2:4 Muscles of Inspiration: Thorax

Question 1

Diaphragm is primary what?

Answer 1

Primary muscle of the thorax and primary muscle of inspiration.

Question 2

Diaphragm separates…

Answer 2

abdominal and thoracic cavities.

Question 3

Intermediate region of the diaphragm is called the…

Answer 3

central tendon.

Question 4

Central tendon is a small…

Answer 4

circle within the diaphragm and this is what makes up the central tendon…it’s a large leafy aponeurosis (sheet-like tendon that lies over some muscles).

Question 5

When diaphragm is contracted…

Answer 5

muscle fibers shorten (central tendon brings it down closer to the bottom part of the diaphragm, squeezing it down to allow for thoracic expansion).

Question 6

Diaphragm O, I, A?

Answer 6

Origin: Inferior boundary of the rib cage, xiphoid process, and the posterior vertebral column.

Insertion: Central tendon

Action: Pulls central tendon down and forward during inspiration (expands lungs in vertical dimension)

Question 7

Accessory Muscles of Thorax (4):

Answer 7

1. External Intercostal Muscles
2. Internal Intercoastal Muscles
3. Levatores Costraum
4. Serratus Posterior Superior

Question 8

Mnemonic for Muscles of the Thorax:

Answer 8

DEILS (Don’t Exercise In Liquid Sand)

Diaphragm
External Intercostal Muscles
Internal Intercostal Muscles
Levatores Costraum
Serratus Posterior Superior

Question 9

External Intercostal Muscles:

Answer 9

• Significant respiratory muscles for speech
• Provides a significant proportion of the respiratory capacity (volume of air that our lungs can hold)
• Found between the 12 ribs
• Create a diagonal slanting and composed of striated muscle

Question 10

External Intercostal Muscles O, I, A?

Answer 10

Origin: lower surface of each rib (except 12)

Insertion: upper surface of rib immediately below

Action: elevate rib cage during contraction/inspiration and helps to increase the cavity size of the ribcage

Question 11

Internal Intercostal Muscles (chondral portion):

Answer 11

• Internal Intercostal Muscles are predominantly muscles of expiration except for the chondral portion.
• *“Parasternal portion” (the portion that is near the sternum) is part of the chondrol portion of the ribs is active during forced inspiration.

Question 12

Internal Intercostal Muscles (chondral portion) O, I, A?

Answer 12

Origin: superior surface of ribs 2-12

Insertion: inferior surface of ribs 1-11

Action: elevate rib cage during inspiration

Question 13

Levatores Costraum:

Answer 13

• Brevis and Longus portions contribute to rib cage elevation.
• They appear to be muscles of the back, but are actually considered thoracic muscles.

Question 14

Brevis Portion (“brief”) O, I, A?

Answer 14

Origin: transverse process of vertebrae C7 through T11 (total of 12 muscles

Insertion: tubercle of the rib below

Action: rib cage elevation

Question 15

Longus Portion O, I, A?

Answer 15

Origin: transverse process of T7 through T11

Insertion: bypass the rib below the point of origin and insert into the next rib

Action: rib cage elevation (greater impact on elevation of rib cage compared to brevis)

Question 16

Serratus Posterior Superior O, I, A?

Answer 16

Origin: spinous processes of C7 and T1-T3

Insertion: ribs 2-5

Action: elevates ribs 2-5 specifically