Module 5.3: The Dermis

Learning Outcomes

  1. Describe the layers and basic structure and components of the dermis

  2. Explain the functions of the dermal papillae

  3. Explain how skin markings such as epidermal ridges form


Layers of Skin

Papillary Layer

  • Most superficial

  • accounts for 20% of depth

  • Made of loose connective tissue

  • contains fibroblasts and phagocytes

  • at the dermis-epidermis junction, special collagen fibers anchor the basement membrane

  • repetitive trauma, may cause the junction to separate thus causing a blister

  • The junction appears to have dermal projections (dermal papillae) fitting the epidermis

  • in these dermal papillae, are capillaries, extending to the superficial part of the dermal papillae to diffuse nutrients

  • They also house tactile (Meissner) corpuscles, which aids to distinguish light touch, texture and shape


Reticular Layer

  • Deeper and thicker

  • Composed of mainly irregular connective tissue

  • continuous with the papillary and hypodermis, making a clear boundary difficult to find

  • contains elastin, but it can tear and will form striae, or stretch marks

  • contains ground substance rich in proteoglycans and fibroblasts

  • the proteoglycans draw water to ground substance, making skin hydrated and firm

  • pockets of adipose tissue are found but are a majority in the hypodermis

  • Blood vessels, sweat glands, hair, sebaceous glands, and many sensory receptors

  • lamellated (Parcinian) corpuscles are sensory receptors that look like onions when cross sectioned

  • Lamellated corpuscles respond to deep pressure and vibrations



Skin Markings

  • The dermal papillae are especially prominent on the plantar surfaces of the hands and toes

  • This then causes thick collagen fibers to arrange them into dermal ridges that enhance gripping

  • occur in patterns: Loop, Arch, and Whorl

  • tiny sweat pores on these surfaces leave a thin film, which is our fingerprint

  • The reticular layer creates skin markings through gaps between the bundles of collagen

  • These gaps are called tension, or cleavage, lines

  • these lines run in circular patterns in neck and trunk, but longitudinally in the limbs and head

  • The direction of the lines are important as if they run parallel to them, it is less likely to scar and heal easier

  • The reticular layer is anchored tight to deeper structures around joints, which creates deeper creases known as flexure lines

  • Flexure lines are found on the palms and posterior of the fingers and toes