Skin Structure,
Growth & Nutrition

The Science Beneath the Surface

Foundations | State Board Exam Aligned

Shear Genius Society Curriculum

The skin is the

Largest Organ in the Body

and every beauty service involves it.

Facials • Waxing • Chemical Peels • Makeup • Nail Services • Massage

What You'll Learn

Describe the structure and composition of the skin
Identify the layers of the epidermis and dermis
Explain the six primary functions of the skin
Understand how melanin is produced and distributed

What You'll Learn

continued

Identify vitamins essential for healthy skin
Explain the role of collagen and elastin in skin health
Differentiate between sudoriferous and sebaceous glands
Describe the process of skin cell renewal and keratinization

SECTION 01

Skin Facts & Functions

The Body's Largest Organ • Six Essential Functions

Skin Quick Facts

THE BASICS YOU NEED TO KNOW

22 SQ FT

Average total surface area of adult skin

6-9 LBS

Weight of the skin on an adult body

THINNEST

Eyelids — as thin as 0.5 mm

THICKEST

Palms and soles — up to 6 mm

The study of the skin is called DERMATOLOGY — the medical branch. HISTOLOGY is the study of tissue.

Six Functions of the Skin

PART 1 — THE BIG THREE

PROTECTION

Think: Shield

First line of defense against bacteria, UV radiation, and physical injury. Acts as a waterproof barrier.

SENSATION

Think: Alarm System

Contains nerve endings that detect heat, cold, touch, pressure, and pain. Keeps you safe from harm.

HEAT REGULATION

Think: Thermostat

Maintains body temperature at ~98.6°F through sweating (cooling) and shivering (warming).

Six Functions of the Skin

PART 2 — THE OTHER THREE

EXCRETION

Think: Detox

Eliminates waste products through sweat — salt, uric acid, and other toxins are released through the pores.

SECRETION

Think: Moisturizer

Sebaceous glands secrete sebum (oil) that lubricates the skin and hair, keeping them soft and pliable.

ABSORPTION

Think: Sponge

The skin can absorb certain substances — topical medications, essential oils, and skincare ingredients.

Signs of Healthy Skin

Slightly moist — not too oily, not too dry
Soft and flexible — moves easily over muscles and bones
Smooth texture — free of visible blemishes or rough patches
Slightly acidic — skin has a pH between 4.5 and 5.5 (acid mantle)
Free of disease — no inflammation, infection, or abnormalities

SECTION 02

Layers of the Skin

Epidermis • Dermis • Subcutaneous Tissue

Three Main Layers

FROM SURFACE TO DEEPEST

EPIDERMIS

Outermost layer — the one you can see and touch

No blood vessels • 5 sub-layers • Constantly shedding

DERMIS

Middle layer — the "true skin" beneath the epidermis

Blood vessels • Nerves • Collagen • Elastin • Glands

SUBCUTANEOUS TISSUE

Deepest layer — also called the hypodermis

Fat cells • Insulation • Cushioning • Energy storage

The Epidermis

FIVE LAYERS — OUTERMOST TO DEEPEST

1

STRATUM CORNEUMOutermost — dead keratinized cells, constantly shed

2

STRATUM LUCIDUMClear layer — only found on palms and soles

3

STRATUM GRANULOSUMGranular layer — cells start to die here

4

STRATUM SPINOSUMSpiny layer — cells begin to change shape

5

STRATUM GERMINATIVUMBasal layer — where new cells are born (mitosis)

Epidermis Key Details

BOARD EXAM ESSENTIALS

The epidermis has NO blood vessels.

