Thorax I

Question 1

What is the role of the thoracic cage?

Answer 1

Protect organs, pressurize thorax, muscular attachment for upper limp, anchoring muscles

Question 2

What are the elevators of the rib cage? (during forced inspiration)

Answer 2

Scalene, Pec Minor, Subclavious, and Serratus anterior

Question 3

What is the common action of the intercostals?

Answer 3

• Decrease the space between the ribs by puling the ribs together, which changes thoracic space of the thoracic cavity.
  
  • Depending on which rib is anchored (1st or 12th) will determine the movement

Question 4

What do the serratus posterior superior and inferior do?

Answer 4

Act on the thoracic wall to either elevate (superior) or depress (inferior) the ribs

Question 5

What Intercostal Nerve innervates the space above the 4th rib?

Answer 5

the 3rd intercostal N, it is based on the number of the rib superior to intercostal space

Question 6

What happens to thoracic volume when the 1st rib is fixed? What about when the 12th is fixed?

Answer 6

(1st rib fixed) - Increase: anterior - posterior diameter & transverse diameter
(12th rib fixed)- Decrease: anterior - posterior diameter & transverse diameter

Question 7

How does Inspiration effect Intrathoracic and abdominal pressures?

Answer 7

• Inspiration: Contraction produces a drop in intrathoracic pressure and raises abdominal pressure

Question 8

How does expiration effect Intrathoracic and abdominal pressures?

Answer 8

-Expiration: Relaxation of diaphragm allows increased abdominal pressure to drive diaphragm upward, thereby increasing the intrathoracic pressure

Question 9

What does a deep breath followed by contraction of diaphragm do? What is another name for this?

Answer 9

• Raises intra abdominal pressure
  
  • Stabilizes vertebral column
  • AKA: Valsalva Maneuver

Question 10

How does Vertical Diameter of thorax increase during quiet inspiration?

Answer 10

• Diaphragm contracts and flattens

Question 11

How does anteroposterior diameter increase during quiet inspiration?

Answer 11

1st rib is fixed

- Scalenes and intercostals contract
- Sternum and ribs are drawn superiorly and anteriorly (Pump Handle)

Question 12

How does transverse diameter increase during quiet inspiration?

Answer 12

Contraction of intercostals raises angles of ribs (Bucket Handle)

Question 13

How does forced inspiration differ from quiet inspiration?

Answer 13

• rib cage is further fixed by securing the shoulder girdle allowing shoulder muscles to assist

Question 14

Which muscles of the shoulder girdle assist in forced inspiration?

Answer 14

Traps, lev scap, serratus anterior, pec minor, pec major and rhomboids.

Question 15

How does quiet expiration occur?

Answer 15

Passively, through the elastic recoils of the lungs and ribs

- Abdominal pressure> intrathoracic pressure, which drives the diaphragm up.

Question 16

Describe Forced Expiration:

Answer 16

• Passive is assisted by muscle recruitment.
  
  • Abs contract to increase abdominal pressure, also ribs pulled down
  • Intercostals contract to depress ribs

Question 17

What forms the intercostal nerves?

Answer 17

Ventral rami of T1-T11 form costal nerves

Question 18

What forms the subcostal nerves?

Answer 18

• Ventral rami of T12 forms subcostal nerves

Question 19

Where do the posterior intercostal arteries arise from?

Answer 19

• 1st and 2nd Posterior intercostals from the supreme intercostal artery (costocervical)
  
  • The descending (thoracic) aorta

Question 20

Where do the anterior intercostal arteries (upper 9) arise from?

Answer 20

• The internal thoracic artery (subclavian I)

Question 21

Beneath the 12th ribs where do the subcostal arteries arise from?

Answer 21

• The thoracic aorta

Question 22

What do the dorsal branches of posterior intercostals supply and what structure accompanies them?

Answer 22

• Accompanied by: dorsal rami

- Supplies: Spinal cord, vertebral column, back muscles, skin

Question 23

Describe how the intercostal vasculature (arteries only) works starting from the aorta:

Answer 23

From the aorta we have the brachiocephalic trunk which gives rise to the subclavian A

• Remember that the subclavian has 3 parts to it:
• Part 1: Internal Thoracic - which gives rise to our Anterior Intercostals
• Part 2: Gives rise to costocervical trunk that gives rise to supreme intercostal A
  
  • SIA: gives rise to 1st and 2nd Posterior Intercostal A.
  • After 2nd space, Aorta gives rise to Posterior Intercostal A. 3-12
• Anterior and Posterior Intercostal A’s anastomose anteriorly Beneath the 12th rib pair the subcostal pair of arteries arise from the thoracic aorta

Question 24

Where do the Posterior Intercostal veins drain?

Answer 24

Posterior Intercostal Veins drain into Azygos vein (R) or Hemiazygos (L)

Question 25

What are the causes of a pneumothorax? How do you treat pneumothorax?

Answer 25

Causes:

• penetrating wound to the chest wall (excess air enters pleural cavity)
• infections, diseases (COPD, emphysema)

Treatment:
-trapped air is removed using a syringe and needle connected to a 3-way tap