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Chapter 10 Lecture Outline

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• Muscles constitute nearly half of the body’s weight and are of central interest in several fields of health care and fitness

Figure 10.5a

10-2 The Structural and Functional Organization of Muscles

• Expected Learning Outcomes – 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 and relate this to their functions. – Explain what is meant by the origin, insertion, belly, action, and innervation of a muscle.

10-3 The Structural and Functional Organization of Muscles

(Continued) – Describe the ways that muscles work in groups to aid, oppose, or moderate each other’s actions. – Distinguish between intrinsic and extrinsic muscles. – Describe, in general terms, the nerve supply to the muscles and where these nerves originate. – Explain how the Latin names of muscles can aid in visualizing and remembering them.

10-4 The Structural and Functional Organization of Muscles

• About 600 human skeletal muscles • Constitute about half of our body weight • Three kinds of muscle tissue – Skeletal, cardiac, smooth • Specialized for one major purpose – Converting the chemical energy in ATP into the mechanical energy of motion • Myology—the study of the muscular system

10-5 The Functions of Muscles • Muscle functions include: movement, stability, control of openings, heat production, and glycemic control • Movement – Move from place to place; move body parts; move body contents in breathing, circulation, and digestion – In communication: speech, writing, facial expressions and other nonverbal communications • Stability – Maintain posture by preventing unwanted movements – Antigravity muscles: prevent us from falling over – Stabilize joints by maintaining tension

10-6 The Functions of Muscles

• Control of openings and passageways – Sphincters: internal muscular rings that control the movement of food, blood, and other materials within body • Heat production by skeletal muscles – As much as 85% of our body heat • Glycemic control – Muscles absorb and store glucose which helps regulate blood sugar concentration within normal range

10-7 Connective Tissues of a Muscle

Tendon

Fascia

Skeletal muscle

Muscle fascicle Nerve Blood vessels Epimysium

Perimysium

Endomysium Muscle fiber

Muscle fascicle Figure 10.1a

Perimysium

Muscle fiber

(a) 10-8 Connective Tissues and Fascicles • Endomysium – Thin sleeve of loose connective tissue around each fiber – Allows room for capillaries and nerve fibers – Provides chemical environment for muscle fiber • Perimysium – Thicker layer of connective tissue that wraps fascicles • Fascicles: bundles of muscle fibers wrapped together – Carries nerves, blood vessels, and stretch receptors • Epimysium – Fibrous sheath surrounding entire muscle – Outer surface grades into fascia; inner surface projections form perimysium • Fascia – Sheet of connective tissue that separates neighboring muscles or muscle groups from each other and the

subcutaneous tissue 10-9 Connective Tissues and Fascicles

Figure 10.1c 10-10 Fascicles and Muscle Shapes

Unipennate Triangular Bipennate Parallel Multipennate Fusiform

Tendon Circular

Belly

Pectoralis major Tendon Palmar interosseous Rectus femoris Rectus abdominis Deltoid Biceps brachii Orbicularis oculi Figure 10.2

• Strength of a muscle and the direction of its pull are determined partly by the orientation of its fascicles

10-11 Fascicles and Muscle Shapes

• Fusiform muscles—thick in the middle and tapered at each end • Parallel muscles—uniform width and parallel fascicles • Triangular (convergent) muscles—broad at one end and narrow at the other • Pennate muscles—feather shaped - Unipennate—fasciles approach tendon from one side - Bipennate—fascicles approach tendon from both sides - Multipennate—bunches of feathers converge to single point • Circular muscles (sphincters)—form rings around body openings

10-12 Muscle Compartments

Anterior Lateral Medial Tibia Fibula Posterior Interosseous membrane Artery, veins, and nerve Intermuscular septa Fasciae Key Subcutaneous Anterior compartment fat Lateral compartment Posterior compartment, deep layer Posterior compartment, superficial layer Figure 10.3

• Muscle compartment—a group of functionally related muscles enclosed by fascia – Also contains nerves and blood vessels that supply the muscle group • Intermuscular septa are very thick fascia that separate one compartment from another

10-13 Muscle Attachments

• Indirect attachment to bone – Tendons connect muscle to bone • Collagen fibers of the endo-, peri-, and epimysium continue into the tendon and from there into periosteum and matrix of bone • Aponeurosis—tendon is a broad, flat sheet (palmar aponeurosis) • Retinaculum—connective tissue band that tendons from separate muscles pass under