Stratum corneum is made of keratin — the same protein in hair and nails
The basal layer (germinativum) is where cell division (mitosis) occurs
Cells take about 28 days to travel from the basal layer to the surface
Melanocytes are found in the basal layer — they produce melanin
The epidermis is thinnest on the eyelids and thickest on the palms

Melanocytes & Melanin

SKIN COLOR AND PROTECTION

MELANOCYTES

Special cells in the basal layer that produce melanin pigment

MELANIN

The pigment that gives skin, hair, and eyes their color

UV DEFENSE

Melanin absorbs UV radiation — it is the skin's natural sunscreen

EQUAL COUNT

All skin tones have the SAME number of melanocytes

VARIATION

Skin color differences come from the amount and type of melanin produced

The Dermis

THE "TRUE SKIN" — CONTAINS BLOOD SUPPLY

PAPILLARY LAYER

Upper portion of the dermis, directly beneath the epidermis

Contains: Dermal papillae (fingerprint ridges), nerve endings, capillaries

RETICULAR LAYER

Deeper, thicker portion of the dermis — provides strength

Contains: Collagen, elastin, oil glands, sweat glands, hair follicles, fat cells

BOARD TIP: The dermis is where collagen and elastin give skin its strength and elasticity!

Subcutaneous Tissue

THE DEEPEST LAYER — ALSO CALLED HYPODERMIS

Made primarily of adipose tissue (fat cells)
Acts as a shock absorber — cushions muscles and bones
Provides insulation — helps regulate body temperature
Connects the skin to underlying muscles and bones
Varies in thickness based on body location, age, and genetics

SECTION 03

Skin Nutrition & Health

Vitamins • Hydration • Collagen • Aging • Sun Damage

Vitamins for Skin Health

NUTRITION FROM THE INSIDE OUT

VITAMIN A

Promotes cell turnover and repair — fights signs of aging. Found in sweet potatoes, carrots, and leafy greens.

VITAMIN C

Essential for collagen production — brightens and protects. Found in citrus fruits, berries, and bell peppers.

VITAMIN D

Supports skin cell growth and repair — "the sunshine vitamin." Produced when skin is exposed to sunlight.

VITAMIN E

Powerful antioxidant — protects against free radical damage. Found in nuts, seeds, and avocados.

Hydration & Skin Health

Skin is approximately 64% water — hydration is critical
Dehydrated skin appears dull, tight, and shows more fine lines
Water helps flush toxins and delivers nutrients to skin cells
Humectants in skincare (hyaluronic acid) attract moisture to skin
Drinking adequate water supports the skin's moisture barrier

Collagen & Elastin

THE STRUCTURAL PROTEINS OF THE DERMIS

COLLAGEN

Most abundant protein in the skin — provides firmness and structure

Makes up about 70-80% of the dry weight of the dermis

ELASTIN

Gives skin its ability to stretch and snap back into place

Decreases with age — leading to sagging and wrinkles

Skin Aging

INTRINSIC vs. EXTRINSIC

INTRINSIC AGING

Internal / Genetic — Cannot be prevented

Genetically programmed — part of natural aging
Collagen production slows over time
Skin becomes thinner and loses elasticity
Cell turnover rate decreases with age

EXTRINSIC AGING

External / Environmental — Can be reduced

Sun exposure (photoaging) — #1 cause
Smoking constricts blood vessels
Pollution and environmental toxins
Poor nutrition and dehydration

Sun Damage & UV Radiation

THE #1 CAUSE OF PREMATURE AGING

UVA RAYS

"Aging rays" — penetrate deep into the dermis. Break down collagen and elastin. Cause wrinkles and age spots. Present year-round — even on cloudy days and through glass.

UVB RAYS

"Burning rays" — affect the epidermis surface. Cause sunburn, redness, and direct DNA damage. Strongest between 10 AM and 4 PM in peak sun hours.

UVC RAYS

Most dangerous — but absorbed by the ozone layer. Do not typically reach the earth's surface. Used in germicidal lamps for sterilization.

