Unit 4 study guide

Integumentary System Overview

• The integumentary system consists of the skin, the body's largest organ.

• Key functions of the skin include:

  • Protection against external dangers like UV radiation and pathogens.
  • Sensation through receptors for touch, temperature, and pain.
  • Temperature regulation through vessel dilation and sweat.
  • Excretion of waste through sweat.
  • Vitamin D synthesis, crucial for bone health.

Skin Structure: Epidermis & Dermis

• Epidermis: The thin outer layer, composed of stratified squamous epithelium.

  • The outermost layer is the stratum corneum, made of keratin and waterproof.
  • Contains melanocytes and keratinocytes.

• Dermis: The thick inner layer, primarily composed of connective tissue.

  • Provides support and elasticity to the skin.

Skin Color: Pigmentation

• Melanin: Pigment ranging from yellow to dark brown.

  • Melanocytes in the base layer of the epidermis produce melanin granules which are packaged into melanosomes.
  • These melanosomes are released and transferred into skin epithelial cells (keratinocytes), giving them color.

• Two Types of Melanin:

  • Eumelanin: Brown-black. More eumelanin results in darker skin.
  • Pheomelanin: Red-yellow. More abundant in people with lighter skin.

• Carotene: Yellowish pigment found in the stratum corneum and fatty layer under the skin.

  • Carotene and melanin together contribute to a yellowish hue.

Skin Color and UV Radiation

• Highly energetic UV radiation from the sun can cause cell damage, DNA mutations, and folate breakdown (essential for reproduction).

• Melanin's Protective Role:

  • Melanin acts as a shield by forming a cap around a cell's nucleus, absorbing UV radiation.
  • UV radiation triggers melanocytes to produce more melanin as a defensive mechanism.

• Geographic UV Intensity & Skin Color:

  • Stronger UV radiation is correlated with darker skin in different populations.
  • Humans don't have uniformly dark skin because UVB radiation is essential for vitamin D synthesis.

• Vitamin D & Skin Color:

  • Vitamin D is crucial for calcium absorption, supporting bone health and a healthy immune system.
  • People in areas with weaker UV radiation have lighter skin (less melanin) to absorb enough UVB for vitamin D production.

Skin Glands: Sebaceous & Sweat Glands

• Sebaceous Glands: Secrete sebum, an oily substance that lubricates and protects the skin and hair.

  • These glands are particularly active during puberty due to hormonal changes and can contribute to acne.

• Sweat Glands:

  • Eccrine Glands: Found throughout the body, primarily involved in temperature regulation by releasing sweat, which evaporates for cooling.
  • Apocrine Glands: Mainly located in the armpits and groin, secreting a thicker sweat that can lead to body odor when broken down by bacteria

Other Integumentary System Components: Hair & Nails

• Hair: Grows in hair follicles within the dermis.

  • Growth starts at the papilla (structure at the follicle base), influenced by hormones and blood flow to the papilla.
  • New cells are formed, pushing existing cells upward and filling them with keratin.
  • The arrector pili muscle causes hair to stand up when cold or stressed.

• Nails: Formed from cells in the epidermis and composed of hard keratin.

  • Key structures include the lunula (visible white part at the nail base) and the nail root (hidden under the skin where growth begins).

• Sensory Receptors: Various receptors in the skin allow us to experience temperature, touch, and pain.

Skin Conditions and Homeostasis: Thermoregulation

• The skin plays a crucial role in maintaining homeostasis by regulating body temperature.

• Thermoregulation Mechanisms:

  • Vasodilation: Widening of blood vessels, helps release heat.
  • Vasoconstriction: Narrowing of blood vessels, helps conserve heat.
  • Sweat Glands: Assist in cooling through evaporation.