The Muscular System: Part A 10 The Muscular System: Part A

Muscle tissue – all contractile tissues Focus on skeletal muscle The Muscular System Muscle tissue – all contractile tissues Skeletal, cardiac, smooth muscle Focus on skeletal muscle How muscles interact to  movement Criteria for naming muscles Principles of leverage © 2013 Pearson Education, Inc.

Actions and Interactions of Skeletal Muscles Muscles can only pull; never push What one muscle group "does", another "undoes" © 2013 Pearson Education, Inc.

Actions and Interactions of Skeletal Muscles Functional Groups Prime mover (agonist) Major responsibility for producing specific movement Antagonist Opposes or reverses particular movement Prime mover and antagonist on opposite sides of joint across which they act © 2013 Pearson Education, Inc.

Figure 10.1 The action of a muscle can be inferred by the position of the muscle relative to the joint it crosses. (Examples given relate to the shoulder joint.) A muscle that crosses on the anterior side of a joint produces flexion* Example: Pectoralis major (anterior view) A muscle that crosses on the posterior side of a joint produces extension* Example: Latissimus dorsi (posterior view) The latissimus dorsi is the antagonist of the pectoralis major. A muscle that crosses on the lateral side of a joint produces abduction Example: Deltoid middle fibers (anterolateral view). A muscle that crosses on the medial side of a joint produces adduction Example: Teres major (posterolateral view) The teres major is the antagonist of the deltoid. *These generalities do not apply to the knee and ankle because the lower limb is rotated during development. The muscles that cross these joints posteriorly produce flexion, and those that cross anteriorly produce extension. © 2013 Pearson Education, Inc.

Skeletal Muscles: Functional Groups Same muscle may be Prime mover of one movement Antagonist for different movement Synergist for third movement © 2013 Pearson Education, Inc.

Naming Skeletal Muscles Muscle location—bone or body region with which muscle associated Muscle shape—e.g., deltoid muscle (deltoid = triangle) Muscle size—e.g., maximus (largest), minimus (smallest), longus (long) Direction of muscle fibers or fascicles—e.g., rectus (fibers run straight), transversus (fibers run at right angles), and oblique (fibers run at angles to imaginary defined axis) © 2013 Pearson Education, Inc.

Naming Skeletal Muscles Number of origins—e.g., biceps (2 origins) and triceps (3 origins) Location of attachments—named according to point of origin and insertion (origin named first) Muscle action—named for action they produce, e.g., flexor or extensor Several criteria can be combined, e.g., extensor carpi radialis longus © 2013 Pearson Education, Inc.

Figure 10.5 Superficial muscles of the body: Anterior view. Facial Epicranius, frontal belly Orbicularis oculi Head Zygomaticus Temporalis Orbicularis oris Masseter Neck Shoulder Platysma Trapezius Sternohyoid Sternocleidomastoid Deltoid Arm Thorax Pectoralis minor Triceps brachii Pectoralis major Biceps brachii Serratus anterior Brachialis Intercostals Forearm Pronator teres Abdomen Brachioradialis Rectus abdominis Flexor carpi radialis External oblique Internal oblique Palmaris longus Transversus abdominis Pelvis/thigh Iliopsoas Thigh Pectineus Tensor fasciae latae Thigh Sartorius Rectus femoris Adductor longus Gracilis Vastus lateralis Vastus medialis Leg Leg Fibularis longus Gastrocnemius Extensor digitorum longus Soleus Tibialis anterior © 2013 Pearson Education, Inc.

Figure 10.6 Superficial muscles of the body: Posterior view. Neck Epicranius, occipital belly Sternocleidomastoid Trapezius Arm Shoulder Triceps brachii Deltoid Brachialis Infraspinatus Forearm Teres major Brachioradialis Rhomboid major Extensor carpi radialis longus Latissimus dorsi Flexor carpi ulnaris Hip Extensor digitorum Gluteus medius Extensor carpi ulnaris Gluteus maximus Thigh Iliotibial tract Adductor magnus Hamstrings: Biceps femoris Semitendinosus Leg Semimembranosus Gastrocnemius Soleus Fibularis longus Calcaneal (Achilles) tendon © 2013 Pearson Education, Inc.