Free Radicals & Antioxidants

FREE RADICALS

Unstable molecules that damage skin cells
Caused by UV exposure, pollution, and smoking
Break down collagen and accelerate aging
Contribute to hyperpigmentation and dullness

ANTIOXIDANTS

Neutralize free radicals — stop the damage
Found in vitamins A, C, and E
Green tea, berries, and dark chocolate are sources
Applied topically in serums and moisturizers

SECTION 04

Glands of the Skin

Sudoriferous (Sweat) • Sebaceous (Oil) • Impact on Services

Sudoriferous Glands

SWEAT GLANDS — TWO TYPES

ECCRINE GLANDS

Found ALL over the body — most abundant on palms, soles, and forehead

Produce clear, odorless sweat • Regulate body temperature • Open directly onto skin surface

APOCRINE GLANDS

Found in the armpits and groin area — connected to hair follicles

Produce thicker secretion • Body odor occurs when bacteria break down this sweat • Activated by stress/emotion

Sebaceous Glands

OIL GLANDS — SEBUM PRODUCTION

Attached to hair follicles — found everywhere except palms and soles
Produce sebum — an oily substance that lubricates skin and hair
Sebum helps maintain the skin's acid mantle (protective pH layer)
Overactive sebaceous glands lead to oily skin and acne
Underactive sebaceous glands lead to dry, flaky skin

How Glands Affect Services

WHY THIS MATTERS IN THE SALON

OILY SKIN

Overactive sebaceous glands — use oil-free products, astringent toners, and lighter moisturizers

DRY SKIN

Underactive sebaceous glands — use rich moisturizers, cream cleansers, and hydrating masks

EXCESSIVE SWEATING

Overactive eccrine glands — may affect product adhesion during makeup or nail services

BODY ODOR

Apocrine gland secretion + bacteria — maintain a comfortable, professional environment

SECTION 05

Skin Growth & Renewal

Cell Turnover • Keratinization • Wound Healing

Cell Turnover Rate

HOW THE SKIN RENEWS ITSELF

~28 DAYS

Average cell turnover cycle in healthy young adults

~45-60 DAYS

Cell turnover rate in older adults (slows with age)

BASAL LAYER

New cells are born here through cell division (mitosis)

Exfoliation speeds up the removal of dead surface cells
Chemical peels and microdermabrasion accelerate cell turnover
Retinoids (vitamin A) stimulate faster cell renewal

Keratinization

THE PROCESS OF CELL HARDENING

1

BIRTHNew skin cell is created by mitosis in the basal layer

2

MIGRATIONCell slowly pushes upward through the epidermis layers

3

FLATTENCell gradually flattens and fills with keratin protein

4

DEATHCell loses its nucleus and dies — becomes fully keratinized

5

SHEDDead cell reaches the surface and naturally sheds off

Wound Healing Basics

HOW THE SKIN REPAIRS ITSELF

INFLAMMATION

Immediate response — blood flow increases, redness and swelling. White blood cells rush to fight bacteria and clean the wound.

PROLIFERATION

New tissue begins to form — collagen is produced. New blood vessels grow. Granulation tissue fills the wound.

REMODELING

Scar tissue matures and strengthens over weeks to months. Collagen reorganizes. Skin regains strength (but not 100%).

NEVER perform services on broken, inflamed, or infected skin — refer to a physician!

How Skin Renews Itself

THE CONTINUOUS CYCLE

New cells are born in the stratum germinativum (basal layer) through mitosis
Cells migrate upward through each layer, changing shape and composition
As cells reach the surface, they become flat, dry, and keratinized
Dead cells naturally shed in a process called desquamation
The entire epidermis is replaced approximately every 28 days

Key Terms Review

PART 1

Epidermis

Outermost layer of the skin — no blood vessels

Dermis

Middle layer — "true skin" — contains collagen and elastin

Melanocyte

Cell in the basal layer that produces melanin pigment

Collagen

Protein that provides firmness and structure to the skin

Elastin

Protein that gives skin its ability to stretch and bounce back

Key Terms Review

PART 2

Keratin

Fibrous protein found in skin, hair, and nails

Sebaceous

Oil glands that produce sebum to lubricate skin and hair

Sudoriferous

Sweat glands — eccrine (all over) and apocrine (armpits)

Desquamation

Natural shedding of dead skin cells from the surface

Acid Mantle

Protective pH barrier on skin surface — pH 4.5 to 5.5

Board Exam Tips

SKIN STRUCTURE EDITION

Memorize the 5 layers of the epidermis in order — corneum to germinativum
Know the 6 functions of the skin — protection, sensation, heat regulation, excretion, secretion, absorption
Understand the difference between eccrine and apocrine glands
Remember: all skin tones have the same number of melanocytes
Know that collagen = firmness and elastin = flexibility

Q1

What is the outermost layer of the skin called?

