The Sarcomere, Bones/Muscles of the Trunk

Sarcomere

runs from Z disc to Z disc (functional contractile unit); many along the length of the muscle fiber

What happens to the sarcomeres when a muscle contracts?

sarcomeres shorten/narrow

Light Bands

I-bands; thin myofilaments only; z-disc runs down the middle

Dark Bands

A-bands; overlapping thick and thin myofilaments; H-zone and M-line runs down the middle

Z-disc

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

H-zone

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

M-line

dark line in the middle of H zone; thick myofilaments attach here

During muscle contraction, thick and thin myofilaments…

slide over one another

During muscle contraction, the length of each sarcomere…

shorten/narrow

During muscle contraction, H-zones…

narrow

During muscle contraction, I-bands…

narrow

During muscle contraction, Z-discs…

stay the same

During muscle contraction, the m-line…

stays the same

During muscle contraction, the A-band…

stays the same

Deep back muscles are… and consists of….

muscles of the vertebral column; the quadratus lumborum and the erector spinae

Quadratus Lumborum

each laterally flexes vertebral column; together they extend the vertebral column

Where does the quadratus lumborum attach?

the iliac crest to lumbar vertebrae and 12th rib

Erector Spinae

group of muscles that help you stand straight; extend vertebral column

What are the muscles of the erector spinae?

the iliocostalis (lateral), longissimus (intermediate), and spinalis (medial)

What are the bony attachments of the deep thoracic muscles?

12 thoracic vertebrae (costal facets and transverse processes) and 12 ribs

Diaphragm (Thoracic)

dome-shaped muscle, contraction pulls the central portion down, increasing the vertical dimensions of the thorax; attaches ribs, sternum and vertebrae

External Intercostals

elevate ribs during inhalation; runs between ribs and the fibers run inferomedially

What muscles are apart of the thorax?

the diaphragm, external intercostals, and internal intercostals

Internal Intercostals

depress ribs during FORCED exhalation; runs between ribs and fibers run inferolaterally

The movements of abdominal muscles bilaterally…

flex the vertebral column and compress the abdominal wall

The movements of abdominal muscles unilaterally…

the external and internal abdominal obliques laterally flex the vertebral column

External Abdominal Oblique

fibers run inferomedially

Internal Abdominal Oblique

fibers run inferolaterally

Transversus Abdominus

fibers run side to side

Rectus Abdominus

fibers run up and down