Anatomy and Physiology of the Skin

• The integumentary system includes skin, hair, nails, and glands.

Skin Layers

• Epidermis is the outermost layer.
• Dermis lies beneath the epidermis.
• Hypodermis is the deepest layer.
• Deep fascia is connective tissue around muscles.

Main Functions of Skin

• Protection of underlying tissues.
• Temperature regulation using capillary networks and sweat glands.
• Sensation via sensory receptors.

Anatomy Basics

• Anatomy is the study of body structure.
• Physiology is the study of body function.

Subdisciplines of Anatomy

• Gross Anatomy: Systemic and regional studies of visible structures.
• Microscopic Anatomy: Includes histology (tissues) and cytology (cells).
• Surface Anatomy: Study of external features.
• Developmental Anatomy: Focuses on embryology and pathological anatomy.
• Radiographic Anatomy: Study using imaging techniques.
• Functional Morphology: Relationship between structure and function.

Components of the Integumentary System

• Skin is the largest organ, accounting for 7% of body weight, with a thickness of 1.5mm to 4.4mm.
• Hair is a flexible strand of keratinized cells and a skin appendage.
• Nails are protective coverings on digits and a modified epidermis.

Glands of the Integumentary System

• Sweat glands: Eccrine and apocrine types, used for cooling.
• Sebaceous glands: Produce sebum, an oil for skin and hair protection.

Functions of the Integumentary System

• Protection against physical and chemical damage to underlying organs.
• Temperature Regulation: Through capillary networks and sweat glands.
• Excretion: Loss of urea, salts, and water via sweat.
• Vitamin D Production: Epidermal cells synthesize vitamin D with UV radiation.
• Sensory Reception: Sensory receptors for touch, pressure, and pain are housed in the skin.

Layers of the Skin

• Epidermis: Composed of keratinized stratified squamous epithelium.

Epidermis Cell Types

• Keratinocytes: Produce keratin; dead at the skin surface.
• Melanocytes: Produce melanin, a pigment.
• Tactile Epithelial Cells: Sensory nerve endings.
• Dendritic Cells: Role in immune response.
• Dermis: Strong, flexible connective tissue.

Dermis Layers

• Papillary Layer: Contains dermal papillae for nutrient exchange.
• Reticular Layer: Provides strength and houses glands and nerve supply.
• Hypodermis: Contains areolar and adipose tissue which anchor skin and insulate the body.

Layers of the Epidermis

• Stratum Corneum: Thick layer of dead keratinocytes for protection.
• Stratum Granulosum: Keratin production begins; cells are far from capillaries.
• Stratum Lucidum: Only in thick skin (palms, soles); contains flat keratinocytes.
• Stratum Spinosum: Has a "spiny" appearance and contains dendritic cells.
• Stratum Basale: Base layer with actively dividing cells and melanocytes.

Skin Coloration

• Pigments include melanin, carotene, and hemoglobin.
• Melanin: Main pigment produced by melanocytes, impacts skin color.
• Carotene: Yellow-orange pigment from diet.
• Hemoglobin: Affects skin tone, especially in individuals with low melanin.

Skin Health Issues

Burns

• First-degree: Only the upper epidermis is affected.
• Second-degree: The upper dermis is affected, and blisters form.
• Third-degree: Full thickness of the skin is involved, causing extensive damage.

Skin Cancers

• Basal Cell Carcinoma: Most common and least malignant.
• Squamous Cell Carcinoma: Arises from keratinocytes.
• Melanoma: Most dangerous; arises from melanocytes.

The Skin Throughout Life

• Fetal Development: The fetus is covered by lanugo, and sebaceous glands produce vernix caseosa.
• Aging Effects: Thinning skin, reduced elasticity, hair loss, and increased skin inflammation occur.

Test your knowledge of skin structure and function. This quiz covers epidermal layers, pigments affecting skin color, burn classifications, and types of skin cancer. It also explores the functions of skin, sebaceous glands, and melanin-producing cells.