Integumentary System Lecture Notes
Overview
- The integumentary system includes:
- Skin
- Accessory structures: hair, fingernails
- Skin glands: sweat glands, sebaceous glands
Skin Layers
- Epidermis (outer layer)
- Made of stratified squamous epithelium
- No direct blood supply
- Functions in protection
- Dermis (inner layer)
- Made of dense irregular connective tissue
- Contains blood vessels, glands, and follicles
- Hypodermis (beneath dermis)
- Made of adipose tissue
- Provides cushioning and insulation
- Not considered a skin layer
Structures within Skin Layers
- Hair Follicles
- Extend from the epidermis into the dermis
- Made of both epidermal and dermal tissue
- Site of hair growth through cell mitosis
- Sweat Glands
- Eccrine glands: produce sweat for cooling, found throughout the skin
- Apocrine glands: found in armpits and genital regions, active after puberty
- Sebaceous Glands
- Produce sebum (oil) that moisturizes skin and hair
- Erector Pili Muscles
- Attached to hair follicles
- Cause hair to stand (goosebumps)
Dermis Layers
- Papillary Layer
- Upper layer of dermis
- Contains dermal papillae which form friction ridges and fingerprints
- Reticular Layer
Epidermis Layers
- Stratum Basale
- Deepest layer
- Undergoes continuous cell division
- Contains melanocytes (produce melanin) and Merkel cells (sensory)
- Stratum Spinosum
- Cells accumulate prekeratin
- Provides strength and flexibility
- Stratum Granulosum
- Cells start dying, accumulating granules
- Preparing for apoptosis due to lack of blood supply
- Stratum Lucidum
- Found only in thick skin (palms and soles)
- Adds extra protection
- Stratum Corneum
- Outermost layer
- Composed of dead keratinized cells
Thick vs Thin Skin
- Thick Skin
- Found on palms of hands and soles of feet
- Contains five layers in the epidermis
- Provides extra protection against abrasion
- Thin Skin
- Found on all other body parts
- Contains four layers in the epidermis
Functions of the Integumentary System
- Protection against environmental hazards
- Regulation of body temperature
- Sensory perception
- Vitamin D synthesis
- Excretion of waste through sweat
Summary
The integumentary system plays a crucial role in protecting the body, regulating temperature, and providing sensory information. Understanding the structure and function of the skin's layers and their components is vital for comprehending how the body maintains homeostasis.