The Muscular System: Part B 10 The Muscular System: Part B

III. Muscles of the Trunk A. Muscles Crossing the Shoulder Joint Move or Stabilize the Humerus Origin can be the scapula, axial skeleton, and/or Os Coxae Insertion = Humerus 1. Prime Movers That Insert on the Humerus and Move Arm a) Pectoralis major Location: Anterior & Superficial Origin: Sternum, Clavicle, Superior Ribs-anterior surface Insertion: Proximal Humerus- laterally Deltoid Sternum Pectoralis major © 2013 Pearson Education, Inc.

b) Deltoid c) Latissimus dorsi Anterior View Location: Shoulder & proximal humerus; Superficial Origin: posterior-superior Scapula Insertion: mid-humerus, laterally c) Latissimus dorsi Location: lower back to humerus- Superficial Origin: Superior Ilium, lower Vertebrae, lower Ribs Insertion: Proximal Humerus-Anteriorly in middle (It goes under the armpit to the humerus. Which explains how it can medially rotate humerus) Anterior View Deltoid Sternum Pectoralis major Deltoid (cut) Latissimus dorsi Posterior View © 2013 Pearson Education, Inc.

Muscles Crossing the Shoulder Joint PLAY A&P Flix™: Pectoralis major PLAY A&P Flix™: Latissimus dorsi PLAY A&P Flix™: Deltoid © 2013 Pearson Education, Inc.

2. Synergists that move humerus Teres Major – to L. dorsi Location: Posterior Scapula, Deep Origin: Posterior-inferior Scapula Insertion: Proximal Humerus-anteriorly b) Coracobrachials- Synergistic to Pectoralis major Location: Deep, Anterior Humerus Spine of scapula Deltoid (cut) Greater tubercle of humerus Infraspinatus* Teres minor* Teres major Latissimus dorsi Origin: Anterior Lateral Scapula Insertion: Anterior Humerus in middle of shaft-medially Subscapularis Pectoralis minor Coracobrachialis

Levator scapulae Supraspinatus Trapezius Clavicle Deltoid Spine of Figure 10.14c Superficial muscles of the thorax and shoulder acting on the scapula and arm. Levator scapulae Trapezius Supraspinatus Clavicle Deltoid Spine of scapula Rhomboid minor Infraspinatus Rhomboid major Teres minor Teres major Humerus Latissimus dorsi © 2013 Pearson Education, Inc.

Figure 10.14a Superficial muscles of the thorax and shoulder acting on the scapula and arm. Sternocleidomastoid Subclavius Clavicle Subscapularis Deltoid Pectoralis minor Pectoralis major Coracobrachialis Sternum Serratus anterior Biceps brachii Humerus PLAY A&P Flix™: Muscles that act on the shoulder joint and humerus: An overview (b) © 2013 Pearson Education, Inc.

a) Supraspinatus: posterior-superior scapula, deep to trapezius 3. Muscles that stabalize the Shoulder Joint Rotator cuff muscles act as synergists and fixators; They are mostly deep muscles located on the surfaces the Scapula. They all originate on the scapula at different surfaces, and insert on the proximal humerus-laterally; their tendons wrap around the proximal humerus and reinforce shoulder capsule to prevent dislocation a) Supraspinatus: posterior-superior scapula, deep to trapezius Supraspinatus Infraspinatus Teres Minor Teres Major © 2013 Pearson Education, Inc.

3. Muscles that stabalize the Shoulder Joint b) Infraspinatus: posterior- inferior scapula, partially covered by Deltoid & Trapezium c) Teres minor: posterior- lateral scapula, inferior to infraspinatus (and connected to it). d) Subscapularis: anterior scapula; it passes anterior to the joint to the lateral proximal humerus. (This explains how it can medially rotate humerus.) Supraspinatus Infraspinatus Teres Minor Teres Major Subscapularis © 2013 Pearson Education, Inc.

