The two layers of the skin consist of the epidermis and dermis. The epidermis is the uppermost part of the skin, which we can see all over our bodies. The epidermis and dermis are composed of their own layers, which we will discuss in a bit. Below the dermis is the hypodermis, which consists of adipose tissue. Below the hypodermis is the subcutaneous layer, which is the location site for many of our injectable drugs, such as insulin. Between the layers there are many hair follicles, which make up the pilosebaceous unit, consisting of hair, sebaceous gland, apocrine and eccrine sweat glands, and the arrector pili muscle. The pilosebaceous unit is particularly important in thermoregulation and electrolyte homeostasis - sweat glands function to release NaCl and H2O from the body, producing a cooling effect and maintaining electrolyte balance.
Before we get into the functions of the skin, I will go back and summarize the various layers in the epidermis and dermis. The epidermis is composed of 5 or 6 layers, depending on the type of skin. These layers include (from bottom up): Stratum basale, spinosum, granulosum, lucidem (only on thick skin - soles of feet, palms of hands), and the stratum corneum. These sit on the basement membrane, which connects the dermis to the epidermis. The stratum basale consists of merkel cells and cuboidal cells. The stratum spinosum contains melanocytes, responsible for color of the skin, and langerhans cells, which are antigen-presenting cells involved in the immune response. The stratum corneum, the uppermost layer, is also the thickest layer of the skin.
The dermis is made up of many types of cells: fibroblasts, which make up the extracellular matrix, including collagen, mast cells, sensory nerve fibers, and capillaries. The dermis is the area of the skin containing the nerves and blood supply for the skin. Different sensations which are felt on the skin are pressure, pain, and temperature.
The functions of the skin are as follows: 1)protection/barrier for the underlying tissues, 2)wound healing, 3)vitamin D synthesis, 4)sensation, 5)thermoregulation, and 6)secretion. The skin acts as a barrier for bacteria (by secreting its own antimicrobials), UV light, and injury. The skin is extremely efficient at wound healing, as evidenced by the quick healing of superficial cuts and scrapes. Vitamin D synthesis occurs when the sun causes the conversion of 7-dehydrocholesterol to cholecalciferol and eventually into active vitamin d, which is crucial in the regulation of calcium. The skin also detects sensations, as mentioned above, pain, temperature, and pressure. The skin also secretes sweat, antimicrobials, and sebum. Sweat helps to regulate temperature, antimicrobials help to prevent bacterial infection on the skin, and sebum acts as a lubricant and fat secretor.
Pharmacologically, the skin conditions which are included in NAPLEX prep are: acne, cold sores, dandruff, alopecia, eczema, hyperhidrosis, fungal infections, diaper rash, hemorrhoids, pinworm, lice/scabies, minor wounds, burns, poison ivy/oak/sumac, inflammation/rash, and sunscreens. I will be delving deeper into these subjects individually throughout the duration of this APPE rotation. Please refer to this GoogleDoc Folder for all NAPLEX review of skin:
https://drive.google.com/drive/folders/1fS5RbT9WIJHUFy1TrVuWnd4XeQHT7LOT?usp=sharing
Skin Cancer: Melanoma Review & Patient Information for Prevention
Skin Cancer is a major health problem in the USA, with 1 in 5 Americans estimated to develop skin cancer in their lifetime. Skin cancer when caught early can be treated. The two types of skin cancer are nonmelanoma skin cancers and melanoma. Prevention and screening have a major impact on detecting cancer early and treating it.
Most commonly, melanomas occur from DNA damage, due to UV radiation, which leads to cellular mutations that transform the cell and result in uncontrolled proliferation and the formation of tumors (1). Primary melanoma can occur in any area of the body with melanocytes. Melanoma cells can evade the immune system by exploiting immune checkpoints (1). Melanomas can occur without nonchronic sun damage due to the activation of different pathway mutations.
There are both patient-related risk factors and external risk factors for melanoma. Some patient-related risk factors are age over 15 years, history of cutaneous melanoma, sunburns easily, or tans rarely. Some external risk factors are history of sunburn and recreational sun exposure.
As skin cancer is a major health problem in the USA, the surgeon general in 2014 released a call to action to prevent skin cancer. This call to action for skin cancer prevention included: increase opportunities for sunprotection in outdoor settings; provide individuals with the information they need to make informed, healthy choices about UV radiation exposure; promote policies to advance the national goal of preventing skin cancer; reduce harms from indoor tanning; and strength research, surveillance, monitoring, and evaluation related to skin cancer prevention (1). By avoiding UVA and UVB exposure, one can protect themselves from the most preventable cause of melanoma. Individuals should avoid the sun during peak hours of sun intensity (10am-4pm), seek shade when outdoors, and use protective clothing when out in the sun. In addition to these measures, patients should regularly use sunscreen to decrease UV exposure. Patients should be counseled on how to appropriately use broad spectrum sunscreen with both UVA and UVB protection with an SPF of 15 or higher. Patients should be told that sunscreen should be applied 30 minutes before going into the sun and reapplied every 2 hours after swimming or after sweating heavily (1).
In addition to prevention measures, patients should be informed on how to conduct a self skin examination. Early detection is key to improved survival rates for melanoma. The American Cancer Society and The American Academy of Dermatology both have great guidelines on how to perform a self examination. Generally, a self skin examination should be done after a shower or bath for ease, one should examine their body in a full length mirror with their arms raised. Next, one should look at their underarms, forearms, and palms. After, one should look at their legs, between their toes, and the soles of their feet. After this, one should use a hand mirror to examine their neck and scalp and to check their back and buttocks (2). These steps are a rough generalization of how to conduct a self skin examination, both resources will be linked for further in depth instructions.
The ABCDE’s of Melanoma is another important resource. When inspecting moles or pigmented spots, patients should look for asymmetry, borders, color, diameter, and evolving (3).
In summary, prevention of skin cancer is important and should be taught to all of our patients.
Resources
(1): O’Bryant C.L., & Davis C.M. Melanoma. DiPiro J.T., & Yee G.C., & Haines S.T., & Nolin T.D., & Ellingrod V.L., & Posey L(Eds.), [publicationyear2] DiPiro’s Pharmacotherapy: A Pathophysiologic Approach, 12th Edition. McGraw Hill. https://accesspharmacy-mhmedical-com.jerome.stjohns.edu/content.aspx?bookid=3097§ionid=271456764
(2): https://www.aad.org/public/diseases/skin-cancer/find/check-skin
(3): https://www.aad.org/public/diseases/skin-cancer/find/at-risk/abcdes