Thorax, Heart and Lungs Flashcards
What muscles assist in inspiration?
Diaphragm
Mainly external intercostals–> expand ribs outwards
Assisted by SCM and scalenes
What law allows respiration?
Boyle’s law
What is FRC?
Amount of air left in lungs at end of passive exhalation
Opposing elastic recoil forces of lungs and chest at equilibrium
What does the thoracic wall consist of?
Skin, fascia, nerves, vessels, muscles, cartilages and bones
What are the functions of the thoracic wall?
- Protects thoracic and abdominal organs
- resists negative internal pressure generated by elastic recoil of lungs and inspiratory movmeent
- Provides attachment for and supports weight of upper limb, neck, abdomen, and back, muscles of respiration
What composes the superior thoracic aperture?
- Allows communication b/w the thoracic cavity and neck and uper limbs
- Bounded
- poteriorly by T1
- Laterally by first pair of ribs and their costal cartialges
- anteriorly by superior border of the manubrium
What composes the inferior thoracic aperture?
- Allows communication between thoracic cavity and abdomen
- Bounded
- posteriorly by the T12 vertebrae
- Posterolaterally by 11-12th pair of rib
- Anterolaterally by joined costal cartilages of 7-10 ribs
- Anteriorly by xiphisternal join
- diaphragm closes this space almost completely, separting the two cavities
What composes the thoracic skeleton?
- 12 pairs of ribs and costal cartilages
- 12 thoracic vertebrae and intervertebral disc
- Sternum
What composes the 12 ribs and costal cartilages?
- True ribs (vertebrosternal ribs) 1-7th ribs
- cartilage attached to sternum
- False ribs (vertebrochondral ribs) 8-10th ribs
- share cartilage
- Floating (free) ribs 11 & 12th ribs
- Protecting for kidney
- Costal cartialges prolong ribs anteriorly and add elasticity
- Intercostal space are names in relation to rib on superior border
- subcostal space is immediately below 12th rib
What parts form the sternum?
- Manubrium
- lies T3-T4
- Clnical landmark
- Jugular (suprasternal) notch
- Sternal angle (of louis)
- oppositie 2nd pair costal cartilages
- level of T4-T5
- Body
- T5-T9
- Xiphoid process
- T10 level
A/I of external intercostals
Action
- forced inspiration elevates ribs
Innervation
-Intercostal Nerve
“fibers go like hands in pockets”
A/I of internal intercostals?
Action
- forced respiration, interosseous part depresses ribs; interchondral part elevates ribs
Innervation
-Intercostal nerve
“muscle fibers go like arms crossed”
A/I innermost intercostal?
Action
- Forced inspiration; interosseous part depresses ribs; interchondral part elevates ribs
Innervation
-Intercostal nerve
A/I Transversus thoracic?
Action
- weakly depresses ribs
Innervation
- Intercostal nerve
A/I subcostal muscle?
Action
- act in same manner as internal intercostal (forced respiration; interosseous part depresses ribs; interchondral part elevates ribs)
Innervation
-Intercostal nerve
How is the intercostal nuroevascular bundle arranged within muscle layers of the thorax?
“VAN” (superior –> inferior)
Vein
Artery
Nerve
NV bundle in between internal and innermost intercostals
Where do the external intercostals run?
Run from vertebral column, stops short of sternum (around costal catilages)
Where do internal intercostals run?
Run from sternum, stops short of vertebral column
Where do innermost intercostals run?
Found at the most lateral parts of intercostal spaces
Where does transversus thoracis muscles run?
anterior thoracic wall
Where do subcostal muscles run?
Posterior thoracic wall
What is the diaphragm?
- Chief muscle of inspiration
- Dome shaped with left and right domes
- right dome is slightly higher than left due to presense of liver
What are the diaphragmatic apertures?
- Caval opening
- Esophageal hiatus
- Aortic hiatus
What is the caval opening?
- Located in central tendon
- Allows IVC and terminal branches of phrenic nerve to pass into abdominal cavity
- During inspiration, diaphragm contracts, causing this opening to widen which allows dilation of IVC and increased blood return to heart


