Thorax, Tracheobronchial Tree & Lungs (Part 1)

Question 1

What is the thorax?

Answer 1

Irregularly cylindrical cavity with openings at top & bottom composed of a thoracic wall, pleural cavities & mediastinum

Question 2

What are the functions of the thorax?

Answer 2

Passageway between abdomen & neck/upper limb for vessels & nerves

Protection of organs

Breathing

Question 3

What are the 2 openings of the thorax called?

Answer 3

Superior thoracic aperture

Inferior thoracic aperture

Question 4

What is the bottom boundary of the thorax?

Answer 4

Diaphragm

Question 5

What is within the mediastinum?

Answer 5

Heart

Great vessels

Question 6

How does the thoracic wall allow breathing?

Answer 6

Able to withstand a range of positive & negative pressures during breathing

Mobile structure but with structural rigidity

Question 7

Describe the structure of the ribs.

Answer 7

12 paired ribs with intercostal muscles in between

Ribs 1-10 end in costal cartilage whilst 11-12 embedded in muscle

Articulate with thoracic vertebra posteriorly around the thoracic inlet and connect to the sternum via costal cartilage anteriorly with variable articulations

Question 8

Why can ribs move?

Answer 8

Articulation of ribs have synovial joints

Question 9

What will happen if the ribs are fractured in terms of breathing?

Answer 9

Paradoxical movement of thoracic wall segment at point of fracture; ribs will not move normally e.g. they will depress rather than expand in inspiration

Question 10

What is the lower border of the costal cartilage called?

Answer 10

Costal margin

Question 11

What structures go through the thoracic apertures?

Answer 11

Part of brachial plexus

Subclavian vessels

Question 12

What can happen if you are born with an cervical rib (at C7 instead of T1)?

Answer 12

May compress brachial plexus -> 1st dorsal webspace of hands looks deflated as these muscles are innervated by the brachial plexus and they atrophy due to lack of stimulation

Question 13

What parts make up the sternum from the top down?

Answer 13

Suprasternal (jugular) notch (T2)
Manibrium
Manubrio/sternal angle (T4/5)
Body
Xiphoid process (T9/10)

Question 14

What bit of the sternum is useful to palpate? What does this give you an indication of?

Answer 14

Sternal angle

Indicates that the 2nd costal cartilage is lateral & the sternal plane (T4/T5 IV disc)

Also divides sternum & mediastinum into superior & inferior parts

Question 15

Are fractures of the sternum common?

Answer 15

No, usually only seen with serious of fatal injury

Question 16

Where are the costal grooves of the rib? Why are they relevant?

Answer 16

On inferior margin

Where neurovascular bundle runs (collateral & accessory bundles inferior too)

Question 17

What is the rib angle useful for?

Answer 17

Used by anaesthetists as a landmark to perform intercostal nerve blocks

Question 18

What is in the neurovascular bundle in order?

Answer 18

V: Vein
A: Artery
N: Nerve

Question 19

What do most ribs articulate with?

Answer 19

Bodies of their own vertebra (w/ synovial joints) AND one above it AND with transverse process of their own

Question 20

What are the 3 classifications of the ribs and what ribs does each one cover?

Answer 20

1. Vertebrosternal (ribs 1-7)
2. Vertebrocostal (ribs 8-10)
3. Floating ribs (ribs 11-12)

Question 21

What are the 3 layers of intercostal muscles that fill the intercostal spaces?

Answer 21

1. External intercostal muscle
2. Internal intercostal muscle
3. Innermost intercostal muscle

Question 22

What muscle layers does the neurovascular bundle run between?

Answer 22

Internal & innermost intercostal muscles

Question 23

What is the function of the intercostal muscles?

Answer 23

Provide support & contribute to thoracic wall movements

Question 24

What muscles control inspiration and expiration mainly? What do they do?

Answer 24

Inspiration: external intercostal muscles (move downwards)

Expiration: internal intercostal muscles (move upwards)

Question 25

Where should chest drains be inserted? Why?

