Integumentary System

​Integumentary
System

Fill in the Blanks

Explanation

The epidermis is avascular, meaning it lacks its own blood supply. Instead, nutrients and oxygen must travel from blood vessels in the dermis to the epidermis by diffusion. This process limits the thickness of viable cells in the epidermis and contributes to the layering pattern as keratinocytes move outward and eventually die.

Multiple Choice

Which combination of structures primarily helps regulate body temperature?

• Sebaceous glands and stratum corneum

• Sweat glands and dermal blood vessels

• Nails and adipose tissue

• Keratinocytes and melanocytes

Explanation

Thermoregulation is a critical function of the integumentary system. Eccrine sweat glands help cool the body by releasing sweat, which evaporates from the skin surface, removing heat. Meanwhile, dermal blood vessels respond to temperature changes through vasodilation (to release heat) and vasoconstriction (to conserve heat). The other choices involve structures with other roles—such as protection, cushioning, or pigmentation—but not active thermoregulation.

Open Ended

Explain the difference between thin skin and thick skin in terms of

structure, function, and location.

Multiple Choice

Which epidermal layer contains the highest number of metabolically active keratinocytes?

• Stratum corneum

• Stratum granulosum

• Stratum basale

• Stratum lucidum

Explanation

The stratum basale contains basal stem cells that are mitotically active and generate new keratinocytes.

Open Ended

Explain the differences between thick and thin skin.

Fill in the Blanks

Desmosomes are cell junctions that hold keratinocytes together and give the stratum spinosum its characteristic appearance under a microscope.

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Multiple Select

Which specialized epidermal cell type is responsible for detecting fine touch? (Select all that apply).

• Merkel cells

• Meissner’s corpuscles

• Pacinian corpuscles

• Ruffini endings

• Merkel cells are slow-adapting mechanoreceptors located in the stratum basale and are responsible for detecting fine touch and texture, especially in areas like fingertips.

• Meissner’s corpuscles are fast-adapting receptors found in the dermal papillae that detect light touch and changes in texture.

• Pacinian corpuscles are deep pressure receptors located in the dermis or hypodermis and respond to vibration and deep pressure.

• Ruffini endings detect skin stretch and sustained pressure and contribute to the perception of object manipulation and grip control.

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Fill in the Blanks

If keratinocytes do not undergo normal apoptosis, they may survive and proliferate abnormally, leading to cancerous growths such as squamous cell carcinoma.

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Open Ended

Why do keratinocytes die as they move toward the surface of the epidermis?

Sample Answer

As keratinocytes migrate upward through the layers of the epidermis, they move farther away from the blood supply in the dermis, leading to reduced access to nutrients and oxygen. At the same time, they undergo terminal differentiation, during which they lose their nuclei and organelles and accumulate keratin and lipids. This process is regulated by signaling molecules and enzymes that trigger apoptosis, allowing the cells to transform into tough, flat, dead corneocytes that make up the protective outer layer of skin.

Multiple Choice

Which structures are not found in the dermis?

• Sweat glands

• Blood vessels

• Meissner’s corpuscles

• Keratinocytes

Keratinocytes are found in the epidermis, not the dermis. The dermis contains blood vessels, glands, and sensory receptors.

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Open Ended

Langer’s lines are natural patterns in the skin formed by the orientation of collagen fibers in the reticular layer of the dermis. Surgeons often make incisions parallel to these lines because doing so reduces skin tension, promotes faster healing, and minimizes scarring.

Based on this information, what do you think might happen if a surgeon makes an incision perpendicular to Langer’s lines instead? Explain your reasoning.

Sample Answer

If a surgeon cuts perpendicular to Langer’s lines, the incision is likely to be pulled open by the natural tension in the skin. This could result in slower healing, increased tension on the wound edges, and more noticeable scarring, because the collagen fibers resist closure in that direction.

Multiple Choice

Which of the following is not a function of the hypodermis?

• Insulation

• Energy storage

• Keratin production

• Shock absorption

Keratin is produced by keratinocytes in the epidermis, not the hypodermis.

