Advanced nurse practitioner concepts and questions

¶ … tissue types that compose the epidermis. Name the tissue types that compose the dermis. List the major layers of the epidermis and dermis and briefly describe the individual functions of each layer.

The epidermis of skin is composed of 4 cell types, which may be stratified or squamous: keratinocytes, melanocytes, Merkel's cells, and Langerhan's cells. The dermis is the layer of skin beneath the epidermis, which consists of three major constituents: collagen, elastic fibers, and reticular fibers. The epidermis layer can have up to five strata while the dermal layer has two. Together, from the outermost to innermost, these strata are: stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale in the epidermis, and the papillary and reticular layer in the dermis.

The functions of these layers are as follows:

Stratum corneum -- composed of dead cells and keratin, prevents desiccation of deeper cells

Stratum lucidum -- composed of dead, flattened keratinocytes and also melanocytes, contains high levels of melanin and helps protect against UV damage

Stratum granulosum -- layer where keratinocytes initiate keratinization and begin producing keratin

Stratum spinosum -- keratinization may also initiate at this stratum, contains spiny cells which interlock, providing additional structure to skin

Stratum basale -- continuously dividing layer of keratinocytes, basement of epidermal layer, typically one cell thick

2. In general, the integument serves a protective function to the body. Briefly describe

Integument provides functions against desiccation, prevents access from pathogenic microorganisms, mitigates UV damage, protects internal structures, and assists in temperature regulation.

3. Name the three pigments that contribute to skin color. Give a brief example of how a specific change in skin color could be used as a clinical sign for certain pathologies.

Skin color is produced by three elements: melanin (pheomelanin or eumelanin), hemoglobin, and oxyhemoglobin. Hypoxia is an example of a condition where skin color is altered by a decrease in oxygenated hemoglobin. Lack of oxygen results in dark red hemoglobin (deoxyhemoglobin), which when seen through the skin appears blue. Thus, people who are experiencing pathological hypoxia may manifest blue skin.

4. In clinical practice, drugs can be delivered by diffusion across the skin, a method termed transdermal administration. Why are fat-soluble drugs more suitable for this type of delivery than drugs that are soluble in water?

Fat-soluble drugs are more suitable for skin diffusion than soluble drugs because they tend to be hydrophobic compounds, which facilitates their diffusion across the lipid membrane of skin cells. Water-soluble drugs are often hydrophilic and thus cannot easily diffuse through a hydrophobic milieu like the plasma membrane.

5. Which cutaneous glands are associated with hair follicles and what is their function?

The sebaceous glands are associated with hair follicles and function to secrete sebum (oil-like composition) into the follicular canal. Sebum helps to waterproof hair and skin, and it also serves to prevent cracking due to dehydration.

6. In which layer(s) of the epidermis does cell division occur?

Cell division occurs primarily in the stratum basale.

7. What is the function of the arrector pili muscles?

Arrector pili are bands of muscle which function to contract, causing hair to stand up on the skin, i.e. goose bumps. Relaxation of the arrector pili conversely reverses the process.

8. A common misconception is that cutting your hair will make it thicker. Explain why this is not true.

Growth of hair is driven by stem cells located within the hair follicle itself, thus cutting the hair outside, which is not alive, should have no effect on the nature of the hair growing within the follicle. It is possible people believe the hair is thicker after cutting because it is shorter and therefore more rigid and rough feeling.