Integumentary System Module 7.1

The Integumentary System

• The integumentary system consists of the skin, accessory organs, and three layers of tissue.
• It provides a physical barrier against most invasions, regulates body temperature, aids in the senses of touch and feel, and protects the body from UV radiation.

The Skin

• The skin is composed of three layers: the epidermis, dermis, and hypodermis.
• The epidermis is made up of stratified squamous epithelium, with no blood vessels to supply nutrients to its cells.
• The dermis is made up of fibrous connective tissue, with collagen and elastic fibers that are continuous with the fibers in the hypodermis.
• The hypodermis is made up of adipose tissue and loose connective tissue, and contains large blood vessels.

Epidermis

• The epidermis has no blood vessels, so nutrients diffuse from the arterioles in the dermis.
• The epidermis has four layers: stratum basale, stratum spinosum, stratum granulosum, and stratum corneum.
• Stratum basale receives most of the nourishment, while stratum corneum is the outermost layer, made up of dead, keratinized cells.
• Keratinization is the process of producing keratin, a protein that makes cells tough and waterproof.

Dermis

• The dermis is made up of fibrous connective tissue.
• It contains arterioles that supply nutrients to the epidermis.
• It also contains collagen and elastic fibers that are continuous with the fibers in the hypodermis.

Hypodermis

• The hypodermis is made up of adipose tissue and loose connective tissue.
• It contains large blood vessels.
• It acts as a heat insulator against the cold climate and stores fat.

Accessory Organs

• The hair, pili arrector muscle, sebaceous gland, sudoriferous gland, and nails are all accessory organs.
• The hair is made up of keratinized cells, and its growth is affected by nutrition and hormones.
• The sebaceous gland produces sebum, which helps to waterproof the skin and hair.
• The sudoriferous gland produces sweat, which promotes evaporation and helps to regulate body temperature.

Functions of the Integumentary System

• Protection: physical, chemical, and biological barriers against external factors.
• Temperature regulation: through sweating, vasoconstriction, and vasodilation.
• Excretion: waste materials such as ammonia, urea, and excess salt are eliminated through sweating.
• Vitamin D synthesis: the epidermal layer of human skin synthesizes vitamin D when exposed to UV radiation.
• Cutaneous sensation: receptors in the skin detect sensations such as heat, cold, pressure, and touch.

Thick Skin vs Thin Skin

• Thick skin has all five layers, and is found in areas where there is a lot of abrasion, such as the fingertips, palms, and soles of the feet.
• Thin skin only has four layers, and is thinner due to the absence of the stratum lucidum layer.### Nails
• Made of keratin
• Protect the ends of fingers and toes
• Prevent over-sensitization of nerve receptors

Burns

• 1st degree burns: only the epidermis is damaged, with redness and swelling
• 2nd degree burns: epidermis and upper region of dermis are involved, with redness, swelling, and blisters
• 3rd degree burns: all layers of skin are burned, requiring a skin graft to repair

Skin Cancer

• Most skin tumors are benign
• Cause of cancer is unknown, but probably due to overexposure to ultraviolet radiation
• Types of skin cancer:
  • Basal cell carcinoma: most common, usually benign, and affects cells in stratum basale
  • Squamous cell carcinoma: arises from keratinocytes in stratum spinosum, more aggressive than basal cell carcinoma
  • Malignant melanoma: most dangerous, cancer of melanocytes in stratum basale, and grows and migrates rapidly

Muscular System

• Types of muscle fibers:
  • Oxidative fibers: rely on aerobic respiration, have many mitochondria, rich blood supply, and large amount of myoglobin
  • Glycolytic fibers: use glycolysis as primary source of ATP, have less myoglobin, and tire more easily
• Skeletal muscles:
  • Striated muscles: have light and dark bands
  • Uses ATP from glycolysis or aerobic respiration
• Muscle contraction:
  • Requires myosin-binding sites to be uncovered
  • Calcium ions bind to troponin complex to expose myosin-binding sites
• Muscle types:
  • Slow-twitch fibers: contract slowly, sustain longer contractions, and are oxidative fibers
  • Fast-twitch fibers: contract rapidly, sustain shorter contractions, and can be glycolytic or oxidative

Nervous Control of Muscle

• Motor unit: consists of a single motor neuron and all the muscle fibers it controls
• Action potential: produced by a motor unit, results in all muscle fibers within the motor unit to contract
• Graded contractions:
  • Can be achieved by varying the number of fibers that contract
  • Can be achieved by varying the rate at which fibers are stimulated
• Recruitment: the recruitment of multiple motor neurons results in stronger contractions

Skeletal System

• Types of skeletal systems:
  • Hydrostatic skeletons: consist of fluid held under pressure in a closed body compartment
  • Exoskeletons: hard external skeletons
  • Endoskeletons: internal skeletons
• Functions of skeletal system:
  • Provides support and protection
  • Allows for movement
  • Produces movement through muscle contractions

Locomotion

• Types of locomotion:
  • Locomotion on land: walking, running, hopping, or crawling
  • Swimming: moving through water
  • Flying: moving through air
• Adaptations for locomotion:
  • Land: support and move against gravity
  • Water: overcome friction
  • Air: develop lift to overcome gravity

This quiz covers the integumentary system, focusing on the skin and its layers, including the stratum corneum and epidermis.