Case 3 - Respiratory Flashcards
How many lobes in the left lung
2
How many lobes in the right lung
3
Explain ventilation/perfusion in the lung
Perfusion much better at the bottom. Ventilation/perfusion ratio most efficient at around rib 3.
How is blood pH controlled by the lungs
The amount of CO2 in the blood controlled by the amount expired
Condition with low lung compliance
Fibrosis
Condition with high lung compliance
emphysema
Lung auscultation sounds and what they indicate
Wheezing - bronchitis, emphysema
Crackling - Fibrosis, COPD
Stridor - epiglottitis, croup
Pleural rub - pleurisy, lung cancer
Risk factors for lung disease
Family history
Smoking
Lack of exercise
Pollutants
What is the purpose of surfactant
To increase pulmonary compliance.
To prevent atelectasis (collapse of the lung) at the end of expiration.
To facilitate recruitment of collapsed airways.
What’s the most common cause of pharyngitis
Streptococcus pyogenes
Describe the impact of chronic respiratory disease on cardiac function
increased vasoconstriction of pulmonary arterioles increases pulmonary blood pressure. This causes right ventricle hypertrophy and therefore decreases the volume of the right ventricle. There is a back-up of blood in the venous system and therefore the symptoms include oedema of the ankles, sacrum or abdomen.
Pulmonary causes of dyspnoea
chronic obstructive pulmonary disease (COPD)
asthma
interstitial lung disease (ILD), including pulmonary fibrosis
bronchiectasis
industrial or occupational lung diseases such as asbestosis, which is caused by being exposed to asbestos
lung cancer
Neural control of ventilation
The muscles responsible for inspiration (the diaphragm and intercostal muscles) are skeletal muscles and so, unlike cardiac muscle, require nervous stimulation to trigger muscle contraction. Several groups of neurons, located in the pons and medulla are responsible for generating the rhythmic pattern of breathing. The cells bodies of these neurons form the respiratory control centre in the medulla, which sends impulses to stimulate the contraction of the diaphragm and intercostal muscles – via the phrenic nerve and intercostal nerves respectively. Once the neurons stop firing, then the inspiratory muscles relax and expiration occurs
Chemical control of ventilation
Central chemoreceptors are located on the ventrolateral surface of the medulla oblongata. They respond indirectly to blood pCO2 but not to pO2. CO2 diffuses across the blood-brain barrier from blood to cerebral spinal fluid (CSF) while H+ and HCO3- are unable to. As the blood CO2 readily passes the blood-brain barrier into the CSF it will react with H2O to make H2CO3, that will split into HCO3- and H+.
CO2 + H2O → HCO3- + H+
An increase in H+ concentration will directly stimulate the chemoreceptor neurons in the medulla oblongata. They will relay this information and cause an increase in ventilation which will lead to a decrease in CO2. The central chemoreceptors are responsible for ~80% of the response to CO2 concentration.
Peripheral chemoreceptors are located in carotid and aortic bodies that have neuro-epithelial cells that contact with sensory nerve terminals. They respond to changes in pO2, pCO2 and pH. When they are stimulated, K+ channels close and Ca2+ channels open. This causes an increase in initiation of dopamine, impulses to respiratory centre via the glossopharyngeal nerves (N IX) and an increase in ventilation. The peripheral chemoreceptors are responsible for ~20% of the response to an increase in pCO2.
How can obesity affect ventilation
Obesity is a restrictive lung disease. It can cause decreased lung volume due to pressure on the chest wall. Fat prevents diaphragm from fully descending so a full breath cannot be achieved. Can cause sleep apnoea and obesity hypoventilation syndrome.
