CHAPTER 10b THE MUSCULAR SYSTEM ANATOMY Copyright 2010

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 Copyright © 2010 Pearson Education, Inc.

External intercostal (a) Copyright © 2010 Pearson Education, Inc. Internal intercostal Figure 10. 10

Muscles of the Thorax PLAY A&P Flix™: External intercostals PLAY A&P Flix™: Internal intercostals

Foramen for inferior vena cava Central tendon of diaphragm Foramen for aorta 12 th rib (b) Copyright © 2010 Pearson Education, Inc. Xiphoid process of sternum Foramen for esophagus Costal cartilage Diaphragm Lumbar vertebra Quadratus lumborum Psoas major Figure 10. 10 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 Copyright © 2010 Pearson Education, Inc.

Pectoralis major Serratus anterior Linea alba Transversus abdominis Internal oblique External oblique Aponeurosis of the external oblique (a) Copyright © 2010 Pearson Education, Inc. Tendinous intersection Rectus abdominis Inguinal ligament (formed by free inferior border of the external oblique aponeurosis) Figure 10. 11 a

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 Copyright © 2010 Pearson Education, Inc.

Rectus abdominis Internal oblique External oblique IIiac crest Pubic tubercle Transversus abdominis Inguinal ligament

Muscles of the Abdominal Wall PLAY A&P Flix™: External obliques PLAY A&P Flix™: Internal obliques PLAY A&P Flix™: Rectus abdominis PLAY A&P Flix™: Transversus abdominis Copyright © 2010 Pearson Education, Inc.

Muscles of the Pelvic Floor • Pelvic floor (pelvic diaphragm) is composed of two paired muscles • Levator ani • Coccygeus • Both are innervated by sacral nerves Copyright © 2010 Pearson Education, Inc.

Muscles of the Pelvic Floor • Functions of the pelvic diaphragm • Seals the inferior outlet of the pelvis • Supports pelvic organs • Lifts pelvic floor to help release feces • Resists increased intra-abdominal pressure Copyright © 2010 Pearson Education, Inc.

Muscles of the Perineum • Urogenital diaphragm • Anterior half of perineum, inferior to pelvic floor • Deep transverse perineal muscle • External urethral sphincter (voluntary control of urination) Copyright © 2010 Pearson Education, Inc.

Levator ani Pubococcygeus IIiococcygeus Anterior Obturator internus Coccyx Levator ani Coccygeus Piriformis (a) Copyright © 2010 Pearson Education, Inc. Symphysis pubis Urogenital diaphragm Urethra Vagina Anal canal Posterior Pelvic diaphragm Figure 10. 12 a

Urethral opening External urethral sphincter Vaginal opening Inferior pubic ramus Deep transverse perineal muscle Central tendon Anus External anal sphincter (b) Male Copyright © 2010 Pearson Education, Inc. Female Figure 10. 12 b

Muscles of the Perineum • Muscles of superficial perineal space • Ischiocavernosus • Bulbospongiosus • Superficial transverse perineal muscles • External anal sphincter (in posterior half of perineum) Copyright © 2010 Pearson Education, Inc.

Urethral opening Vaginal opening Clitoris Anus Penis Midline raphe Ischiocavernosus Bulbospongiosus Superficial transverse perineal muscle Levator ani Gluteus maximus (c) Male Copyright © 2010 Pearson Education, Inc. Female Figure 10. 12 c

Superficial Muscles of the Thorax • Most are extrinsic shoulder muscles • Act in combination to fix the shoulder girdle (mostly the scapula) and move it to increase range of arm movements • Actions include elevation, depression, rotation, lateral and medial movements, protraction, and retraction • Two groups of muscles: anterior and posterior PLAY A&P Flix™: Muscles that act on the shoulder joint and humerus: An overview (a) A&P Flix™: Muscles that act on the shoulder joint and humerus: An overview (b) Copyright © 2010 Pearson Education, Inc.

Superficial Muscles of the Thorax • Anterior extrinsic shoulder muscles • Pectoralis minor • Serratus anterior • Subclavius • (Pectoralis major considered later with muscles that act on the humerus) PLAY A&P Flix™: Muscles of the pectoral girdle (a) PLAY A&P Flix™: Muscles of the pectoral girdle (b) Copyright © 2010 Pearson Education, Inc.

Sternocleidomastoid Subclavius Clavicle Subscapularis Pectoralis minor Deltoid Pectoralis major Sternum Coracobrachialis Serratus anterior Biceps brachii Humerus (a) PLAY A&P Flix™: Muscles that act on the shoulder joint and humerus: An overview (b) Copyright © 2010 Pearson Education, Inc. Figure 10. 13 a

Superficial Muscles of the Thorax PLAY A&P Flix™: Pectoralis minor PLAY A&P Flix™: Serratus

Superficial Muscles of the Posterior Thorax • Posterior extrinsic shoulder muscles • Trapezius • Levator scpulae • Rhomboids (major and minor) • (Latissimus dorsi considered later with muscles that act on the humerus) PLAY A&P Flix™: Muscles of the pectoral girdle (c) PLAY A&P Flix™: Movement of the pectoral girdle Copyright © 2010 Pearson Education, Inc.

Levator scapulae Trapezius Supraspinatus Clavicle Deltoid Rhomboid minor Rhomboid major Spine of scapula Infraspinatus Teres minor Teres major Humerus Latissimus dorsi (c) Copyright © 2010 Pearson Education, Inc. Figure 10. 13 c

Superficial Muscles of the Posterior Thorax PLAY A&P Flix™: Trapezius PLAY A&P Flix™: Levator scapula PLAY A&P Flix™: Rhomboid major PLAY A&P Flix™: Rhomboid minor Copyright © 2010 Pearson Education, Inc.