Week 4 Flashcards
What happens during alveolar ventilation
During inhalation, not all alveoli are ventilated equally. Alveoli at base receive most, apex receive least (50% difference)
Where is the weight of fluid in the plural cavity the greatest?
Base of lung (due to gravity)
Where are the alveoli with the highest compliance?
At the base (due to increased intrapleural pressure resulting from weight of fluid in the pleural cavity). These alveoli also are less expanded so they can be filled with more air.
What are the elements of the respiratory zone?
Respiratory bronchioles
Alveolar ducts- Controls the flow of air to the alveoli
Alveolar sacs
Alveoli
Where is the greatest perfusion in the lungs
At the base. Gravity results in more blood flowing to the lower sections of the lung
What does the ventilation to perfusion ratio tell us and what is its general equation.
It tells us whether there are any areas of imbalance with either ventilation or perfusion within the lungs.
V/Q where V= ventilation, Q= perfusion
In a healthy individual, what are the normal ranges for V/Q ratios
In middle of lung: 1 because ventilation and perfusion are the same
At base of lung: 0.3 greater perfusion
At apex: 2.1 where ventilation is greater
Systemic Circuit
High pressure system
Vascular resistance regulates blood flow
Pulmonary Circuit
Low pressure system
Parallel pathways to blood flow
Low vascular resistance
Restrictive Pulmonary disorders
Pulmonary fibrosis, pulmonary oedema
Obstructive Pulmonary disorders
Asthma, chronic bronchitis, emphysema
Pathology of pulmonary fibrosis
Scarring of lung tissue
Reduces lung compliance
Inhibits oxygen diffusion
Caused by: autoimmune, TB, asbestosis
Pathology of pulmonary oedema
Most commonly caused by heart problems: Congestive heart failure (Left ventricle of left AV valve dysfunction causing blood to back up into pulmonary vessels which forces fluid to pool in alveoli), Hypertensive episode ( increased after load inhibiting. Left ventricle SV)
Asthma pathology
Asthma is associated with chronic inflammation of the bronchial tubes. Characterised by bronchospasms, increased mucus secretion, and airway obstruction
Chronic bronchitis pathology
Inflammatory condition resulting in:
Excess thick mucus secretion
Loss of ciliary function
Increased risk of infection
Emphysema pathology
Causes the loss of alveolar walls
Results in:
Large air spaces that remain full of air after exhalation which prevents new oxygen rich air from entering the lungs
Air flow equation
Flow= pressure gradient/ resistance
Modulators of airway diameter
Muscarinic receptors (bind acetylcholine- causes bronchoconstricition)
B adrenergic receptors (bind epinephrine - causes bronchodilation)
Effect of acidosis
Depression of CNS - loss of synaptic transmission
Effect of alkalosis
Causes overexcitement of CNS and PNS - nervousness, muscle spasms, convulsions
Respiratory Acidosis
Results from high carbon dioxide concentration. Failure to maintain adequate alveolar ventilation and/or perfusion to remove carbon dioxide.
Causes: lung diseases
Metabolic acidosis
Too much acid is produced by working cells. Failure of the kidneys to remove hydrogen ions.
Causes:
Ketoacidosis
Lactic acidosis
Severe diarrhoea resulting in loss of bicarbonate ions
Respiratory alkalosis
A decrease in carbon dioxide resulting in decreased production of carbonic acid.
Causes:
Hyperventilation
Anxiety
Altitude changes
Metabolic alkalosis
High systemic blood concentration of hydrogen carbonate ions. These bind to readily free hydrogen ions neutralising them and decreasing pH
Causes:
Extreme vomiting
