Lower Respiratory Tract

Question 1

1. what are the 2 principle divisions of the central respiratory centre?
2. During normal inspiration, which central respiratory group sends impulses to the respiratory muscles, and via which nerve?
3. What is the pre-bötzinger complex? What is its role and how does it execute it?
4. When do VRG neurons become activated?
5. what is the role of the pontine respiratory group?

Answer 1

1. medullary (further divided into dorsal and ventral) and pontine respiratory groups
2. DRG neurons via phrenic nerve - causes contraction of inspiratory muscles. Silenced after 2 seconds, enabling inspiratory muscles to relax
3. part of the VRG. Important in the generation of breathing rhythm. It is thought to provide input to DRG neurons
4. when forceful breathing is required - send impulses to accessory muscles
5. plays a role in modifying basic rhythm as when exercising or speaking, by sending impulses to the DRG

Question 2

1. Where are central chemoreceptors found? What do they detect?
2. where are peripheral chemoreceptors found?
   What do they detect?
3. What conditions activate chemoreceptors? How do they adjust breathing rate accordingly?
4. Name 2 hormones that increase the rate of breathing

Answer 2

1. medulla. Detect pH and p[CO2]
2. aortic and carotid bodies. Detect pH, [CO2] and [O2]
3. increased [CO2], decreased [O2] and decreased pH
   Act to increase output from the DRG therefore increase the rate of breathing.
4. Adrenaline. Progesterone

Question 3

Describe the following:

1. Tidal Volume
2. Total Lung Capacity
3. Vital Capacity
4. Residual Volume
5. Functional Residual Capacity
6. Inspiratory Capacity
7. FEV1

Answer 3

1. volume of air displaced during inspiration and expiration of normal breathing with no extra effort
2. total volume of air that can be contained in the lungs
3. maximum amount of air that can be expelled after maximal inspiration
4. volume of air that remains in the lungs following maximal expiration
5. volume of air left in the lungs after tidal exhalation
6. maximum volume of air that can be inhaled
7. forced expiratory volume in 1 secoind

Question 4

1. What is the purpose of cough?
2. what are the gender differences in the cough reflex?
3. name 2 substances that can stimulate the cough reflex
4. name 3 substances/conditions that don’t activate the cough reflex but hypersensitise the cough reflex
5. Name channels that play a role in the cough reflex
6. Name a type of receptor that induces the cough reflex when activated. How do they become activated?

Answer 4

1. to clear the throat and airways of foreigh particles, irritants, microbes, fluids and mucous
2. women are more likely to suffer with cough related problems
3. capsaicin and smoke
4. ACE inhibitors. viruses, respiratory tract infection/inflammation
5. TRP channels - become sensitised by inflammatory mediators
6. Purine receptoers P2X3 and P2Y. ATP is released upon cell damage

Question 5

1. Which nerve is the afferent pathway of the cough reflex?
2. which nerve is the efferent pathway of the cough reflex?
3. Describe the stages of the cough mechanism

Answer 5

1. laryngeal branch of vagus
2. vagus and superior laryngeal nerve
3. diaphragm and external intercostal muscles contract. Creates negative pressure around the lumg
   air rushes into lungs
   epiglottis and vocal cords contract to shut larynx
   contraction of abdominal and expiratory muscles to increase air pressure in lungs
   vocal cords relax and rima glottis opens; air is forced out of lungs

Question 6

1. where do the pleural membranes meet?
2. what are the spaces between the pleurae called?
3. Name 2 places in which these spaces are found normally

Answer 6

1. at the hilum
2. recesses
3. costodiaphragmatic recesses - bottom of the lungs
   costomediastinal recesses - found medially near the mediastinum

Question 7

1. what is the cardiac notch?
2. what is the lingual process?
3. how many lobes do the right and left lungs have?
4. What are the names of the lung lobes? What are they separated by?

Answer 7

1. indent of the anterior border of the left lung, made by impression of heart
2. process of the left superior lobe that extends below the cardiac notch
3. right - 3
   left - 2
4. Right superior, middle and inferior lobes
   S and M lobe separated by horizontal fissure
   M and I lobes separated by oblique fissure

Left superior and inferior lobes, separated by the oblique fissure

Question 8

What are the lung borders co-incident with (surface anatomy)

• anteriorly
• laterally
• posteriorly

Answer 8

2nd and 4th ribs at the sternal line anteriorly
6th rib at midclavicular line
8th rib at mid-axillary line laterally
10th rib at the mid-scapular line posteriorly

Question 9

1. What is the hilum of the lung surrounded by?
2. what is the pulmonary ligament?
3. What are contained within the hilum?
4. Describe the relationship between the pulmonary artery and bronchus in the:
   a) left hilum
   b) right hilum

Answer 9

1. visceral and parietal pleura
2. downward extention of parietal pleura from the hilum
3. principle bronchus, plumonary artery and veins and bronchial arteries
   4a) pulmonary artery is found superiorly to the bronchus
   4b) pulmonary artery is found anteriorly to the bronchus

Question 10

1. what is the mediastinum?
2. what are the boundaries of the mediastinum?
3. how is the mediastinum divided into its superior and inferior parts
4. Where is the anterior mediastinum?
5. What does the anterior mediastinum contain?
6. Where is the middle mediastinum
7. What does the middle mediastinum contain
8. Where is the posterior mediastinum?
9. What does the posterior mediastinum contain?
10. What does the anterior mediastinum contain?

