Respiration Flashcards
Which lung lobe does a horse lack?
Right middle
What is the difference between respiration and ventilation?
Respiration=exchange of gases at the alveoli
Ventilation=movement of air through the airways
Which epithelium lines the airways?
What does this also contain?
Ciliated columnar epithelium
Goblet cells and submucosal glands
What is the name of the function which moves mucus up towards the pharynx to be swallowed?
Mucociliary escalator function
Particles how small may still reach the alveoli despite the mucociliary escalator function?
Less than 5um
The epithelial lining of the terminal bronchioles contain which cells? What do they produce?
What does the lining lack?
Clara cells
Produce surfactant
Lacks cilia and goblet cells
What is a bronchovascular bundle composed of?
A bronchus, artery and vein
Which arteries supply the lung itself? Where do they arise from?
Bronchial arteries which arise from aorta
How does venous drainage of the lung tissue occur?
Via bronchial veins which empty into the azygous vein, or sometimes directly into the left atrium.
Which nerve provides parasympathetic supply to the lungs?
Vagus
What is the structural difference between bronchi and bronchioles?
Bronchioles have no cartilage in their walls
What are the names of the 5 developmental stages of the lungs?
Embryonic, pseudoglandular, canalicular, terminal sac and alveolar
When do respiratory muscles start contracting in the foetus?
From the first trimester
What is the normal respiratory rate of a dog?
What about a horse?
20-30 brpm
10-12 brpm
Which word means normal breathing?
Eupnoea
Which word means increased resp rate?
Tachypnoea
Which word means increased respiratory depth?
Hyperpnoea
Which word means increased respiratory effort?
Dyspnoea
Which word means absence of breathing?
Apnoea
What is compliance?
What does it depend on?
The degree to which a change in transpulmonary pressure leads to a change in volume of the lung
Depends on elasticity of lungs and thoracic cage, and surface tension in the alveoli
What is meant by tidal volume?
What is the value in a normal dog?
Volume of air moved during a respiratory cycle
10-15ml/kg
How do you calculate minute ventilation?
Tidal volume x respiratory rate
What is the partial pressure of oxygen in normal room air?
160mmHg
What is meant by dead space?
Areas which are ventilated but don’t participate in gas exchange
In which part of the airways is the speed of air flow highest?
Trachea and large bronchi
How do you increase the minute ventilation, eg during exercise?
By increasing respiratory rate, tidal volume, or both
What is the residual volume (of the lungs)?
The volume of air that remains after a full expiration
One litre of plasma can carry how much O2 in solution?
3ml
When fully saturated, how much O2 can one gram of Hb carry?
1.36-1.39ml
What is the oxyhaemoglobin dissociation curve affected by?
Temperature, pH, PCO2, and concentration of 2,3-diphosphoglycerate in RBCs
Which animals’ Hb does not bind 2,3-DPG?
Ruminants and foetus’
In which 3 ways are CO2 transported in the blood?
- Dissolved in plasma (5%)
- As carbamino compounds (30%)
- As bicarbonate (HCO3-) ions (65%)
What are lobar bronchi?
Secondary bronchi
Why does a dog have very obvious external fissures between lung lobes yet a horse has barely any?
All to do with gait
Those species with a more bounding gait require greater freedom of movement, and hence more external separation
What is a the name given to the junction between cartilage and bone on ribs?
Costochondral junction
In which species is there obvious surface marbling of the lung?
Pig
Why is the lung a common site for spread of neoplasia and secondary infections?
There are no arteriovenous anastomoses in the lungs, meaning all blood must pass through a capillary bed. Therefore the lungs act as a sieve, filtering infectious agents, emboli and neoplastic cells from the blood.
In respiratory embryology, what is the difference between the positions of the left and right principal bronchi?
The right bronchus continues in a more midline position, while the left deviates laterally
Which bronchi supply the bronchopulmonary segments?
Segmental bronchi
Describe the 5 stages of development of the lungs
- Embryonic: from the formation of the laryngo-tracheal groove to the formation of segmental bronchi. Mucosal and submucosal glands develop in epithelium. Smooth muscle, cartilage and connective tissue form.
- Pseudoglandular: Lungs extend, conducting branches of the bronchial tree form and vascularisation begins.
- Canalicular: Airway lumens enlarge, respiratory bronchioles form
- Terminal sac: Respiratory bronchioles give off terminal sacs lined with cuboidal epithelium which organises into Type 1 and 2 alveolocytes. Surfactant production.
- Alveolar: Capillaries associate closely with alveolar lining. Surfactant production increases. Continues post-natally.
How does the early embryo achieve gaseous exchange?
Diffusion through uterine fluids
How does a foetus cope with its state of relative hypoxia? (2)
- Higher cardiac output ensures tissues receive more blood per minute
- Higher affinity of foetal haemoglobin for O2
What is meant by respiratory rate?
Number of breaths taken in one minute
What is the respiratory rate of a horse?
10-12 brpm
Movement of air occurs due to what?
Changes in the pressure inside the alveoli
What action does contraction of the external intercostal muscles have on the ribs?
Lifts them out and cranially
How are the lungs held against the thoracic wall?
By negative pressure within the pleural space
What action does contraction of the internal intercostal muscles have on the ribs?
Lifts the ribs caudally and inwards
How do you calculate compliance?
Increase in volume of lung
divided by
Increase in transpulmonary pressure
When may compliance be altered?
Some disease states, and in obese animals
Why do neonates often struggle to survive?
Inadequate production of surfactant which can lead to respiratory distress syndrome, which presents with severe dyspnoea (laboured breathing). Reduced surfactant means increased surface tension in the alveoli
Why, when a large alveolus adjoins a small alveolus, doesn’t the small alveolus collapse?
(Would expect collapse due to high surface tension)
The total amount of surfactant inside an alveolus is the same regardless of size; a small alveolus will have a higher concentration of surfactant, and hence a lower surface tension
How are horses able to reduce resistance to nasal airflow?
Have very distensible nares
Are able to reduce the size of blood vessels in their nasal passages
What make up the respiratory zone?
Respiratory bronchioles, alveolar ducts, alveolar sacs
Why is PAO2 (alveolar partial pressure) always lower in the alveoli than in the airways?
Because of the constant diffusion of O2 into the blood
What are the normal values for PAO2 and PACO2? (alveolar)
PAO2=100mmHg
PACO2=40mmHg
Why is hypoxia common in pulmonary disease?
Oxygen is not very soluble and is bound to haemoglobin, so over-ventilated alveoli can not transfer enough O2 to compensate for under-ventilated ones
What is meant by cooperative binding?
Binding of one O2 molecule to haemoglobin increases the affinity for other units of O2
What is meant by the chloride shift?
HCO3- (formed from CO2+H2O) diffuses out of RBCs in exchange for Cl- ions to maintain the electrochemical neutrality of the cell
What are the 2 kinds of vessels which supply the lung and what do they do?
Alveolar=capillaries which run in the alveolar septa and participate in gas exchange
Extra-alveolar=pulmonary arteries, arterioles, venules and veins which move blood to and from the lung
The blood supply of the lung is preferentially distributed where?
Why
To the dorsocaudal regions, due to the branching pattern of the arteries
How do you calculate pulmonary vascular resistance (PVR)?
(P pulmonary artery-P left atrium) / Q
P=pressure
Q=cardiac output