Anatomy 231 Thoracic and abdominal Muscles: origin insertion and action

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  1. External intercostals
    • Origin= inferior border of rib above.
    • Insertion= Superior border of rib below.
    • Action= With first ribs fixed, pulls ribs toward one another to elevate rib cage; aid in inspiration;synergisst of diaphragm.
  2. Internal intercostals.
    • Origin= superior border of rib below
    • Insertion= Inferior border (costal groove) of rib above.
    • Action= With 12th ribs fixed,draw ribs together and depress rib cage; aid in forced expiration; antagonist to external intercostals.
  3. Diaphragm
    • Origin=  inferior internal surface of rib cage and sternum, costal cartilages of last six ribs and lumbar vertebrae.
    • Insertion= Central tendon.
    • Action= Prime mover of inspiration; flattens on contraction, increasing vertical dimensions of thorax; when strongly contracted, increases intra-abdominal pressure.
  4. External Oblique
    • Origin= By fleshy strips from puter surfaces of lower eight ribs
    • Insertion= Most fibers insert into linea alba, some insert into pubic crest and tubercle and iliac crest.
    • Action= When the pair contract simultaneously, Flex vertebral column and copress abdominal wall; Insividually they help back muscles in Trunk rotation and lateral flexion
  5. Internal oblique
    • Origin= Lumbar fascia, iliac crest and inguinal ligament.
    • Insertion= Linea alba, pubic crest, last 3 or 4 ribs and costal margin.
    • Action= As for external oblique
  6. Transversus Abdominis.
    • Origin= Inguinal ligament, lumbar fascia, cartilages of last six ribs; iliac crest.
    • Insertion= Linea alba, pubic crest.
    • Action= Compresses abdominal contents.
  7. Rectus abdominis
    • Origin= Pubic crest and symphysis.
    • Insertion= Xiphoid process and costal cartilages of ribs 5-7.
    • Action= Flex and rotate lumbar region of vertebral column.
  8. Pectoralis Minor
    • Origin= Anterior surfaces of ribs 3-5 
    • Insertion= coracoid process of scapula.
    • Action= With fixed ribs, moves scapula forward and downward; with fixed scapula, draws rib cage superiorly.
  9. Serratus anterior
    • Origin= by a series us muscle slips from ribs 1 to 8.
    • Insertion= Entire anterior surface of vertebral border of scapula.
    • Action= rotates angle of scapula laterally and upward. Raises point of shoulder; important role in abduction and raising of arm and horizontal movements( pushing and punching)
  10. Trapezius
    • Origin= Occipital bone, ligamentum nuchae, and spines of C7 and all thoracic vertebrae.
    • Insertion= a continuous insertion along acromion and spine of scapula and lateral third of clavicle.
    • Action= Stabilizes, raises, retracts, and rotates scapula; middle fibers retract (adduct) scapula; superior fibers raise scapula, inferior fibers depress scapula; when scapula is fixed head extends
  11. Pectoralis Major
    • Origin= Sternal end of clavicle, sternum, cartilage of ribs 1-6, and aponeurosis of external oblique.
    • insertion= Fibers converge  to insert by a short tendon into greater tubercle of humerus.
    • Action= Prime mover of arm flexion, rotates arm medially, adducts arm.
  12. Deltoid
    • Origin= embraces insertion of the trapezius; lateral third of clavicle; acromion and spine of scapula.
    • Insertion= Deltoid tuberosity of humerus.
    • Action= Abduction of arm when all fibers contract; antagonist of pectoralis and latissimus dorsi which adducts the arm; anterior fibers flex and medial rotation of humerus, therefore synergist of pectoralis major; posteriors fibers cause extension and lateral rotation of arm.
  13. Latissimus dorsi
    • Origin= indirect attachment via thoracolumbar fascia into spines of lower six thoracic vertebrae, lumbar vertebrae, lower 3 to 4 ribs and iliac crest.
    • Insertion= Spirals around teres major to insert in floor of intertubercular sulcus of humerus.
    • Action= Arm extension, adduction and medial rotation of shoulder
  14. Subscapularis
    • Origin= Subscapular fossa
    • Insertion= Lesser tubercle of humerus.
    • Action= Chief medial rotator of humerus
  15. Supraspinatus
    • Origin= supraspinous fossa
    • Insertion= Superior part of greater tubercle in humerus.
    • Action= Initiates abduction
  16. Infraspinatus
    • Origin= Infraspinous fossa
    • Insertion= Greater tubercle of humerus, posterior to insertion from supraspinatus.
    • Action=Rotates humerus laterally
Card Set
Anatomy 231 Thoracic and abdominal Muscles: origin insertion and action
Thoracic and Abdominal muscles: Origin, insertion and action
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