Answer 25

Inferior part of intercostal spaces to avoid damaging the MAIN neurovascular bundle

Question 26

What layer is on the inside of the innermost intercostal muscle?

Answer 26

Endothoracic fascia

Question 27

Where do the intercostal nerves come from and what do they innervate?

Answer 27

Ventral rami of spinal nerves Provide motor & sensory to the intercostal space & surrounding tissue (e.g. skin, cartilage, bone, muscle & parietal pleura)

Question 28

Why is the dermatomal arrangement of intercostal nerves relevant clinically?

Answer 28

Pleuritic pain can refer to dermatome Shingles can distribute to dermatome

Question 29

Where does the sympathetic chain run?

Answer 29

Along posterior thoracic wall (T1-L2)

Question 30

What can compress the sympathetic chain in its apical region? What can this cause? Why?

Answer 30

Pancoast tumour i.e. apical lung tumour -> Horner's syndrome; this chain sends branches to head & neck so symptoms will show in face mainly e.g. ptosis, miosis & loss of hemifacial sweating (on same side as tumour)

Question 31

Describe the arrangement of the anterior (AIA) and posterior intercostal arteries (PIA).

Answer 31

PIA from descending aorta & AIA from internal thoracic artery + musculophrenic -> join to form anastomosis in middle Allows a collateral circulation that can provide a potential bypass in aortic coarctation

Question 32

What can the internal thoracic arteries (ITA) be used for? Why?

Answer 32

Coronary artery bypass grafting (CABG) because ITA resists plaque build up better than most arteries in body so good to harvest & replace a artery that doesn't work anymore

Question 33

How is the thoracic wall drained?

Answer 33

Unpaired azygous system: - Upper intercostal spaces drain directly in brachiocephalic veins -> subclavian veins - Right sided structures drain in azygous vein -> SVC - Left sided structures drain via accessory azygous/hemiazygous veins-> cross midline into azygous -> SVC

Question 34

Where is the thoracic duct? What does it do?

Answer 34

Runs through posterior & superior mediastinum, anterior to vertebral bodies Drains majority of bodies lymph fluid into left subclavian vein

Question 35

What is special about the left subclavian vein?

Answer 35

Extra supraclavicular nodes sit around this region due to the amount of lymph fluid draining at this point

Question 36

What is the diaphragm?

Answer 36

Muscular & tendinous structure that domes into the thoracic cavity & fills inferior thoracic aperture

Question 37

What are the characteristic features of the diaphragm?

Answer 37

Right & left domes - Central tendinous part for heart - Attaches to costal margin & ribs 10-12 - Diaphragmatic crura attach to lumbar vertebrae

Question 38

What happens to the diaphragm during inspiration?

Answer 38

Drops down & flattens = thoracic cavity volume increases -> decreased pressure allowing air to move into the lungs

Question 39

Describe the innervation of the diaphragm.

Answer 39

Phrenic nerve (C3-5) provides motor & sensory Additional sensory innervation on periphery from intercostal nerves

Question 40

What will occur if there is unilateral damage to the phrenic nerve?

Answer 40

Hemidiaphragmatic palsy

Question 41

Where can gallbladder inflammation cause pain?

Answer 41

Shoulder due to the phrenic nerve Regional pain in right hypochrondium due to intercostal nerve As its in the midclavicular line around the 9th rib

Question 42

What structures pierce the diaphragm? Why can this be problematic?

Answer 42

IVC (T8) Oesophagus (T10-12) Aorta (T12) Creates relative weak spots through which a sliding or rolling hernia can form

Question 43

Where can congenital diaphragmatic defects occur?

Answer 43

Posterolaterally (Bochdalek): part of liver pops up into diaphragm Retrosternally (Morgagni): tranverse colon & greater omentum coming up behind diaphragm behind midline of sternum If severe must be fixed early in life

Question 44

The diaphragm separates the thoracic cavity from the ___ __.

Answer 44

Abdominal cavity