Lecture Notes: The Integumentary System

Overview

• The integumentary system includes the skin, hair, and nails.
• Primary function: Protection
  • Keeps bacteria and foreign objects out.
  • In animals: scales (reptiles), feathers (birds).
• Other functions:
  • Sensation (tactile receptors in the skin).
  • Thermoregulation (goosebumps, vasodilation, sweat glands).
  • Synthesis of Vitamin D from sunlight.

Importance

• Protection against environmental hazards.
• Sensation of touch and pain.
• Regulation of body temperature.
• Synthesis of Vitamin D critical for bone health (prevents rickets).

Structure of the Skin

Epidermis

• Top layer of the skin, consists of four main layers.
• Layers of the Epidermis
  • Stratum Basale
    • Location of mitosis; new cells are created here.
    • Contains melanocytes which produce melanin.
  • Stratum Spinosum
    • Spiny appearance due to dye; contains melanosomes for skin color.
  • Stratum Granulosum
    • Granular appearance; cells begin to die as they move up.
  • Stratum Lucidum
    • Found only in thick skin (palms and soles).
  • Stratum Corneum
    • Top layer, composed of dead cells.
• Mnemonic: 'Come, Let's Get Sunburned' (Corneum, Lucidum, Granulosum, Spinosum, Basale).

Dermis

• Contains capillaries and glands (sweat and sebaceous).
• Contains nerve receptors for light and deep touch.
• Pain receptors present to prevent skin damage.

Hypodermis (Subcutaneous Layer)

• Contains connective tissue, fat cells, and stem cells.
• Contains fibers (reticular and elastic).

Accessory Structures

Hair

• Composed of dead cells pushed up from the matrix.
• Contains keratin for durability.
• Surrounded by sebaceous glands that secrete oil.

Nails

• Formed similarly to hair, from a matrix at the base.
• Contains keratin and forms cuticle (epinysium).
• Evolved from claws to aid in tool use.

Conclusion

• The integumentary system is crucial for protection, sensation, thermoregulation, and vitamin D synthesis.
• Remember the three layers: epidermis, dermis, hypodermis.
• Remember the four layers of epidermis using the mnemonic.
• Key structures include hair and nails.