PP - Tissue repair Flashcards
Polyp Def:
- a mass, that projects above the mucosal surface to form macroscopically visible structure
- this term says us nothing about its histological structure
Where are the polyp the most common?
in the gut- the mass that protrudes into the lumen
What are the shapes of a polyp?
- pedunculated
- sessile
What can be the cause of polyp?
- hyperplasia or abnormal mucosal maturation, inflammation or architecture
^these polyps are NON-neoplastic - others may be caused by submucosal or mural tumours
True neoplastic lesions:
the polyps that arise as a result of epithelial proliferation and dysplasia
Hypertrophy:
- increase in the size of cells resulting in increase in the size of the organ
- no new cells, just bigger, enlarged cells
Hyperplasia:
increase in cell number
What can only undergo hypertrophy?
The striated cell muscle cells in both skeletal muscles and heart can undergo only hypertrophy because in the adult they have limited or no capacity to divide
What are the mechanism of myocardial hypertrophy?
- mechanical triggers such as strech
- trophic triggers such as activation of alfa-adrenergic receptors
In which cases do we have pressure-overloaded ventricles?
- hypertention
- aortic valve stenosis
Developed concentric hypertrophy:
increased wall thickness and reduction of the cavity diameter
In which cases do we have volume overload?
in aortic valve insufficiency
What develops concentric hypertrophy?
pressure-overloaded ventricles
Eccentric hypertrophy (myocardial hypertrophy):
volume overload (in aortic valve insufficiency) -hypertrophy with ventricular dilation - eccentric hypertrophy
Concentric hypertrophy (Ma=macro level):
ventricular wall is thick, the heart wight is increased (normal weight ranges from 300-350g)
Concentric hypertrophy (Mi=micro level):
- myocyte diameter increases (thickening and elongation)
- typically associated with prominent irregular nuclear enlargement and hyperchromasia.
- no mitoses
- increased interstitial fibrosis
Generally, how are tissues repaired?
tissues can be repaired by regeneration with completely restoration of form and function or by replacement with CT and scar formation
How does repair by CT start?
repair by CT starts with the formation of granulation tissue and culminates in the laying down of fibrous tissue
What are the three main phases of wound healing?
- inflammation
- formation of granulation tissue
- ECM deposition and remodeling
Neutrophils:
- ingest and kill bacteria
- release enzymes destroying damaged tissue
Macrophages:
phagocytose debris, when filled with indigestible material, lose motility and turn into epitheloid histiocytes, release chemoattractants (see this slide)
Granulation (Mi=micro level):
proliferation of fibroblast and new, thin-walled, delicate capillaries in a loose ECM
Young, new tissues:
- oedematous
- highly vascular
- rich in fibroblast
- minimal mature collagen
remodeling by digestive enzymes are in ECM
-> metalloproteinases MMPs
Healing by primary intention:
wound with closely opposed edges -> small scar
Healing by secondary intention:
wound with tissue loss -> large scar
Sequence of wound healing:
- early stage
- mid-stages
- late stage
Early stage (wound healing)
- plasma fibrins -> blood clot
- next: neutrophils, macrophages
Mid-stage (wound healing)
fibroblast, formation of granular tissue
Late stage (wound healing)
contraction of the wound site, type I collagen (bone, skin) replaces type III collagen
Metaplasia:
the reversible change of differentiation of maternal cells in which one adult cell type (epithelial or mesenchymal) is replaced by another cell type (transformation of a mature tissue into another, also mature one)
