Lecture 10 - Gross Structure of the Lungs

Question 1

How does inspiratory ventilation of the gross lung occur?

Answer 1

expands passively due to change in volume of thoracic cavity –> inflow of oxygen rich air

Question 2

how does expiratory ventilation of the gross lung occur?

Answer 2

contracts due to elastic tissue throughout the lung –> outflow of carbon dioxide rich air

Question 3

the lungs seperate the heart from the rib cage except for at what point?

Answer 3

at the cardiac notch - 3-5th intercostal space

Question 4

what is the base of the lung?

Answer 4

the diaphragmatic surface - concave

Question 5

where is the apex of the lung located?

Answer 5

adjacent to the thoracic inlet

Question 6

is the costal surface convex or concave?

Answer 6

convex - against thoracic wall

Question 7

what is the medial surface?

Answer 7

surface facing and indented by the heart - region of the 3rd - 6th ribs

Question 8

what does the root of the lung contain?

Answer 8

• grouped, principle bronchi, pulmonary artery, veins and nerves all wrapped together in pleural covering
• also the location of the tracheobronchial lymph nodes

Question 9

where does the root enter the lung?

Answer 9

at the hilus

Question 10

how many lung lobes does the dog have?

Answer 10

2 left lobes,

4 right lobes

Question 11

how many lung lobes does the horse have?

Answer 11

2 left

3 right

Question 12

How are lobes defined?

Answer 12

defined as structures supplied by a secondary lobar broncos, subdivided into lobules by connective tissue (septa)

Question 13

what do lobules contain? what are the implications for spread of infection?

Answer 13

contain collagen, elastin, blood vessels
vary in consistency - implicates spread of infection
thick in ruminant and pig
thin and incomplete in horse
almost non existent in dog

Question 14

what are the two lobes of the left lung?

Answer 14

• cranial lobe - has cranial and caudal portions in species other than the horse
• caudal lobe

Question 15

what are the lobes of the right lung?

Answer 15

divided into 3-4 lobes

• cranial lobe
• middle lobe - not present in horse, separated from cranial lobe by cardiac notch
• caudal lobe - in contact with diaphragm
• accessory lobe - located in mid-ventral region of right lung

Question 16

in ruminants and pigs what is the cranial right lobe ventilated by?

Answer 16

the tracheal bronchus

Question 17

describe the path of the pulmonary arteries

Answer 17

oxygen depleted blood from the right ventricle, into the pulmonary trunk into the L and R pulmonary arteries –> lungs
follow bronchi down to the level of the alveolus

Question 18

describe the path of the pulmonary veins

Answer 18

oxygen rich blood from the lungs into the left atrium
also provides venuous return from the bronchi
variable in number - usually 1 from each lobe

Question 19

where does the bronchial artery arise from?

Answer 19

arises from the aorta to supply the bronchi and CT - tissues not participating in gas exchange

Question 20

what are the 2 networks of lymphatic vessels within the lung?

Answer 20

superficial network - drains sub pleural tissue into vessel at hills of lung
deep network - drains deeper tissues via vessels running along airways

Question 21

where do both sets of lymphatic networks merge? what is the common pathway after merging?

Answer 21

at the hilus –> tracheobroncial lymph nodes –> cramoal mediastinal nodes –> tracheal lymphatic vessels or thoracic duct

Question 22

what are the 2 lymphatic networks responsible for?

Answer 22

removal of material phagocytosed by macrophages in airways

mounting an immune response to infectious agents

Question 23

how are the lungs innervated?

Answer 23

autonomic supply from pulmonary plexus within the mediastinum
efferent: regulates activity of bronchial glands, smooth muscle of bronco (constriction, dilation)

afferent supply from: stretch receptors –> sneezing, mechanoreceptors –> coughing

Question 24

where is the location of the lung within the bird, does it wrap around the heart?

Answer 24

dorsally located against vertebrae and ribs - does not wrap around heart

Question 25

are the lungs of birds involved with ventilation

Answer 25

no - they are fixed volumes, air sacs expand for inspiration and ventilatin

Question 26

what is hypoventilation?

Answer 26

insufficient airflow to the lungs due to partial obstruction of upper or lower airways = O2 depletion and CO2 accumulation in alveoli –> accumulation in blood

Question 27

what is hyperventilation?

Answer 27

breathing more rapidly or deeply than necessary to maximally oxygenate blog floor
= surplus of fresh air into and out of lungs –> CO2 decrease in blood –> only slight increase in O2 in blood; almost already saturated

Question 28

is ventilation uniform within the lung?

Answer 28

no

Question 29

what are some localised variationsin alveolar perfusion?

Answer 29

• blood flow depend on body position (greater in ventral position due to hydrostatic pressure diff)
• pulm artery pressure may fall below alveolar pressure in dorsal part of lung –> capillaries squashed flat preventing blood flow
• during anaesthesia of large animal mismatching occurs due to pooling of blood in dorsal lung need to administer pure O2

Question 30

how does alveolar airflow regulate in response to local hypoventilation

Answer 30

local hypoventilation = increased PCO2 in alveolus –> dilation of bronchiole –> localised increase in air flow

Question 31

how does capillary blood flow regulate in response to local hypoventilation

Answer 31

local hypoventilation = decrease PO2 in alveolus = vasoconstriction of arterioles (hypoxic pulmonary vasoconstriction) –> localise reduction in blood flow

no point having blood to regions of lung without enough air, want blood going to regions with insufficient blood and too much air

Question 32

how does alveolar airflow regulate in response to local hyperventilation

Answer 32

local hyperventilation = decrease in PCO2 in alveolus –> bronchiolar constriction –> localised decrease in airflow

Question 33

how does capillary blood flow regulate in response to local hyperventilation

Answer 33

location hyperventilation = increase in PO2 in alveolus –> vasodilation –> localised increase in blood flow