Functions of Skin
Name two primary protective functions of the vertebrate integumentary system
Protection from pathogens and physical/chemical damage; prevents water loss.
List the three main layers of vertebrate skin from outermost to innermost.
Epidermis, dermis, hypodermis (subcutaneous).
Name the four major cell types in the epidermis.
Keratinocytes, melanocytes, Langerhans cells, Merkel cells.
Define mutation and explain its potential role in altering cell behavior.
Mutation: change in DNA sequence; can activate oncogenes or inactivate tumor suppressors, altering proliferation, apoptosis, or DNA repair and promoting uncontrolled growth.
A runner completes a marathon on a hot day. During the race, her body produces sweat to prevent her temperature from rising too high. Which skin structure is responsible for this response, and what function of the integumentary system is being demonstrated?
Sweat glands; temperature regulation.
Explain how the skin contributes to temperature regulation; include the roles of blood vessels and sweat glands.
Vasodilation increases cutaneous blood flow to release heat; vasoconstriction reduces flow to conserve heat. Sweat glands produce sweat; evaporation of sweat cools the body.
What is the difference between epithelial tissue and connective tissue?
Epithelial tissue acts as a protective covering and lining for body surfaces and organs, whereas connective tissue supports, binds, and protects other body tissues and structures
Which cells make most of the skin’s outer layer?
Keratinocytes
Summarize how errors during the cell cycle can lead to uncontrolled cell growth.
Malfunctioning checkpoints, overactive cyclin/CDK activity, or defective DNA repair allow damaged cells to replicate, producing clonal expansion and tumor formation.
A 42-year-old lifeguard has spent years working in direct sunlight. He rarely wears sunscreen. During a routine exam, doctors discover a cancerous tumor that developed from cells in the deepest layer of the epidermis that normally produce a protective pigment. Identify the cell type involved and explain how its normal function is related to this person's increased cancer risk.
Melanocytes are involved. They produce melanin, which helps protect DNA from UV damage. Repeated UV exposure can cause DNA mutations in melanocytes, potentially leading to melanoma.
Describe how the integumentary system participates in sensory perception and identify two types of sensory receptors found in the skin.
Skin contains receptors that detect stimuli: mechanoreceptors (e.g., Merkel cells, Meissner corpuscles) for touch/pressure and nociceptors for pain (thermoreceptors detect temperature).
Name one role of the hypodermis.
Insulation (keeps the body warm) or energy storage.
Which is the difference between Merkle cells and Langerhaus cells?
Merkel cells are tactile sensors. Langerhaus cells are for the immune response.
Describe how UV radiation can cause skin cancer.
A patient suffers a severe burn that destroys the epidermis and much of the dermis over a large portion of the body. Doctors are most concerned with infection, dehydration, and body temperature changes. Explain why damaging these skin layers affects all three of these problems.
The epidermis normally acts as a protective barrier that prevents pathogen entry and water loss. The dermis contains blood vessels and sweat glands that help regulate body temperature. Damage to both layers disrupts protection, fluid balance, and thermoregulation.
What is keratinization and why is it important?
Keratinization is the process where keratinocytes (skin cells) in the epidermis produce increasing amounts of keratin, flatten out, lose their nuclei, and eventually die as they move upward through the layers of the epidermis. It creates a tough, durable layer of protection.
Stratum Corneum, Stratum Lucidum, Stratum Granulosum, Stratum Spinosum, Stratum Basale
Discuss the functions of keratinocytes beyond keratin production, including their role in barrier formation and signaling.
Keratinocytes form the physical barrier via keratin and lipid secretion, produce cytokines and antimicrobial peptides, participate in innate immune signaling, and aid wound repair.
What are the ABCDs of skin cancer/melanoma?
A chemical factory worker is exposed to a substance that damages keratinocytes throughout the epidermis. Although the cells are not cancerous, many die and can no longer perform their normal function. What problems would this cause for the body, and which function of the integumentary system would be most directly affected?
The protective barrier of the skin would weaken, increasing the risk of injury, infection, and water loss. Protection would be the most directly affected function.
Explain how the skin contributes to fluid balance and why severe burns can be life-threatening.
Intact skin prevents excessive fluid loss (barrier to evaporation). Severe burns disrupt this barrier causing large fluid/electrolyte loss and risk of dehydration, infection, and shock.
Identify the primary tissue types found in the epidermis and dermis.
Epidermis: keratinized stratified squamous epithelium. Dermis: dense irregular connective tissue rich in collagen and elastin, with blood vessels, nerves, and glands.
Describe the function of melanocytes and how they influence skin pigmentation.
Melanocytes synthesize melanin in melanosomes and transfer pigment to keratinocytes; increased melanin production or transfer darkens skin and protects DNA from UV.
Name a gene type that, when mutated, can cause increased cell growth.
An oncogene.
Two siblings spend an afternoon at the beach without sunscreen. Both receive the same amount of UV exposure. One develops a mild sunburn and recovers. The other later develops skin cancer because a mutation disabled an important cell-cycle checkpoint. Using the terms UV radiation, DNA damage, mutation, cell cycle, and cancer, explain why the outcomes were different.
UV radiation damaged DNA in both individuals. In one sibling, the cell cycle checkpoints detected the damage and the DNA was repaired or the damaged cells died. In the other sibling, a mutation disabled a checkpoint, allowing damaged cells to continue dividing. This led to uncontrolled growth and eventually cancer.