4.3 The Dermis

• The dermis is immediately deep to epidermis, consists of loose connective tissue above a dense network of connective tissue fibers
• Two laters of dermis are the superficial papillary and the deeper reticular
• Papillary later is superficial of dermis, consists of loose connective tissue
• Papillary layer provides mechanical attachment for superficial epidermis
• Papillary layer contains capillaries and axons of neurons
• Papillary layer gets name from dermal papillae projecting between epidermal ridges
• Reticular layer consists of fiber interwoven in dense irregular connective tissue around glands, vesicles, and nerves
• Reticular layer name comes from interwoven collagen fiber bundles
• Reticular layer some of its fibers extend into the papillary layer, making the boundary unclear
• Reticular layer is responsible for strength, toughness, and elasticity of the skin
• Interwoven collagen fibers of the reticular layer have tension and elastic fibers of the dermis which allow it to stretch and recoil
• Age, hormones, and UV reduce the thickness and flexibility of the skin
• Skin wrinkles and creases, creating a network of stretch marks
• Tension lines or clevage lines are the pattern of fiber bundles
• Cutaneous plexus: arteries and veins with interconnected network between reticular layer of dermis and subcutaneous later
• The cutaneous plexus branches supply adipose tissue of subcutaneous layer
• The cutaneous plexus has small arteries toward epidermis, branches supply glands, follicles, etc
• Subpillary plexus: a branching network of small arteries entering into the papillary layer
• The subpillary plexus contains capillaries then empty and rejoin papillary plexus
• The subpillary plexus contains larger veins then drain into vein network in deeper cutaneous plexus
• Thermoregulation is the control of body temperature
• Greater body temperature leads to increased circulation to skin which permits loss of excess heat
• Lesser body temperature leads to decreased circulation to skin which promotes heat retention
• The total blood volume remains constant
• Nerve fiber functions

  • control blood flow
  • adjust gland secretion rates
  • monitor sensory receptors in dermis and deeper layers of epidermis
• Tactile discs are sensory nerve endings
• What is the relationship between dermis' collagen bundles and tension lines of the skin.

  A cut parallel to the tension line closes easily and heals better. Cuts made at right angles to tension lines sever elastic fibers
• Explain the anatomy of cutaneous plexus.

  A network of arteries and veins between the reticular layer of the dermis and the subcutaneous layer.