Thoracic Cavity: Musculature, Innervation, & Vasculature

Question 1

What are the muscles of the thoracic cavity?

Answer 1

Most superficial to Deep;

External Intercostal m.

*Membrane of EIC overlies medial portion of IIC

Internal intercostal m.

Innermost intercostal m.

Transversus Thoracis (continuation of innermost)

Question 2

How can the External, Internal, & Innermost Intercostals be differentiated?

Answer 2

1. Fiber Direction:

EIC fibers go down & in (like hands in pockets) while IIC & ImIC fibers move up & in.

(IIC & ImIC both have identical fiber direction)

2. Location relative to IC neurovascular bundle:

IIC fibers are located superficial to the IC-NB, while the ImIC fibers are deep

Question 3

The Diaphragm is innervated by which nerve?

What is the spinal n. contribution?

Answer 3

The Phrenic n. innervates the diaphragm;

Spinal nerves;

C3, C4, C5

“C3,C4,C5 keep the diaphragm alive”

The Phrenic n. also innervates a couple soft tissue structures. If irritated, they send referred pain back to the C3,4,5.

Question 4

Which muscles are involved in Inspiration?

Answer 4

Primary:

Diaphragm

External Intercostals

Secondary:

Scalenes

Sternocleidomastoid

Internal Intercostals (parasternal part)

Question 5

Describe the changes in thoracic volume relative to changes in the axis

Answer 5

Vertical Axis:

Contraction of the diaphragm & upward pull on the superior thoracic aperture by the scalenes & SCM.

Intercostals contract to maintain inter-rip spacing

A-P Axis:

Upper ribs (2-6) are raised by pulling on the thorax and contraction of intercostals (pump handle)

Transverse Axis:

Lower ribs (7-10) are raised by pulling on thorax & contraction of intercostals (bucket handle)

*Diaphragm accounts for 2/3 of total change in thoracic cavity capacity

Question 6

Which muscles are involved in Force Expiration?

Answer 6

Abdominal muscles:

Transversus Abdominus

Abdominal Obliques

Rectus Abdominus

Internal Intercostals:

Lateral part

Innermost intercostals?

Quadratus lumborum?

Question 7

What is the primary respiratory function of the abdominal muscles?

Answer 7

Abdominal muscles will increase intraabdominal pressure, forcing the diaphragm upwards and forcefully exhaling air from the lungs.

Question 8

Identify which letters belong to the Thoracic musculature

Answer 8

E. External Intercostals

F. External Intercostal membrane

G. Internal Intercostals (EI membrane removed)

Question 9

ID each letter

Answer 9

A. Left Vagus n.

B. Phenic n.

C. Phrenic n.

D. Fibrous Pericardium

E. Pleura

F. Costodiaphragmatic Recess