2.2 diaphragm and mechanisms of breathing

Question 1

what is the attachment between thoracic cage and diaphragm?

Answer 1

fibres on bottom of thoracic cage project superiorly and attach to the central tendon

Question 2

what are the three types of arcuate ligaments projecting from the diaphragm?

Answer 2

median arcuate ligament
medial arcuate ligament
lateral arcuate ligament

Question 3

what is the purpose of the median arcuate ligament?

Answer 3

attaches to vertebral bodies

Question 4

what is the purpose of the medial and lateral arcuate ligament?

Answer 4

because the psoas major and quadratum lumborum are in front of the posterior thoracic cage, the arcuate ligaments attach to those muscles instead

Question 5

what is the purpose of the median arcuate ligament

Answer 5

attaches diaphragm to vertebral bodies

Question 6

where do the crura of the diaphragm attach to the vertebral body?

Answer 6

left crus: L1-L3/4
right crus: L1-L2/3

Question 7

what is the purpose of the crura?

Answer 7

anchor the diaphragm posteriorly around the aorta

Question 8

how does diaphragmatic movement affect central tendon?

Answer 8

diaphragm contracts, pulls central tendon down, depresses diaphragm

Question 9

what are the 3 structures that pierce the diaphragm?

Answer 9

IVC - T8
oesophagus - T10
aorta - T12

Question 10

what happens to the IVC during inspiration?

Answer 10

• diaphragm depresses
• stretches central tendon and IVC
• intraabdominal pressure increases
• blood rushes through IVC towards thorax

Question 11

why can’t swallowing and inspiration occur at the same time?

Answer 11

when diaphragm contracts, pulls crura sling around oesophagus

Question 12

what type of sphincter does the crura act as around the oesophagus

Answer 12

functional sphincter

Question 13

what nerve innervates the diaphragm, performing motor function?

Answer 13

phrenic nerve

Question 14

how does the sympathetic trunk pass through the diaphragm?

Answer 14

runs lateral to the crura and through the medial arcuate ligament

Question 15

what dermatomes is pain from the central diaphragm referred to?

Answer 15

C3, C4, C5 from phrenic nerve

Question 16

where is pain from the peripheral diaphragm referred to?

Answer 16

dermatomes of the thoracic wall

Question 17

what innervates the peripheral diaphragm

Answer 17

lower intercostal nerves

Question 18

how does the phrenic nerve (L and R) descend and access the diaphragm?

Answer 18

• passes anteriorly to root of lung
• descends through thorax

Question 19

what parts of the thorax does the phrenic nerve supply?

Answer 19

• motor to all diaphragm
• sensory to central diaphragm
• sensory to pericardium

Question 20

how does air move into lungs?

Answer 20

air moves from high pressure to low pressure to equalise the pressure gradient

Question 21

what happens during inspiration (in terms of volume and pressure?)

Answer 21

• increases volume
• decreases pressure
• atmospheric pressure is greater than lung pressure

Question 22

what happens during expiration (in terms of volume and pressure?)

Answer 22

• decreases volume
• increases pressure
• lung pressure is greater than atmospheric pressure

Question 23

how does the relationship between the visceral and parietal pleura affect lung movement?

Answer 23

• parietal pleura firmly attached to thoracic cage and diaphragm
• visceral pleura on surface of lungs
• the surface tension between these two layers and the fluid inside the pleural cavity pulls the lungs to expand when the thoracic cage expands

Question 24

what muscle controls quiet breathing, and how does it perform this function (or what controls its contractions)?

Answer 24

diaphragm. rhythmic contractions are controlled by the respiratory centre of the brainstem

Question 25

explain the pump handle movement of the ribs

Answer 25

elevation of upper ribs (2-6) result in movement forward of sternum because of attachments to sternum

Question 26

explain the bucket action

Answer 26

elevation of lower ribs pulls ribs laterally outwards