Thorax

Question 1

What are the two main purposes of the musculoskeletal component of the thorax?

Answer 1

1) protective

2) helps you breathe

Question 2

Describe the thoracic wall.

Answer 2

12 vertebrae
12 ribs (from thoracic vertebrae)

Question 3

Describe the twelve ribs.

Answer 3

7 true ribs (1-7)(articulates directly to sternum in front)
3 false ribs (8-12)(articulate indirectly through costal arch)
2 “floating ribs” - no anterior articulation, embedded in muscle (11th and 12th)

Question 4

Describe the sternum.

Where is the sternal angle?

Answer 4

manubrium- suprasternal notch at T2, sternal angle of Louis T4
body- composed of sternebrae
xiphoid process (inferior part) -xipersternal joint (T9-T10)

sternal angle is between manubrium and body. 2nd rib articulates at this place. (can’t feel 1st because its covered by clavicle)

Question 5

How do the ribs angle? Why is this important?

Answer 5

angle inferiorly back to front… important for breathing!
lifting ribs on each other because angled down you increase the volume in the thoracic cavity and increase negative pressure that allows passive inflow to lungs

Question 6

The angle of the ribs also affects the sternal angle and its projection posteriorly. Where does it project posteriorly?

Answer 6

because it projects posteriorly to 3rd or 4th thoracic vertebrae

Question 7

Describe the muscles of the thoracic wall

Answer 7

back muscles

muscles of upper extremity ( serratus anterior, latissimus dorsi, pec major and minor, rhomboids)

intercostal muscles (external and intern intercostal, innermost intercostal, transversus thoracis… attaches to ribs from inferior part of sternum but not technically between ribs)

diaphragm

Question 8

Describe the intercostal muscles.

Answer 8

Posteriorly mostly but become aperneurotic or membranic as swing around front.

external layer (3)
internal intercostal muscle -90 degree angle to external layer
innermost intercostal- up/down

Question 9

What is the function of the intercostal muscles?

Answer 9

raise ribs superiorly onto next rib with 1st rib anchored to SCM/manubrium and some scalene muscles.

increase the volume of thoracic cavity as inspire.

Question 10

Describe the blood supply to the anterior thoracic wall.

Answer 10

supplied by anterior intercostals which are branches of the internal thoracic (branch off subclavian, runs down sternum) and musculophrenic arteries (up to 7th intercostal spaces, above that supplied by internal thoracic)

also supreme thoracic artery

Question 11

Describe the blood supply to the posterior thoracic wall. (arteries)

Answer 11

supplied by posterior intercostals which are branches of the aorta and costocervical trunk. (off subclavian, 1st/2nd intercostal spaces)

(aorta starts 3rd/4th intercostal spaces)

Question 12

Describe the venous drainage of the thoracic wall.

Answer 12

venous drainage is into the corresponding veins (internal thoracic, etc) anteriorly,
 brachiocephalic 
azygos veins (posteriorly)

Question 13

What innervates the intercostal muscles?

Answer 13

innervates intercostal spaces

ventral rami of thoracic nerves (intercostal nerves)

12th- called subcostal nerve because its below the ribs. (only 11 intercostal spaces)

Question 14

Describe intercostal muscles and neurovascular supply superior to inferior.

Answer 14

VAN

Veins, arteries, nerves

Question 15

Where would you place a needle in the thoracic space? Why?

Answer 15

above the rib because below the rib could cut nerve and/or vessels.

Question 16

Describe the three major compartments of the thorax.

Answer 16

2 lungs (each enclosed by its pleural cavity)
space between the pleural cavities (mediastinum)

Question 17

Describe the asymmetry of the superior mediastinum.

What are the clinical implications for this?

Answer 17

R brachiocephalic vein is more vertical and left is more horizontal

Superior vena cava drains to R side of heart so L brachiocephalic vein is longer

• easier to enter right side.

Question 18

Describe the location of veins/arteries within the superior mediastinum.

Answer 18

veins in front, arteries posterior to that

Remember: (with subclavian artery behind ant. scalene…vein in front of ant. scalene)

Question 19

Describe the location of the phrenic n/ vagus nerve in superior mediastinum.

Answer 19

phrenic goes on surface of pericranium of heart to get to diaphragm and follows right brachiocephalic vein on the right side. follows arch of aorta on left side of heart.

vagus nerve follows esophagus into abdominal cavity so will go posteriorly.

phrenic and vagus will cross each other.

Question 20

What occurs with the trachea at the sternal angle?

Answer 20

divides into bronchii

trachae is pushed off to the side of esophagus– so right bronchus is shorter than left because shoved by arch of aorta which goes to the left.

Question 21

What do the left and right brachiocephalic veins join to form?

Answer 21

superior vena cava which delivers blood to right atrium of heart

Question 22

What are the 3 true cavities?

think of as closed sac

Answer 22

pleural- lungs
pericardium- heart
peritineal- abdominal viscera

Question 23

Describe the two layers of the cavities.

Answer 23

visceral- closest

parietal- outer

Question 24

Describe the thoracic inlet and outlet.

Answer 24

thoracic inlet (superior aperture) is bounded by the manubrium, first rib, and T1 vertebrae

thoracic outlet (inferior aperture) bounded by the xiphoid process, costal arch, and rib 12. This aperture is closed off by the diaphragm.

Question 25

Describe the boundaries of the mediastinum.

Answer 25

area between the right and left pleura cavities

superior-thoracic inlet
inferior- thoracic outlet (diaphragm)
antero-lateral-sternum and ribs
posterior- thoracic vertebrae

Question 26

Describe the boundaries and contents of the superior mediastinum.

Answer 26

bounded superiorly by thoracic inlet and inferiorly by a horizontal line through the sternal angle

contains:
aortic arch, brachiocephalic trunk, left common carotid a, left subclavian a, superior vena cava, brachiocephalic v (thymus and trachea and esophagus), vagus and phrenic n (recurrent laryngeal and thoracic duct)

Question 27

Describe the boundaries of the middle mediastinum and its contents.

Answer 27

area around the heart. Contains: pericardium, heart and great vessls, root of lungs, phrenic nerves

Question 28

Describe the boundaries of the anterior mediastinum and its contents.

Answer 28

area in front of heart and behind sternum. Contains: areolar tissue and lymph nodes

Question 29

Describe the posterior mediastinum and its contents.

Answer 29

area behind heart

contains: descending aorta, azygos and hemiazygos v, esophagus, vagus n, thoracic splanchnic n, thoracic duct