middle scalene, and posterior scalene muscle—which flex, laterally flex, and rotate the head. They also contribute to deep inhalation.
MUSCLES OF THE TRUNK There are four pairs of abdominal muscles covering the anterior and lateral abdominal wall. These include the rectus abdominis, transverse abdominis, internal obliques, and external obliques. These are the muscles you need to know about: •
External and internal obliques—these direct twisting at the waist and side bending of the vertebral column. They are seen in the lower ribs to the pelvis.
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Transverse abdominus—these will squeeze the abdomen and are important in defecation and urination. It is seen from the lower ribs to the pubis.
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Rectus abdominis—these help the body to sit up. It starts in the pubis and ends in the sternum and lower ribs.
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Quadratus lumborum—this muscle causes side bending. It is seen from the ilium up to the ribs.
Figure 53 shows the abdominal muscles:
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