Epidermis, Dermis, and Hypodermis

Function of Epidermis

protects, sensations (pressure, heat, pain), temperature regulation, excretion (sweat), production (Vitamin D)

Layers of the Epidermis

From Superficial to deep: Stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, stratum basale

Stratum Corneum

Layer of dead, thick, keratinized cells; Regulary sheds

Stratum Lucidum

Clear layer; thin layer of translucent cells only found in thick skin of palms and feets

Stratum granulosum

Cells begin to flatter; accumulate keratin granules responsible for water-proofing the skin

Stratum Spinosum

“spiny layer” named for irregular shape of the cells- Contain pre-keratin filaments

Stratum Basale

Constantly dividing and pushing up cells into the next layer

Melanocytes

spider-shaped epithealial cells found in bottom 2 layers of the epidermis

What do Melanocytes produce?

A pigment called melanin (which is absorbed by nearby epidermal cells)

Difference of melanocytes in dark and light-skinned people

Both have the same amount of melanocyte, but the amount of melanin produced is different

Purpose of Melanin

protects the skin against UV rays

Skin Cancer

When UV radiation mutates a skin cell’s DNA and the cell begins to divide uncontrollably

Types of Skin Cancer

Melanoma, Basal Cell Carcinoma, Squamos Cell Carcinoma

Melanoma

Uncontrolled divison of melanocytes

Basal Cell Carcinoma

Uncontrolled division of cells in the Stratum Basale

Squamous Cell Carcinoma

Uncontrolled division of cells in the Stratum Spinosum Layer

Dermis

dense, irregular connective tissue; contains nerves, blood vessels, sweat glands, and hair folliclles

Dermal Papillae

Boundary between epidermis and the dermis- Wavy layer; this irregular surface is the cause of your fingerprint

Epidermal ridges

Fingerprint

Layers of the Dermis

Papillary layer and reticular layer

Papillary layer

Loose connective tissue

Reticular tissue

Bundles of collagen fiber

Lines of Cleavage

Arrangement of collage fibers from reticular layer

Surgeons and Cleavage Lines

Surgeons should make cuts parallel to lines of cleavage so it heals better and doesn’t leave a scar

Erythema

Swelling of blood vessels in the dermis during exercise- causes skin to appear red

Decubitis Ulcers

Bedsores- When blood supply to the skin is restricted for a long time

Hypodermis

Subcutaneous layer NOT PART OF THE SKIN

Composition of Hypodermis

Loose, fatty connective tissue that connects the skin to muscles or bones

Purpose of hypodermis

Insulates and stores nutrients