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Fill in the Blanks

• _{Burns are classified based on how deeply they penetrate the layers of the skin:}

  • _{A first-degree burn affects only the epidermis, causing redness and mild pain (e.g., sunburn).}

  • _{A second-degree burn damages the epidermis and part of the dermis, often resulting in blisters, swelling, and more intense pain.}

  • _{A third-degree burn extends through the entire epidermis and dermis, and may also affect the hypodermis or deeper tissues.}

​Burns

Multiple Choice

Why is the hypodermis a preferred site for subcutaneous injections?

• It is part of the epidermis and regenerates quickly.

• It contains dense irregular connective tissue.

• It has a rich blood supply and loose matrix for rapid absorption.

• It contains melanocytes that process medication.

The vascularity and loose connective tissue of the hypodermis allow medications to be absorbed quickly when injected.

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Open Ended

_{Which specific skin structures would likely be damaged or destroyed in a third-degree burn? Explain your reasoning.}

​Sample Answer:
In a third-degree burn, the damage includes the epidermis, dermis, and possibly the hypodermis. Structures that would be destroyed include keratinocytes, melanocytes, sensory receptors (like Merkel cells and Meissner’s corpuscles), sweat glands, sebaceous glands, blood vessels, hair follicles, and collagen fibers in the dermis. Because the nerve endings are also damaged, the area may be numb despite the severity. If the burn reaches the hypodermis, adipose tissue and larger blood vessels may also be affected.

Multiple Choice

Which structure is responsible for supplying blood to the growing hair follicle?

• Arrector pili muscle

• Inner root sheath

• Hair papilla

• Hair shaft

The hair papilla is located at the base of the hair bulb and contains capillaries that nourish the hair matrix.

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Multiple Choice

Which of the following best describes the function of the arrector pili muscle?

• Protects the hair matrix from UV radiation

• Detects fine touch and vibration

• Anchors the hair bulb to the dermis

• Contracts to raise the hair shaft during cold or emotional stimuli

The arrector pili is a small smooth muscle that pulls the hair upright, creating goosebumps.

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Multiple Choice

Where are melanocytes located within the layers of the epidermis?

• Stratum corneum

• Stratum spinosum

• Stratum granulosum

• Stratum basale

Melanocytes reside in the stratum basale, where they produce melanin and transfer it to keratinocytes.

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Multiple Choice

In albinism, melanocytes are present but unable to produce melanin due to:

• Lack of keratin production

• Loss of blood flow to the skin

• Deficiency of the enzyme tyrosinase

• Autoimmune destruction of melanocytes

​Steps of Melanin Production (Melanogenesis)

1. It starts with an amino acid called tyrosine.
   Melanocytes take in tyrosine from the body.

2. An enzyme called tyrosinase turns tyrosine into dopaquinone.
   This is the key step—if tyrosinase doesn’t work, melanin can’t be made (like in albinism).

3. Dopaquinone turns into either eumelanin or pheomelanin.

   • Eumelanin is brown to black pigment

   • Pheomelanin is yellow to red pigment
     Your genetics determine which type you make more of, affecting your skin and hair color.

4. Melanin is packed into melanosomes.
   These are little vesicles (containers) that carry melanin.

5. Melanosomes are transferred to keratinocytes.
   The pigment ends up in the skin cells and sits above their nuclei to protect DNA from UV radiation.

Multiple Choice

Which type of sweat gland is primarily involved in thermoregulation?

• Apocrine

• Sebaceous

• Eccrine

• Ceruminous

Eccrine glands help cool the body through evaporative sweating.

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Multiple Choice

What makes apocrine sweat thicker than eccrine sweat?

• It contains high levels of glucose

• It is mixed with sebum

• It includes lipids and proteins

Apocrine sweat has proteins and lipids, making it thicker than eccrine sweat.

Fill in the Blanks

Sebaceous glands open into hair follicles, aiding lubrication of hair and skin.

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Open Ended

What questions do you have?