Thoracic Skeleton, Ventilation & Thoracic Wall Flashcards
What is the function of the thoracic skeleton?
- attachment for upper limb muscles (bony landmarks)
- protection and landmarks to the underlying viscera of the thorax (heart & lungs) and superior abdominal cavity
- openings for communication with superior and inferior region (aperatures)
- movement for respiration (ribs)
What 3 bones make up the sternum?
Manubrium
Body
Xiphoid process
What internal structures make up the sternal angle?
superior and inferior mediastinum
Where is the sternal angle found in the transverse thoracic plane?
between T4 & T5
Where is the sternocostal joint?
Between the sternum and the costal cartilage
where is the costochondral joint?
between the costal cartilage and the ribs
what is the function of costal cartilage?
increases elasticity of the structure
better for movement
What are the true ribs?
Ribs 1-7
What are the false ribs?
ribs 8-10 (attaches to the superior costal cartilage)
what are the floating ribs?
ribs 11 & 12 (attaches to T11 and T12 vertebral bodies)
Where is the costal margin located?
inferior boundary anterior thoracic wall
what does the costal margin do?
attachment for diaphragm and abdominal wall muscles
Where is the costovertebral joints located?
between the vertebral body and rib (costal facet)
where is the costotransverse joint located?
between the tubercle of rib with the transverse process
What does the tubercle of rib 5 articulate with?
- transverse process of T5
What is the relationship between the rib and vertebral body?
number rib attaches to same number vertebral body
What does the head of rib 5 articulate with?
superior costal facet of T4
interior costal facet of T5
T4/T5 intervertebral disc
what is unique about the 1st rib?
only has one articulation - T1 vertebrae
where is the costal groove located and why is it significant?
located on inferior border of rib and the intercostal neurovascular bundle can be found here
what is the weakest part of the rib?
anterior to the angle - many trauma related fractures occur here
why are rib fractures painful?
- can puncture the lining resulting in pneumothorax
- neurovascular bundle is located within the costal groove
what is the order of the neurovascular bundle?
rib –> thoracic wall
Vein
Artery
Nerve
[muscle]
Nerve
Artery
Vein
(rib)
describe the location of the superior thoracic aperature
1st rib, T1 vertebra, jugular notch of sternum
describe the passageway for vital structures in and out of the thoracic cavity to the superior thoracic aperature
thoracic cavity neck
thoracic cavity upper limb
describe the passageway for vital structures in and out of the thoracic cavity to the inferior thoracic aperture
thoracic cavity abdominal cavity
describe the location of the inferior thoracic aperature
enclosed by the diaphragm
during inhalation and exhalation, how do the structures move?
everything moves up and down together
What happens to the thoracic skeleton during inhalation?
volume increases
pressure decreases
ribs move up and out
diaphragm flattens
what happens to the thoracic cavity during exhalation?
volume decreases
pressure increases
ribs fall
diaphragm moves up
what nerve innervates the diaphragm?
phrenic nerve (C3, C4, C5)
where does the diaphragm sit at the right dome?
liver inferior
level of the 5th rib at rest
where does the diaphragm sit at the left dome?
stomach and spleen inferior
level of the 5th intercostal space at rest
what is the superior attachment of the diaphragm?
central tendon
what are the functions of the diaphragm?
- separates thoracic cavity and abdominal cavity
- encloses inferior thoracic aperture
- primary muscle for ventilation
what are the inferior attachments to the diaphragm?
- xiphoid process of sternum
- costal margin
- ends of ribs 11 and 12
- arcuate ligaments across posterior wall
- lumbar vertebrae
What major structure passes through the caval opening/vena caval hiatus and at what level?
Inferior vena cava
Level T8
what major structure passes through the esophageal hiatus and at what level?
Esophagus
Level T10
what major structure passes through the aortic hiatus and at what level?
thoracic aorta
level T12
what other structures pass through the caval opening?
right phrenic nerve
what other structures pass through the esophageal hiatus?
vagal trunks
what other structures pass through the aortic hiatus?
azygos vein
thoracic duct
sympathetic trunks
what are the accessory muscles used in forced inspiration?
external intercostals neck muscles (sternocleidomastoid and scalene group)
what are the accessory muscles of expiration?
internal intercostals abdominal muscles (external oblique and rectus abdominus)
name the thoracic wall muscles
pec major pec minor serratus anterior sternocleidomastoid anterior, middle, posterior scalenes external oblique rectus abdominus
name the true muscles of thoracic wall (muscles directly on the ribs)
transversus thoracis
subcostal (found in between each rib)
serratus posterior superior and inferior
levatores costarum longus and brevis
what are the functions of the intercostal muscles?
- maintain structure of thoracic wall
- rib movement during respiration
- inner layers enclose neurovascular bundle
what does the external intercostal layer do and what way does the fibers run?
- elevates ribs during inspiration
- fibers run hands in pockets
where is the external intercostal membrane located?
sternum anteriorly
what does the internal intercostal muscles do and which way does the fibers run?
- depress ribs during exhalation
- “oh my” muscle fiber direction
where is the internal intercostal membrane located?
vertebral bodies posteriorly
which intercostal muscle layer is the most deep and has same fiber direction as the internal layer?
innermost intercostal muscles
between which layers are the intercostal vein, artery and nerve found?
between internal and innermost layers - innermost does not have intercostal membrane
describe the posterior intercostal vein system
posterior intercostal veins drain into azygos vein
accessory hemi-azygos vein and hemi-azygos vein drain into azygos vein
azygos vein drains into the superior vena cava
superior vena cava branches to the right and left brachiocephalic veins
at superior levels where does the posterior intercostal veins sometimes drain into?
straight into the brachiocephalic vein
describe the anterior vein drainage
anterior intercostal veins drain into internal thoracic veins
internal thoracic veins drain into brachiocephalic veins
which two main sources does the intercostal arteries originate from?
subclavian artery
thoracic aorta
describe the anterior drainage from the subclavian artery
suclavian artery supplies blood to the internal thoracic artery
internal thoracic artery supplies blood to anterior intercostal arteries
describe the posterior blood supply of the subclavian artery
subclavian artery supplies blood to costocervical trunk
costocervical trunk supplies blood to 1st and 2nd posterior intercostal arteries
describe the blood supply from the thoracic aorta
thoracic aorta supplies blood to posterior intercostal arteries (T3-T11) AND subcostal artery (T12)
where do the intercostal and subcostal nerves arise from?
anterior rami of thoracic spinal nerves
describe the pathway of the intercostal nerve
intercostal nerve –> lateral cutaneous branch –> anterior cutaneous branch
what is the motor innervation of the intercostal nerve?
intercostal mm
transversus thoracis mm
subcostal mm
rectus abdominus and external oblique (abdominal wall muscles)
what is the sensory innervation for the intercostal nerves?
skin at each thoracic nerve level (dermatomes)
- can overlap 1-2 dermatome levels
lower thoracic nerves (T6-T11) and subcostal nerve cross the costal margin
what does sympathetic innervation in the periphery do?
- activate sweat glands
- cause hair follicles to stand on end
- vasoconstricts blood vessels in the skin
what is involved in the sympathetic pathway?
sympathetic chain - will see its location in the posterior mediastinum
