Overview
This lecture covers the structure, functions, and clinical significance of the integumentary system, with a focus on the skin's layers, accessory structures, and related disorders for the ATI TEAS 7 exam.
Functions and Importance of the Integumentary System
- The skin is the largest organ and regulates body temperature and fluid balance.
- Acts as a barrier against physical damage and pathogens.
- Site for vitamin D synthesis and provides sensory information.
Structure and Layers of the Skin
- The skin has three main layers: epidermis, dermis, and hypodermis (subcutaneous tissue).
- Epidermis layers (from outermost to innermost): Stratum corneum, lucidum, granulosum, spinosum, and basale ("Come Let's Get Sunburned").
- Stratum corneum: Dead, tough, keratin-filled cells.
- Stratum lucidum: Transparent layer found in thick skin (palms/soles).
- Stratum granulosum: Cells flatten, accumulate granules, and form a water barrier.
- Stratum spinosum: Contains keratinocytes and Langerhans cells (immune function, phagocytosis).
- Stratum basale: Single layer of dividing cells, contains melanocytes (produce melanin) and Merkel cells (touch sensation).
Dermis and Hypodermis
- Dermis contains blood vessels, nerves, sweat glands, hair follicles, collagen, and elastin fibers.
- Divided into papillary (loose connective tissue) and reticular (dense connective tissue) layers.
- Deep cuts into the dermis can cause scarring due to irregular collagen alignment.
- Hypodermis is mainly adipose (fat) tissue, providing insulation and connecting skin to bones/muscles.
Accessory Structures
- Sweat glands cool the body via perspiration and aid temperature regulation.
- Sebaceous glands secrete oil to lubricate and waterproof skin/hair.
- Hair follicles originate in the dermis; hair shaft is made of dead keratinocytes.
- Nails grow from the nail root (epidermis) and protect finger/toe tips; made from dead keratinocytes.
Clinical Significance: Skin Disorders
- Skin cancer is common; types include basal cell carcinoma, squamous cell carcinoma, and melanoma.
- Skin cancers often result from uncontrolled cell growth due to UV radiation.
- Burns are classified by depth (first to fourth degree); deeper burns can destroy nerves and cause less pain but greater risk for infection and fluid loss.
Key Terms & Definitions
- Keratinocytes — Cells producing keratin for waterproofing and toughness in the epidermis.
- Melanocytes — Cells in the stratum basale that produce melanin pigment.
- Langerhans cells — Immune cells in the epidermis that phagocytize debris and pathogens.
- Fibroblasts — Dermal cells that produce collagen and elastin.
- Adipose tissue — Fat-storing tissue in the hypodermis.
- Sebaceous glands — Oil-producing glands for skin/hair lubrication.
- Basal cell carcinoma — Skin cancer arising from stratum basale cells.
- Melanoma — Cancer arising from melanocytes.
- Burn degrees — Classifications of burns by depth: first (epidermis), second (dermis), third (full skin), fourth (tissue/muscle/bone).
Action Items / Next Steps
- Review and memorize the skin layers with the mnemonic “Come Let's Get Sunburned.”
- Study types and causes of skin cancers.
- Understand burn classifications and associated complications.