Thorax 1 - Thoracic Wall Flashcards
what are the two main parts of the thorax?
thoracic wall
thoracic cavity
what are the primary functions of the thoracic wall?
protects internal organs
facilitates breathing & coughing
what are the primary functions of the thoracic cavity?
- houses vital organs - heart, lungs
- contains blood vessels and nerves that control breathing (sympathetic and parasympathetic chains)
which region of the thorax contains blood vessels & nerves that control breathing - the thoracic wall or thoracic cavity?
thoracic cavity
which ribs are classified as ‘true’ ribs? why?
ribs 1-7 - attach directly to the sternum via their costal cartilage
which ribs are classified as ‘false’ ribs? why?
ribs 8-10 - join the costal cartilage of the 7th rib & attach indirectly to the sternum via shared cartilage
which ribs are classified as ‘floating’ ribs? why?
ribs 11-12 - don’t connect to the sternum, only posteriorly to thoracic vertebrae
what rib level (anteriorly) does the angle of Louis correspond to?
level of the 2nd rib
what thoracic vertebrae (posteriorly) does the angle of Louis correspond to?
T4
what are the intercostal spaces?
spaces that lie beneath each rib - i.e. the 1st intercostal space is beneath the 1st rib
how do typical ribs articulate with the vertebrae? (3)
head of the rib has 2 facets:
1. inferior articular facet articulates with the vertebrae of the same number (e.g. 4th rib IAF = T4 vertebral body)
2. superior articular facet articulates with the vertebrae above (e.g. 4th rib SAF = T3 vertebral body)
- tubercle on neck of ribs - articulates with transverse process of the sane number vertebrae (e.g. 4th rib tubercle = T4 transverse process)
what does the inferior articular facet on the head of the rib articulate with?
vertebral body of the same number vertebrae - e.g. 4th rib IAF with T4 vertebral body
what would the superior articular facet of rib 6 articulate with?
the vertebral body of T5
what would the tubercle of rib 3 articulate with?
T3 transverse process
what are the true, false and floating ribs?
true ribs (1-7)
false ribs (8-10)
floating ribs (11-12)
what are the typical and atypical ribs?
typical = ribs 3-9
atypical = ribs 1,2,10,11,12
what structures form the boundaries of the thoracic inlet - anterior, posterior, lateral?
anterior - superior border of the manubrium
posterior - T1 vertebral body
lateral - first pair of ribs
what is the angle of Louis?
junction between the manubrium & body of the sternum
what structures form the triangle-shaped costal margin? (3)
lower borders of the ribs
sternum
xiphoid process
what are the boundaries of the thoracic outlet - anterior, posterior, lateral, floor?
anterior - costal cartilages of ribs 7-10 & xiphosternal joint
posterior - T12 vertebral body
lateral - 11th and 12th ribs
floor - diaphragm
which structure is NOT part of the thoracic inlet boundaries?
A. Body of T1 vertebra.
B. Superior border of the manubrium.
C. First pair of ribs.
D. Costal cartilage of the 7th rib.
D. costal cartilage of the 7th rib
which of the following statements about floating ribs (ribs 11 and 12) is FALSE?
A. They do not attach to the sternum.
B. They articulate with the transverse processes of T11 and T12.
C. They provide some protection for the kidneys.
D. They have no anterior articulation.
B - don’t articulate with transverse processes as they lack a tubercle; only articulate posteriorly with vertebrae
what is the jugular notch?
palpable area at the top of the manubrium between the two clavicles
what features make the 1st rib atypical?
- only one articular facet on head of rib - articulates with T1 vertebral body
- tubercle articulates with T1 transverse process
- superior surface has a groove for the subclavian artery & vein
- scalene tubercle for insertion of the scalene muscle
- wide & broader than typical ribs
which rib has a roughened area on its superior surface for the attachment of the serratus anterior?
2nd rib
what are the three parts of the sternum?
manubrium
body of sternum
xiphoid process
what landmark is formed by the junction of the manubrium and the body of the sternum?
sternal angle/ angle of Louis
which ribs directly articulate with the body of the sternum?
ribs 3-7 via the costal notches
what is the function of the thoracic vertebrae in relation to the ribcage and thoracic cavity? (3)
- maintains spinal alignment through its natural curvature
- provides structural support for the ribcage
- protects vital organs in the thoracic cavity
which part of the sternum is the insertion point for the pectoralis major?
body of the sternum
how are ribs classified based on their connection to the sternum?
true ribs (1-7) - directly connected to the sternum via their own costal cartilage
false ribs (8-10) - indirectly connected via the costal cartilage of the 7th rib
floating ribs (11-12) - no connection to the sternum, only posteriorly to the thoracic vertebrae
what are the three main components of a typical rib?
head - inferior & superior articular facets
neck - tubercle
body/ shaft - includes the costal angle & costal groove
what are the typical ribs?
ribs 3-9
what are the atypical ribs?
ribs 1, 2, 10, 11, 12
what is the function of the costal groove on typical rib?
located on the internal surface along the inferior border - protects intercostal nerves & vessels
which rib contains a groove for the subclavian artery and vein?
