Skin Layers

Which layer of the epidermis is responsible for continuous cell division?

• Stratum spinosum

• Stratum lucidum

• Stratum basale

• Stratum granulosum

Answer explanation

The stratum basale is the deepest layer of the epidermis and is responsible for continuous cell division, producing new keratinocytes that migrate upwards to replenish the skin.

Tags

NGSS.HS-LS1-4

What protein is produced as cells move toward the outer epidermis, making skin tough and water-resistant?

• Melanin

• Collagen

• Keratin

• Elastin

Answer explanation

Keratin is the protein produced as skin cells move toward the outer epidermis, providing toughness and water resistance. Melanin is for pigmentation, collagen supports structure, and elastin provides elasticity.

Which layer is present only in thick skin such as the palms and soles?

• Stratum spinosum

• Stratum lucidum

• Stratum corneum

• Stratum basale

Answer explanation

The stratum lucidum is a clear layer found only in thick skin, such as the palms and soles, providing an extra barrier. The other layers, like stratum spinosum, stratum corneum, and stratum basale, are present in both thick and thin skin.

Which epidermal layer is also called the “grainy layer” due to keratin granules?

• Stratum corneum

• Stratum granulosum

• Stratum spinosum

• Stratum basale

Answer explanation

The stratum granulosum is known as the "grainy layer" because it contains keratin granules, which are essential for the skin's barrier function. This distinguishes it from the other layers listed.

Which layer of the epidermis contains melanocytes?

• Stratum lucidum only

• Stratum granulosum only

• Stratum corneum

• Stratum basale

Answer explanation

The stratum basale is the deepest layer of the epidermis and contains melanocytes, which are responsible for producing melanin, the pigment that gives skin its color. The other layers do not contain melanocytes.

What is the correct order of the epidermis layers from deepest to most superficial?

• Corneum → Basale → Spinosum → Lucidum → Granulosum

• Basale → Spinosum → Granulosum → Lucidum → Corneum

• Basale → Granulosum → Spinosum → Lucidum → Corneum

• Spinosum → Basale → Granulosum → Lucidum → Corneum

Answer explanation

The correct order of the epidermis layers from deepest to most superficial is Basale → Spinosum → Granulosum → Lucidum → Corneum. This sequence reflects the progression of skin cell development and maturation.

Which layer of the skin is avascular (has no blood supply)?

• Dermis

• Hypodermis

• Epidermis

• Papillary layer

Answer explanation

The epidermis is the outermost layer of the skin and is avascular, meaning it does not have a direct blood supply. Instead, it receives nutrients through diffusion from the underlying dermis.

Why do superficial cuts not bleed?

• Lack of nerves

• Lack of pigments

• Lack of blood vessels

• Lack of collagen

Answer explanation

Superficial cuts do not bleed because they lack blood vessels. When the skin is only slightly damaged, the deeper layers containing blood vessels remain intact, preventing bleeding.

Which epidermal layer is responsible for immune defense?

• Stratum corneum

• Stratum basale

• Stratum spinosum

• Stratum lucidum

Answer explanation

The stratum spinosum contains Langerhans cells, which play a crucial role in immune defense by detecting pathogens and initiating immune responses, making it the key epidermal layer for immune protection.

What cells in the stratum spinosum protect against pathogens?

• Merkel cells

• Melanocytes

• Langerhans cells

• Fibroblasts

Answer explanation

Langerhans cells in the stratum spinosum are specialized immune cells that play a crucial role in detecting and presenting pathogens to the immune system, thus providing protection against infections.