2. Muscles of the chest and abdomen a. Chest 1. Pectoralis major- adducts arm, draws it across the chest a. Originates at clavicle, sternum and costal cartilage of true ribs b. Inserts at the humerus

b. Abdomen 1. Rectus abdominus- compresses abdomen when expelling waste, forced breath, child birth, and flexes vertebral column a. Originates at pubic crest and pubic symphysis b. Inserts at cartilage of 5th –7th ribs and the xiphoid process

2. External oblique- laterally bends and rotates as compresses abdomen a. Originates from the lower 8 ribs b. Inserts at iliac crest and linea alba 3. Transverse abdominal compresses abdomen a. Originates at the iliac crest, inguinal ligament, lumbar fascia and cartilage of last 6 ribs b. Inserts at the xiphoid process , linea alba and pubis

4. Diaphragm- floor of he. thoracic cavity pulls 4. Diaphragm- floor of he thoracic cavity pulls downward during inspiration a. Originates from the xiphoid process and costal cartilages of the last 6 ribs b. Inserts at the central tendon just behind the sternum

5. Intercostals- elevates and compresses ribs during breathing a. Originates from upper rib b. inserts at lower rib