- Function: protection, temperature regulation, moisture retention
- Major cell types: keratinized squamous epithelial cells and melanocytes
- Layers (top to bottom):
- stratum corneum
- stratum lucidum
- stratum granulosum
- stratum spinosum
- stratum basale (contains pluripotent stem cells)
- "Californians Like Girls in String Bikinis"
- From basale to corneum, cells mature and lose their organelles and become keratinized
- Function: Structure, sensation, wound healing.
- Contains hair follicles, sebaceous glands, apocrine glands , specialized nerve endings, and vasculature
- Mostly made up of extracellular matrix: collagen, glycosaminoglycans, proteoglycans, and glycoproteins
- Major cell types: fibroblasts, langerhans cells, pluripotent stem cells (in hair follicles), endothelial cells
- Layers (top to bottom)
- papillary dermis
- reticular dermis
- Subcutaneous Tissues
- Consist of fat, muscle, tendon, ligament, bone, etc.
|Normal Wound Healing
- Phases: not discrete, but rather overlapping
- Hemostasis (1-24h)
- Endothelial damage leads to exposure of the basement membrane, activation of intrinsic and extrinsic coagulation cascade, and ultimately deposition of fibrin with creation of a platelet plug.
- Platelets are integral to initiating wound healing. They release cytokines that cause leukocyte migration and chemotaxis into the wound.
- Inflammation (1-5d)
- Mast Cells
- Native cells Initiate the inflammatory phase
- Secrete cytokines that cause vasodilation and increase vascular permeability
- Allows influx of neutrophils and macrophages to the wound bed
- present early in inflammatory phase
- clear intralesional pathogens
- prepare the wound bed by removing damaged cells
- secrete cytokines that stimulate infux of macrophages.
- Present late in inflammatory phase
- Early on act in coordination with neutrophils to phagocytose bacteria and dead cells
- Secrete cytokines and growth factors that drive fibroblast proliferation and angiogenesis
- Also act to downregulate the initial infammatory response
- Proliferation (3-7d)
- Fibroblasts lay down type III collagen
- Myofibroblasts (fibroblasts with contractile filaments) initiate wound contraction
- Angiogenesis and vasculogenesis lay down new blood vessels
- Granulation tissue (newly laid collagen with neovascularization) forms
- Epithelialization occurs from surrounding basal keratinocytes and hair follicle basal cells
- Maturation (Up to 1 year)
- Type III collagen remodeled to type I collagen
- Vessels mature, and excess vasculature involutes
- Erythema and raised appearance of wound resolves
|Types of Wound Healing
- Primary Intention - Wound edges are approximated. Grafts and flaps are considered primary closure.
- Secondary Intention - Wound edges are left open and allowed to fill in
- Tertiary Intention - Wound edges are left open and allowed to granulate, and are approximated and closed at a later time. Also known as delayed closure.
AVERAGE 4.0 of 2 RATINGS
Qbank (0 Questions)
Level of Evidence 5 and Other Journal Articles (includes Case Reports, Expert Opinions,
Personal Observations, and Biomechanic Studies)
Shah N. Hidradenitis suppurativa: a treatment challenge. Am Fam Physician. 2005 Oct 15;72(8):1547-52.
PMID:16273821 (Link to Abstract)
- First Aid for the USMLE STEP 1. Le, Tao. New York: McGraw-Hill Medical, 2013.
- Rapid Review Pathology Revised Reprint. Goljan, Edward. New York: Mosby, 2011.
- Clinical Microbiology Made Ridiculously Simple 5th Ed. Gladwin, Mark. Miami: MedMaster Inc, 2011.
- medEssentials for the USMLE Step 1. Manley, Michael. New York: Kaplan Publishing, 2012.
- Katzung & Trevnor's Pharmacology Examination and Board Review. Trevor, Anthony. New York: Lange Medical Books, 2012.
Wilke, K.; Martin, A.; Terstegen, L.; Biel, S. S. (June 2007). "A short history of sweat gland biology" (PDF). International journal of cosmetic science 29 (3): 169–179. doi:10.1111/j.1467-2494.2007.00387.x. ISSN 1468-2494.