Thorax I Flashcards
What is the role of the thoracic cage?
Protect organs, pressurize thorax, muscular attachment for upper limp, anchoring muscles
What are the elevators of the rib cage? (during forced inspiration)
Scalene, Pec Minor, Subclavious, and Serratus anterior
What is the common action of the intercostals?
- 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
What do the serratus posterior superior and inferior do?
Act on the thoracic wall to either elevate (superior) or depress (inferior) the ribs
What Intercostal Nerve innervates the space above the 4th rib?
the 3rd intercostal N, it is based on the number of the rib superior to intercostal space
What happens to thoracic volume when the 1st rib is fixed? What about when the 12th is fixed?
(1st rib fixed) - Increase: anterior - posterior diameter & transverse diameter
(12th rib fixed)- Decrease: anterior - posterior diameter & transverse diameter
How does Inspiration effect Intrathoracic and abdominal pressures?
- Inspiration: Contraction produces a drop in intrathoracic pressure and raises abdominal pressure
How does expiration effect Intrathoracic and abdominal pressures?
-Expiration: Relaxation of diaphragm allows increased abdominal pressure to drive diaphragm upward, thereby increasing the intrathoracic pressure
What does a deep breath followed by contraction of diaphragm do? What is another name for this?
- Raises intra abdominal pressure
- Stabilizes vertebral column
- AKA: Valsalva Maneuver
How does Vertical Diameter of thorax increase during quiet inspiration?
- Diaphragm contracts and flattens
How does anteroposterior diameter increase during quiet inspiration?
1st rib is fixed
- Scalenes and intercostals contract - Sternum and ribs are drawn superiorly and anteriorly (Pump Handle)
How does transverse diameter increase during quiet inspiration?
Contraction of intercostals raises angles of ribs (Bucket Handle)
How does forced inspiration differ from quiet inspiration?
- rib cage is further fixed by securing the shoulder girdle allowing shoulder muscles to assist
Which muscles of the shoulder girdle assist in forced inspiration?
Traps, lev scap, serratus anterior, pec minor, pec major and rhomboids.
How does quiet expiration occur?
Passively, through the elastic recoils of the lungs and ribs
- Abdominal pressure> intrathoracic pressure, which drives the diaphragm up.
Describe Forced Expiration:
- Passive is assisted by muscle recruitment.
- Abs contract to increase abdominal pressure, also ribs pulled down
- Intercostals contract to depress ribs
What forms the intercostal nerves?
Ventral rami of T1-T11 form costal nerves
What forms the subcostal nerves?
- Ventral rami of T12 forms subcostal nerves
Where do the posterior intercostal arteries arise from?
- 1st and 2nd Posterior intercostals from the supreme intercostal artery (costocervical)
- The descending (thoracic) aorta
Where do the anterior intercostal arteries (upper 9) arise from?
- The internal thoracic artery (subclavian I)
Beneath the 12th ribs where do the subcostal arteries arise from?
- The thoracic aorta
What do the dorsal branches of posterior intercostals supply and what structure accompanies them?
- Accompanied by: dorsal rami
- Supplies: Spinal cord, vertebral column, back muscles, skin
Describe how the intercostal vasculature (arteries only) works starting from the aorta:
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
Where do the Posterior Intercostal veins drain?
Posterior Intercostal Veins drain into Azygos vein (R) or Hemiazygos (L)
What are the causes of a pneumothorax? How do you treat pneumothorax?
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
