Thoracic Wall Flashcards
What are the component of the thoracic wall?
Skin
Bone
Fascia
Muscles
What are the boundaries of the thoracic wall?
Superior:
- vertebra T1, rib 1, manubrium
Inferior
- vertebra T12, rib 12, costal margin, xiphoid process
Transversely
- thoracic cage
What are the borders of the thoracic cavity?
Superior border of the liver
Inferior borders of the lungs
Inferior border of pleura
A stab wound below rib _ can pierce the abdominal cavity.
5
Stab wound in the ______ can pierce the lungs.
neck
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What are the functions of the thoracic wall?
- Protects internal air and fluid-filled organs
- Provide rigid exterior wall to prevent collapse of elastic lungs
- Provides for lung expansion
- Privides attachment and support to upper limbs
What are the reference lines of the thoracic wall?
- Jugular (suprasternal) notch
- Sternal angle
- Anterior median (midsternal) line
- Midclavicular lines
- Axillary fossa
- Anterior axillary line
- Midaxillary line
- Posterior axillary line

What are the surface landmarks of the thoracic wall?
Jugular notch
Clavicle
Anterior axillary fold
Manubrium
Sternal angle and manubriosternal joint
Body of sternum
Xiphisternal joint
Infrasternal (subcostal) angle
Costal margin
What is the significance of the sternal angle?
- used to ascertain the position of rib 2
- Marks plane through T4-5 intervertebral disc
- Marks the superior edge of the heart
- Marks the bifurcation of the trachea
- Marks the level of azygos arch
What is the signiicance of the orientation of the ribs?
Downward slope of ribs is critical to function
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Which part of the rib articulates with the vetebrae above?
Articular facet
Which part of the rib articulates with the numerically corresponding vertebrae?
Tubercle
Which part of the rib is for the intercostal vein, artery, and nerve?
Costal groove
Which ribs are considered “atypical”?
1,2, 11, and 12
Which muscles articulates with the first rib?
Levator costae
Scalenus medius
Serratus anterior
Scalenus anterior
Subclavius
*NOTE: The costaclavicular ligament also articulates with the 1st rib
Label
1st rib
Which ribs are considered true ribs?
Ribs 1-7
*True ribs are ribs that are attached directly to the sternum by costal cartilage
Which ribs are considered false ribs?
Ribs 7-12
*False ribs do not attach to the sternum directly but are attached to the 7th rib by cartilage
Which ribs are considered floating ribs?
Ribs 11-12
*Floating ribs are important or anchoring of rib cage by abdominal muscles.
Vertebrae, sternum and ribs contain ____________ marrow; a source of blood cells.
red
The thoracic vertebrae have two different articulations: intervertebral and costal. What does each articulation allow for?
Intervertebral: slight rotation of the trunk
Costal (costal facts of transverse processes): Elevation of ribs
*The discs found in between each vertebrae allows for weight bearing
Demi facets are found on __________ of the thoracic vertebrae.
Body
Rib has same number as the _________ (superior/inferior) vertebra and its transverse process.
Inferior
As ribs rotate and elevate along ___________ joint, thorax expands both laterally and anteriorly.
costovertebral
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Sternum
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List the 4 sternal joints
•Sternocostal:
- rib 1 (fibrocartilaginous)
- ribs 2-7 (synovial)
- Interchondral: synovial
- Manubriosternal: symphysis
- Xiphisternal: symphysis
NOTE: Symphsis and costal cartilage ossify with age

If multiple rib fractures produce an isolated segment, get _____________: paradoxical movement produces pain and impairs breathing.
flail chest
Rib dislocation
an injury where one or more of the ribs are moved from their normal location in the chest cavity
Where do rib separations occur?
At the costochondral joint
Where do rib fractures usually occur?
Just anterior to the angle
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The internacostal vein, artery and nerve run between which two muscles?
Internal intercostal
Innermost intercostal
NOTE: These muscles are numbered by the superior rib
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What are the attachment point for transversus thoracis?
The inferior attachment of the transversus thoracis muscle is on the sternum and its superior attachments are on costal cartilages 2 to 6.
What is the function of transversus thoracis?
The transversus thoracis muscle depresses the ribs.
Label
Proprioceptive muscles
What are the major muscles of inspiration and expiration respectively?
Inspiration: Diaphragm
Expiration: Abdominal wall muscle
What is the major function of intercostal muscles?
Stiffen wall to resist elastic forces
What actions are involved in quiet inspiration?
