5. Thoracic Flashcards
External intercostal
Location
Action
L-11 pairs lie b/w ribs; fibers run obliquely (down and forward) from each rib to rib below; in lower intercostal spaces, fibers are continuous w/external oblique muscle forming part of abdominal wall
A- pull ribs toward one another to elevate rib cage - aid in inspiration, synergists of diaphragm
Internal intercostal
Location
Action
L- 11 pairs lie b/w ribs, fibers run deep to and at right and,es to those of external intercostal (run downward and posteriorly); lower intercostal muscles are continuous with fibers of internal oblique muscle or abdominal wall
A-draw ribs together and depress rib cage - aid in forced expiration, antagonistic to external intercostals
Transverse thoracis
Location
Action
L- The transversus thoracis muscle lies internal to the thoracic cage, anteriorly. It is a thin plane of muscular and tendinous fibers, situated upon the inner surface of the front wall of the chest.
A-Depresses ribs
Diaphragm
Origin
Insertion
Action
Broad muscles pierced by the aorta, inferior vena cava, and esophagus; forms floor of thoracic cavity; in relaxed state it is dome shaped; fibers converge from margins of thoracic cage toward a boomerang shaped central tendon
O- inferior internal surface of rib cage and sternum, costal cartilage of last six rubs, lumbar vertebrae
I- central tendon
A- prime mover of inspiration, flattens on contraction - increasing vertical dimensions of thorax, when strongly contracted, dramatically increases intra-abdominal pressure