1st rib - groove on its superior surface
why is the 1st rib clinically important?
has a close relationship to the lower nerves of the brachial plexus and
subclavian vessels - fractures will risk these structures
TRUE/FALSE: rib 1 has smooth superior and sharp inferior borders
FALSE - has a smooth inferior border and a sharp superior border
TRUE/FALSE: the 1st rib doesn’t have a costal groove, but does have grooves for the subclavian artery & vein
TRUE
which part of the rib is most susceptible to fractures in case of trauma?
A) shaft of the rib
B) angle of the rib
C) neck of the rib
D) head of the rib
B: angle of the rib
what distinguishes the 10th, 11th, and 12th ribs from other ribs?
10th rib - single articular facet on its head
11th & 12th ribs - single articular facet on its head, no neck or tubercle, shorter & more slender
what ribs don’t have a neck or tubercle?
11th and 12th ribs
what joint is formed when ribs articulate with their associated costal cartilage?
costochondral cartilage
what type of joint is the costovertebral joint? what does this mean in terms of movement?
synovial plane-type movement - very limited movement
what articulations form the costotransverse joint?
tubercle of rib with the transverse process of the same number vertebrae (e.g. 3rd rib with T3)
at what vertebral level does the jugular notch lie?
T2/T3
at what vertebral level does the sternal angle lie?
T4/T5
at what vertebral level does the xiphoid process lie?
T9
at what vertebral level does the costal margin lie?
T9-L3
what structures lie at the sternal angle? (think RAT PLANT)
Rib 2
Aortic arch
Tracheal bifurcation into bronchi
Pulmonary trunk
Ligamentum arteriosum
Azygous vein
Nerves - cardiac plexus & recurrent laryngeal nerve (branch of the vagus nerve)
Thoracic duct
+ oesophagus & pre-vertebral and pre-tracheal fascia
what does the aortic arch do at the level of the sternal angle?
aortic arch curves at the level of the sternal angle
what does the trachea do at the level of rib 2?
bifurcates into left & right bronchi
what is the ligamentum arteriosum?
fibrous structure connecting the aorta & pulmonary trunk
what vein drains into the superior vena cava at the level of the sternal angle?
azygos vein
where does the thoracic duct collect lymphatic fluid from? what does it to at the level of T4/5?
collects fluid form the lower limbs & abdomen
shifts from the right to left side at the level of T4/5 (sternal angle) before exiting the thoracic inlet
what do the pre-vertebral & pre-tracheal fascia do at the sternal angle?
they’re boundaries of the neck compartment - end at the sternal angle
what is the role of the thoracic wall in respiration?
facilitates respiratory movements - works with diaphragm & intercostal muscles to increase/decrease intrathoracic volume and pressure to allow airflow in/out of the lungs
what is the primary muscle for inspiration?
diaphragm
what happens to intrathoracic volume and pressure during inspiration?
increase in intrathoracic volume
decrease in intrathoracic pressure
allows air from outside into lungs
describe the pump-handle movement and its role in respiration - what dimension does it affect?
occurs when superior ribs 1-6 pull the sternum up & outward - increase the anteroposterior dimension of the thoracic cavity
which ribs are involved in the bucket-handle movement? what dimension does it increase?
lower ribs 7-12 involved in bucket-handle movement during relaxed inspiration
increases transverse dimension as the lower ribs go laterally and outward
how does the diaphragm contribute to changes in the vertical dimension of the thoracic cavity during breathing?
during inspiration - diaphragm contracts & flattens, increases the vertical dimension of the thoracic cavity = increases intrathoracic volume
during expiration - diaphragm relaxes & moves upwards, decreases the vertical dimension & intrathoracic volume
describe what happens in relaxed inspiration
- diaphragm contracts and flattens
- external intercostal muscles contract & elevate ribs
- increase thoracic cavity volume, decreases pressure = air flows into lungs
describe what happens in relaxed expiration
- diaphragm relaxes and moves upward
- external intercostals relax
- increase in intrathoracic volume = air can leave the lungs
what are the primary and accessory muscles involved in forced inhalation?
primary - diaphragm & external intercostal muscles
accessory - sternocleidomastoid, pectoralis minor, scalene muscles
TRUE/FALSE: the innermost muscle of the thoracic cage is responsible for assisting in forced exhalation
TRUE (along with the internal intercostal muscle)
what do the accessory muscles do during forced inspiration?
elevate the ribs and sternum - increase thoracic volume
which two of these are NOT an accessory muscle involved in forced inspiration?
