Integumentary System Overview - Dermis and Hypodermis

Introduction to the Integumentary System (Part 2)

  • Focus on the Dermis, Hypodermis, and associated structures.

Dermis

  • Location: Lies between the epidermis and hypodermis.
  • Composition: Connective tissue containing blood vessels, lymphatics, and nerves.
  • Thickness: Thinner in women than in men.

Components of the Dermis

  • Papillary Layer:

  • Composed of areolar tissue.

  • Contains capillaries, lymphatics, and sensory neurons.

  • Named for dermal papillae that project between epidermal ridges.

  • Reticular Layer:

  • Deep to the papillary layer, made of dense irregular connective tissue.

  • Contains collagen and elastic fibers.

  • Collagen fibers blend into the papillary layer and extend into hypodermis.

  • Contains connective tissue cells and accessory organs (hair follicles, sweat glands).

  • Has networks of blood vessels and nerve fibers.

Dermal Strength and Elasticity

  • Collagen Fibers: Strong, resist stretching but bend easily.
  • Elastic Fibers: Allow stretching and recoil to original length.
  • Skin Turgor:
  • Refers to skin's flexibility and resilience (measured with skin pinching).
  • Loss of turgor indicates dehydration.
  • Aging Effects:
  • UV exposure reduces elastin, causing wrinkles and sagging.
  • Stretch marks form from excess stress, e.g., during pregnancy or rapid weight gain.

Cleavage Lines

  • Definition: Arrangements of collagen and elastic fibers in the skin.
  • Clinical Significance:
  • Cuts parallel to cleavage lines heal better with less scarring.
  • Cuts at right angles to lines result in more scarring due to fiber recoil.

Dermal Blood Supply

  • Arterial Supply: Forms networks (cutaneous plexus) at the hypodermis-dermis interface.
  • Supplies dermis and hypodermis, enabling nutrients and oxygen transfer.
  • Papillary Plexus: Smaller arterial branches supplying the papillary layer.
  • Bruises (Contusions): Result from blood vessel rupture, leading to discoloration.

Innervation of the Skin

  • Sensory Receptors: Respond to touch, pain, and temperature.
  • Nerve Fiber Functions:
  • Control blood flow and gland secretion rates.
  • Monitor tactile and other sensory receptors.
  • Types of Receptors:
  • Tactile Corpuscles: Detect light touch, located in papillae.
  • Lamellated Corpuscles: Detect deep pressure and vibration, found in reticular layer.

Hypodermis

  • Structure:Composed of areolar and adipose tissues, providing elasticity.
  • Function: Stabilizes skin position relative to underlying structures while allowing movement.
  • Vascular Supply: Contains large arteries and veins, acting as a blood reservoir.
  • Subcutaneous Fat:
  • Provides insulation and energy reserves for children.
  • Distribution changes with age and hormonal influences (puberty impacts fat distribution).
  • Notably affects body areas: women typically accumulate fat in breasts, hips; men in abdomen and back.