Rotator Cuff Anatomy and Function PLAY A&P Flix™: Subscapularis PLAY A&P Flix™: Supraspinatus PLAY A&P Flix™: Infraspinatus PLAY A&P Flix™: Teres minor PLAY A&P Flix™: Rotator cuff muscles © 2013 Pearson Education, Inc.

B. Muscles that move the Scapula 1. Anterior Surface, Deep Serratus Anterior Location: Lateral- posterior rib cage Origin: via slips of muscle that look serrated to upper ribs Insertion: anterior scapula-medially b) Pectoralis Minor Location: superior ribcage- anteriorly Clavicle Subscapularis Pectoralis minor Coracobrachialis Serratus anterior Origin: upper ribs on anterior surface Insertion: superior-lateral Scapula-anteriorly © 2013 Pearson Education, Inc.

Superficial Muscles of the Thorax PLAY A&P Flix™: Pectoralis minor PLAY A&P Flix™: Serratus anterior © 2013 Pearson Education, Inc.

Figure 10.14a Superficial muscles of the thorax and shoulder acting on the scapula and arm. Sternocleidomastoid Subclavius Clavicle Subscapularis Deltoid Pectoralis minor Pectoralis major Coracobrachialis Sternum Serratus anterior Biceps brachii Humerus PLAY A&P Flix™: Muscles that act on the shoulder joint and humerus: An overview (b) © 2013 Pearson Education, Inc.

Trapezius: Superficial B. Muscles that Move the Scapula-Posterior Surface, Deep ,,, 2. Posterior Surface Trapezius: Superficial Location: upper back to head Origin: Insertion: b) Levator Scapulae: Deep Location: upper back & neck c) Rhomboids: Deep (major & minor) Location: middle of upper back Levator Scapulae Trapezius Rhomboids Major/Minor PLAY A&P Flix™: Muscles of the pectoral girdle (c) PLAY A&P Flix™: Movement of the pectoral girdle © 2013 Pearson Education, Inc.

Levator scapulae Supraspinatus Trapezius Clavicle Deltoid Spine of Figure 10.14c Superficial muscles of the thorax and shoulder acting on the scapula and arm. Levator scapulae Trapezius Supraspinatus Clavicle Deltoid Spine of scapula Rhomboid minor Infraspinatus Rhomboid major Teres minor Teres major Humerus Latissimus dorsi © 2013 Pearson Education, Inc.

Clavicle Deltoid Sternum Pectoralis major Coracobrachialis Figure 10.15a Muscles crossing the shoulder and elbow joints, causing movements of the arm and forearm, respectively. Clavicle Deltoid Sternum Pectoralis major Coracobrachialis Triceps brachii: Lateral head Long head Medial head Biceps brachii Brachialis Brachio- radialis Anterior view © 2013 Pearson Education, Inc.

Supraspinatus* Spine of scapula Deltoid (cut) Greater tubercle Figure 10.15b Muscles crossing the shoulder and elbow joints, causing movements of the arm and forearm, respectively. Supraspinatus* Spine of scapula Deltoid (cut) Greater tubercle of humerus Infraspinatus* Teres minor* Teres major Triceps brachii: Lateral head Long head Latissimus dorsi Humerus Olecranon of ulna Anconeus Posterior view © 2013 Pearson Education, Inc.

C. Breathing Muscles of Thorax Muscles of respiration 1. Intercostals = short slips of muscle going inbetween adjacent ribs; Intercostal nerves a) External intercostals—more superficial muscles; Direction of fibers– “hands in pocket” b) Internal intercostals—deeper muscles, except anteriorly; Direction of fibers– at approximately 90 degrees to External Intercostals © 2013 Pearson Education, Inc.

Figure 10.11a Muscles of respiration. External intercostal Internal intercostal © 2013 Pearson Education, Inc.

Muscles of the Thorax A&P Flix™: External intercostals PLAY A&P Flix™: External intercostals PLAY A&P Flix™: Internal intercostals © 2013 Pearson Education, Inc.

