Integumentary System Overview

Integumentary System

• Composed of cutaneous membrane and accessory structures.
• Cutaneous membrane consists of the epidermis and dermis.

Hypodermis

• Contains loose connective tissue separating the integument from deeper organs and fascia.

Functions of Skin and Hypodermis

• Provides protection to underlying tissues and organs.
• Facilitates excretion of salts, water, and organic wastes.
• Regulates body temperature.
• Produces keratin for protection.
• Synthesizes vitamin D from UV exposure.
• Stores lipids for energy.
• Detects sensations like touch, pressure, pain, and temperature.

Skin Layers

• Thick skin contains the stratum lucidum; thick skin found on palms and soles.
• Skin layers from deep to superficial: stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum.

Epidermis Color Factors

• Influenced by dermal blood supply and epidermal pigmentation.

Perspiration Types

• Insensible perspiration: imperceptible water loss.
• Sensible perspiration: noticeable water loss.

Skin Pigments

• Carotene: orange-yellow pigment found in epidermal cells.
• Melanin: brown to black pigment produced by melanocytes, located in stratum basale, protects skin from UV radiation.
• Hemoglobin: pigment in red blood cells affecting skin color.
• Cyanosis indicates blue coloration of the skin due to lack of oxygen.

Vitamin D Production

• Vitamin D3 synthesized when epidermal cells in lower layers convert cholesterol-related substances upon UV exposure.

Skin Cancer Characteristics

• ABCDE: Asymmetry, Border, Color, Diameter, Evolution.

EGF Functions

• Promotes cell division in basal and spinosum layers.
• Accelerates keratin production in keratinocytes.
• Stimulates skin development and repair after injury.
• Enhances the activity of epithelial glands.

Dermis Structure

• Composed of papillary and reticular layers.
• Dermatitis is inflammation affecting the papillary layer.

Cut Healing

• Cutting parallel to cleavage lines leads to faster healing with minimal scarring.

Nerve Fiber Functions

• Regulate blood flow and adjust gland secretion.
• Monitor sensory receptors in dermis and epidermis.

Sensory Receptors

• Tactile discs: detect touch, located in deepest epidermal layer.
• Tactile corpuscles: sensitive to light touch in dermal papillae.
• Lamellated corpuscles: responsive to deep pressure and vibration in reticular layer.

Hypodermis Importance

• Stabilizes skin position relative to underlying tissues and allows independent movement.

Functions of Subcutaneous Fat

• Provides insulation, reduces heat loss, serves as energy reserve, and acts as a shock absorber.

Hair Follicles

• Surrounded by a sensory nerve plexus.
• Arrector pili muscle contraction causes goosebumps.
• Club hair results from inactive hair follicles.
• Vellus hairs are fine body hairs; terminal hairs are thicker, pigmented, and may be curly.
• White hair results from lack of pigment or presence of air bubbles in hair shaft.

Sebaceous Glands

• Oil glands that secrete oily substances into hair follicles.
• Sebum inhibits bacterial growth, lubricates hair, and conditions skin.
• Sebaceous follicles release sebum directly onto the epidermis.

Sudoriferous Glands

• Apocrine sweat glands located in specific areas (armpits, nipples) and discharge into hair follicles.
• Merocrine glands secrete directly onto skin surface, aiding in cooling, excretion, and protection.

Ceruminous Glands

• Modified sweat glands in the external ear pathway.

Nervous System Control

• Autonomic Nervous System regulates activation of sebaceous and apocrine glands subconsciously.

Nail Anatomy

• Nail production occurs at the nail root.
• Nail body consists of dead, keratin-packed cells.

Wound Healing

• Involves granulation tissue—a mix of blood clot, fibroblasts, and capillaries.
• Keloid refers to thick, raised scar tissue.

Wound Repair Phases

• Four key phases: Inflammatory, Migratory, Proliferation, and Maturation.