation, keep their nucleus, and cause inflamed rashes with poor barrier function.

actinic keratosis (AK)- scaly, red, inflamed skin caused by cronic sun exposure, mostly seen on face, ears, and forearms

keratoacanthoma (KA)- found in same area as AK, but one nodule of growth instead of affecting entire area.

hemostasis, platelett aggregation and blood clotting
inflammation
proliferation
remodeling

Found all across the skin, is innervated by cholinergic nerves, and stimulated by an increase in body temperature

Found in hair follicles, innervated by adrenergic nerves, and stimulated by emotion or pain

nail plate

matrix

lunala