Integumentary System Lecture - Part 2

Overview

• The integumentary system includes the skin and its appendages: hairs, glands, nails, and the erector pili muscles.
• Skin is considered an organ because it consists of different tissues performing a common function.
• Main skin tissues:
  • Epithelial Tissue: Epidermis
  • Connective Tissue: Dermis
  • Hypodermis: Not technically part of the skin but closely associated

Skin Appendages

• Hairs & Hair Follicles
• Glands: Sweat glands and sebaceous glands
• Nails
• Erector Pili Muscle

Glands

Types

• Sebaceous Glands:
  • Derived from epithelial tissue
  • Associated with hair follicles
  • Produce oily product called sebum (moisturizer for skin and hair)
  • Hormone-regulated (sex hormones like androgens)
  • Linked to acne due to overproduction during puberty
• Sweat Glands:
  • Derived from substances in the blood
  • Eccrine Sweat Glands:
    • Most numerous, produce true sweat (99% water, 1% salt)
    • Simple coiled tubular glands
    • Involved in thermoregulation (cooling via evaporation)
  • Apocrine Sweat Glands:
    • Found in armpits, anal, and genital regions
    • Produce special sweat (milky or yellow)
    • Start to function at puberty
    • May be analogous to sexual scent glands

Hair and Hair Follicles

• Function: Primarily sensory, sense things that lightly touch the skin
• Structure:
  • Medulla: Core with large cells and air spaces
  • Cortex: Surrounds medulla
  • Cuticle: Single layer of cells, prevents flaking; damages lead to split ends
• Color: Determined by melanocytes (combination of black/brown and yellow pigment)
• Hair Follicles: Invaginations of the epidermis surrounded by dermis

Erector Pili Muscle

• Smooth muscle connected to hair follicles
• Causes hair to stand up when cold or scared (goosebumps)
• Creates insulating layer of warm air when hairs stand up

Nails

• Scale-like modification of the epidermis
• Made of hard keratin (do not flake off)
• Structure:
  • Free edge, body, root
  • Nail matrix (responsible for growth)
• Color: Pink due to underlying blood vessels, white area (lunula) due to thickness

Disorders

Skin Cancer

• Caused by uncontrolled cell division, often due to UV light mutations

Burns

• First-degree: Only epidermis damaged
• Second-degree: Epidermis and part of the dermis
• Third-degree: Full thickness burn, through epidermis and dermis
• Threats: Loss of body fluids, risk of infection
• Treatment: Skin grafting for severe burns

Conclusion

• This lecture covered the appendages of the skin, focusing on the glands, hair structures, nails, and related disorders.