Muscles Of The Anterior Thoracic Wall

Question 1

Intercostobrachial Nerve

Answer 1

It exits below rib 2 to innervate skin of the medial aspect of the arm

Question 2

External Intercostal Muscles (“hands in pocket”)

Answer 2

Origin: lower margin of one rib
Insertion: upper margin of the next rib
-course obliquely forward and downward from the costal tubercle to the costochondral junction
-innervation: 1st-11th intercostal nerves
Action: raise the ribs during inspiration, to support the intercostal spaces and to stabilize the chest wall

Question 3

External Intercostal Membrane

Answer 3

Replaces the external Intercostal muscles at the costochondral junction

Question 4

Internal Intercostal Muscle

Answer 4

-deep to the external intercostal membrane (and muscle)
Origin: from the lower margin of one rib
Insertion: onto the upper margin of the next lower rib
Course: obliquely forward and upward from the costal angle to the sternum
Innervation: 1st to 11th intercostal nerves
Action: lower the ribs during expiration, to support the Intercostal spaces and to stabilize the chest wall
—fibers run perpendicular to the external intercostal muscles

Question 5

Innermost Intercostal Muscles

Answer 5

-fiber direction similar to the internal intercostal muscles
Origin: from the lower margin of one rib
Insertion: onto the upper margin of the next rib
Course: obliquely forward and upward from the costal angle to the sternum
Innervation: 1st to 11th Intercostal nerves
Action: lower the ribs during expiration, to support the Intercostal spaces, and to stabilize the chest wall

Question 6

Intercostal artery, vein, nerve

Answer 6

Course: in between the internal and innermost Intercostal muscle layers

Question 7

Transversus Thoracis

Answer 7

-radiating from the inferior aspect of the sternum
Origin: inner surface of the body and xiphoid process of the sternum
Insertion: inner surface of ribs 2-6 as well as too the costal cartilages at these levels
Innervation: 2nd to 7th Intercostal nerves
Action: weakly lower the ribs during expiration

Question 8

Parietal Pleura and Endothoracic Fascia

Answer 8

Costal portion is covering the deep surface of the thoracic cage

• underneath costal pleura is the endothroacic fascia
• —-this fascia is a layer of connective tissue responsible for binding the parietal pleura to the body wall.

Question 9

Internal Thoracic Artery and Vein

Answer 9

-just under the parietal pleura on either side of the body of the sternum
-vein is often split into two on either side of the artery in a venae comitantes relationship that helps facilitate blood through the vein
-Artery: arises from the subclavian artery in the root of the neck
-they give off the anterior intercostal arteries and veins
Eventually the artery bifurcated into the musculophrenic and superior epigastric arteries (near lower border of the ribs)