Layers of the Skin and Types of Epithelium

Layers of the Skin

• Epidermis
  • Protects the Dermis
  • Prevents toxins and bacteria from entering the body
  • Reduces friction
  • Prevents fluid loss
  • Provides skin flexibility and strength
  • Develops new skin cells
• Dermis
  • Nourishes and supports the Epidermis
  • Contains hair follicles and dermal papillae that generate hair shafts
  • Houses sensory receptors including tactile and lamellated corpuscles
• Hypodermis
  • Provides insulation and structure to the skin

Components of the Epidermis

• Stratum Corneum
  • Outermost layer
  • Composed of dead skin cells, providing a barrier against environmental damage
• Stratum Lucidum
  • Present in thick skin (palms, soles)
  • Provides an additional layer of protection
• Stratum Granulosum
  • Contains keratinocytes that produce keratin
  • Prevents fluid loss
• Stratum Spinosum
  • Provides strength and flexibility to the skin
  • Contains keratinocytes and immune cells
• Stratum Basale
  • Deepest layer where new skin cells are generated
  • Contains melanocytes (pigment production) and Merkel cells (touch sensation)

Glands Associated with the Skin

• Sebaceous Gland
  • Releases sebum (oil)
  • Helps keep skin moisturized
• Apocrine Sweat Gland
  • Scent glands located in specific areas (e.g., armpits, groin)
  • Associated with hair follicles
• Eccrine (Merocrine) Sweat Gland
  • Distributed widely across the skin
  • Helps cool the surface of the skin through sweat secretion

Sensory Receptors

• Tactile Corpuscle
  • Transmits touch vibrations
  • Provides sensitivity to light touch
• Lamellated (Pacinian) Corpuscle
  • Sensitive to deep pressure and vibration

Types of Skin

• Thin Skin
  • Lacks stratum lucidum
  • Contains four layers of skin
• Thick Skin
  • Contains all five layers, including stratum lucidum
  • Typically found on palms and soles

Types of Epithelium

• Stratified Squamous Epithelium
  • Non-keratinized and keratinized forms
  • Provides protection against pathogens (e.g., esophagus)
• Simple Squamous Epithelium
  • Reduces friction, found in alveoli of lungs
• Simple Cuboidal Epithelium
  • Secretion role, found in kidney tubules
• Simple Columnar Epithelium
  • Secretion and absorption, found in the lining of the stomach
• Transitional Epithelium
  • Permits stretching, found in the urinary bladder
• Pseudostratified Ciliated Columnar Epithelium
  • Moves mucus with cilia, found in the nasal cavity

Connective Tissue Types

• Areolar Connective Tissue
  • Surrounds nerves and organs
  • Provides cushioning
• Adipose Connective Tissue
  • Stores fat
  • Provides padding and insulation, particularly in the buttocks and deep skin
• Dense Regular Connective Tissue
  • Found between skeletal muscles, reduces friction
• Dense Irregular Connective Tissue
  • Found in the dermis of the skin, prevents overexpansion
• Hyaline Cartilage
  • Provides flexible support, found between tips of ribs
• Bone Tissue (Osseous)
  • Provides structure and support to the body
• Blood Tissue
  • Vascular tissue that circulates nutrients and gases

Muscle Tissue Types

• Skeletal Muscle Tissue
  • Stabilizes the skeleton, voluntary control
• Cardiac Muscle Tissue
  • Circulates blood in the heart, involuntary control
• Smooth Muscle Tissue
  • Regulates diameter of blood vessels, involuntary control