Glossary of Anatomy Chapter 10B: Anterior Trunk Muscles
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- External Intercostals
- 11 pairs lie between ribs, form part of abdominal wall
O: inferior border of superior rib
I: superior border of inferior rib
A: pull ribs toward one another to elevate rib cage
- Internal Intercostals
- 11 pairs lie between ribs, at right angles to the fibres of the external instercostals.
O: superior border of inferior rib
I: inferior border of superior rib
A: draw ribs together and depress rib cage
- Broad muscle that forms floor of thoracic cavity.
O: inferior, internal surface of rib cage and sternum, costal cartilages of last 6 ribs and lumbar vertebrae
I: central tendon
A; prime mover of inspiration
- Rectus Abdominus
- Medial superficial muscle pair extending from the pubis to the rib cage. Segmented by 3 tendinous intersections.
O: pubic crest and symphysis
I: xiphoid process and costal cartilages of ribs 5-7
A: flex and rotate lumbar region of vertebral column
- External Oblique
- Largest and most superficial of the lateral anterior trunk muscles.
O: attached to outer surfaces of lower eight ribs by fleshy strips.
I: insert to linea alba via broad aponeurosis, some into pubic crest and iliac crest
A: aid rectus abdominis muscles (synergist) in flexing vertebral column and in compressing abdominal wall and increasing intra-abdominal pressure.
- Internal Oblique
- Muscle fans along sides, above hips, deep to the external obliques.
O: lumbar fascia, iliac crest, and inguinal ligament
I: linea alba, pubic crest, last three or four ribs, and costal margin
A: Aids rectus abdominis and external oblique (synergist) in flexing vertebral column and in compressing the abdominal wall and increasing intra-abdominal pressure.
- Transversus Abdominus
- Deepest muscle of the abdominal wall.
O: inguinal ligament, lumbar fascia, cartilages of last six ribs, iliac crest
I: linea alba, pubic crest
A: compresses abdominal contents.
- Pectoralis Minor
- Flat, thin muscle directly beneath and obscured by pectoralis major
O: anterior surfaces of ribs 3-5
I: coracoid process of scapula
A: draws scapula forward and downward
- Serratus Anterior
- Lies deep to scapula, beneath and inferior to pectoral muscles on lateral rib cage.
O: attached by a series of muscle slips to ribs 1-8
I: entire anterior surface of vertebral border of scapula
A: prime mover to protract and hold scapula against chest wall
- Thick, multipennate muscle forming rounded shoulder muscle mass
O: embraces insertion of the trapezius, lateral third of clavicle, acromion and spine of scapula
I: deltoid tuberosity of humerus
A: prime mover of arm abduction
- Pectoralis Major
- Large, fan-shaped muscle covering the upper portion of the chest.
O: sternal end of clavicle, sternum, cartilage of ribs 1-6, and aponeurosis of external oblique muscle
I: fibres converge to insert by a short tendon into intertubercular groove of humerus
A: Prime mover of arm (upper arm) flexion
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