Respiratory Week 4: Revision Based Questions

Respiratory Week 4 Revision Based Questions 1. Compliance and elasticity are important factors that much be kept in balance. (5 marks) 2. Define elasticity and compliance (1 mark) 3. Explain how ONE pathology may increase compliance while decreasing elasticity and how may this affect the normal functioning of the lungs. (2 marks) 4. Explain how ONE pathology may decrease compliance while increasing the elasticity of the lungs and how may this affect the normal functioning of the lungs. (2 marks) Answer: a. Compliance refers to the ability of lungs to expand. Elasticity refers to the ability of the lungs to resists stretch. b. Emphysema increases compliance and decreases elasticity. This is because in emphysema there is increased elastase which destroys the elastin of the lungs which destroys the alveolar sacs decreasing the surface area. This means that when air gets in it will be trapped and the alveolar will not be able to causing recoiling due to decreased elastin. c. Pneumonia increases elasticity and decreases compliance. This is because in this condition there is increased inflammation and thus leading to fibrosis of lung tissue. Due to this the lungs will not be able to expand due to dead and dysfunctional tissue, this causes decreased compliance as dysfunctional tissue cannot expand or stretch. Moreover, these tissue cause increase tendency to be recoiled since they do not expand. 5. Answer the following questions about airway resistance. (9 marks) a. b. c. d. Define airway resistance (0.5 marks) Write down the formula for airway resistance. (0.5 marks) Explain how the parasympathetic nervous system affects air flow and resistance (4 marks) Explain how the sympathetic nervous system affects air flow and resistance (4 marks) Answer: a. Airway resistance refers to the force that opposes airflow b. c. The parasympathetic nervous system releases Ach which binds on M3-R which stimulates Gaq pathway. This will stimulate PLC, which leaves IP3 into DAG and PIP2 these will increase the concentration of calcium within the airway smooth muscle. Since there will be increased levels of Ca2+ there will be increased interaction between myosin and actin hence the contraction of the airways. This will decrease the diameter and hence increase the resistance and decrease blood flow as per formula in part b. d. The sympathetic nervous system releases catecholamines which as epinephrine and norepinephrine which bind to beta 2 androgenic receptors on smooth muscle. This will stimulates of AC -> conversion of ATP into CAMP -> activation of PKA -> prevent the activation of myosin light chain kinase and allows phosphatase to dominate -> this will prevent the phosphorylation of L-type Ca2+ channels and prevents the addition of phosphate to myosin heads -> this prevents the formation of cross bridge -> hence prevents contraction which increase the radius thus the diameter. This will decrease airway resistance and increase airflow. 6. Describe the three functions of the pleural space (3 marks) Answer: • • • Allows chest expansion during inspiration to draw air in Provides cohesion to keeps the of the lungs attached to the thoracic wall Allows movement between the visceral and parietal pleura 7. Name the two fasciae of the pleural cavity and what each of the covers. (2 marks) Answer: • • Fascial membrane: covers the suprapleura, mediastinal pleura and fibrous pericardium Endothoracic fascia covers all parts of the pleural except the suprapleura. It separates the pleura from the thoracic wall 8. A. Describe the structure and function of Clara cells (2 marks) B. In which main bronchi are foreign particles more likely to go. Justify. (1 mark) C. what is the role of alveolar pores (1 mark) Answer: a. • Clara cells are non-ciliated bronchial secretory cells • • They make surfactant like substances to aid in respiration They also make products that degrade toxins in the inhaled air b. Right main bronchi because it is more vertical and larger c. Equalise pressure between different pulmonary segments