lecture 9

Chapter 1: Introduction

Keratin and Lipids

• Provide essential protection to the skin, acting as a barrier against pathogens and environmental hazards.

• Aid in waterproofing the skin, significantly reducing water loss to maintain hydration levels in the body.

• Keratin, being a fibrous protein, also contributes to the structural integrity and strength of hair and nails.

Skin Thickness

• Skin thickness varies across different body parts, contributing to mechanical protection against external damage such as cuts, abrasions, and impacts. Thicker skin is found on areas like the palms of hands and soles of feet, which face more friction and wear.

• The epidermis, the top layer of skin, houses cells that continually regenerate, helping to maintain skin integrity.

Dermis

• Composed of two distinct layers: the papillary layer (upper layer containing blood vessels and nerve endings) and the reticular layer (thicker and denser layer).

• Reticular Layer: Comprises the bottom 80% of the dermis, rich in collagen fibers which provide strength and elasticity. It houses critical structures, including hair follicles, sweat glands, and nerve endings.

• The dermis also plays a vital role in thermoregulation through its blood vessels.

Keratin Protein

• The main structural component in hair and skin, keratin plays a vital role in the integrity and resilience of these tissues.

• Proteins, including keratin, have versatile structures that are utilized in a variety of body functions, ranging from structural support to facilitating biochemical reactions.

• Keratinocytes, the primary cells in the epidermis, are responsible for producing keratin, and they undergo a process known as keratinization as they move towards the skin surface.

Chapter 2: A Little Surface

Nail Structure

• Nails possess a body that is arranged to include a closed-off area underneath called the nail bed, which is richly supplied with blood vessels. This vascularization is crucial for nail growth and health.

• Nails also protect the tips of the fingers and toes from injury and enhance the ability to pick up small objects.

Hair Structure

• Hair Shaft: This is the visible part of hair above the skin, composed primarily of keratin. The health and appearance of hair are influenced by factors such as genetics, nutrition, and environmental conditions.

• Hair growth occurs in cycles that include a growth phase (anagen), a transitional phase (catagen), and a resting phase (telogen).

Chapter 3: Number Of Melanocytes

Hair Root vs. Hair Shaft

• Hair roots lie beneath the epidermis, embedded in the hair follicle, while hair shafts are the visible sections emerging from the skin's surface.

• The hair follicle contains cells that produce melanin, influencing the color of the hair.

Melanocytes

• The number of melanocytes is roughly consistent across all individuals, but variations in skin tone are attributed to the activity levels of these cells.

• Higher melanin production corresponds to darker skin tones, providing greater protection against UV radiation.

• Melanocytes can be affected by hormonal changes, aging, and UV exposure, which may alter their functioning.

Chapter 4: Think Of Melanin

Melanin and Its Uses

• Melanin is primarily recognized for its role in determining skin color. It increases in production in response to UV exposure, leading to tanning during summer months.

• There are different types of melanin (eumelanin and pheomelanin), which influence variations in skin and hair color among individuals.

Purpose of Melanin

• Beyond pigmentation, melanin serves a protective function against harmful UV radiation by absorbing and dissipating UV rays, thereby diminishing the risk of skin cancer.

• Areas of the skin that receive more sun exposure generally exhibit higher levels of melanin as a natural adaptive response.

Chapter 5: Tons And Tons

Protective Function of Melanin

• Melanin acts as a shield for cellular structures, specifically protecting the DNA in skin cells from UV damage.

• Historical data has shown that individuals living in sunny regions have statistically developed increased melanin levels over generations to mitigate UV exposure risks.

Exposure and Skin Color

• Populations residing in hotter climates usually possess darker skin tones as an evolutionary response to cope with sustained sun exposure, which helps in regulating body temperature and minimizing sun damage.

• Lighter skin provides an advantage in lower UV radiation areas by allowing better synthesis of vitamin D.

Importance of Monitoring Moles

• Understanding the biological role of melanin is central to evaluating skin health, particularly in relation to the development of moles and their potential risks.

• Regular self-examination of skin for new moles or changes in existing moles is recommended for early detection of skin conditions.

Chapter 6: A Dangerous Environment

Skin Surface Area and Burns

• Accurate estimation of total body surface area affected by burns is crucial for treatment; for example, approximately 9% of skin surface area is found on the front of each leg.

• The Rule of Nines is a tool used in assessing burn extent, helping guide treatment decisions and fluid resuscitation efforts.

Survival Mechanisms

• During life-threatening situations, the body may alter its pain response mechanisms to allow individuals to escape from danger or fight back more effectively, showcasing the intricacy of the human survival instincts.

• Stress hormones like adrenaline are released, which can temporarily decrease the sensation of pain and increase physical performance.

Chapter 7: Level Of Metastasis

Understanding Metastasis

• Metastasis refers to the process by which cancerous cells spread from their original site to other parts of the body, complicating treatment options.

• Early detection and management are crucial factors in improving prognosis and survival rates for metastatic cancer patients.

Cancer Indicators

• Early signs of squamous cell carcinoma may present as red, dry patches resembling chronic rashes, often originating from the spinosum layer of the skin. Regular skin evaluations for unusual changes are recommended.

• Other indicators may include changes in the texture, color, or shape of existing moles.

Chapter 8: Conclusion

Melanocyte Concerns

• Melanocytes can present health concerns, particularly when situated near existing moles, as changes in these cells can indicate potential malignancies.

