Layers of the skin

Epidermis: The outermost layer of the skin.
- Relatively thin and cell-rich.
- Contains pores, which allow hair follicles and sweat glands to surface.
- Stratified epithelial layer, which means it consists of multiple layers of cells.
- Keratinized stratified squamous epithelium (surface cells are flattened and rich in keratin).
- Living cells are in the lower half, nourished by tissue fluid from the dermis.
Dermis: The thicker layer beneath the epidermis.
- Contains blood vessels, hair follicles, and glandular structures.
- Has a rich blood supply via arterioles and capillaries, which provides nutrients to the epidermis.
- Sensitive to pain and temperature due to various nerve receptors (nociceptors for pain, thermoreceptors for temperature).
Hypodermis: The layer below the dermis.
- Composed mostly of adipose (fat) tissue.
- Provides insulation and cushioning for the body.

Pores/Hair Follicles:
- Hair grows from hair follicles, which extend down into the dermis.
- Hairs vary in length based on their location on the body.
Sweat Glands:
- Ducted structures that release sweat through ducts onto the skin's surface.
- Comprised of coiled tubes located in the derma.

Blood Supply:
- The epidermis has no blood supply; relies on tissue fluid from the dermis.
- Oxygen and nutrients pass through the tissue fluid to reach epidermal cells.
Nerve Sensitivity:
- The dermis contains nociceptors (pain receptors) and various other sensory receptors for temperature and pressure.
- Epidermis lacks nerve fibers and is not sensitive to pain.

The junction is wavy which increases the surface area for attachment.
- Rough shapes prevent blisters by maintaining connection between epidermis and dermis.
- Enhances oxygen and nutrient transfer through an incomplete basement membrane.

The epidermis dips into skin pores such as sweat glands and hair follicles, giving it a three-dimensional structure.

Types of Injuries:
- Superficial Injury: Affects only the epidermis.
- Superficial Partial Thickness Injury: Extends into the top part of the dermis.
- Deeper Partial Thickness Injury: Affects deeper layers of the dermis.
- Full Thickness Injury: Affects the entire thickness of the skin.
Healing Strategies:
- Healing can occur via regeneration (preferable) or fibrosis (forming scars).
- Regeneration requires the presence of some original cells to undergo mitosis for healing without scarring.
Painful nature of partial thickness injuries:
- Nociceptors in the dermis become exposed due to the loss of epidermal coverage, triggering pain signals.

The skin consists of three primary layers: epidermis, dermis, and hypodermis.
Each layer serves distinct functions crucial for protecting the body and facilitating healing processes.