Satia Cellula Injury Flashcards
What are the two major forms of cell death?
Necorsis and apoptosis
What is coagulative necrosis?
Desaturation of intracytoplasmic proteins
dead tissue is firm then soft
typically in ischaemic injury EXCEPT THE BRAIN
WHAT IS COLLQUATIVE NECROSIS?
Seen in brain e.g. stroke
glial reaction at periphery with cyst formation
What is caseous necrosis?
Characteristic of TB
macro - cheese like
micro - no structure
What is gangrenous necrosis?
Necrosis with putrefaction of tissues due to certain bacteria e.g. Clostridia or Streptococci
What makes tissue black in gangrenous necrosis?
Iron sulfide from degraded haemoglobin
What causes gas gangrene?
C perfringens
What type of necrosis is seen in malignant hypertension?
Fibrinoid necrosis
What are some mediators of apoptosis?
p53
bcl-2
fas (CD 95)
Caspases
How is bcl-2 related to tumours
inhibits apoptosis, therefore expression leads to failure of initiation of apoptosis
overexpressed in neoplasia
What is pyknosis
nuclear shrinking
what is karyorrhexis
nuclear fragmentation
What disease increase apoptosis?
HIV
Neurodegenerative diseases
What are labile cells?
Good capacity for regeneration
e.g. surface epithelial cells constantly being replaced by cells from deeper
What are stable cells?
divide at a slower rate under physiological conditions
replaced by mitotic division of mature cells and lost cells are rapidly replaced e.g. liver and renal tubular epithelium
What are permanent cells?
Never divide in post natal life cannot be replaced if lost
e.g. nerve cells
Outline the process of organisation
Fibrinous exudate
Removal of fibrin and dead tissue by phagocytes
Migration of fibroblasts and capillaries forming granulation tissue
Replacement of exudate by vascularised fibrous tissue
eventually a collagen rich scar develops
Describe the formation of granulation tissue
Capilary endothelial cells grow into the area to be repaired
Fibroblasts are stimulated to divide
Fibroblasts secrete collagen and matrix components
Fibroblasts acquire muscle filaments and become myofibroblasts
What is proud flesh?
excessive granulation tissue protruding above the wound surface
Issues with organisation
Fibrous adhesions in the peritoneum ma cause intestinal obstruction
obliteration of the pericardial space - constrictive pericarditis
Issues with wound contraction
Stenosis
Stricture
Scarring in muscle = contracture
Contractures following burns
Describe healing by primary intention
Edges opposed
Fibrin helps to stick the edges together
Capillaries bridge the gap
Fibroblasts invade fibrin network
After 10 days wound is strong and sutures can be removed
remodelling
Describe healing by secondary intention
Tissue loss
Phagocytes remove debris
Formulation of granulation tissue at base of wound
Myofibroblasts cause contraction
Re-epithelialisation
Tissue deficit replaced by scar tissue
What is keloid?
Excessive fibroblast proliferation and collaagen production
Collagen deposits beyond and above wound
covered by normal epithelium
Describe Hyperophic scar
Does not extend beyond wound borders
Describe bone repair
Haematoma
Macrophages invade haematoma with polymorphs and fibroblasts
new vessels grow
Fibrosis by the end of the week
Osteoblasts grow into haematoma and form trabeculae of woven bone
The new bone is called callus
Internal callus is within the medullary cavity
External callus is related to the periosteum
Woven bone replaced by lamellar bone
Remodelling takes place in the direction of mechanical stress
What factors affect bone remodelling?
Movement
misalignment
interposition of soft tissues
infection
pre-existing bone disease
What is wallerian degeneration
Is the process that occurs when a nerve is cut or crushed.
- It occurs when the part of the axon separated from the neuron’s cell nucleus degenerates.
- It usually begins 24 hours following neuronal injury and the distal axon remains excitable up until this time.
- The degeneration of the axon is followed by breakdown of the myelin sheath, a process that occurs by infiltration of the site with macrophages.
- Eventually regeneration of the nerve may occur although recovery will depend on the extent and manner of injury
What is Neuropraxia?
Nerve intact but electrical conduction is affected
Full recovery
Autonomic function preserved
Wallerian degeneration does not occur
What is neurotmesis?
Disruption of the axon, myelin sheath and surrounding connective tissue.
Wallerian degeneration occurs
What is axontmesis
Axon is damaged and the myelin sheath is preserved. The connective tissue framework is not affected.
Wallerian degeneration occurs
Erosion vs Ulcer of GIT
Erosion is loss of part of thickness of mucosa
Ulcer is loss of full thickness
Where in the GI tract do anastomoses heal the best?
Upper
What tumours are produced by UV light?
BCC SCC and malignant melanoma