• Direct (fleshy) attachment to bone – Little separation between muscle and bone – Muscle seems to emerge directly from bone

10-14 Muscle Origins and Insertions

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • Origin – Bony attachment at stationary end of Origins Origins Humerus muscle Scapula Bellies • Belly Extensors: Flexors: Triceps brachii Biceps brachii – Thicker, middle region Long head Brachialis of muscle between Lateral head origin and insertion

Insertion Radius • Insertion Insertion Ulna

– Bony attachment to Figure 10.4 mobile end of muscle

10-15 Muscle Origins and Insertions

• Some anatomists prefer nontraditional descriptions of attachments by proximal vs. distal or superior vs. inferior

• Some muscles insert not on bone but on the fascia or tendon of another muscle or on collagen fibers of the dermis – Example: many facial muscles insert in the skin

10-16 Functional Groups of Muscles

• Action—effect produced by a muscle to produce or prevent movement • Four categories of muscle action: prime mover, synergist, antagonist, and fixator – Prime mover (agonist) • Muscle that produces most of force during a particular joint action – Synergist: muscle that aids the prime mover • May contribute additional force, modify the direction of movement, or stabilize a nearby joint

10-17 Functional Groups of Muscles

(Continued) – Antagonist: opposes the prime mover • Prevents excessive movement • Sometimes relaxes to give prime mover control over an action • Antagonistic pairs—muscles that act on opposite sides of a joint – Fixator: muscle that prevents movement of bone

10-18 Functional Groups of Muscles

Origins Origins For elbow flexion: Humerus Scapula • Prime mover—brachialis Bellies • Synergist—biceps brachii

Extensors: Flexors: Triceps brachii Biceps brachii • Antagonist—triceps brachii Long head Brachialis Lateral head • Fixator—muscle that holds scapula firmly in place – Rhomboids Insertion Radius Insertion Ulna

Figure 10.4

10-19 Intrinsic and Extrinsic Muscles

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • Intrinsic muscle— entirely contained Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Common Tendon sheath First dorsal flexor within a region, interosseous tendon Tendon of flexor Adductor digitorum profundus pollicis such as the hand Tendon of flexor digitorum superficialis Tendon of flexor Lumbricals pollicis longus Flexor – Both origin and Opponens digiti minimi Flexor pollicis digitorum brevis Flexor digiti superficialis insertion there Abductor pollicis brevis Abductor digiti Flexor minimi Opponens pollicis Flexor retinaculum pollicis longus Tendons of: Tendons of: Abductor pollicis • Extrinsic Flexor carpi ulnaris longus Flexor carpi Flexor digitorum radialis superficialis Flexor pollicis muscle—acts on a Palmaris longus longus Flexor digitorum designated region, (a) Palmar aspect, superficial superficialis tendons but has its origin Figure 10.31a Flexor digitorum elsewhere profundus tendons – Fingers: extrinsic

(b) Intermediate flexor muscles in the forearm Figure 10.28b 10-20 Muscle Innervation

• Innervation of a muscle—refers to the identity of the nerve that stimulates it – Knowing innervation enables diagnosis of nerve, spinal cord, and brainstem injuries from muscle tests

• Spinal nerves arise from the spinal cord – Emerge through intervertebral foramina – Immediately branch into posterior and anterior rami – Innervate muscles below the neck – Plexus: web-like network of spinal nerves adjacent to the vertebral column

10-21 Muscle Innervation

• Cranial nerves arise from the base of the brain – Emerge through skull foramina – Innervate the muscles of the head and neck – Numbered CN I to CN XII

10-22 Blood Supply

• Muscular system receives about 1.24 L of blood per minute at rest (one-quarter of the blood pumped by the heart)

• During heavy exercise, total cardiac output rises and the muscular system’s share is more than three-quarters (11.6 L/min)

• Capillaries branch extensively through the endomysium to reach every muscle fiber

10-23 How Muscles Are Named

• Latin names – Depressor labii inferioris, flexor digiti minimi brevis • Describes distinctive aspects of the structure, location, or action of a muscle • Footnotes throughout chapters show interpreted names of muscles • Pronunciation of muscles available online at www.aprevealed.com

