Muscles of thoracic wall

Question 1

muscles

Answer 1

Serratus post. sup. 
Serratus post.inf. 
Levatores costarum
Intercostal muscles: External, internal 
and inner most which is (divided into subcostal and transversus thoracis)

Question 2

Answer 2

Serratus post. sup.

Question 3

Serratus post. sup.

Answer 3

Nerve: Intercostal nerves 2-5
Prox: spinous processes of C7 -T3
Dis: inf. Borders of ribs 2-5
Action: Elevates ribs 2 – 5 involved in inspiration

Question 4

Answer 4

Serratus post.inf.

Question 5

Serratus post.inf.

Answer 5

Nerve: Intercostal nerves 9-11, T2= subcostal nerve
Prox: SP t11-L2
Dis: inf. Borders ribs 9-12
Action: Depresses inf. Ribs (9-12) involved in expiration However both serrati appear to be largely proprioceptive

Question 6

Answer 6

Levatores costarum:

Question 7

Levatores costarum:

Answer 7

Nerve: Posterior rami of spinal nerves T1 – T12
Prox: C7-T11
Dis: On ribs just below vert. so T1-T12
Action: Elevate ribs during forced inspiration, role normal inspiration uncertain

Question 8

Intercostal muscles:

Answer 8

Primary role in respiration is to support intercostal space.
Intercostal muscles and diaphragm main resp. muscles.

Question 9

Intercostal muscles: From superficial to deep:

Answer 9

External intercostals
Internal intercostals
Innermost intercostal muscles:
    > Subcostal
    > Transversus thoracis

Question 10

Question 11

Answer 11

External intercostals

Question 12

External intercostals characteristics

Answer 12

Most active during inspiration.
Elevate ribs during forced inspiration.
Fibres run inferior, anteriorly- run from inf. Border of the rib above to the sup. Border of the rib below - mostly in a medial direction
Anteriorly, towards sternum, they are replaced by membrane = external intercostal mem.

Question 13

Answer 13

Internal intercostals

Question 14

Internal intercostals characteristics

Answer 14

Interosseous part depresses ribs, and interchondral part elevates ribs during active (forced) respiration.
Most active during expiration.
Run inf. Posteriorly - from floor of costal groove to sup. Border of the rib below
Run perpendicularly to external intercostal muscles run outwards
Replaced by a membrane posteriorly ( close to vert. column)

Question 15

Answer 15

Innermost intercostal muscles:

Question 16

Innermost intercostal muscles: Characteristics

Answer 16

Likely same actions as those of int. intercostals. ( forced expiration)
- Run over two adjacent ribs, whereas EIM and IIM run
in-between adjacent ribs.
Divided into:

Subcostal
- Assumed that they act with int. intercostals (may depress ribs).
- Runs mainly in the posterior region of the ribcage
- Cross one or two intercostal spaces
( easier to identify because they’re not just found between adjacent ribs)

Transversus thoracis
- Depresses ribs. Weak expiratory function.

Question 17

Answer 17

Transversus thoracis

Question 18

Answer 18

Subcostal

Question 19

Intercostal vessels: (A/V/N)

Answer 19

Found between internal and innermost intercostal muscles

Question 20

Pleura

Answer 20

membrane that lines inside of the ribs

Question 21

Order of structures (muscles)

Answer 21

1. External intercostal – fibers run medially and downwards
2. Internal intercostal – fibers run at right angles to external ic
3. Intercostal nerves and veins run deep into the internal intercostal muscles
4. Innermost intercostal – are on same ‘level’ as intercostal nerves and veins
5. Endothoracic fascia – between the rib and the pleura
6. Pleura – Deeper than Endo. fascia

Question 22

External intercostals:

Answer 22

Nerve: intercostal nerves
Prox: lower border of rib
Dist: ventrocaudally to the upper border of the rib below
Action: elevation of the ribs

Question 23

Internal intercostals:

Answer 23

Nerve: intercostal nerves
Prox: upper border of rib
Dist: Ventrocranially at lower border of the rib above
Action: lower the ribs ( expiratory breathing muscles)

Question 24

Innermost intercostal muscles:

Answer 24

Nerve: intercostal nerves
Prox: Separate from internal intercostal muscles
Dist: Behind costal groves (bordered by internal thoracic fascia)
Action: lower the ribs ( expiratory breathing muscles)

Question 25

What do all intercostals do?

Answer 25

All these muscles tense the intercostal spaces during deep inspiration and support the breathing mechanism

Question 26

Intercostal tunnel:

Answer 26

Fibrous space between internal and innermost intercostal muscles, and the lower border of the rib above
- Provides passage for intercostal arteries, veins and nerves
Intercostal nerves supply the intercostal muscles and arise from the thoracic nerves

Question 27

Accessory muscles of respiration:

Answer 27

Muscles from the head and neck that insert into the rib cage

• Can be used to expand the ribcage if the intercostal movements of the diaphragm aren’t enough
• If sprinting or in resp. distress.

Pectoralis maj. , pect. min. and serratus anterior
Scalene muscles
abdominal muscles

Question 28

Pectoralis maj. , pect. min. and serratus anterior

Answer 28

• elevate ribs to expand thoracic cavity during forced inspiration.

Question 29

Scalene muscles

Answer 29

• fix 1st and 2nd rib , enabling muscles connecting below to elevate lower ribs during forced inspiration

Question 30

abdominal muscles

Answer 30

• To push up organs against diaphragm for forced expiration

Question 31