variation in skin pigmentation is an evolutionary adaption to the intensity of UV radiation. 

Pigmentation

                    Integumentary System

Acne occurs on parts of the skin that exhibit a lot of
sebaceous glands (face/back). Hormones stimulate the release of sebum. Then hair follicles become blocked due to an overproduction and accumulation of sebum and keratin. This plug is initially white = whitehead. The sebum is then oxidized (when exposed to air) and
turns black = blackhead. Acne results from infection by acne-causing bacteria.

Vitamin D synthesis

Accessory Structures

Scars occur when collagen-rich skin is made during wound healing by fibroblasts.
The scar tissue is fibrous and does not regenerate hair follicles, sweat or sebaceous glands.

glands

Innervation

Psoriasis is thought to be an auto-immune condition (T-cells attack the body's own skin cells)
which causes the body to make new skin cells more often. These extra skin cells pile up on the surface of the skin forming scales and itchy, dry patches. Psoriasis may be triggered by infections, stress, and cold. Although it usually affects the skin, sometimes it can affect nails or joints.

hair

Epidermis

Marcia
​and Millie Biggs

Dermis

Pathology

nails 

The papillary layer of the dermis contains loose, areolar connective tissue, while the reticular layer is made up of a dense meshwork of fibers. Elastin fibers give the skin elasticity for movement, and collagen fibers offer  structure and tensile strength.

      Burns are classified by extent of the injury                      and the surface area affected  

​1. first-degree burns are superficial, affects only the epidermis and usually heal in a few day; think sunburn.

2. second-degree burns affects both the epidermis and a portion of the dermis and cause blistering of the skin.

3. third-degree burns extend deep into the epidermis and dermis, destroying the tissue and nerve endings.

​4. fourth-degree burns are most damaging, affecting the both the dermis, epidermis as well as underlying muscle and bone. 

Folate is a B vitamin that your body requires for blood cell production, cellular respiration and nucleic acid synthesis. 

Epidermal Growth Factor binds to epidermal growth factor receptor (EGFR) on the cell surface that ultimately leads to DNA synthesis and mitosis.
  Here's how as an FYI...
EGF binding activates the intrinsic protein-tyrosine kinase activity of the receptor. The tyrosine kinase activity, in turn, initiates a signal transduction cascade that results in a variety of biochemical changes within the cell including a rise in intracellular calcium levels, increased glycolysis and protein synthesis, and increases in the expression of certain genes including the gene for EGFR. 

                                               Cancer
1. basal cell carcinoma affects the stem cells in the stratum basale often on the head, neck, arms, and back which are exposed to the sun. Basal cell carcinomas spread along the stratum basale and then start to grow toward the surface and become an uneven patch, bump, growth, or scar on the skin surface. 

​
​​2. squamous cell carcinoma affects the keratinocytes of the stratum spinosum. This cancer, seen as 
lesions often on the scalp, ears, and hands, is the second most common skin cancer with 2 of 10 skin cancers are squamous cell carcinomas. Because it is more aggressive than basal cell carcinoma, it must be surgically removed in order to prevent the cancer from metastasizing.


3. melanoma is characterized by an uncontrolled growth of melanocytes. Aa melanoma often develops from a mole. It can be hard to detect before it has metastasized. Melanomas usually appear as asymmetrical brown and black patches with uneven borders and a raised surface. Treatment usually requires surgical removal and chemo. 

 Rosacea is a chronic inflammatory skin condition.
Often mistaken for acne or eczema, rosacea usually affects the face. Symptoms include flushing, irritated skin, broken blood vessels, lesions and eye problems.

Eczema is an allergic reaction that manifests as dry, itchy patches of skin that resemble rashes often with 
swelling of the skin, flaking, and sometimes bleeding. 

Wound Healing