Molecular
What players are first on the scene of a wound?
Platelets
This subtype of collagen predominates in granulation tissue and is later replaced during remodeling (2 extra points if you name the type of collagen it is converted to)
Collagen Type III (Type 1)
What vitamin antagonizes the effects of corticosteroids on wound healing and collagen formation?
Vitamin A
These scars remain within the borders of the original wound
Hypertrophic scars
What skin substitute contains keratinocytes and fibroblasts from neonatal foreskin cells?
Apligraf
What cell type produces collagen and ECM proteins? (100 pts) In what phase do they predominate? (100 pts)
Fibroblasts, proliferative phase
When is type III collagen laid down?
Proliferative phase
A serum albumin <___g/dl indicates malnutrition
Albumin of <3.5g/dl
Myofibroblasts
Name the three phases of skin graft healing. (50 points extra per timeline)
1. Imbibition (24-48hrs)
2. Inosculation (48-72hrs)
3. Neovascularization (72hrs- 7days)
What cell type drives capillary growth and angiogenesis?
Endothelial cells through VEGF stimulation
What form of bone healing occurs through a cartilage intermediary?
Endochondral ossification
What lab value is useful for assessing acute protein malnutrition (150pts) and what numerical value marks malnutrition (150pts)?
Prealbumin, <15 mg/dl
What is the recommended surgical principle for excising a keloid?
Subtotal excision - leaving a small rim of keloid tissue as the body will likely have a decreased healing response and less likely to trigger excessive collagen production
What are the layers/components of Integra?
Bovine collagen, glycosaminoglycans, silicone
Describe the order in which inflammatory cells arrive to a wound?
1. Neutrophils arrive 0 to 48 hours to kill bacteria and remove dead tissue
2. Macrophages/monocytes arrive 48 to 72 hours phagocytose debris and secreted growth factors for angiogenesis and extracellular matrix formation
3. Lymphocytes/mast cells arrive day 5 to 7 regulate inflammation and play a role in the transition from the inflammatory to the proliferative phase, helping to form granulation tissue and promoting angiogenesis
Name the phases of wound healing (100 points extra for timeline of each)
1. Inflammatory (0 to 6 days)
2. Proliferative (4 to 24 days)
3. Remodeling (21 days to 1+ years)
+/- hemostasis as a phase.
What element is a crucial cofactor for MMPs in epithelial regeneration?
Zinc
Keloids are associated with an increased expression of what cytokine?
TGF-B, increases fibroblast proliferation
Describe the differences in primary and secondary contraction between the two types of skin grafts?
STSG: less primary contracture, increased secondary contracture
FTSG: increased primary contracture, decreased secondary contracture
Full thickness grafts contain higher dermal collagen thus primarily contract more, but due to preservation of dermal appendages there is minimal secondary contraction and a better long-term aesthetic/functional outcome
What enzymes break down type III collagen? (Name both of its its names)
Matrix metalloproteinases (MMPs; MMP-1, MMP-8, MMP-13), collagenase
all collagenases are MMPs but not all MMPs are collagenase
Tensile strength is restored by what biochemical modification of collagen
Lysyl oxidase cross-linking
A vitamin c deficiency impairs wound healing due to the lack of a hydroxylation of these two amino acids, destabilizing collagen.
Proline and lysine
At 3 weeks, scars regain what % of their final tensile strength?
30%
7 days= 3%
21 days = 30%
60 days = 80%
NEVER REACHES 100%
Using the phases of skin graft healing, describe why a full thickness graft in a poorly prepared recipient bed is more likely to fail?
Failure of plasmatic imbibition results in inadequate inosculation leading to necrosis from lack of oxygen and nutrition