A225 Lecture - Sarcomeres and Trunks and Bones - 9/18

light bands (I bands)

thin myofilaments only (actin)

dark bands (A bands)

has overlapping between thick and thin filaments

Z disc

dark structure in the middle of an I band where thin myofilaments attach

H zone (H band)

lighter, central region in the middle of A band; contains only thick myofilaments

M line

dark line in middle of H zone where thick myofilaments attach to

sarcomere

runs from z disc to z disc (functional contractile unit)

H zones and I bands

these narrow/disappear during muscle contraction

A band, Z disc, M line, thick and thin myofilaments

these do not narrow during muscle contraction

quadratum lumborum

laterally flexes vertebral column

unilateral function of quadratus lumborum

extends lumbar vertebral column

bilateral function of quadratus lumborum

iliac crest, lumbar vertebrae, 12th rib

attachment points for quadratus lumborum

erector spinae

extend vertebral column and maintain erect posture

functions of the erector spinae

iliocostalis

lateral part of erector spinae

longissimus

intermediate part of the erector spinae

spinalis

medial part of the erector spinae

superifical thorax muscles

these move the upper limb

diaphragm

contraction pulls the central portion down, increasing the vertical dimensions of the thorax

ribs, sternum, vertebrae

attachment points of the diaphragm

external intercostals

elevate the ribs during inhalation

internal intercostals

depresses ribs during forced exhalation

thoracic vertebrae (12)

vertebrae that articulate with the ribs

flex vertebral column and compress abdominal wall

bilateral function of all abdominal muscles

laterally flexes vertebral column

unilateral action of external and internal abdominal oblique

external abdominal oblique

fibers run inferomedially; similar to external intercostals

internal abdominal oblique

fibers run inferolaterally, similar to internal intercostals

transversus abdominis

compresses abdomen, fibers run toward belly button

rectus abdominus

abs