Epidermis Layers Overview

Study Notes

Epidermis Layers

Stratum Basale: Also known as stratum germinativum; the deepest layer of the epidermis composed of a single layer of keratinocytes, 10-25% melanocytes, and some Merkel cells; known for rapid cell division.
Stratum Spinosum: Referred to as the prickly layer; consists of several layers; contains a web-like system of intermediate filaments with melanocytes and Langerhans' cells contributing to its structure.
Stratum Granulosum: Known as the granular layer; a thin layer, typically 3-5 layers thick; cells flatten and accumulate keratohyalin and lamellar granules; plasma membrane thickens in this layer.
Stratum Lucidum: Called the clear layer; composed of a few rows of flattened dead keratinocytes; found only in thick skin.
Stratum Corneum: Also known as the horny layer; 20-30 cells thick and comprises about 3/4 of the epidermis; consists of keratin and lamellar bodies, providing protection against various assaults.

Cell Types and Functions

Keratinocytes: Continuously reproduce, move to the surface, and eventually flake off; cycle through every 25-45 days; found mainly in the top layers of the epidermis.
Melanocytes: Produce melanin in the stratum basale; melanin is responsible for skin color and offers protection against light; use a branching process to distribute melanin.
Langerhans' Cells: Also known as epidermal dendritic cells; derived from bone marrow; located in the stratum spinosum; function as macrophages activating the immune response.
Merkel Cells: Located at the dermal-epidermal junction; associated with sensory nerve endings to help perceive touch.

Homeostatic Imbalances

Common Skin Issues: Skin manifests over 1,000 conditions and ailments, including cancer and burns.
Burn Causes: Result from damage due to intense heat, electricity, radiation, or chemicals.
Immediate Threat of Burns: Loss of body fluids leading to dehydration.
Secondary Threat of Burns: Risk of infection.

Burn Classifications

First-Degree Burns: Affect only the epidermis causing redness, swelling, and pain; sunburn is an example.
Second-Degree Burns: Damage both the epidermis and upper dermis; characterized by blistering; also called partial-thickness burns.
Third-Degree Burns: Involve full thickness of the skin and are not painful due to nerve destruction; require skin grafting; classified as full-thickness burns.

Skin Cancer Detection

ABCDE Rule for Skin Lesions:
- Asymmetrical: Sides do not match.
- Border Irregularity: Borders are uneven.
- Color: Various colors present, including black, brown, tan, blue, and red.
- Diameter: Lesions larger than 6mm.
- Evolving: Changes in size, shape, or color over time.

Hair and Nails

Hair Composition: Formed from keratinized cells produced by hair follicles; melanin provides hair color.
Hair Structure: Divided into root (in the skin) and shaft (protects from external environment).
Hair Follicle Sheath: Composed of inner and outer sheaths; inner sheath promotes hair growth, while the outer sheath offers protection with strong keratin.
Arrector Pili: Smooth muscle bundles that contract and cause hair to stand upright.
Nail Structure: Composed of a free edge, body, proximal root, nail matrix (responsible for growth), and lunula (region covering the root).

Description

This quiz covers the different layers of the epidermis, including their specific characteristics and functions. You'll explore details about the stratum basale, spinosum, granulosum, lucidum, and corneum, enhancing your understanding of skin anatomy.