10-24 The Muscular System

Superficial Deep

Frontalis

Orbicularis oculi Masseter Zygomaticus major Orbicularis oris Sternocleidomastoid Platysma Trapezius Pectoralis minor Deltoid Coracobrachialis Pectoralis major Serratus anterior Brachialis Biceps brachii Rectus abdominis Supinator Flexor digitorum Brachioradialis profundus Flexor pollicis longus Flexor carpi radialis Transverse abdominal External abdominal oblique Internal abdominal Tensor oblique Pronator quadratus fasciae latae

Adductor longus Sartorius Adductors Rectus femoris Vastus lateralis Vastus lateralis Vastus intermedius Vastus medialis Gracilis

Fibularis longus Gastrocnemius

Tibialis anterior Soleus

Extensor digitorum Extensor digitorum longus longus Figure 10.5b Figure 10.5a

(a) Anterior view 10-25 A Learning Strategy

• Examine models, cadavers, dissected animals, or a photographic atlas • Palpate muscles on yourself if possible • Locate origins and insertions of muscles on an articulated skeleton • Study derivation of each muscle name – Usually describes the muscle’s location, appearance, origin, insertion, or action • Say the names aloud to yourself or study partner, and spell them correctly

10-26 Muscles of the Head and Neck

• Expected Learning Outcomes – Name and locate the muscles that produce facial expression. – Name and locate the muscles used for chewing and swallowing. – Name and locate the neck muscles that move the head. – Identify the origin, insertion, action, and innervation of any of these muscles.

10-27 Muscles of Facial Expression

• Muscles that insert in the dermis and subcutaneous tissues • Tense the skin and produce facial expressions • Innervated by facial nerve (CN VII) • Paralysis causes face to sag • Found in scalp, forehead, around the eyes, nose, and mouth, and in the neck

10-28 Muscles of Facial Expression

Superficial Deep

Galea aponeurotica

Frontalis

Corrugator supercilii

Orbicularis oculi

Nasalis

Levator labii superioris Levator anguli oris

Zygomaticus minor

Zygomaticus major Masseter

Risorius Buccinator

Modiolus Orbicularis oris Depressor anguli oris

Depressor labii inferioris Mentalis (cut)

Platysma

(a) Anterior view Figure 10.8a 10-29 Muscles of Facial Expression

Galea aponeurotica Frontalis (cut)

Temporalis Corrugator supercilii

Orbicularis oculi

Occipitalis Nasalis

Levator labii superioris Zygomatic arch Zygomaticus minor

Zygomaticus major

Orbicularis oris Masseter

Sternocleidomastoid Modiolus Levator scapulae Inferior pharyngeal Risorius (cut) constrictor Mentalis Thyrohyoid Depressor labii Sternothyroid inferioris Omohyoid Depressor anguli oris Sternohyoid (b) Lateral view Buccinator Figure 10.8b 10-30 Muscles of Chewing and Swallowing • Extrinsic muscles of the tongue – Tongue is very agile organ – Pushes food between molars for chewing (mastication) – Forces food into the pharynx for swallowing (deglutition) – Crucial importance to speech • Intrinsic muscles of tongue – Vertical, transverse, and longitudinal fascicles

Styloid process

Palatoglossus Mastoid process

Styloglossus Posterior belly of digastric (cut)

Superior pharyngeal constrictor (cut) Inferior longitudinal muscle of tongue Stylohyoid Middle pharyngeal constrictor Genioglossus Hyoglossus

Mylohyoid (cut) Hyoid bone

Geniohyoid

Larynx

Inferior pharyngeal constrictor

Trachea Esophagus

Figure 10.9 10-31 Muscles of Chewing and Swallowing

– Depression: to open mouth Temporalis – Elevation: biting and grinding

Orbicularis oris

– Protraction: incisors can cut Buccinator – Retraction: make rear teeth meet Masseter (cut) (a) Lateral view – Lateral and medial excursion: grind food • Temporalis, masseter, medial Lateral pterygoid plate pterygoid, and lateral pterygoid Medial pterygoid plate Lateral pterygoid muscle Medial pterygoid muscle Interior of oral cavity • Innervated by mandibular nerve, a branch of the (b) Posterior view trigeminal (CN V) Figure 10.10a,b

