Muscles of the Thorax, Abdomen, and Back

Vocabulary flashcards covering the origins, insertions, actions, and structural details of the abdominal, breathing, and posterior deep back muscles.

Aponeuroses

Broad bands of connective tissue to which abdominal muscles attach before reaching their insertions.

Linea alba

A connective tissue band meaning 'white line' that extends from the sternum to the pubic symphysis, serving as an insertion site for the abdominal muscles.

Rectus abdominis

Abdominal muscle originating at the pubic symphysis and inserting at the xiphoid process and costal cartilages. Actions: Compresses abdomen; flexes vertebral column; retains contents of abdomen; stabilizes pelvis during walking.

External oblique

Abdominal muscle originating on the outer surfaces of the lower 8 ribs and inserting at the linea alba. Actions: Compresses abdomen; flexes vertebral column laterally.

Internal oblique

Abdominal muscle originating at the iliac crest and inserting at the linea alba. Actions: Compresses abdomen; flexes vertebral column laterally.

Transverse abdominis

Abdominal muscle originating at the iliac crest and inserting at the linea alba. Action: Compresses the abdomen.

Diaphragm

Primary breathing muscle separating the thoracic and abdominal cavities, originating at the bottom of the rib cage, sternum, and lumbar vertebrae, and inserting at the central tendon. Action: Prime mover for inspiration (inhalation).

External intercostals

Superficial intercostal muscles originating at the inferior border of the rib above and inserting at the superior border of the rib below. Action: Elevates the ribs for inspiration.

Internal intercostals

Deep intercostal muscles originating at the superior border of the rib below and inserting at the inferior border of the rib above. Action: Depresses the ribs for forced expiration.

Erector spinae group

Largest deep back muscle group consisting of the iliocostalis, longissimus, and spinalis. Actions: Prime movers for extension of the vertebral column to maintain upright posture; may laterally flex the vertebral column to the same side.

Iliocostalis

Muscle of the erector spinae group originating at the iliac crest and inserting on the ribs. Action: Extends the vertebral column and may laterally flex it to the same side.

Longissimus

Muscle of the erector spinae group originating at the transverse processes of lumbar vertebrae and inserting at the transverse processes of thoracic vertebrae. Action: Extends the vertebral column and may laterally flex it to the same side.

Spinalis

Muscle of the erector spinae group originating at the spinous processes of upper lumbar and lower thoracic vertebrae and inserting at the spinous processes of upper thoracic vertebrae. Action: Extends the vertebral column and may laterally flex it to the same side.