Muscles of the Head Two groups Muscles of facial expression Muscles of mastication and tongue movement © 2013 Pearson Education, Inc.

Muscles of Mastication Four pairs involved in mastication; all innervated by cranial nerve V (trigeminal nerve) Prime movers of jaw closure Temporalis and masseter Grinding movements Medial and lateral pterygoids Chewing role - holds food between teeth Buccinator © 2013 Pearson Education, Inc.

Figure 10.8a Muscles promoting mastication and tongue movements. Temporalis Orbicularis oris Masseters Buccinator © 2013 Pearson Education, Inc.

Figure 10.8b Muscles promoting mastication and tongue movements. Lateral pterygoid Medial pterygoid Masseter pulled away © 2013 Pearson Education, Inc.

Muscles of the Anterior Neck and Throat Two groups Suprahyoid muscles Infrahyoid muscles Most involved in swallowing © 2013 Pearson Education, Inc.

Muscles of the Neck and Vertebral Column Two functional groups Muscles that move head Muscles that extend trunk and maintain posture © 2013 Pearson Education, Inc.

Muscles of the Neck and Vertebral Column: Head Movement Sternocleidomastoid—major head flexor Suprahyoid and infrahyoid—synergists to head flexion Sternocleidomastoid and scalenes—lateral head movements Splenius capitis and cervicis portions - head extension, rotation, and lateral bending Semispinalis capitis—synergist with sternocleidomastoid © 2013 Pearson Education, Inc.

Base of occipital bone 1st cervical vertebra Mastoid process Middle Figure 10.10a Muscles of the neck and vertebral column that move the head and trunk. Base of occipital bone 1st cervical vertebra Mastoid process Middle scalene Sternocleido- mastoid Anterior scalene Posterior scalene Anterior © 2013 Pearson Education, Inc.

Platysma (cut) Sternocleidomastoid (cut) Internal jugular vein Figure 10.10c Muscles of the neck and vertebral column that move the head and trunk. Platysma (cut) Sternocleidomastoid (cut) Internal jugular vein Omohyoid Sternohyoid Sternothyroid Sternocleidomastoid Pectoralis major © 2013 Pearson Education, Inc.

Muscles of the Neck and Vertebral Column: Trunk Extension Deep (intrinsic) back muscles Erector spinae (sacrospinalis) group—prime movers of back extension and lateral bending Iliocostalis Longissimus Spinalis Semispinalis and quadratus lumborum—synergists in extension and rotation © 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.

Deep Muscles of the Thorax: Breathing Muscles of respiration External intercostals—more superficial muscles; elevate ribs for inspiration Internal intercostals—deeper muscles; aid forced expiration Diaphragm Partition between thoracic and abdominal cavities Most important muscle in inspiration Innervated by phrenic nerves © 2013 Pearson Education, Inc.

Figure 10.11a Muscles of respiration. External intercostal Internal intercostal © 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.

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.

Muscles of the Abdominal Wall Four paired muscles, their fasciae and aponeuroses form lateral and anterior abdominal wall Rectus abdominis External obliques Internal obliques 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.

Muscles of the Abdominal Wall run at angles to one another, provide added strength All innervated by intercostal nerves Actions of these muscles Lateral flexion and rotation of trunk Help promote urination, defecation, childbirth, vomiting, coughing, and screaming © 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.

Superficial Muscles of the Thorax Most - extrinsic shoulder muscles Act in combination to fix shoulder girdle (mostly scapula); move it to increase range of arm movements Actions - 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) PLAY A&P Flix™: Muscles that act on the shoulder joint and humerus: An overview (b) © 2013 Pearson Education, Inc.

Superficial Muscles of the Thorax Muscles of anterior thorax Pectoralis minor Serratus anterior Subclavius PLAY A&P Flix™: Muscles of the pectoral girdle (a) PLAY A&P Flix™: Muscles of the pectoral girdle (b) © 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.

Superficial Muscles of the Posterior Thorax Posterior extrinsic shoulder muscles Trapezius Levator scapulae Rhomboids (major and 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.