Week 5: Tissue Damage and Trauma Flashcards
What are the causes of tissue damages?
Physical and Chemical Trauma
What are the 3 mechanisms of damage?
Disruption
Metabolic Interference
Free Radicals
What are some causative agents?
Trauma Thermal Injury (Hot or Cold) Poisons Drugs Infectious Organisms Ionising Radiation
Ischaemia is caused by __________ and results in _________________________. The damage caused is _________________________________.
Reduced Blood flow
Accumulation of Metabolites
Repairable until a point of no return
Shock is a pathological process characterised by ____________________ resulting in life threatening ___________ of the bodies vital organs. Compensatory mechanisms maintain blood pressure until ________________________.
Profound circulatory failure
Hypo-perfusion
They fail leading to hypotension
What is Cardiogenic Shock?
Shock commonly due to myocardial infarction - it is the failure of the heart’s pumping mechanism
What is Hypovolemic Shock?
Shock due to reduction in the effective circulation blood volume - loss of blood, loss of fluid, shift of fluid into the cellular component and body cavities and away from the circulation
What are the consequences of shock?
Irreversible neural damage
Renal failure
Cerebral infarction
Infarction in any area/organ
What is inflammation?
Initial reaction of tissue to injury
Vascular phase - dilation and increased permeability
Exudative phase - fluid and cells escape from the permeable venules
What happens if the nucleus or nucleolus is damaged?
- Damages both transcription and translation
- If the cell goes into mitosis before the damage is repaired it leads to cell death
- Damaged DNA can lead to mutations
What happens if the mitochondria is damaged?
- Damage to mitochondria leads to impairment of the metabolic pathways
- This results in energy deficiency, particularly of ATP within the cell
What is hypertrophy?
Increase in the size of individual cells resulting in overall increase in organ size
Example - increased workload on a muscle
What is hyperplasia?
Increase in the number of cells in an organ, also resulting in an increase in organ size
Example - Thickened keratinising squamous epithelium of skin in area of rubbing or chronic irritation
What is Atrophy?
Decrease in cell size and number of cells
Example - Disuse limb immobilised following fracture or loss of innervation
What is Metaplasia?
Reversible change from one differentiated cell type to another
Example - Intestinal metaplasia in the oesophagus in the setting of reflux disease
The effect of injury is dependent on:
Duration of the injury
Type of injurious agent
Type and number of cells involved
Ability of the tissue to resolve and regenerate
What are the possible outcomes after trauma?
Necrosis Apoptosis Inflammation Cell Renewal Organisation/Fibrosis
What is/are Bruising/Contusions?
Blunt impact tears the capillaries and larger blood vessels deep to the skin surface, leading to bleeding into the extravascular space
What are Lacerations?
When the blunt object injury exceeds the elastic capacity of the skin and underlying tissues forceful tearing of the skin occurs
What is Avulsion?
Tearing away of tissue from its attachments for instance skin torn from thigh after fall from height
What is the difference between a stab and an incision?
A stab is deeper than it is long
An incision is longer than it is deep
What is Myocardial Infarction?
Irreversible necrosis of myocardium due to inadequate blood supply
The site and degree of damage of myocardial ischaemia or infarction is dependent on:
- Which vessel is affected and how far along
- How narrow the stenosis
- How great the demands
- How long the imbalance (30 minutes)
- How soon intervention
- Other medical conditions i.e. lung disease
What are the risk factors for atherosclerosis?
Family History Cigarette smoke Diabetes Hyperlipidaemia Infections Haemodynamic forces (Hypertension) Immune mechanisms
What are some complications of atherosclerosis?
Ulceration, Rupture, Haemorrhage, Thrombosis
What are the signs and symptoms of myocardial infarction?
Angina - Radiating chest pain
Nausea and vomiting
Shortness of Breath
What sign on an ECG tell you a heart attack has occurred?
The ST segment is markedly raised above the baseline
What signs in a blood test tell you if a heart attack has occurred?
1 - 4 Hours after symptoms = Myoglobin
3 Hours - Days = Creatine Kinase
3 Hours - Days = Troponin
What are the general treatment options for heart attacks?
Rest, lying f lat, O2
Glyceryl trinitrate GTN (dilates arteries)
Beta blockers (slows heart rate)
What are the acute treatments for heart attacks?
Thrombolysis (dissolves the clot)
Stenting (opens up the stenosis)
What are the chronic treatments for heart attacks?
Aspirin (decreases platelet stickiness)
Stenting
Bypass
What are the Acute consequences of heart attacks?
- Sudden death (40%) > from acute left ventricular failure > from an arrythmia - Other arrythmias - Mural thrombus and thromboembolism - Rupture (free wall or septum or papillary muscle)
What are the Acute consequences of heart attacks?
- Heart failure
- Left ventricular or bi-ventricular
- Arrythmias
- Ventricular aneurysm
> Mural thrombus
> Thromboembolism
What is a stroke/Cerebro-Vascular Accident?
A focal neurological deficit that persists for >24hr
and is due to a vascular cause
What are the causes of CVA/stroke
- Narrowing or blockage of blood vessels supplying the
brain
- Thrombus (50%)
- Embolus (30%) - Rupture of a vessel (hypertension or aneurysm) with
haemorrhage (20%)
The brain is highly dependent on ___________ and therefore is very sensitive to ________.
Aerobic Respiration
Hypoxia
Critical ischaemia occurs when the neuron receives ___% of it’s normal blood supply, then it will __________.
30%
Shut-Down
The site and degree of damage due to a CVA depends on:
Which vessel is affected and where
How complete the block
How long the ischaemia (30 minutes)
How soon intervention
What are the macroscopic features of CVA?
- Soften, loss of definition, pale or haemorrhagic
- Shrunken, yellow, cystic
What are the microscopic features of CVA?
- Neuronal necrosis, pallor of myelin, oedema, haemorrhage
- Macrophages, gliosis but no fibrosis, cystic
change instead of scarring - Haemosiderin
What are the symptoms of CVA?
- Pain
- A decrease or loss of consciousness, ie coma.
- Symptoms and signs are variable and depend on the site of damage and the function of that area
Why might a patient die from a CVA?
- Critical areas are affected (brain stem)
- The damage is too massive
- Increased intracranial pressure can cause coning,
i. e. trying to squeeze the brain out of the skull through the foramen magnum
What are the acute treatments for CVA?
- Support
- Thrombolysis
- Clipping of an aneurysm
- Evacuation of blood clot
What are the chronic treatments for CVA?
Aspirin
How do we prevent CVA?
Prevention of risk factors:
- Atherosclerosis
> HT, smoking, hypercholesterolaemia, DM
- Stent, bypass, surgery of atherosclerotic stenoses
- Aneurysm repair
- Anti-platelet agents
