Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 10 The Muscular System

Introduction In this chapter we will cover: –Structural and functional organization of muscles –Muscles of the head and neck –Muscles of the trunk –Muscles acting on the shoulder and upper limb –Muscles acting on the hip and lower limb 10-2 Figure 10.5

The Structural and Functional Organization of Muscles –Describe the varied functions of muscles. –Describe the connective tissue components of a muscle and their relationship to the bundling of muscle fibers. –Describe the various shapes of skeletal muscles. –Explain what is meant by the origin, insertion, belly, action, –Describe the ways that muscles work in groups to aid, oppose, or moderate each other’s actions. 10-3

The Structural and Functional Organization of Muscles About 600 human skeletal muscles Specialized for one major purpose –Convert chemical energy in ATP to mechanical energy of motion Myology—the study of the muscular system Three kinds of muscle tissue –___________, _____________, ______________ 10-4

Skeletal Muscle Long threadlike unbranched cells Striations perpendicular to fibers Voluntary Skeletal muscle, tongue esophagus lips, eyelids, urethra anus Voluntary control of movement. –Movement, facial expressions posture, speech, control of urination and defecation, assistance in child birth

Smooth muscle Short cells overlapping Nonstriated Involuntary muscle Walls of viscera, iris, arrector pili, urethra anus Moving material through body

Cardiac muscle Short branched cells Intercollated discs Involuntary Heart Pumping blood throughout body

The 5 Functions of Muscles 1. Movement –Move from place to place, movement of body parts and body contents in breathing, circulation, feeding and digestion, defecation, urination, and childbirth –Role in communication: speech, writing, nonverbal communications 2. Stability –Maintain posture by preventing unwanted movements –Antigravity muscles: resist pull of gravity and prevent us from falling or slumping over –Stabilize joints 10-8

The Functions of Muscles 3. Control of openings and passageways –Mouth (food), eyelids and pupils (light) –Includes sphincters: internal muscular rings that control the movement of food, bile, blood 4. Heat production by skeletal muscles –85% of our body heat 5. Glycemic control –Regulation of blood glucose concentrations within its normal range Deconditioned muscles, obesity, old age increase risk of Type 2 Diabetes 10-9

Skeletal Muscle and Connective Tissues Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Skeletal muscle Perimysium Endomysium (a) Muscle fascicle Perimysium Epimysium Nerve Blood vessels Muscle fiber Tendon Fascia Muscle fiber Muscle fascicle Figure 10.1a Skeletal muscle cell is a fiber; long thread-like

Skeletal Muscle and Connective Tissues Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Skeletal muscle Perimysium Endomysium (a) Muscle fascicle Perimysium Epimysium Nerve Blood vessels Muscle fiber Tendon Fascia Muscle fiber Muscle fascicle Figure 10.1a Endomysium - Loose connective tissue that surrounds each muscle fiber - pink filling - Allows room for capillaries and nerve fibers

Skeletal Muscle and Connective Tissues Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Skeletal muscle Perimysium Endomysium (a) Muscle fascicle Perimysium Epimysium Nerve Blood vessels Muscle fiber Tendon Fascia Muscle fiber Muscle fascicle Figure 10.1a Perimysium- -Thicker layer of connective tissue wrapping fascle - Allows larger nerves and blood vessels -Fascicles: bundles of muscle fibers wrapped in perimysium

Skeletal Muscle and Connective Tissues Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Skeletal muscle Perimysium Endomysium (a) Muscle fascicle Perimysium Epimysium Nerve Blood vessels Muscle fiber Tendon Fascia Muscle fiber Muscle fascicle Figure 10.1a Epimysium -Fibrous sheath surrounding the entire muscle -Connects perimysium to fascia - Fascia -External sheath of connective tissue -Separates whole muscles

Connective Tissues of a Muscle Figure 10.1c Endomysium Perimysium Muscle fiber, c.s. Fascicle, c.s. Fascicle, l.s. Muscle fiber, l.s. (c) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Victor Eroschenko 10-14

Fascicles and Muscle Shapes Figure 10.2 Strength of a muscle and the direction of its pull are determined partly by the orientation of its fascicles Fusiform Parallel Triangular Unipennate Bipennate Multipennate Circular Biceps brachii Rectus abdominis Pectoralis major Palmar interosseous Rectus femoris Deltoid Orbicularis oculi Tendon Belly Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display

Muscle Attachments Tendons attach muscle and bony ends Collagen fibers of the endo-, peri-, and epimysium of muscle continue into the tendon From there into the periosteum and the matrix of bone Very strong structural continuity from muscle to bone 10-16

Muscle Origins and Insertions Origin –stationary end of muscle –Usually proximal end Belly –Thicker, middle region of muscle between origin and insertion Insertion –mobile end of muscle –Usually distal end Movement is insertion toward origin Figure 10.4 Scapula Bellies Radius Insertion Humerus Ulna Insertion Origins Long head Extensors: Lateral head Flexors: Biceps brachii Brachialis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Triceps brachii 10-17

