Respiratory Muscles

Question 1

Intercostal spaces

Answer 1

> Muscles (fibres run at 90 degrees to each other)

• External Intercostal
• Internal Intercostal
• Innermost Intercostal

> Contents (between internal and innermost intercostals)

• Intercostal arteries and veins
• Intercostal nerve
• Narrowing spinal canal (due to growing vertebral bodies) as we descend can lead to neuritis of intercostal nerve - pain radiating around chest wall (follows sloping path of ribs)

Question 2

Muscles of Respiration includes:

Answer 2

Muscles of:

• Pharynx (epiglottis stops breathing when swallowing)
• Larynx (prevents collapse of upper airways during inspiration - creates positive pressure)
• Ribcage
• Thoracic spine
• Neck
• Abdominal wall
• Lumbar spine

Question 3

Functions of thoracic muscles

Answer 3

> Increase thoracic dimensions during inspiration
Support thoracic cage
Prevent recession (paradoxical breathing)/bulging of intercostal spaces
Prevent lungs tendency to collapse (ie. splint the airways open)

Question 4

Inspiration:

Answer 4

> Active process

• diaphragm
• external intercostals + interchondral aspects of internal and innermost intercostals

+Accessory muscles

• sternocleidomastoid
• scaleni
• serratus posterior superior
• levatores costarum
• serratus anterior
• pectoralis major and minor
• latissimus dorsi

Question 5

Expiration

Answer 5

> Passive relying primarily on elastic recoil of lungs
+ Accessory muscles
- Internal intercostal (not interchondral aspect)
- Innermost intercostals (not interchondral aspect)
- Transversus Thoracis
- Subcostals
- Serratus posterior inferior
- Abdominals
- Latissimus dorsi
- Quadratus Lumborum (depresses 12th rib)

Question 6

Diaphragm P/O/I

Answer 6

> Double- domed musculotendinous sheet that forms the inferior most aspect of thoracic cage = inferior thoracic aperture (floor of thoracic cavity + roof of abdominal cavity)
Origins (slopes inferiorly from xiphoid process to median arcuate ligament ~L1-2 level)
- Xiphoid process
- Costal cartilages of ribs 7-10
- ends of ribs 11+12
- lumbar vertebrae
- ligaments of posterior abdominal wall
(form tendinous ‘crura’ right crus = L1-L3 and left crus = L1-2)
Insertions
- all combine to central tendon which ascend to fuse with inferior pericardium (domes form either side of pericardium + right is higher due to liver)

*Zone of apposition is the attachment of diaphragm to thoracic cage - is key to function

Question 7

Diaphragm Openings/Actions/Innervation

Answer 7

> Openings

• Vena Caval opening (within central tendon) - T8 level for Inferior VC + phrenic nerve
• Oesophageal opening (in muscle left of midline) - T10 level - oesophagus + vagus nerve
• Aortic opening (between crura - behind diaphragm)- T12 level - aorta

> Action: Contracts + flattens increasing vertical diameter of thoracic cavity for inspiration (also used for core stability/micturition/parturition)
Innervation: Phrenic Nerve C3-5

Question 8

External Intercostals

Answer 8

> P: Superficial in intercostal spaces
> O: inferior border of ribs 
> I: Superior border of rib below 
> A: Elevates ribs (allows diaphragm to create pressure changes)
      : Stabilises chest wall

Question 9

Sternocleidomastoid

Answer 9

> O: sternal - superior anterior sternum
: clavicular - superior medial 1/3 of clavicle
P: Lateral mastoid process
: Lateral half of superior nuchal line
A: Elevates sternum - expanding pump handle of thoracic cavity

Question 10

Scaleni

Answer 10

> anterior + mid scaleni elevates rib 1 whilst posterior scaleni elevates rib 2
Transverse processes of C2-7 to upper part of first 2 ribs

Question 11

Serratus Posterior Inferior

Answer 11

> Spinous processes of C7 -T3 to ribs 2-5

> elevates ribs

Question 12

Levatores Costarum

Answer 12

> Transverse processes of C7-T11 to superior aspect of rib below
Elevates ribs

Question 13

Internal Intercostals

Answer 13

> P: Middle muscle of intercostal space
> O: Costal groove of rib 
> I: Superior border of rib immediately below
> A: Depresses ribs 
      : Supports intercostal spaces 
(Interchondral aspect elevates ribs)

Question 14

Innermost intercostal

Answer 14

> P: Deepest muscle of intercostal space
> O: Medial edge of costal groove
> I: Superior surface of rib below (+inferior margins of ribs 2-6 + costal cartilages of ribs 4-7 + xiphoid process)
> A: Depresses ribs
      : Supports intercostal spaces
*Interchondral aspect elevates ribs

Question 15

Transversus Thoracis

Answer 15

> P: Inner surface of anterior chest wall
O: inferior body of sternum + xiphoid process
: sternal ends of costal cartilages 4-7
I: Internal aspects of costal cartilages 2-6
A: Depresses ribs (specifically costal cartilages)

Question 16

Subcostals

Answer 16

> P: Inner surface of posterior thoracic wall
O: Internal aspect of ribs (near angles)
I : Internal aspect of ribs 2-3 below
A: Depresses ribs

Question 17

Serratus Posterior Inferior

Answer 17

> O: Spinous processes of T11 - L2
I: Ribs 9-12
A: Depresses ribs