Skin Structure and Function - Dermis
Nerve cells
(receptors terminate in epidermis): provide sensation for pain, touch, pressure, and temperature.
Papillary dermis
- The upper part of the dermis located just below the basement membrane. - The dermal papillae interlock with the epidermal rete ridges. -The dermal papillae contain capillary loops that deliver nourishment to the epidermal basal layer. -(Papillary loops supported by plexus that runs horizontal to skin - more vulnerable to vertical "point pressure" than to evenly distributed horizontal forces.
Reticular dermis
- the area that lies beneath the papillary dermis. It contains an extensive vascular plexus, lymphatics, and collagen. - Normal dermis is comprised primarily of Type 1 collagen (77 - 85%).
Key cells: fibroblast
-The fibroblasts synthesize connective tissue proteins such as collagen and elastin - the 2 primary proteins found in the skin. -Collagen provides the skin with tensile strength and elastin provides recoil/memory to the skin -skin can stretch and then return to normal.
Subcutaneous Tissue:
-The hypodermis contains adipose tissue, connective tissue, blood vessels, lymphatics,and nerve endings. -The adipose tissue provides protection from pressure and padding against shear forces. Patients with inadequate subcutaneous tissue- such as neonates and the elderly) are at high risk for deep tissue damage causedby shear force and pressure - especially if the patient is allowed to slide. -Subcutaneous tissue cannot regenerate
Dermis.
-The inner layer of the skin, also called the corium; has two layers/zonesand important cellular and structural components. -Thickness varies from 2 - 4 mm but averages 2 mm.
Fascia and muscle:
-This tissue layer is very well-vascularized and is therefore the most sensitive to ischemia - pressure damage usually begins here. -Fascia and muscle do not regenerate when there is tissue death
Mast Cells
-produce histamine and other proteins important to inflammation and defense. -Mast cells, macrophages, and lymphocytes jointly form the skin immune system.
Dermal layers/zones
1) Papillary dermis 2) Reticular dermis 3) Key Cells: Fibroblast 4) Key cells: Macrophage 5) Mast Cells 6) Nerve cells 7) Epidermal Appendages
Key cells: macrophage
Macrophages are phagocytic cells derived from monocytes; they provide defense against pathogens for the skin and for any open wounds.
Regeneration capability
Most dermal structures capable of regeneration; deep dermal structures (epidermal appendages) do NOT regenerate
Epidermal appendages
Structures located in the dermis but lined with epidermal cells that can reproduce (e.g., hair follicles, sebaceous glands, sweat glands). Note: Most dermal structures capable of regeneration;
