The muscular system (part b), This chapter presents the following content: Muscles of the thorax, muscles of the abdominal wall, muscles of the pelvic floor, muscles of the perineum, superficial muscles of the thorax, superficial muscles of the posterior thorax. | 10 The Muscular System: Part B Muscles of the Thorax Muscles of respiration External intercostals—more superficial muscles that elevate ribs for inspiration Internal intercostals—deeper muscles that aid forced expiration Diaphragm Partition between thoracic and abdominal cavities Most important muscle in inspiration Innervated by phrenic nerves Figure External intercostal (a) Internal intercostal Muscles of the Thorax PLAY A&P Flix™: Internal intercostals PLAY A&P Flix™: External intercostals Figure Foramen for esophagus Costal cartilage Lumbar vertebra Xiphoid process of sternum Diaphragm Quadratus lumborum Psoas major Foramen for inferior vena cava Central tendon of diaphragm Foramen for aorta 12th rib (b) Muscles of the Abdominal Wall Four paired muscles; their fasciae and aponeuroses form the lateral and anterior abdominal wall Internal obliques External obliques Transversus abdominis Rectus abdominis Figure Transversus abdominis Internal oblique External oblique Aponeurosis of the external oblique (a) Pectoralis major Linea alba Tendinous intersection Rectus abdominis Inguinal ligament (formed by free inferior border of the external oblique aponeurosis) Serratus anterior Muscles of the Abdominal Wall Fascicles of these muscles run at angles to one another, providing added strength All are innervated by intercostal nerves Actions of these muscles Lateral flexion and rotation of the trunk Help promote urination, defecation, childbirth, vomiting, coughing, and screaming Figure Transversus abdominis Inguinal ligament Lumbar fascia Lumbar fascia Internal oblique Pubic tubercle Rectus abdominis External oblique (b) IIiac crest Muscles of the Abdominal Wall PLAY A&P Flix™: Internal obliques PLAY A&P Flix™: External obliques PLAY A&P Flix™: Rectus abdominis PLAY A&P Flix™: Transversus abdominis Muscles of the Pelvic Floor Pelvic floor (pelvic diaphragm) is composed of two paired muscles Levator ani Coccygeus Both are innervated by sacral . | 10 The Muscular System: Part B Muscles of the Thorax Muscles of respiration External intercostals—more superficial muscles that elevate ribs for inspiration Internal intercostals—deeper muscles that aid forced expiration Diaphragm Partition between thoracic and abdominal cavities Most important muscle in inspiration Innervated by phrenic nerves Figure External intercostal (a) Internal intercostal Muscles of the Thorax PLAY A&P Flix™: Internal intercostals PLAY A&P Flix™: External intercostals Figure Foramen for esophagus Costal cartilage Lumbar vertebra Xiphoid process of sternum Diaphragm Quadratus lumborum Psoas major Foramen for inferior vena cava Central tendon of diaphragm Foramen for aorta 12th rib (b) Muscles of the Abdominal Wall Four paired muscles; their fasciae and aponeuroses form the lateral and anterior abdominal wall Internal obliques External obliques Transversus abdominis Rectus abdominis Figure Transversus abdominis Internal oblique External .