- Diaphragm contracts
- External intercostal muscles pull rib up and out
What actions are involved in forced inspiration?
- Sternocleiodomastoid elevates sternum
- Pectoralis minor elevates rib
- Diaphragm contracts more (than in quiet inspiration)
What actions are involved in quiet expiration?
Abdominal organs recoil and press diaphragm upward
What actions are involved in forced expiration?
- Posterior internal intercostal muscles pull ribs down and inward
- Abdominal organs force diaphragm higher
- Abdominal wall muscles contract and compress abdominal organs
What are the accessory respiratory muscles?
Trapezius
Scalenus
Sternocleidomastoid
*People with dyspnea (asthma, emphysema, heart failure, etc.) fix the pectoral girdle and use accessory respiratory muscles
Where does the intercostal nerve arise from?
Anterior rami of the spinal nerves of T1 to T11
Intercostal nerves arise from the ___ nervous system.
Somatic
Posterior ramus of the intercostal nerve supplies what?
Skin of back
The intercostal enrves primarily supply which structures?
Motor to intercostal muscles
Sensory to overlying skin and parietal pleura
Which intercostal nerves are considered atypical? Which are considered typical?
Atypical: 1,2, and 7-11
Typical: 3-6
Which branch of the first intercostal nerve joins the brachial plexus?
The superior part
What are the branches of the second intercostal nerve? What are it’s functions?
Intercostobrachial nerve (lateral cutaneous branch)
Functions: Supplies skin of axilla and communicates with medial cutaneous nerve
The seventh to eleventh intercostal nerve cross costal margin and become the ______________ nerves of the anterior abdominal wall.
Thoracoabdominal
What is the course of the intercostobrachial nerve?
- T2 exits anterior armpit
- Courses over to humerus as it goes thru axilla under pectoralis muscles
- Splits into intercostobrachial nerve branches near bottom-most crease of axilla.
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Thoracentesis
an invasive procedure to remove fluid or air from the pleural space for diagnostic or therapeutic purposes
Where should a thoracocentesis be performed?
midaxillary line, in the eighth, ninth, or tenth intercostal space
What arteries supply the thoracic wall?
- Costocervical trunk
-
Superior intercostal aa.
- Posterior intercostal aa. (1st and 2nd)
-
internal thoracic aa.
* Anterior intercostal aa.
3. Aorta
- Posterior intercostal aa. (3-11)
Why does shingles affect a single dermatome?
Shingles is a herpes zoster infection of a spinal ganlion that is transported along axons, so it affects a single dermatome.
Why are the right posterior intercostal arterieslonger than the left ones?
Becuase they cross over the vertebral bodies
Thoracic aorta runs along the _______ (left/right) side of the vertebral bodies.
Left
________________ arteries run along the posterior and anterior roots of the spinal nerves and supply them with blood.
Radicular
*Radicular arteries are branches of posterior intercostal arteries. A blood clot here could result in infarction of the spinal cord
The ___________ artery supplies the first and second intercostal spaces.
Superior intercostal
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What is the clinical signifance of the internal thoracic artery?
- used for by-pass
- Important to avoid during pericardiocentesis
The internal thoracic artery birfurcates into which two arteries?
Superior epigastric artery
Musculophrenic artery
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There are 9 anterior intercostal arteries. From where does each artery arise?
Internal thoracic artery: 1-6
Musculophrenic artery: 7-9
NOTE: The anterior intercostal artteries are absent from the 10th and 11th intercostal spaces
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The medial mammary branches are branches of the ___________ artery, while the lateral mammary branches are branches of the ___________ artery.
Internal thoracic; lateral thoracic
Where do intercostal veins drain?
Internal thoracic veins
- Then drain in to brachiocephalic vein
Azygos veins
- Then drain into the superior vena cava
What is the clinical significance of the azygos vein?
It is an alternate route back to the heart when IVC or SVC are blocked
The _________ vein provides alternate circulation when there is liver disease.
Thoracoepigastric vein
The ventromedial portion of somites develop into __________ and _____.
Vertebrae and ribs
*This is the sclerotome
The dorsolateral portion of somites develop into _________- and ___________.
Dermatome (skin and subcutanenous)
Myotome (muscles)
How is the sternum formed?
- Sternal bars form from somatic mesoderm in the ventral body wall
- Sternebrae fuse at puberty
Sternebrae are supposed to fuse at puberty. What happens if this does not occur?
Failure to fuse results in bifid or perforated sternum