Answer 10

1. central compartment of the thoracic cavity
2. thoracic inlet (root of neck), diaphragm and mediastinal pleura
3. by the thoracic plane, at the level of the manubriosternal joint/secind costal cartilage/T4/T5
4. between sternum and pericardium
5. thymus gland, lymph nodes, sternopericardial ligaments and internal thoracic vessles
6. bounded by pericardium
7. pericardium, heart, phrenic nerve, adjoining great vessels, cardiac plexus
8. between pericardium and throacic vertebrae
9. Oesophagus, vagus nerve, thoracic duct, descending aorta
10. aortic arch and branches, trachea, oesophagus, thoracic duct and vagus nerve

Question 11

1. Smoking increases the risk of what diseases?

2. At what age does smoking cessation have the potential to bring health experience back to that of a non-smoker

Answer 11

1. lung, oesophageal, bladder, throat and moth cancer
ischaemic heart disease
stroke
aortic aneurism
chronic bronchitis and emphysema
pneumonia
2. 40

Question 12

1. Name the three types of cells found in the conducting zone. What are their roles?
2. Describe the histology change at the level of the bronchioles

Answer 12

1. ciliated epithelial cells - involved in the mucocilliary escalator
   goblet cells - secrete mucous
   basal cells - stem cells
2. in nasal cavities, trachea and bronchi, cells are COLUMNAR
   in the bronchioles, cells are CUBOIDAL. CLUB CELLS replace goblet cells

Question 13

1. what is the lamina propria?

2. what does it contain (5)

Answer 13

1. thin layer of connective tissue below the basemement membrane of mucous membranes
2. loose connective tissue, blood vessels and nerves, secretory glands, lymphocytes and rigid components to keep airways open.

Question 14

1. what is the mucocilliary escalator?
2. what are the 2 layers formed by mucous?
3. what is the function of mucous?
4. what is required for good mucocilliary clearance?
5. How does smoking affect mucocilliary clearance?
6. How does pollution affect mucocilliary clearance?
7. What is the main component of mucous?
8. How is the fluidity of the sol phase controlled?
9. name 3 other components of mucous

Answer 14

1. consists of mucous and beating cillia. Cillia beat to move the mucous towards the throat and mouth
2. gel phase and underlying sol phase
3. creates a semipermeable barrier that allows the exchange of nutrients, water and gasses, but is impermeable to pathogens. It traps particles.
4. number, structure and co-ordination of the cillia
5. stimulates goblet cells to produce mucous. Greater amount of mucous affects clearance
6. particles become trapped in the mucous layer by sedimentation or impaction, which slows mucocilliary clearance
7. MUCINS
8. by epithelial secretions
9. antiproteases such as alpha1-antitrypsin
   lysozyme
   antimicrobial proteins

Question 15

1. describe the bronchial tree
2. what structures in respiratory bronchioles mediate gas exchange?
3. what type of epithelial cells are type 1 pneumocytes
4. what type of cell junctions are found between type 1 pneumocytes
5. how are neighbouring alveoli connected to one another?
6. what type of epithelial cells are type 2 pneumocytes
7. what is the role of type 2 pneumocytes

Answer 15

1. trachea > bronchi > conducting bronchioles > terminal bronchioles > respiratory bronchioles > alveolar sacs
2. thin evaginations from wall from which the respiratory alveoli emerge
3. simple squamous
4. tight junctions
5. via pores of Kohn
6. Cuboidal
7. produce surfactant

Question 16

1. what is the role of alveolar macrophages? (3)
2. What is the role of mast cells?
3. what is the principle immunoglobulin of the respiratory tract?
4. what is the role of natural killer cells? (2)

Answer 16

1. migrate throughout respiratory tract and phagocytose particles/pathogens that manage to migrate that far
   act as APCs
   secrete interleukins and TNFs to activate the adaptive immune response
2. secrete inflammatory mediators and enzymes involved in allergy
3. IgA
4. release granules containing hydrolytic enzymes
   secrete intetferons and TNF

Question 17

Name and describe protective reflexes

Answer 17

1. Coughing - deep inspiration followed by forced expiration against a closed glottis
2. sneexing - deep inspiration followed by forced expiration against an open glottis
3. Swallowing

Question 18

1. Where are stretch receptors located?
2. What reflexes are they involved in?
3. What are juxtapulmonary receptors?
4. what are they activated by?
5. What does their activation lead to?

Answer 18

1. smooth muscle of bronchial walls.
2. Hering Breuer inspiratory reflex - lung inflation inhibits inspiratory muscle activity to prevent overinflation
3. receptors located on bronchial and alveolar walls close to capillaries
4. increased alveolar wall fluid, pulmonary oedema, micro-embolisms and inflammatory mediators.
5. apnoea, decrease in HR and BP, laryngeal constriction.