Monitoring Moles

• It is advised to conduct regular checks on moles larger than 6mm, focusing on the characteristics of diameter, elevation, and evolution of size and shape. Early detection is paramount for effective treatment.

• The ABCDE method (Asymmetry, Border, Color, Diameter, Evolving) is a helpful guide for identifying suspicious moles.

Body Percentage of Burn Surface Area

• Accurate estimation of total body surface area (TBSA) affected by burns is crucial for effective treatment and management, particularly in determining fluid resuscitation needs and potential complications.

Rule of Nines

• The Rule of Nines is a widely used method for estimating the percentage of body surface area burned, dividing the body into sections that represent approximately 9% or multiples thereof of the TBSA:

  • Head and neck: 9%

  • Each arm: 9%

  • Each leg: 18% (9% front, 9% back)

  • Anterior trunk (chest and abdomen): 18%

  • Posterior trunk (back): 18%

  • Perineum (genital area): 1%

Lund and Browder Chart

• The Lund and Browder chart is a more precise tool that adjusts for age-related body proportions and provides a more accurate assessment, especially for children whose body surface area ratios differ from adults.

Implications of Burn Surface Area

• The percentage of burn surface area is directly linked to treatment protocols:

  • Burns involving more than 20-25% TBSA in adults or 10% in children warrant fluid resuscitation to prevent shock.

  • Assessment of TBSA also helps guide decisions about transfer to specialized burn centers.

Secondary Effects of Burns

• Besides immediate treatment implications, the extent of burn surface area affects caloric needs, the risk of infection, potential for hypothermia, and long-term healing processes.

Skin Layers

1. Epidermis

• The epidermis is the outermost layer of skin, providing a protective barrier against environmental hazards such as pathogens and chemicals.

• Composed primarily of keratinocytes, which are responsible for producing keratin, a fibrous protein that aids in waterproofing and protecting the skin.

• Contains several distinct sub-layers:

  • Stratum Corneum: The outermost layer consisting of dead keratinized cells that are continuously shed and replaced. This layer plays a critical role in preventing water loss and protecting against external insults.

  • Stratum Basale: The deepest layer where new keratinocytes are formed. This layer also contains melanocytes (cells that produce melanin, contributing to skin color) and Merkel cells (involved in touch sensation).

2. Dermis

• Located beneath the epidermis, the dermis is much thicker and comprised primarily of connective tissue, providing structural support and elasticity to the skin.

• Divided into two primary layers:

  • Papillary Layer: The upper layer of the dermis is composed of loose areolar connective tissue, containing fine collagen and elastin fibers. It houses blood vessels, lymphatics, and sensory nerve endings, and it forms projections called dermal papillae, which create fingerprints.

  • Reticular Layer: The thicker, deeper layer of the dermis is made up of dense irregular connective tissue that contains a network of collagen and elastin fibers. This layer provides strength, resilience, and houses larger blood vessels, hair follicles, sweat glands, and other structures. The reticular layer is critical for thermoregulation due to its blood vessel distribution.

3. Hypodermis (Subcutaneous Layer)

• While not technically a layer of the skin, the hypodermis lies beneath the dermis and consists of loose connective tissue and adipose (fat) tissue.

• It serves as an energy reservoir, insulation to help regulate body temperature, and a cushion to protect underlying muscles and bones.

• The hypodermis also contains larger blood vessels and nerves that branch into the dermis.

ABCDE Method for Monitoring Moles

The ABCDE method is a widely recognized guideline used for evaluating moles and skin lesions to identify potentially malignant changes. Each letter in the acronym represents a key characteristic to assess:

A - Asymmetry

• A mole is considered asymmetrical if one half differs from the other half in shape. Healthy moles typically have a uniform shape (round or oval).

• Asymmetry can be an early indicator of melanoma, a serious form of skin cancer.

B - Border

• The border of a mole should be smooth and even. Moles with irregular, notched, or scalloped edges are often suspicious.

• Uneven borders may indicate growth that is not typical of benign moles, which appear well-defined.

C - Color

• A variety of colors within a mole can be a warning sign. Healthy moles typically have a uniform color, such as tan or brown.

• Suspicious moles may display multiple shades of brown, black, red, white, or blue. Such color variation can indicate malignancy.

D - Diameter

• A mole with a diameter larger than 6mm (the size of a pencil eraser) is considered concerning. However, melanoma can occur in smaller moles, so this criterion alone is not definitive.

• Regular monitoring of mole size is essential for early detection of changes.

E - Evolving (sometimes included)

• Evolving refers to any change in a mole over time, including changes in size, shape, color, or elevation.

• New symptoms such as bleeding, crusting, or itching can also indicate that a mole may be problematic.

Importance of the ABCDE Method

• Regular self-examinations using the ABCDE method can aid in early detection of melanoma and other skin cancers.

• If any characteristics of a mole change or if there are concerns based on these criteria, it is crucial to consult a healthcare professional for further evaluation, which may include a biopsy.

• Being proactive with skin checks can significantly impact treatment outcomes and overall skin health.

Stratum Basale:

• The stratum basale is the deepest layer of the epidermis where new keratinocytes (skin cells) are formed through cell division.

• Contains melanocytes, which produce melanin and contribute to skin color.

• Also includes Merkel cells, which are involved in touch sensation, providing the skin with sensory function.

• The stratum basale serves as the foundation for the epidermis, constantly renewing the skin by generating new cells that move upward through the layers of the epidermis.