L10 Lung Structure & regional gas exchange

Question 1

where is the lung apex

Answer 1

the most cranial aspect (at the sternum) adjacent to thoracic inlet

Question 2

where is the base of the lung

Answer 2

diaphragmatic surface.

Question 3

What is the location of the cardiac notch?

Answer 3

3-5th intercostal space

Question 4

What structures are found at the lung roots?

Answer 4

principle bronchus + pulmonary artery + veins + nerves + pleura + tracheobronchial lymph nodes

Question 5

Where does the root enter the lung

Answer 5

hilus

Question 6

How many lobes does the L lung have?

Answer 6

2x (cranial and caudal)

Question 7

Which lung lobe is larger?

Answer 7

R

Question 8

How many lung lobes does the R lung have?

Answer 8

3-4

cranial, middle, caudal

Question 9

name and describe the lobation of the R lung, including species differences

Answer 9

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

Question 10

What ventilates the R cranial lung lobe?

Answer 10

tracheal bronchus in ruminants & pigs

Question 11

How many R lung lobes does a horse have

Answer 11

cranial, caudal and accessory – NO middle!

Question 12

where do pulmonary arteries enter the lungs and what type of blood do they carry??

Answer 12

enter @ principle bronchi

carry O2 depleted blood from R ventricle via pulmonary trunk

Question 13

Which BV supplies the lung parenchyma? I.e not for gas exchange

Answer 13

bronchial artery which arises from the aorta and supplies the bronchi and CT

Question 14

Describe the two networks of lymphatic drainage of the lungs

Answer 14

superficial lymphatics drains the subpleura into vessels located at the hills

Deep lymphatics drain the deeper tissues via vessels that travel along the airways

Question 15

Describe the path the superficial and deep lymphatics take once they merge

Answer 15

merge at the lung hilus > trachea-bronchial lymph nodes > cranial mediastinal nodes > tracheal lymphatic vessels/ thoracic duct

Question 16

which nervous system innervates the lungs?

Answer 16

autonomic (both para and sympathetic)

Question 17

What is the central integrating centre for the lungs?

Answer 17

pulmonary plexus (pulmonary branches of sympathetic trunk & vagus nerve) in the mediastinum

Question 18

describe the lobation and lobulation of horse, ruminant and carnivore lungs

Answer 18

horse= almost no lobation & very inconspicuous lobulation

ruminant & pig= conspicuously lobated and lobulated

carni= deeply fissured into lobes but little lobulation

Question 19

How is the blood not involved in gas exchange returned from the lungs to the heart

Answer 19

bronchial veins return blood to L heart via azygous vein

Question 20

What effect do the efferent nerves from the pulmonary plexus in the mediastinum have on the lungs?

Answer 20

regulation of bronchial glands and bronchial SMC. Sympathetic activation causes dilation and parasympathetic causes constriction.

Question 21

What action do the afferent nerves innervating the lungs have?

Answer 21

stretch receptors for reflex modifications when at rest

mechanoreceptors for reflex coughing

Question 22

And increase in O2 demand will result in what in terms of the lung function?

Answer 22

increase depth and rate of ventilation

recruitment and distension of pulmonary capillaries

Question 23

Describe what changes occur in the alveoli and blood during hypoventilation

Answer 23

O2 is depleted and CO2 accumulates in alveoli and blood

Question 24

Describe what changes occur in the alveoli and blood during hyperventilation

Answer 24

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

Question 25

is ventilation uniform throughout the lung?

Answer 25

nope

Question 26

what can cause lung hypoxia?

Answer 26

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.)

Question 27

a local decrease in PCO2 in an alveolus causes bronchiolar _____ and thus a localised _____ in airflow.

What would cause a local decrease in PCO2?

Answer 27

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

Question 28

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?

Answer 28

a local increase in PO2 in an alveolus causes vasodilation and thus a localised increase in bloodflow.

hyperventilation causes a local increase in PO2

Question 29

A local increase in PCO2 in an alveolus causes ____ of bronchiolar ____ (aka ___dilation/constriction___) and thus a localised ____ in airflow

Answer 29

A local increase in PCO2 in an alveolus causes relaxation of bronchiolar SMC (aka dilation) and thus a localised increase in airflow

Question 30

a local decrease in PO2 in an alveolus causes _____ of arterioles and thus a localised _____ in blood flow

Answer 30

a local decrease in PO2 in an alveolus causes vasoconstriction and thus a localised reduction in BF

Question 31

How do the lungs change after birth?

Answer 31

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