EP

• Skin is the largest organ in the human body and is part of the integumentary system
• Skin helps maintain internal body temperature and fluid balance
• Skin acts as a physical barrier, protecting internal structures and organs from damage and invasion of pathogens
• Vitamin D is produced in the skin
• Skin has sensory functions, allowing us to be aware of external stimuli like a ladybug landing on our arm
• Epidermis layers:

  • Stratum corneum: outer top layer consisting of dead cornified cells
  • Stratum lucidum: found in thick skin areas, also consisting of cornified cells with a transparent appearance
  • Stratum granulosum: contains keratinocytes with granules, eventually becoming cornified cells
  • Stratum spinosum: contains layers of keratinocytes and cells that act like macrophages, looks spiny under a microscope
  • Stratum basale: deepest layer with basal cells constantly undergoing mitosis, also contains melanocytes and Merkel cells
• Dermis:

  • Contains blood vessels, sweat glands, hair follicles, and nerves
  • Made of collagen and elastin fibers produced by fibroblasts
  • Consists of papillary and reticular layers
  • Scars can form in the dermis if cuts penetrate this layer
• Hypodermis:

  • Located under the dermis, connects skin to bone and muscle tissue
  • Contains adipose tissue for insulation
• Accessory structures of the integumentary system:

  • Sweat glands help regulate body temperature
  • Sebaceous glands produce oil to waterproof skin and hair
  • Hair follicles are found in the dermis, with cells rapidly dividing to push outward as hair grows
  • Nails are made of dead keratinocytes, with the nail root containing cells undergoing mitosis
• Importance of studying the integumentary system:

  • Understanding the system helps in diagnosing and treating skin cancers like basal cell carcinoma and melanoma
  • Knowledge of the system is crucial in treating conditions like burns, which can compromise skin functions and lead to infections
• The integumentary system is composed of the skin and its associated structures, such as hair, nails, sweat glands, and sebaceous glands
• Functions of the skin:

  • Maintaining internal body temperature
  • Protecting internal organs from damage
  • Serving as a barrier against pathogens
  • Producing vitamin D
  • Facilitating sensory functions
• Keratinocytes are cells found in the epidermis that produce keratin, a protein that helps cells be water-resistant and tough
• Layers of the epidermis, from outer to inner:

  • Stratum corneum
  • Stratum lucidum (only in thick skin areas)
  • Stratum granulosum
  • Stratum spinosum
  • Stratum basale
• Melanocytes produce melanin, a pigment that gives skin its color and protects it from UV rays
• The dermis is composed of connective tissue, blood vessels, sweat glands, hair follicles, and nerves. It contains collagen and elastin fibers produced by fibroblasts
• Scars form when cuts penetrate the dermis layer of the skin, causing the body to produce collagen to repair the damage. The arrangement of collagen in scars is different from the original skin, leading to visible differences in texture and appearance
• The hypodermis is the layer of tissue beneath the dermis that connects the skin to underlying bone and muscle tissue. It contains adipose tissue, which serves as stored body fat and provides insulation
• Accessory structures of the integumentary system:

  • Sweat glands
  • Sebaceous glands
  • Hair
  • Nails
• Sweat glands help regulate body temperature by producing sweat, which evaporates from the skin surface, cooling the body
• The integumentary system regulates body temperature through mechanisms such as sweating, dilation or constriction of blood vessels in the dermis, and insulation provided by adipose tissue in the hypodermis
• Hair is composed of keratin and is non-living. It grows from hair follicles located in the dermis
• Nails grow from the nail root, where cells undergo mitosis and are pushed outward, forming the nail body
• Studying the integumentary system is important for understanding skin conditions, such as skin cancer, burns, and infections, and for developing effective treatments for these conditions
• Common types of skin cancer:

  • Basal cell carcinoma
  • Squamous cell carcinoma
  • Melanoma
• Burns are classified based on the depth of tissue damage:

  • First-degree burns (superficial)
  • Second-degree burns (partial thickness)
  • Third-degree burns (full thickness)
  • Fourth-degree burns (involving muscle and bone)
• Burns can damage the skin's ability to regulate temperature, protect against infection, and maintain fluid balance, posing serious health risks. Severely burned areas may require medical intervention to restore skin function and prevent complications
• The dermis has two general layers: 

  papillary layer – which has connective tissue   that is more loose and a deeper reticular layer  – where connective tissue is more tightly packed.
• Scar to Keloid

  • the fibroblasts are generating collagen   to fix the damage, they tend to not arrange  it in the pattern that had originally been   there before and accessory structures that  we’ll get to later (like sweat glands or   hair) won’t be re-created there.
  • Scar tissue  also tends to have less elasticity – meaning   really large scars from large wounds can even  affect range of movement.