10-32 Muscles of Chewing and Swallowing • Hyoid muscles—suprahyoid group • Aspects of chewing, swallowing, and vocalizing • Eight pairs of hyoid muscles associated with hyoid bone • Digastric—opens mouth widely • Geniohyoid—depresses mandible • Mylohyoid—elevates floor of mouth at beginning of swallowing • Stylohyoid—elevates hyoid

Digastric: Anterior belly Posterior belly Suprahyoid group Stylohyoid Mylohyoid Hyoid bone Common carotid artery Levator scapulae Internal jugular vein

Thyrohyoid Sternohyoid Infrahyoid group Infrahyoid Omohyoid: Sternothyroid group Superior belly Inferior belly Sternocleidomastoid Clavicle

(a) Anterior view Figure 10.11a 10-33 Muscles of Chewing and Swallowing • Hyoid muscles—infrahyoid group • Fix hyoid bone from below, allowing suprahyoid muscles to open mouth • Omohyoid—depresses hyoid after elevation • Sternohyoid—depresses hyoid after elevation • Thyrohyoid—depresses hyoid and elevates larynx • Sternothyroid—depresses larynx after elevation

Stylohyoid Digastric (posterior belly) Hyoglossus Splenius capitis Mylohyoid Digastric Inferior pharyngeal constrictor (anterior belly) Sternocleidomastoid Hyoid bone Trapezius Thyrohyoid Levator scapulae Omohyoid (superior belly) Scalenes Sternothyroid Omohyoid (inferior belly) Sternohyoid

(b) Lateral view Figure 10.11b 10-34 Muscles of Chewing and Swallowing

Styloid process

Palatoglossus Mastoid process

Styloglossus Posterior belly of digastric (cut)

Superior pharyngeal constrictor (cut) Inferior longitudinal muscle of tongue Stylohyoid Middle pharyngeal constrictor Genioglossus Hyoglossus

Mylohyoid (cut) Hyoid bone

Geniohyoid

Larynx

Inferior pharyngeal constrictor

Trachea Esophagus Figure 10.9

• Pharynx: three pairs pharyngeal constrictors – Encircle pharynx forming a muscular funnel – During swallowing, drive food into the esophagus

10-35 Muscles Acting on the Head

• Originate on vertebral column, thoracic cage, and pectoral girdle • Insert on the cranial bones • Actions – Flexion (tipping head forward) – Extension (holding the head erect) – Lateral flexion (tipping head to one side) – Rotation (turning the head to the left and right)

10-36 Muscles Acting on the Head

• Neck flexors – Sternocleidomastoid – Scalenes

• Neck extensors – Trapezius – Splenius capitis – Semispinalis capitis

Figure 10.12

10-37 Muscles Acting on the Head

• May cause contralateral movement: movement of the head toward the opposite side

• May cause ipsilateral movement: movement of the head toward the same side

10-38 Muscles of the Trunk

• Expected Learning Outcomes – Name and locate the muscles of respiration and explain how they affect airflow and abdominal pressure. – Name and locate the muscles of the abdominal wall, back, and pelvic floor. – Identify the origin, insertion, action, and innervation of any of these muscles.

10-39 Muscles of the Trunk

• Three functional groups – Muscles of respiration – Muscles that support abdominal wall and pelvic floor – Movement of vertebral column

10-40 Muscles of Respiration

• Breathing requires the use of muscles enclosing thoracic cavity – Diaphragm, external intercostal, internal intercostal, and innermost intercostal muscles

• Inspiration—air intake

• Expiration—expelling air

10-41 Muscles of Respiration

• Other muscles of chest and abdomen that contribute to breathing – Sternocleidomastoid, scalenes of neck – Pectoralis major and serratus anterior of chest – Latissimus dorsi of back – Abdominal muscles: internal and external obliques, and transverse abdominis – Even some anal muscles

10-42 Muscles of Respiration

abdominal cavities Xiphoid process of sternum Inferior • Muscle fascicles extend to vena cava a fibrous central tendon Ribs Esophagus

Central • Contraction flattens tendon of diaphragm diaphragm Aorta

Vertebral – Enlarges thoracic cavity column (inspiration) • In relaxation of diaphragm it (b) Inferior view of diaphragm rises – Shrinks the thoracic cavity Figure 10.13b (expiration)

