A&P1 3.2 Integumetary System Pt 2 Lecture Notes

Integumentary System Functions

  • Protective barrier against environment.

  • Contains receptors for touch, pain, temperature (mechanoreceptors, thermoreceptors, nociceptors).

  • Involves thermoregulation to maintain body temperature.

  • Stores and metabolizes energy, nutrients, vitamins.

  • Excretes waste through sweat and skin oils.

Skin Responsiveness

  • Largest sensory organ; houses the majority of receptors.

  • Sensitivity varies by receptor density across the body.

  • Sensory receptors send information to the brain's sensory cortex, which processes this information.

Hair and Nails Structure

  • Hair composed of visible hair shaft and root, surrounded by hair follicle.

  • Hair root has a matrix similar to skin's regenerative structure; uses different keratin type compared to skin.

  • Nails mirror hair growth, contributing to sensation through counterforce on mechanoreceptors.

Skin Thermoregulation

  • Skin area approximately 15-20 square feet.

  • Thermoregulation involves regulation of blood vessels (BV): dilation (wider) or constriction (narrower).

  • Mechanisms for heat loss and conservation are vital for homeostasis.

Skin Metabolic Functions

  • Hypodermal fat is a significant energy storage site.

  • Adipose tissue breaks down triglycerides for energy.

  • Vitamin D production through 7-dehydrocholesterol, essential for calcium and phosphate absorption.

Skin Excretory Functions

  • Sweat glands participate in excretion; duct openings in the skin.

  • Composition includes sodium, chloride, urea (waste product from breakdown).

  • Uremic frost indicates kidney failure, showing high urea levels on the skin surface.

Study Guide Points

Questions:

  1. Know the three types of body receptor found in the skin

  2. Know what determines the sensitivity of the skin to stimuli and where the densest collections of sensory receptors are found in the skin

  3. Know how and where sensory information from the skin is mapped and processed in the brain, and how skin receptor density correlates with the amount of processing area in the brain

  4. Know the structure of skin and nails, including the names and functions of all parts of both discussed in class and the difference between soft and hard keratin

  5. Know and be able to define the following terms: crosslinking (keratin), root hair plexus, hair shaft, hair root, hair follicle, hair matrix, nail root, nail matrix

  6. Know how the hair/hair matrix and nail/nail matrix are similar to the regenerative/keratinized layers of the epidermis

  7. Know how skin and nails contribute to the responsiveness function of skin

  8. Know how thermoregulation occurs in skin and know the homeostatic control mechanisms involved in heat conservation and heat loss (stimulus, receptor, controller, effector, response)

  9. Know the metabolic functions of the skin

  10. Know the excretory functions of the skin

Answers:

  1. The three types of body receptors found in the skin are mechanoreceptors (for touch), thermoreceptors (for temperature), and nociceptors (for pain).

  2. The sensitivity of the skin to stimuli is determined by receptor density. The densest collections of sensory receptors are found where sensitivity is highest, though the note doesn't specify exact locations, it states sensitivity varies by receptor density across the body.

  3. Sensory information from the skin is sent to the brain's sensory cortex, where it is mapped and processed. Skin receptor density correlates with the amount of processing area in the brain; areas with higher receptor density (e.g., fingertips) have larger representation in the sensory cortex.

  4. Hair Structure: Composed of a visible hair shaft and a root, surrounded by a hair follicle. The hair root has a matrix similar to the skin's regenerative structure. The note differentiates that hair uses a different keratin type compared to the skin (implying 'hard' vs 'soft' keratin, with hard keratin for hair and nails).
    Nail Structure: Nails mirror hair growth and contribute to sensation.

  5. The note provides partial definitions for some terms:

    • Hair shaft: Visible part of the hair.

    • Hair root: Part of the hair surrounded by the hair follicle, containing a matrix.

    • Hair follicle: Structure surrounding the hair root.

    • Hair matrix: Regenerative structure in the hair root, similar to the skin's regenerative structure.

    • Nail matrix: (Implied by "nail/nail matrix are similar to the regenerative/keratinized layers of the epidermis").
      (Other terms like crosslinking (keratin), root hair plexus, nail root are mentioned but not defined within the provided text).

  6. The hair matrix and nail matrix are similar to the regenerative/keratinized layers of the epidermis because they are sites of active cell division and keratin production that lead to growth and regeneration, much like the stratum basale of the epidermis.

  7. Skin, as the largest sensory organ, houses the majority of receptors for touch, pain, and temperature, directly contributing to responsiveness. Nails contribute to sensation by providing counterforce on mechanoreceptors, enhancing tactile discrimination.

  8. Thermoregulation in the skin occurs through the regulation of blood vessels (BV), which can undergo dilation (widen to release heat) or constriction (narrow to conserve heat). Homeostatic control mechanisms for heat loss involve blood vessel dilation and sweat production; for heat conservation, they involve blood vessel constriction.

  9. The metabolic functions of the skin include: storage of energy in hypodermal fat, breakdown of triglycerides by adipose tissue for energy, and Vitamin D production through 7-dehydrocholesterol, which is essential for calcium and phosphate absorption.

  10. The excretory functions of the skin involve sweat glands, whose duct openings are in the skin. Sweat composition includes sodium, chloride, and urea. High urea levels on the skin surface (uremic frost) can indicate kidney failure.