Question 19

1. What is ventilation?
2. What is pulmonary ventilation?
3. what is alveolar ventulation?
4. What is anatomical dead space?
5. what is physiological dead space?

Answer 19

1. movement of air in and out of the lungs
2. movement of gasses in and out of the lungs
3. volume of air that participates in gas exchange
4. conducting airways
5. poorly or non-perfused area

Question 20

1. which 2 measures of ventilation can’t be measured by spirometry
2. how can they be measured instead (2)
3. Which 2 measures of ventilation are examined clinically to measure the degree to which airflow is limited?
4. how are these affected in:
   a) obstructive lung disease
   b) restrictive lung disease

Answer 20

1. residual volume and functional residual capacity
2. helium dilution
   plethysmography
3. FEV1 and forced vital capacity
   4a) decrease in FEV1 but no affect on FVC
   4b) decrease in FEV1 and FVC

Question 21

1. What type of gradients are responsible for the movement of air between the air and blood and blood and tissues?
2. what does Dalton’s Law state?
3. what percentage of air is O2?
4. What does the rate of diffusion of O2 and CO2 from alveoli to blood depend upon? (4)
5. What does the respiratory membrane consist of?

Answer 21

1. pressure gradients
2. pressure exerted by a mixture of gases is the sum of the individual partial pressures exerted by each each gas in the same volume.
3. 21%
4. partial pressure of gas
   solubility of gas in liquid
   area available for gas exchange
   thickness of alveolar membrane
5. fluid and surfactant layer
   alveolar epithelium
   epithelial basement membrane
   endothelial basemement membrane
   capillary endothelium
   RBC wall

Question 22

1. how is the majority of oxygen transported in the body?
2. what is CaO2?
3. what is SaO2?
4. what is PaO2?

Answer 22

1. bound to Haemoglobin (only partially dissolves in water)
2. arterial O2 content - amount bound to Hb and dissolved in blood
3. oxygen saturation of Hb
4. arterial oxygen pressure (amount dissolved in blood)

Question 23

1. what happens to beta Hb chains when O2 is unloaded? What does this lead to?
2. what is the arteriovenous difference?
3. What is the Bohr shift?
4. under what conditions does the bohr shift occur? (4)
5. what is 2,3 bisphosphoglycerate?
6. under what conditions does a shift to the left in the oxygen dissociation curve occur?
7. What is different about the foetal oxygen dissociation curve compared to that of adults?

Answer 23

1. they are pulled apart. Enables 2,3, bisphosphate to enter Hb which helps lower the affinity of O2 for Hb
2. difference in O2 content across arterial and venous load
3. a shift to the right in the oxygen dissociation curve. Lowered affinity for O2
4. decreased pH, increased PCO2, increased temperature and increased 2,3, bisphosphoglycerate
5. binds with greater affinity to deoxygenated Hb than to oxygenated Hb. Acts allosterically to lower affinity of Hb for O2, therefore promoting release of remaining O2 bound to Hb.
6. increased pH, decreased temp, decreasd PCO2 and decreased 2,3, BPG
7. curve is more leftward, thus higher affinity for O2

Question 24

1. what is carboxyhaemoglobin?
2. How is the majority of carbon dioxide transported in blood?
3. How else can it be transported?
4. What is the Haldane effect?

Answer 24

1. CO bound to Hb with very high affinity. It is unable to carry O2.
2. as bicarbonate
3. dissolved in blood or bound to Hb
4. removing O2 from Hb increases the ability of Hb to pick up CO2.

Question 25

1. What is the equilibrium reaction of bicarbonate?
2. what enzyme catalyses this reaction?
3. what is the expiration of CO2 the same as?
4. whar is retaining CO2 the same as?
5. In terms of acid base balance, what does:
   a) hyperventilation cause?
   b) hypoventilation cause?

Answer 25

1. H2O + CO2 ⇌ H2CO3 ⇌ H+ + HCO3-
2. carbonic anhydrase
3. loosing H+
4. gaining H+
   5a) hypocapnea and alkalosis
   5b) hypercapnea and acidosis

Question 26

1. name 3 metabolic causes of pH changes and what type of pH change they cause
2. How does Hb act as a buffer? What is a compensatory mechanism for this?
3. How do ventilation changes act to counterract pH changes?
4. how do renal mechanisms act to counterract pH changes?
5. What is respiratory acidosis?
6. What is respiratory alkalosis?

Answer 26

1. diabetic ketoacidosis > acidosis
   renal failure > acidosis (lack of H+ secretion)
   vomiting > alkalosis
2. acts as a weak base by accepting H+ ions
   Chloride Shift - leftover bicarbonate is transported out of the cell in exchange for Cl
3. hyper or hypoventilation. Rapid response, but impossible if cause is respiratory
4. changes in renal excretion of H+ or HCO3-. Slower response and limited if cause is renal
5. lungs retain CO2. Kidneys compensate by retaining HCO3- and secreting CO2-
6. lungs loose excess CO2. Kidneys compensate by secreting HCO3- and retaining CO2.