Epidermis and Dermis Lecture Review

A comprehensive set of Q&A flashcards covering epidermal cell types, skin pigmentation, layers of the epidermis, structural and functional aspects of the dermis, and associated sensory receptors.

What tough, fibrous protein is produced by keratinocytes and what is its primary function?

Keratin; it provides mechanical protection against abrasion.

Which type of cell junction tightly binds neighboring keratinocytes together?

Desmosomes.

What is a callus and why does it form?

A localized thickening of the epidermis created by persistent pressure that accelerates keratinocyte production.

Which epidermal cells synthesize melanin and in which epidermal layer are they primarily found?

Melanocytes; they reside mainly in the stratum basale.

How does melanin protect skin cells from ultraviolet radiation?

It absorbs UV light, shielding the DNA of dividing cells from damage.

If almost all humans have roughly the same number of melanocytes, what two factors account for differences in skin color?

The color of the melanin produced and the size of the melanosomes.

What causes freckles and pigmented moles?

Local accumulations of melanin in the skin.

Name the star-shaped antigen-presenting cells of the epidermis and describe their immune function.

Langerhans cells; they phagocytose foreign antigens, migrate to lymph nodes, and present the processed antigens to T-cells, initiating immune responses such as delayed hypersensitivity.

Which specialized epidermal cells act as touch receptors and what structure do they form with sensory nerves?

Merkel cells; they form Merkel discs with sensory nerve endings.

What is the deepest layer of the epidermis and approximately what percentage of its cells are melanocytes?

The stratum basale; about 10–25 % of its cells are melanocytes.

In which epidermal layer are most Langerhans cells found, and what mechanical property does this layer provide?

The stratum spinosum; it provides tension-resisting strength.

Keratohyaline and lamellated granules appear in which layer, and what are their respective roles?

The stratum granulosum; keratohyaline granules support keratin filaments, while lamellated granules secrete a waterproofing glycoprotein.

Which thin, clear epidermal layer is present only in thick skin (palms and soles)?

The stratum lucidum.

Approximately how many cell layers form the stratum corneum on the palms and soles?

About 100 layers.

What two substances in the stratum corneum provide its protective qualities?

Keratin (for abrasion resistance) and glycolipids (for waterproofing).

Of what type of connective tissue is the dermis primarily composed?

Dense irregular connective tissue.

List four principal cell types found within the dermis.

Fibroblasts, macrophages, mast cells, and adipocytes (plus dermal dendrocytes).

What structures are housed in the dermal papillae and what sensations do they detect?

Free nerve endings (pain) and Meissner’s corpuscles (light touch).

What are epidermal ridges and why are they functionally important?

Friction-enhancing ridges on the palms and soles that increase grip and create fingerprints.

Define tension lines and explain their clinical significance.

Parallel bundles of collagen fibers in the reticular dermis; surgical incisions made along them gape less and heal more readily.

How do flexion lines form?

At joints where the dermis is tightly bound to deeper structures, causing the skin to fold and crease when the joint moves.

What causes striae (stretch marks) in the skin?

Dermal tearing produced by extreme stretching of the skin.

Explain how a blister forms.

Trauma separates the epidermis from the dermis, and the resulting space fills with fluid.

What dual properties characterize dermal dendrocytes and what roles do they play?

They possess both phagocytic and antigen-presenting capabilities; they participate in immune response, wound healing, blood clotting, and inflammation.

Which mechanoreceptors are slow-adapting versus fast-adapting in the skin?

Slow-adapting: Merkel discs & Ruffini endings; Fast-adapting: Meissner’s corpuscles & Pacinian corpuscles.

How does increased exposure to ultraviolet light affect melanin production?

It stimulates melanocytes to produce more melanin, resulting in a tan.