Epidermis, Acid Mantle & Esthetician Essentials

Question-and-answer flashcards covering epidermal structure, skin barrier science, acid mantle care, and esthetician treatment insights.

What are the three main divisions of the skin?

Epidermis, Dermis, and Subcutaneous (Hypodermis) layer.

Which skin layer contains no blood vessels but many nerve endings?

The Epidermis.

What is the epidermal-dermal junction?

The area where the epidermis attaches to the papillary dermis for support and nutrient exchange.

Name the five layers (strata) of the epidermis from deepest to most superficial.

Stratum basale, Stratum spinosum, Stratum granulosum, Stratum lucidum, Stratum corneum.

Which epidermal layer is also called the basal layer?

Stratum basale (stratum germinativum).

Where are melanocytes located and what is their role?

Located in the stratum basale; they produce the pigment melanin to protect against UV radiation and give skin color.

Which cell type in the epidermis functions as sensory receptors for touch?

Merkel cells (found in the stratum basale).

What immune cells reside in the epidermis and help fight infection?

Langerhans cells.

What is keratinization?

The process by which basal cells mature into keratinocytes, migrate upward, die, and form the tough, outer stratum corneum.

Define desquamation.

The natural shedding of dead skin cells from the stratum corneum.

How long is complete cell turnover in young adults versus elderly adults?

28–30 days in young adults; 45–50 days in elderly adults.

What are keratinocytes?

Primary epidermal cells that produce keratin, creating a protective, moisture-retaining barrier.

When keratinocytes reach the stratum corneum, what are they called?

Corneocytes.

Why does exfoliation improve skin texture?

It removes dead, fully keratinized corneocytes, revealing fresher cells beneath.

What substance fills spaces between corneocytes, acting as the “mortar”?

Lipids (ceramides, cholesterol, and fatty acids) released from lamellar bodies.

Why is the lipid ‘mortar’ important for estheticians?

It maintains barrier integrity; treatments or products must replenish lipids to prevent dehydration and sensitivity.

What are lamellar granules and their function?

Organelles that release lipids in the granular layer to form the skin’s waterproof barrier.

Describe desmosomes.

Protein ‘glue spots’ that tightly bind epidermal cells, granting mechanical strength.

Which epidermal layer is nicknamed the ‘horny layer’?

Stratum corneum.

How many layers of dead cells typically make up the stratum corneum?

Approximately 10–30 layers.

Which protein is the principal component of the stratum corneum, hair, and nails?

Keratin.

Where is the stratum lucidum found?

Only on palms of the hands and soles of the feet.

Why is the stratum lucidum beneficial on palms and soles?

Provides extra protection against mechanical stress.

What granule-filled layer intensifies keratin production and starts programmed cell death?

Stratum granulosum.

Name two key proteins found in keratohyalin granules.

Filaggrin and other keratin-aggregating proteins.

Which layer is called the ‘spiny layer’ and why?

Stratum spinosum; desmosomal connections make cells appear spiny under a microscope.

What do glycolipids released in the stratum spinosum do?

Reduce water loss, aiding the skin’s waterproof barrier.

Which specialized immune cells patrol the stratum spinosum?

Langerhans cells.

List three major functions of the epidermis.

Protection from pathogens, continual skin renewal, and providing skin color.

How does the epidermis help regulate body temperature?

By adjusting sweat production and blood flow to release or conserve heat.

Which skin layer’s damage causes bleeding from a shallow paper cut?

The papillary dermis, because the epidermis itself has no blood vessels.

Define the acid mantle.

A thin, slightly acidic film (pH 4.5–6.0) on the stratum corneum composed of sebum, sweat, dead cells, and natural acids.

Give two functions of the acid mantle.

1) Prevents pathogen invasion; 2) Reduces transepidermal water loss (TEWL).

What is the skin’s microbiome?

A community of beneficial microorganisms living on the skin that support immunity and pH balance.

List three factors that can damage the acid mantle.

Over-cleansing, alkaline soaps, over-exfoliation, extreme weather, UV exposure, or products with irritating ingredients like SLS.

Name three signs of a damaged acid mantle.

Dryness/flakiness, redness/irritation, tightness after cleansing, breakouts, or increased sensitivity.

Why should pH-balanced cleansers be used?

They preserve the acid mantle’s natural acidity, protecting barrier function.

How often should exfoliation generally be performed to avoid barrier damage?

1–2 times per week with gentle methods.

What are moisturizers with cholesterol used for?

To repair and protect the skin barrier by replenishing natural lipids alongside ceramides and fatty acids.

Which ingredient in cleansers is commonly too harsh and strips the acid mantle?

Sodium lauryl sulfate (SLS).

Describe three ways estheticians use knowledge of the acid mantle in practice.

Selecting pH-balanced products, educating clients to avoid over-cleansing, and tailoring post-treatment barrier repair routines.

What is transepidermal water loss (TEWL)?

Water that passively evaporates through the epidermis; controlled by the lipid barrier and acid mantle.

How thick is the epidermis on eyelids compared to palms/soles?

Thinnest on eyelids (~0.05 mm) and thickest on palms/soles (up to 1.5 mm).

What are the three types of skin barriers mentioned?

Physical barrier, Chemical barrier, Biological barrier.

Which layer contains “bricks and mortar” analogy, and what are bricks?

Stratum corneum; bricks are corneocytes.

Why must strong chemical peels be neutralized?

To quickly restore the skin’s natural pH and avoid prolonged acid mantle disruption.

What role do ceramides play in the skin?

They are key lipids that fill intercellular spaces, locking in moisture and strengthening the barrier.

Explain why desmosome integrity matters during exfoliation.

Harsh exfoliation can break desmosomal bonds, causing sensitivity and impaired barrier function.

What does a tight, squeaky-clean feeling after washing indicate?

Likely stripping of the acid mantle and lipid barrier.

Why should estheticians avoid hot water and rough washcloths during cleansing?

Heat and friction strip lipids and irritate the acid mantle, leading to barrier compromise.

Give one client education tip to maintain a healthy microbiome.

Use gentle, pH-balanced cleansers and avoid over-sanitizing, which disrupts beneficial bacteria.

How do lamellar bodies demonstrate semi-permeability?

They regulate passage of certain substances and gases into and out of the stratum corneum.

What happens to keratinocytes as they ascend the epidermis?

They produce more keratin, lose their nucleus, die, and become flattened corneocytes.

Why do estheticians recommend barrier-repair serums after peels?

To replenish ceramides, cholesterol, and fatty acids lost during exfoliation, restoring barrier integrity.

What is the pH range of healthy skin’s acid mantle?

Approximately 4.5 to 6.0.

Name two benefits of glycolipids besides moisture retention.

Rebuilding the barrier and supporting cell-to-cell communication for healing.

Which layer’s keratin production begins the visible hardening of the skin?

Stratum spinosum.

What everyday habit often harms the acid mantle yet is perceived as ‘clean’?

Using alkaline bar soap or foaming cleansers multiple times a day.

How long can it take to fully repair a damaged acid mantle?

Several weeks, even though skin pH may normalize in about 30 minutes.

Why should estheticians understand keratin production timing?

To time treatments (exfoliation, hydration) that target either live keratinocytes or dead corneocytes effectively.