Axial Musculature: Thorax and Abdomen Flashcards Preview

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Flashcards in Axial Musculature: Thorax and Abdomen Deck (8)
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Muscles of the Thorax

Diaphragm - main muscle of respiration
-->diaphragm contracts (depresses)
-->increases size of thoracic cavity
-->diaphragm relaxes
-->thoracic cavity decreases in size
Origin: inside body wall and ribs
Insertion: central tendon

Intercostals - respiratory muscles (accessory)
--external intercostals
-->elevate ribs, inspiration
--internal intercostals
-->depress ribs, expiration (forced)
Origin: ribs
Insertion: ribs


Muscles of the Abdominal Wall

Rectus abdominus, External Oblique, Internal Oblique, Transversus Abdominus


Rectus Abdominus (RA)

Midline; "6-pack"

action: flexes trunk
fibers run superior/inferior

Origin: pubis
Insertion: ribs and xiphoid process


External Oblique (EO) and Internal Oblique (IO; deep to EO)

action: flex and rotate trunk
fibers run obliquely (same direction as intercostals)

Origin: lower ribs
Insertion: pelvis and linea alba


Transversus Abdominus (T) - deep to IO

action: compress abdominal cavity
deepest abdominal muscle; fibers horizontally

Origin: posterior body wall
Insertion: anterior body wall


Pelvic Diaphragm

3 layers of muscles that form the pelvic floor:
--levator ani muscles
--coccygeus muscle
--pelvic fascia

Spans from ischium and pubis to sacrum and coccyx
Support pelvic viscera (organs)
Also contains 2 hiatuses (holes) to allow passage of urethra/vagina and rectum

Origin: pelvic outlet
Insertion: midline


Intrinsic Back Muscles

Erector spine muscles (includes) [lateral to medial]:

--bilateral: extend trunk, neck, head
--unilateral: laterally flex trunk, neck, head

Origin: pelvis
Insertion: ribs, vertebrae, cranium


"Spare Tire" mnemonic [deepest to superficial]

Transverse abdominus
Internal oblique
Rectus abdominus
External oblique