Action and movement Figure 10.4 Scapula Bellies Radius Insertion Humerus Ulna Insertion Origins Long head Extensors: Lateral head Flexors: Biceps brachii Brachialis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Triceps brachii Action—the effects produced by contraction a muscle –To produce or prevent movement Muscle must cross a joint for that joint to move Movement is described by an action on a joint (not a muscle)

Muscle Origin and Insertions Movement is insertion toward origin Movement occurs as a result of a muscle contraction Some muscles can insert on the tendon of another muscle or on collagen fibers of the dermis –Distal tendon of the biceps brachii inserts on the fascia of the forearm –Facial muscles insert in the skin 10-19

Actions of Muscles Action—the effects produced by contraction a muscle –To produce or prevent movement Movement is described by an action on a joint Movement occurs only by contraction of a muscle –Not relaxation of a muscle 10-20

Four categories of muscle action 1.Prime mover (agonist) - produces most of force during a joint action 2. Synergist: aids the prime mover Stabilize joint or modify direction 3. Antagonist: opposes the prime mover Relaxes to give prime mover control over an action Preventing excessive movement and injury Antagonistic pairs—muscles that act on opposite sides of a joint 4. Fixator: muscle that prevents movement of bone rhomboids in back contract to hold scapula in place when flexing Bicep 10-21

Functional Groups of Muscles Prime mover—brachialis Synergist—biceps brachii Antagonist—triceps brachii Fixator—muscle that holds scapula firmly in place –Rhomboids Figure 10.4 Scapula Bellies Radius Insertion Humerus Ulna Insertion Origins Extensors: Lateral head Flexors: Biceps brachii Brachialis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Long head Triceps brachii 10-22

Muscle Innervation Innervation of a muscle—the identity of the nerve that stimulates a muscle –Enables the diagnosis of nerve, spinal cord, and brainstem injuries from their effects on muscle function Spinal nerves arise from the spinal cord –Emerge through intervertebral foramina –Innervate muscles below the neck Cranial nerves arise from the base of the brain –Emerge through skull foramina –Innervate the muscles of the head and neck 10-23

Ch 10 Exam Question 1. Notes Previous slides 2. Identification of muscles or actions using the diagram on the next 2 pages (delete names to quiz yourself) Only need to identify muscles on the 2nd Skeletal Muscles Powerpoint (Skeletal muscles ID on Moodle)

The Muscular System Figure 10.5b Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 10.5a Semispinalis capitis Levator scapulae Rhomboideus minor Rhomboideus major Infraspinatus Internal abdominal oblique Erector spinae Flexor carpi ulnaris Extensor digitorum (cut) Serratus posterior inferior Serratus anterior Supraspinatus Splenius capitis Gluteus minimus Lateral rotators Triceps brachii (cut) External abdominal oblique Trapezius Latissimus dorsi Extensor carpi radialis longus and brevis External abdominal oblique Iliotibial band Soleus (cut) Deltoid (cut) Teres minor Triceps brachii Gluteus maximus Gastrocnemius Soleus Calcaneal tendon (b) Posterior view Sternocleidomastoid Occipitalis Infraspinatus Fibularis longus Flexor digitorum longus Extensor hallucis longus Tibialis posterior Gastrocnemius (cut) Teres major Adductor magnus Iliotibial band Biceps femoris Semitendinosus Semimembranosus Gluteus medius Extensor carpi ulnaris Extensor digitorum Deep Superficial Biceps femoris Gracilis Frontalis Orbicularis oculi Masseter Orbicularis oris Trapezius External abdominal oblique Pronator quadratus Gastrocnemius Soleus Adductor longus Rectus abdominis Serratus anterior Sternocleidomastoid Deltoid Pectoralis major Biceps brachii Brachioradialis Sartorius Tensor fasciae latae Rectus femoris Fibularis longus Extensor digitorum longus Tibialis anterior Zygomaticus major Vastus lateralis Gracilis Vastus intermedius Adductors Extensor digitorum longus Supinator Flexor digitorum profundus Flexor pollicis longus Transverse abdominal Brachialis Coracobrachialis Platysma Flexor carpi radialis (a) Anterior view Vastus medialis Pectoralis minor Internal abdominal oblique DeepSuperficial Vastus lateralis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display

Muscles of Facial Expression Frontalis (cut)Galea aponeurotica Orbicularis oculi Sternohyoid Orbicularis oris Occipitalis Omohyoid Sternothyroid Inferior pharyngeal constrictor Sternocleidomastoid Masseter Thyrohyoid Zygomatic arch Levator labii superioris Zygomaticus minor Zygomaticus major Depressor labii inferioris Depressor anguli oris Buccinator Risorius (cut) Nasalis Corrugator supercilii Mentalis Levator scapulae (b) Lateral view Modiolus Temporalis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Figure 10.8b 10-26