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
Glaucoma is a progressive eye condition that damages the optic nerve and can lead to vision loss, including reduced peripheral and central vision. A key characteristic of glaucoma is elevated intraocular pressure (IOP), which typically exceeds the normal range of 12–22 mmHg. This elevated pressure is a major risk factor, though glaucoma can also occur with normal IOP levels. Factors such as genetics, age, and certain medications can increase the risk of developing glaucoma. “The only sure way to diagnose glaucoma is with a complete eye exam. A glaucoma screening that only checks eye pressure is not enough to find glaucoma”(AAO). Left untreated, glaucoma can cause irreversible blindness, making early detection and treatment crucial. There are two main types of glaucoma: open-angle and angle-closure (or closed-angle). Open-angle glaucoma is the most common form and often develops gradually without symptoms, making regular eye exams vital for early diagnosis. In contrast, angle-closure glaucoma is a medical emergency caused by a sudden and severe increase in IOP. It presents with symptoms such as eye pain, headaches, and blurred vision, requiring immediate surgical intervention to prevent permanent vision loss. Regardless of the type, the primary goal of treatment is to lower IOP to preserve vision and prevent further optic nerve damage. Drug treatments for glaucoma work by either decreasing the production of aqueous humor, the fluid in the eye, or enhancing its outflow. Prostaglandin analogs are among the most effective and commonly prescribed drugs, reducing IOP by up to 30%. These medications, such as bimatoprost (Lumigan) and latanoprost (Xalatan), are safe, require only once-daily dosing, and are well-tolerated. However, they can cause side effects, including darkening of the iris, eyelash thickening, and changes to eyelid skin. Beta-blockers like timolol are another option, reducing IOP by about 22%. A beta-blocker is preferable if the pressure is high in only one eye only because the darkening of the iris and eyelash thickening seen with PG analogs is not desirable in only one eye” (UWorld RxPrep). Other drugs, including alpha-2 agonists and carbonic anhydrase inhibitors, can also help by reducing aqueous humor production, while combination therapies are available for patients who need more aggressive IOP control. Successful glaucoma treatment requires not only effective medications, but also proper patient adherence and eye drop application techniques. Patients should be educated on how to administer eye drops correctly to ensure maximum efficacy and to minimize potential side effects. Adherence to treatment is often challenging, especially for those with open-angle glaucoma, as the condition progresses silently without noticeable symptoms. Regular follow-ups, combined with patient education, are essential to maintaining long-term treatment success and preventing vision loss. Patients with glaucoma or at risk for the condition should also avoid certain medications that can increase IOP. These include anticholinergics (such as antihistamines and tricyclic antidepressants), decongestants like pseudoephedrine, steroid-containing eye drops, and specific systemic drugs like topiramate. Consulting a healthcare provider before using these medications is essential to prevent worsening of the condition. Glaucoma is a complex and potentially blinding disease, but early diagnosis and appropriate management can preserve vision and improve quality of life. By lowering IOP through medications or surgery and ensuring patient adherence to treatment regimens, the progression of this disease can often be slowed or halted. Ongoing education and regular monitoring are key components of effective glaucoma management.
https://www.aao.org/eye-health/diseases/what-is-glaucoma
UWorld RxPrep NAPLEX Review 2025 Chapter 38 Common Conditions of the Eyes and Ears Page 511