Anatomy and Wound Healing of the Skin: Epidermis, Dermis, and Wound Phases, Exams of Medicine

Download Anatomy and Wound Healing of the Skin: Epidermis, Dermis, and Wound Phases and more Exams Medicine in PDF only on Docsity! NAWCO WCC REVISION QUESTIONS AND ANSWERS. Epidermis - \Thin, outer layer of skin Dermis - \Thicker, inner layer of skin Subcutaneous fatty tissue - \Layer of loose connective tissue Deeper tissues - \Muscle, tendon, ligament, joint capsule, and bone Basement Membrane Zone (BMZ) - \Anchors the epidermis to the dermis, affected in blister formation. disrupted during wound healing and must be reformed. Lamina Lucida - \Zone in the BMZ (electron-translucent zone) Lamina Densa - \Layer in the BMZ (electron-dense zone) Major Proteins of BMZ - \Fibronectin, Laminin, Type IV Collagen, Heparin Sulfate Proteoglycan Stratum Basale - \Layer of the epidermis - one cell thick. only layer of epidermis in which cells undergo mitosis, forms the BMZ Stratum Spinosum - \Layer of the epidermis - Consists of several rows of more mature keratinocytes, which appear spiny under a microscope. Stratum Granulosum - \Layer of the epidermis - Contains 3-5 flattened cell rows with increasing concentrations of keratin. Stratus Lucidum - \Layer of the epidermis - Thin, clear layer of dead skin cells found in thick skin. Stratum Corneum - \Layer of the epidermis - Consists of dead cells, sheds easily, contains keratin, functions as a barrier to the environment and prevents trans-epidermal water loss. Cells of the epidermis - \Keratinocytes, Langerhans' cells, Melanocytes, Merkel's cells Keratinocytes - \Responsible for the toughness of the skin, produces keratin - the basic component of hair, skin., and nails. Langerhan's Cells - \Help protect the body against infection - provide allergen recognition and assist with immunity Melanocytes - \Responsible for producing melanin Merkel's Cells - \Mechanoreceptors that provide information on light tough sensation Epidermal Appendages - \Sebaceous glands, hair follicles, eccrine sweat glands, apocrine sweat glands, nails. Sebaceous Glands - \Secrete sebum into hair follicles Hair follicles - \Contribute to appearance, body temperature, protection, and sensation Eccrine sweat glands - \Produce sweat to help regulate body temperature and assist with elimination of waste products Apocrine Sweat Glands - \Produce sweat - responsible for body odor. Nails - \Made of dead cells containing keratin Functions of the epidermis - \Protective barrier to the outside environment, mitosis, pigmentation, self image, and Vitamin D production. Dermal Layers - 3. Eventually granulation tissue is replaced by scar tissue 4. Granulation tissue is red, beefy and shiny with a granular appearance vii. Contraction 1. Wound contraction decreases the size of the defect 2. After skin trauma or injury, fibroblasts in the wound bed are transformed into myofibroblasts which are instrumental in achieving wound contraction 3. Myofibroblasts pull the wound together, decreasing the size of the defect viii. Epithelialization 1. Resurfacing of the wound with keratinocytes 2. Epithelial cells at the wound margins and epidermal appendages multiply 3. In a leapfrog fashion, these cells migrate across the wound bed 4. Epithelial cells cannot migrate over nonviable tissue 5. A moist wound bed facilitates movement Maturation & Remodeling - \i. The granulation-tissue matrix, laid down during the proliferative phase, must be strengthened and reorganized to fit the surrounding tissue ii. As new collagen is formed, old collagen is broken down iii. Immature scars are red, raised, and rigid iv. Mature scars are pale, planar, and pliable v. Remodeling continues up to 2 years following wound closure vi. Scar tissue has at most only 80% of the original tissue's strength and elasticity vii. An immature scar is modifiable viii. A mature scar is no longer modifiable ix. Scar contracture describes the pathological shortening of scar tissue resulting in deformity Primary Intention - \i. Simplest and fastest type of wound closure ii. Principally involves regeneration and resurfacing of the wound iii. Involves re-epithelialization only iv. Superficial wounds v. Deeper wounds with well-approximated edges vi. Lower risk of infection, minimal tissue loss, and minimal scarring Secondary Intention - \i. Consists of wound repair, unlike primary intention which involves regeneration and resurfacing ii. Wound edges are not approximated iii. Granulation tissue must be built iv. Greater degree of tissue loss v. Higher risk of infection vi. Longer healing times vii. Visible scarring Delayed Primary (Tertiary) Intention - \i. Combination of healing by primary and secondary intention ii. Use with contaminated wounds to decrease the risk of infection