L10 Lung Structure & regional gas exchange Flashcards
where is the lung apex
the most cranial aspect (at the sternum) adjacent to thoracic inlet
where is the base of the lung
diaphragmatic surface.
What is the location of the cardiac notch?
3-5th intercostal space
What structures are found at the lung roots?
principle bronchus + pulmonary artery + veins + nerves + pleura + tracheobronchial lymph nodes
Where does the root enter the lung
hilus
How many lobes does the L lung have?
2x (cranial and caudal)
Which lung lobe is larger?
R
How many lung lobes does the R lung have?
3-4
cranial, middle, caudal
name and describe the lobation of the R lung, including species differences
All species have cranial lobe.
Middle lobe is separated from the cranial lobe by the cardiac notch and is absent in horses.
Caudal is closest to diaphragm.
Accessory lobe is irregular & found mid-ventral
What ventilates the R cranial lung lobe?
tracheal bronchus in ruminants & pigs
How many R lung lobes does a horse have
cranial, caudal and accessory – NO middle!
where do pulmonary arteries enter the lungs and what type of blood do they carry??
enter @ principle bronchi
carry O2 depleted blood from R ventricle via pulmonary trunk
Which BV supplies the lung parenchyma? I.e not for gas exchange
bronchial artery which arises from the aorta and supplies the bronchi and CT
Describe the two networks of lymphatic drainage of the lungs
superficial lymphatics drains the subpleura into vessels located at the hills
Deep lymphatics drain the deeper tissues via vessels that travel along the airways
Describe the path the superficial and deep lymphatics take once they merge
merge at the lung hilus > trachea-bronchial lymph nodes > cranial mediastinal nodes > tracheal lymphatic vessels/ thoracic duct
which nervous system innervates the lungs?
autonomic (both para and sympathetic)
What is the central integrating centre for the lungs?
pulmonary plexus (pulmonary branches of sympathetic trunk & vagus nerve) in the mediastinum
describe the lobation and lobulation of horse, ruminant and carnivore lungs
horse= almost no lobation & very inconspicuous lobulation
ruminant & pig= conspicuously lobated and lobulated
carni= deeply fissured into lobes but little lobulation
How is the blood not involved in gas exchange returned from the lungs to the heart
bronchial veins return blood to L heart via azygous vein
What effect do the efferent nerves from the pulmonary plexus in the mediastinum have on the lungs?
regulation of bronchial glands and bronchial SMC. Sympathetic activation causes dilation and parasympathetic causes constriction.
What action do the afferent nerves innervating the lungs have?
stretch receptors for reflex modifications when at rest
mechanoreceptors for reflex coughing
And increase in O2 demand will result in what in terms of the lung function?
increase depth and rate of ventilation
recruitment and distension of pulmonary capillaries
Describe what changes occur in the alveoli and blood during hypoventilation
O2 is depleted and CO2 accumulates in alveoli and blood
Describe what changes occur in the alveoli and blood during hyperventilation
surplus air in lungs leads to DEC CO2 in blood due to constant removal (hypocapnia)
will see a v slight increase in [02] in blood b/c it’ll already be saturated
is ventilation uniform throughout the lung?
nope
what can cause lung hypoxia?
anything causing compromisation of capillaries/BF involved in gas exchange.
DEC PO2 in alveolus –> hypoxic pulmonary vasoconstriction
e.g. pulmonary artery pressure falling below alveolar pressure (low BP, haemorrhage, inc alveolar pressure etc.)
a local decrease in PCO2 in an alveolus causes bronchiolar _____ and thus a localised _____ in airflow.
What would cause a local decrease in PCO2?
a local decrease in PCO2 in an alveolus causes bronchiolar constriction and thus a localised dec in airflow
hyperventilation causes a local decrease in PCO2
a local increase in PO2 in an alveolus causes _____ and thus a localised __inc/dec___ in __blood/airflow___.
What would cause an increase in PO2 in an alveolus?
a local increase in PO2 in an alveolus causes vasodilation and thus a localised increase in bloodflow.
hyperventilation causes a local increase in PO2
A local increase in PCO2 in an alveolus causes ____ of bronchiolar ____ (aka ___dilation/constriction___) and thus a localised ____ in airflow
A local increase in PCO2 in an alveolus causes relaxation of bronchiolar SMC (aka dilation) and thus a localised increase in airflow
a local decrease in PO2 in an alveolus causes _____ of arterioles and thus a localised _____ in blood flow
a local decrease in PO2 in an alveolus causes vasoconstriction and thus a localised reduction in BF
How do the lungs change after birth?
Hypoxic pulmonary vasoconstriction occurs in the foetus, and results in only 15% of cardiac output flowing through pulmonary circulation.
At birth, with the first breath there is a sudden increase in alveolar PO2, resulting in a dramatic relaxation of the vascular smooth muscle, resulting in increased pulmonary blood flow
