BIOL413: Muscle Sheet Two

Thorax

external oblique origin

muscular slips from the outer surfaces of lower 8 ribs (5-12)

external oblique insertion

lateral lip of iliac crest, aponeurosis ending in midline raphe: linea alba

external oblique action

compress abdominal contents.
individual: bends trunk to same side, turning anterior part of abdomen to opposite side
both: flex trunk

internal oblique origin

thoracolumbar fascia, iliac crest between origins of external/transversus, lateral 2/3 of inguinal ligament

internal oblique insertion

inferior border of lower 3-4 ribs, aponeurosis ending in linea alba, pubic crest and pectineal line

internal oblique action

compress abdominal contents.
individual: bends trunk and turns anterior part of abdomen to same side
both: flex trunk

transversus abdominis origin

thoracolumbar fascia, medial lip of iliac crest, lateral 1/3 of inguinal ligament, costal cartilages of lower 6 ribs (7-12)

transversus abdominis insertion

aponeruosis ending in linea alba, pubic crest and pectineal line

transversus abdominis action

compress abdominal contents

rectus abdominus origin

pubic crest, pubic tubercle, and pubic symphysis

rectus abdominis insertion

costal cartilages of ribs 5-7, xiphoid process

rectus abdominis action

compress abdominal contents, flex vertebral column, tense abdominal wall

thoraco-abdominal nerves (T7-L1)

external oblique, internal oblique, tranversus abdominis, and rectus abdominis innervation

sternocleidomastoid origin

upper part of anterior surface of manubrium of sternum, superior surface of medial one-third of clavicle

sternocleidomastoid insertion

lateral ½ of superior nuchal line, lateral surface of mastoid process

sternocleidomastoid innervation

Motor: accessory nerve (XI)
Sensory and proprioception: branches from anterior rami of C2-C3

sternocleidomastoid action

individually: tilt head toward shoulder on same side, rotate head to face opposite side
together: draw head forward

internal intercostal origin

lateral edge of costal groove of rib above

internal intercostal insertion

superior margin of rib below, deep to attachment of related external intercostal

internal intercostal innervation

intercostal nerves (T1-T11)

internal intercostal action

most active during expiration, supports intercostal space, moves ribs inferiorly

external intercostal origin

inferior margin of rib above

external intercostal insertion

superior margin of rib below

external intercostal innervation

intercostal nerves (T1-T11)

external intercostal action

most active during inspiration, supports intercostal space, moves ribs superiorly

diaphragm origin

xiphoid process, costal margin of thoracic wall, ends of ribs 11 and 12, ligaments spanning posterior abdominal wall, lumbar region of vertebrae

diaphragm insertion

central tendon

diaphragm innervation

phrenic nerve (C3-C5)

diaphragm action

vital in respiration: flattens and lowers to create air flow/pressure gradient