A. pectoralis minor
B. scalene muscle
C. pectoralis major
D. sternocleidomastoid
E. serratus anterior
C. pectoralis major
E. serratus anterior
what muscles are involved in forced expiration?
primary muscles - diaphragm & external intercostal muscles
internal & innermost intercostal muscles
accessory abdominal muscles - internal & external obliques, rectus abdominis & transversus abdominis
what do the internal & innermost intercostal muscles & the accessory abdominal muscles do during forced expiration?
internal & innermost intercostals: depress the ribs - reduce the transverse dimension
accessory abdominal muscles: compress the abdominal cavity, increase intra-abdominal pressure and forcefully expel air
describe what happens during forced inspiration
diaphragm contracts & flattens - increases vertical dimension
external intercostals contract & elevate ribs - increase AP + transverse dimensions
accessory muscles (sternocleidomastoid, pec minor & scalene muscles) elevate ribs & increase thoracic volume
forces air into lungs
describe what happens during forced expiration
diaphragm & external intercostals relax
internal & innermost intercostals contract - depress ribs, reduce transverse dimension
accessory abdominal muscles compress abdominal cavity, increase intra-abdominal pressure
forces air out of lungs
the diaphragm is shaped as two domes. which dome is higher, and why?
right dome is higher due to the presence of the liver inferiorly
what nerve innervates the diaphragm? its nerve roots?
phrenic nerve - from anterior rami of C3,4,5
finish the saying - … keep the diaphragm alive!
C3, 4, 5
what are the three major openings of the diaphragm & their vertebral levels? what passes through these openings?
caval opening (T8) - IVC & right phrenic nerve
oesophageal hiatus (T10) = oesophagus & vagus nerves
aortic hiatus (T12) - aorta, thoracic duct & azygos vein, nervous plexus
what 4 structures pass through the aortic hiatus at T12?
- abdominal aorta into thorax
- thoracic duct with lymphatic fluid from lower limbs & abdomen
- nervous plexuses
- azygos vein
what is the nerve root of the phrenic nerve?
combined anterior rami of C3,4,5
describe the course of the phrenic nerve - how does it lie relative to the scalene muscle lungs & heart
from the combined anterior rami of C3,4,5 - runs across ANTERIOR surface of the scalene muscles
enters thoracic cavity and runs anterior to the hilum of the lungs
descends on either side of the LATERAL aspects of the heart & lies on the pericardium
what two areas/structures does the phrenic nerve provide somatosensory & sympathetic innervation to?
diaphragm & fibrous pericardium of the heart
what three muscles do the intercostal spaces contain - from superficial to deep?
external intercostal muscle
internal intercostal muscle
innermost intercostal muscle
where is the neurovascular bundle located in the intercostal space, and what is its order?
between the internal & innermost intercostal muscles - in order of vein, artery, nerve (VAN)
why is it important to aim ABOVE the rib during procedures involving the intercostal space?
avoids damaging the main neurovascular bundle
in which intercostal space and anatomical line is the needle inserted for tension pneumothorax decompression?
into the 2nd intercostal space at the midclavicular line (just above the 3rd rib - avoids damaging the main neurovascular bundle)
differentiate the positions of the main intercostal neurovascular bundle & its smaller collateral bundle
main neurovascular bundle - runs along the costal groove of the inferior border of the superior rib in the intercostal space (strict vein-artery-nerve order)
small collateral bundle - along the superior border of the inferior rib in the intercostal space
what is the external intercostal muscle responsible for?
elevating the ribs - increases AP thoracic dimension for inhalation
how do the fibres of the external intercostal muscle run?
from the inferior border of one rib to the superior border of the rib below - ‘hands in pockets’ fibre direction
what structure do the external intercostal muscles transition into as they approach the anterior thoracic wall?
external intercostal membrane (covers front of thoracic cavity)
what is the middle layer of intercostal muscle called?
Internal intercostal muscle
how do the fibres of the internal intercostal muscle run?
from the superior border of one rib to the inferior border of the rib above - ‘hands on opposite-side chest’ direction
during which respiratory phase do the internal intercostal muscles primarily function? how?
forced expiration - help depress the ribs & brings adjacent ribs closer together
how is the innermost intercostal muscle separated from the internal intercostals?
via the main (intercostal) neurovascular bundle
how is the innermost intercostal muscle structured?
two subdivisions: transversus thoracis and subcostalis
what is the origin & insertion of the transversus thoracis muscle?
origin: xiphoid process & lower sternum
insertion: costal cartilages of ribs 3-6
- located on the deep surface of the anterior thoracic wall
what is the neurovascular supply to intercostal spaces?
each intercostal space has a separate blood and nervous supply (neurovascular bundle)
describe the arrangement of the intercostal neurovascular bundle
Intercostal vein → artery → nerve (superior to inferior order ALWAYS)
Where does the neurovascular bundle run in relation to the rib?
along the inferior aspect of the rib in the costal groove
TRUE/FALSE: the innermost intercostal muscles are easy to differentiate from internal intercostals during dissection
FALSE- difficult to differentiate due to their deep position
