Anatomy & Physiology Unit 3 Notes 3/20/26

Epidermis

1) Outer layer

2) Stratified squamous epithelium composed

3) Keratinized (hardened by keratin)

Dermis

1) Dense connective tissue

Hypodermis

1) Subcutaneous tissue deep to dermis

2) Not part of skin

3) Anchors skin to underlying organs

4) Composed mostly of adipose tissue

Stratum Basal

1) Deepest layer of epidermis

2) Lies next to dermis

3) Cells undergoing mitosis

4) Daughter cells get pushed upward and become more superficial

Stratum Spinosum

1) Region between stratum basale and stratum granulosum

2) Provides skin with strength, flexibility

3) Binds keratinocytes together initiating keratin production

Stratum Granulosum

1) Region located between stratum spinosum & stratum corneum

2) Produces keratin & lipids

3) Help waterproof skin, seal cells together, & limit moisture loss

Stratum Lucideum

1) Formed from dead cells of the deeper strata

2) Occurs only in thick, hairless skin of the palms of hands and soles of feet

Stratum Corneum

1) Outermost layer of epidermis composed

2) Shingle-like dead cells filled with keratin (protective protein prevents water loss from skin)

Epidermis Layers Acronym:

Come-Corneum

Let’s-Lucideum

Get-Granulosum

Sun-Spinosum

Burn-Basale

Melanin

1) Pigment (melanin) produced by melanocytes

2) Melanocytes are mostly in stratum basale

3) Color is yellow to brown to black

4) Amount of melanin produced depends upon genetics & exposure to sunlight

Papillary Layer (upper dermal region)

1) Projections called dermal papillae

-Some contain capillary loops

-Offer house pain receptors & touch receptors

Reticular Layer (deepest skin layer)

1) Blood vessels

2) Sweat & oils glands

3) Deep pressure receptors

Structure of Dermis:

1) Collagen & elastic fibers located throughout the dermis

-Collagen fibers give skin it’s toughness

-Elastic fibers give skin elasticity

2) Blood vessels play role in body temperature regulation

Normal Skin Color Determinants:

1) Melanin:

-Yellow, brown, or black pigments

2) Carotene:

-Orange, yellow pigment from some vegetables

3) Hemoglobin:

-Red coloring from blood cells in dermal capillaries

-Oxygen content determines the extent of red coloring