2. Diaphragm Partition between thoracic and abdominal cavities Most important muscle in inspiration Innervated by phrenic nerves Inserts along bottom boundary of rib cage Contraction moves diaphragm downward  increases vertical dimensions of rib cage  air flows in  inspiration Xiphoid process of sternum Central tendon of diaphragm Foramen for inferior vena cava Lumbar vertebra © 2013 Pearson Education, Inc.

Figure 10.11c Muscles of respiration. Central tendon of diaphragm Body of thoracic vertebra Pericardium (cut) Aorta Diaphragm (muscular part) Inferior vena cava Esophagus Pericardial sac © 2013 Pearson Education, Inc.

Figure 10.11b Muscles of respiration. Xiphoid process of sternum Foramen for inferior vena cava Foramen for esophagus Costal cartilage Central tendon of diaphragm Diaphragm Foramen for aorta Lumbar vertebra 12th rib Quadratus lumborum Psoas major © 2013 Pearson Education, Inc.

D. Muscles that move the Vertebral Column 1. Abdominal Wall Pectoralis major Fascicles run at angles to one another, provide added strength Ext. Oblique– (Hands in pocket) Int. Ob.– 90 degrees to above All innervated by intercostal nerves Serratus anterior Linea alba Tendinous intersection Transversus abdominis Rectus abdominis Internal oblique External oblique Inguinal ligament (formed by free inferior border of the external oblique aponeurosis) Aponeurosis of the external oblique © 2013 Pearson Education, Inc.

D. Muscles that move the Vertebral Column 1 . Abdominal Wall Actions of these muscles– know for each In General: Lateral flexion and rotation of trunk Help promote urination, defecation, childbirth, vomiting, coughing, and screaming Pectoralis major Serratus anterior Linea alba Tendinous intersection Transversus abdominis Rectus abdominis Internal oblique External oblique Inguinal ligament (formed by free inferior border of the external oblique aponeurosis) Aponeurosis of the external oblique © 2013 Pearson Education, Inc.

d) Transversus abdominis Four paired muscles, their fasciae and aponeuroses form lateral and anterior abdominal wall Rectus abdominis b) External obliques c) Internal obliques d) Transversus abdominis Pectoralis major Serratus anterior Linea alba Tendinous intersection Transversus abdominis Rectus abdominis Internal oblique External oblique Inguinal ligament (formed by free inferior border of the external oblique aponeurosis) Aponeurosis of the external oblique © 2013 Pearson Education, Inc.

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 © 2013 Pearson Education, Inc.

Figure 10.12a Muscles of the abdominal wall. Pectoralis major Serratus anterior Linea alba Tendinous intersection Transversus abdominis Rectus abdominis Internal oblique External oblique Aponeurosis of the external oblique Inguinal ligament (formed by free inferior border of the external oblique aponeurosis) © 2013 Pearson Education, Inc.

Figure 10.12b Muscles of the abdominal wall. Rectus abdominis Lumbar fascia External oblique Internal oblique Lumbar fascia Iliac crest Transversus abdominis Inguinal ligament Pubic tubercle © 2013 Pearson Education, Inc.

Figure 10.12c Muscles of the abdominal wall. Peritoneum Linea alba Transversus abdominis Rectus abdominis Internal oblique External oblique Aponeuroses Skin © 2013 Pearson Education, Inc.

2. Trunk Extension & Posture Deep (intrinsic) back muscles a) Erector spinae (sacrospinalis) group—prime movers of back extension and lateral bending © 2013 Pearson Education, Inc.

Iliocostalis cervicis Longissimus cervicis Figure 10.10d Muscles of the neck and vertebral column that move the head and trunk. Ligamentum nuchae Mastoid process of temporal bone Semispinalis capitis Longissimus capitis Semispinalis cervicis Iliocostalis cervicis Longissimus cervicis Semispinalis thoracis Iliocostalis thoracis Longissimus thoracis Spinalis thoracis Iliocostalis Erector spinae Longissimus Spinalis Multifidus Iliocostalis lumborum Quadratus lumborum External oblique © 2013 Pearson Education, Inc.