A) Dermis
B) Hypodermis
C) Epidermis
D) Subcutaneous tissue

Click to reveal answer

Q2

Which layer of the epidermis is where new cells are produced?

A) Stratum corneum
B) Stratum lucidum
C) Stratum granulosum
D) Stratum germinativum

Click to reveal answer

Q3

What protein gives the skin its firmness and structure?

A) Melanin
B) Elastin
C) Collagen
D) Keratin

Click to reveal answer

Q4

Which type of sweat gland is found all over the body?

A) Apocrine
B) Sebaceous
C) Eccrine
D) Sudoriferous

Click to reveal answer

Q5

What is the primary function of melanin in the skin?

A) Moisturize the skin
B) Absorb UV radiation
C) Produce sweat
D) Create new skin cells

Click to reveal answer

Q6

How long does the average cell turnover cycle take in a healthy young adult?

A) 7 days
B) 14 days
C) 28 days
D) 60 days

Click to reveal answer

Q7

Sebaceous glands produce what substance?

A) Sweat
B) Melanin
C) Keratin
D) Sebum

Click to reveal answer

Q8

Which vitamin is called the "sunshine vitamin" and supports skin cell growth?

A) Vitamin A
B) Vitamin C
C) Vitamin D
D) Vitamin E

Click to reveal answer

Skin Structure,
Growth & Nutrition

Chapter Complete

sheargeniussociety.com

Skin Structure,Growth & Nutrition

The skin is the

Largest Organ in the Body

and every beauty service involves it.

What You'll Learn

What You'll Learn

Skin Facts & Functions

Skin Quick Facts

22 SQ FT

6-9 LBS

THINNEST

THICKEST

Six Functions of the Skin

PROTECTION

SENSATION

HEAT REGULATION

Six Functions of the Skin

EXCRETION

SECRETION

ABSORPTION

Signs of Healthy Skin

Layers of the Skin

Three Main Layers

EPIDERMIS

DERMIS

SUBCUTANEOUS TISSUE

The Epidermis

Epidermis Key Details

Melanocytes & Melanin

The Dermis

PAPILLARY LAYER

RETICULAR LAYER

Subcutaneous Tissue

Skin Nutrition & Health

Vitamins for Skin Health

VITAMIN A

VITAMIN C

VITAMIN D

VITAMIN E

Hydration & Skin Health

Collagen & Elastin

COLLAGEN

ELASTIN

Skin Aging

INTRINSIC AGING

EXTRINSIC AGING

Sun Damage & UV Radiation

UVA RAYS

UVB RAYS

UVC RAYS

Free Radicals & Antioxidants

FREE RADICALS

ANTIOXIDANTS

Glands of the Skin

Sudoriferous Glands

ECCRINE GLANDS

APOCRINE GLANDS

Sebaceous Glands

How Glands Affect Services

OILY SKIN

DRY SKIN

EXCESSIVE SWEATING

BODY ODOR

Skin Growth & Renewal

Cell Turnover Rate

~28 DAYS

~45-60 DAYS

BASAL LAYER

Keratinization

Wound Healing Basics

INFLAMMATION

PROLIFERATION

REMODELING

How Skin Renews Itself

Key Terms Review

Key Terms Review

Board Exam Tips

Skin Structure,Growth & Nutrition

Skin Structure,
Growth & Nutrition

Skin Structure,
Growth & Nutrition