Integumentary System Overview

Overview of the Integumentary System

• Composed of skin, glands, hair, nails, blood vessels, nerves, and sensory organs.
• Has three layers: epidermis, dermis, hypodermis.
• Integument means covering; cutaneous refers to skin.

Structure of the Epidermis

• Surface layer made of stratified squamous keratinizing epithelial tissue.
• Lacks blood vessels; outermost cells are routinely lost.
• Key layers include:
  • Stratum Germinativum (innermost): Site of cell mitosis, pushes older cells to the surface.
  • Stratum Corneum (outermost): Composed of dead cells, provides waterproof barrier.

Stratum Germinativum Details

• Also known as stratum basale, is where new cells are produced.
• Cells take about one month to move from the basal layer to the surface.
• Contains keratinocytes that produce keratin and Merkel cells for touch sensation.
• Converts cholesterol to Vitamin D via UV exposure.

Other Epidermis Layers

• Stratum Spinosum: Contains cells that reproduce and have a shiny appearance due to keratin.
• Stratum Granulosum: Flattened cells rich in keratin, acts as a barrier.
• Stratum Lucidum: Present in thick skin (palms, soles), offers protection against friction.

Stratum Corneum Details

• Protects underlying layers, consists mainly of dead keratinized cells.
• Acts as a barrier to pathogens and chemicals; keratin aids in water retention.
• Flaking helps remove microorganisms from skin surface.

Immune and Pigmentation Cells

• Langerhans Cells: Originating from bone marrow, these macrophages initiate an immune response.
• Melanocytes: Located in lower epidermis, produce melanin which protects against UV damage and provides color to skin and hair.

Structure of the Dermis

• Known as true skin; made of elastic connective tissue, blood vessels, and nerves.
• Contains hair follicles, sweat and oil glands, and sensory receptors.
• Fibroblasts generate collagen and elastin, providing strength and elasticity.

Hair and Nail Follicles

• Hair follicles are epidermal tissue; new hair cells are produced at the hair root.
• Hair functions include insulation, protection from dust and sweat.
• Nail follicles produce nails to protect fingers and toes, involving keratin production.

Sensory Receptors

• Situated in the dermis, responsible for touch, pressure, heat, cold, and pain sensations.
• Specific receptor types include free nerve endings (for heat, cold, pain) and encapsulated nerve endings (for touch and pressure).

Glands Types and Functions

• Sebaceous Glands: Secretes oil (sebum) to inhibit bacterial growth and prevent skin drying.
• Ceruminous Glands: Located in ear canals, secrete earwax (cerumen) to keep eardrum pliable and repel insects.
• Sweat Glands:
  • Apocrine Glands: Found in axillae and genital areas, active during stress, produce odor.
  • Eccrine Glands: Distributed across the body, vital for temperature regulation via sweat.

Blood Vessels Function

• Arterioles in the dermis regulate temperature through vasodilation and vasoconstriction.
• Prolonged pressure may lead to decubitus ulcers due to reduced blood flow, risking skin necrosis.

Hypodermis/Subcutaneous Tissue

• Connects skin to underlying muscles, consists of loose connective tissue and adipose tissue.
• Contains white blood cells that help in pathogen destruction and inflammation.

Functions of Adipose Tissue

• Stores fat for energy, provides cushioning, and insulation.
• Women typically have higher adipose tissue percentage compared to men.

Functions of the Skin

• Protection: Serves as a barrier against infection and environmental toxins.
• Fluid Retention: Prevents dehydration, maintaining a wet environment for cells.
• Waste Elimination: Excretes wastes through perspiration.
• Temperature Regulation: Manages heat through sweat evaporation and blood vessel adjustments.
• Sensory Function: Contains various nerve endings making the skin a key sensory organ.