Hair Sweat and Nails and Skin Notes

Layers of Skin:
- Epidermis: Outer layer of skin, primarily composed of stratified squamous epithelium.
- Dermis: Inner layer consisting of connective tissues.
- Subcutaneous Tissue: Also known as hypodermis, this tissue lies beneath the skin, composed of loose connective tissue and fat, providing insulation and cushioning.

Tissue Type: Composed primarily of keratinized stratified squamous epithelium.
Major Layers:
- Stratum Corneum: Outermost layer composed of dead keratinized cells that provide a barrier against environmental hazards.
- Stratum Lucidum: Only present in thick skin, providing an extra layer of protection.
- Stratum Granulosum: Contains granules that help to waterproof the skin.
- Stratum Spinosum: Provides strength and flexibility to the skin. Contains desmosomes that bind cells together.
- Stratum Basale: Deepest layer where cell division occurs, producing new cells for the outer layers.
Functions of Each Layer:
- Barrier Protection: Prevents pathogens and water loss.
- Cell Renewal: Maintains skin integrity through continuous cell turnover.

Tissue Types: Composed of connective tissues, mainly collagen and elastin.
Major Layers:
- Papillary Layer: Upper layer; contains dermal papillae which increase surface area for nutrient exchange and sensation.
- Reticular Layer: Deeper layer providing strength, elasticity, and structure to the skin.
Functions of Each Layer:
- Support and Nourishment: Provides structural support and houses blood vessels, nerves, and other structures.

Factors Contributing to Skin Colour:
- Melanin Production: Varies in type and amount among individuals, providing pigment.
- Blood Flow: Increased circulation can cause redness, while decreased blood flow can result in paleness.
- Carotene Levels: Another pigment influencing skin tone.

Changes in Skin Colour: Can indicate various health conditions.
- Cyanosis: Bluish discoloration indicating lack of oxygen.
- Jaundice: Yellow skin due to liver dysfunction.
- Erythema: Redness due to inflammation or infection.

Definition: Hairs (pili) are flexible strands made of dead, keratinized cells produced by hair follicles.
Comparison: Hairs and nails are formed from hard keratins, leading to more durable structures compared to epidermal keratin.
Functions of Hair:
- Warning of parasites, insulation, cushioning against trauma, and protection from sunlight.
Parts of a Hair:
- Shaft: Part of the hair that extends above the skin surface.
- Root: Part of the hair embedded in the skin.

Layers of a Hair:
- Medulla: Inner core of the hair; absent in very fine/blonde hair.
- Cortex: Middle layer containing pigment, which determines hair color.
- Cuticle: Outer layer protecting the cortex.
Hair Pigments: Melanins produced by melanocytes determine hair color.
- Pheomelanin: Red pigment contributing to red hair.
- Gray/White Hair: Results from decreased melanin and air bubbles replacing pigments.

Definition: Hair follicle is a skin structure that houses the hair root.
Parts of a Follicle:
- Epithelial Root Sheath: Composed of inner and outer root sheaths.
- Dermal Root Sheath: Surrounds the epithelial sheath from the dermis.
Associated Muscle: Arrector pili muscle—smooth muscle that causes hair to stand upright when contracted.

Hair Matrix: Group of dividing cells producing hair and melanocytes.
Hair Papilla: Dermal tissue providing nutrients via capillaries to the hair.
Hair Root Plexus: Nerve ending that makes hair sensitive to touch.
Hair Growth Cycles: Hair grows for 2-7 years before resting for 2-4 months.

Definition: Sebaceous glands secrete sebum, an oily substance.
Location: Found throughout the body, except palms and soles.
Function: Lubricate hair and skin, prevent water loss, and have bactericidal properties.

Sudoriferous Glands: Responsible for sweat production.
Eccrine Sweat Glands:
- Account for most of the body's sweat, especially in palms and forehead.
- Ducts connect to skin surface, facilitating temperature regulation via evaporation.
Apocrine Sweat Glands:
- Located in specific body areas (armpits, genital regions).
- Produce thicker sweat; body odor results from bacterial breakdown.

Definition: Nails are protective coverings made of hard keratin.
Parts of a Nail:
- Free Edge: Extends past the finger or toe.
- Nail Body: Visible part attached to the skin.
- Nail Root: Non-visible part embedded within the skin.
Nail Matrix: Area of dividing cells responsible for nail growth.

Core vs. Skin Temperature:
- Core: Highest temperature (brain, thoracic, abdominal organs).
- Skin: Lowest temperature.
Heat Distribution: Blood flow carries heat to the skin for loss; mechanisms for controlling temperature are crucial.
Heat-Promoting Mechanisms: Include blood vessel constriction and shivering.
Heat-Loss Mechanisms: Include vessel dilation and sweating.

Frostbite: Occurs when blood flow to skin is restricted due to cold, leading to cell death.
Hypothermia: Defined as low core body temperature, which could lead to severe consequences like coma or death.

Cancer Overview: Occurs when cells grow uncontrollably due to DNA damage.
- Carcinoma: Epithelial tissue cancer.
- Sarcoma: Cancer of connective tissues.
Skin Cancer Types:
- Basal Cell Carcinoma: Most common; originates in stratum basale.
- Squamous Cell Carcinoma: Arises from keratinocytes; grows rapidly.
- Melanoma: Most dangerous skin cancer, highly metastatic.

Rule of Nines: Method to estimate burn extent and associated fluid loss by dividing the body into sections.

First-Degree Burns: Affect epidermis, causing redness, swelling, and pain.
Second-Degree Burns: Affect epidermis and upper dermis, resulting in blisters.
Third-Degree Burns: Full-thickness burns affecting epidermis, dermis, and potentially deeper layers.

Understand hair structure and pigmentation.
Know hair follicle anatomy and function.
Comprehend mechanisms of heat regulation and implications of extreme temperatures.
Recognize characteristics and risks of different skin cancers.
Distinguish between degrees of burns and their treatment implications.