10-43 Muscles of Respiration

inflow of air External intercostals • Internal intercostals

Internal – Depresses and retracts ribs intercostals – Compresses thoracic cavity – Expelling air (a) Lateral view of intercostal muscles • Innermost intercostals Figure 10.13a – Same action as internal intercostals 10-44 Muscles of the Anterior Abdominal Wall • Internal abdominal oblique – Intermediate layer of lateral abdominal muscles – Unilateral contraction causes ipsilateral rotation of waist – Aponeurosis • Tendons of oblique and transverse muscles • Broad, fibrous sheets

Subclavius

Pectoralis minor (cut)

Pectoralis minor Internal intercostals

Serratus anterior

External intercostals Rectus abdominis (cut)

Rectus sheath

External abdominal oblique (cut)

Internal abdominal Internal abdominal oblique oblique (cut) Posterior wall of rectus sheath (rectus abdominis removed) Inguinal ligament Transverse abdominal (cut)

(b) Deep Figure 10.15b 10-45 Muscles of the Anterior Abdominal Wall

• Transverse abdominal – Deepest of lateral abdominal muscles – Horizontal fibers – Compresses abdominal contents – Contributes to movements of vertebral column

Subclavius

Pectoralis minor (cut)

Pectoralis minor Internal intercostals

Serratus anterior

External intercostals Rectus abdominis (cut)

Rectus sheath

External abdominal oblique (cut)

Internal abdominal Internal abdominal oblique oblique (cut) Posterior wall of rectus sheath (rectus abdominis removed) Inguinal ligament Transverse abdominal (cut)

(b) Deep Figure 10.15b 10-46 Muscles of the Anterior Abdominal Wall • Rectus abdominis – Flexes lumbar region of vertebral column – Produces forward bending at the waist – Extends from sternum to pubis – Rectus sheath encloses muscle – Three transverse tendinous intersections divide rectus abdominis into segments, sometimes called a “six pack”

Pectoralis major

Latissimus dorsi

Serratus anterior Tendinous intersections Rectus sheath (cut edges)

Rectus sheath Transverse abdominal Umbilicus Linea semilunaris Internal abdominal oblique (cut) Linea alba External abdominal oblique (cut) Aponeurosis of Rectus abdominis external abdominal oblique Inguinal ligament (a) Superficial Figure 10.15a 10-47 Muscles of Back

• Back muscles extend, rotate, and laterally flex vertebral column

• Most prominent superficial back muscles: latissimus dorsi and trapezius

• Upper limb movement

• Deep muscles Superior nuchal line Semispinalis capitis Longissimus capitis • Erector spinae Splenius capitis Semispinalis cervicis – Iliocostalis, longissimus, Serratus posterior spinalis superior

Splenius cervicis – From cranium to sacrum Semispinalis Erector spinae: thoracis Iliocostalis – Extension and lateral Longissimus flexion of vertebral column Spinalis

Serratus posterior inferior

• Semispinalis thoracis Internal abdominal Multifidus oblique Quadratus lumborum – Extension and External abdominal contralateral rotation of oblique (cut) vertebral column

Figure 10.18 10-49 Muscles of the Back

(Continued) • Quadratus lumborum – Aids respiration – Ipsilateral flexion of lumbar vertebral column

• Multifidus – Stabilizes adjacent vertebrae – Maintains posture

10-50 Muscles of the Pelvic Floor

• Layers of muscles and fasciae that span pelvic outlet – Penetrated by anal canal, urethra, and vagina • Perineum—diamond-shaped region between the thighs – Bordered by four bony landmarks • Pubic symphysis anteriorly • Coccyx posteriorly • Ischial tuberosities laterally – Urogenital triangle: anterior half of perineum – Anal triangle: posterior half of perineum

10-51 Muscles of the Pelvic Floor

• Layers or compartments of the perineum – Superficial perineal space • Ischiocavernosus, bulbospongiosus – Deep perineal space • Deep transverse perineal, compressor urethrae – Anal triangle • External anal sphincter – Pelvic diaphragm: deepest (most superior) layer • Levator ani

10-52 Muscles of the Pelvic Floor

Figure 10.20a

• Superficial perineal space – Ischiocavernosus—maintains erection – Bulbospongiosus—aids in erection, expels remaining urine

10-53 Muscles of the Pelvic Floor

Figure 10.20b

• Deep perineal space – Urogenital triangle—contains deep transverse perineal muscle and compressor urethrae in females • Anal triangle—external anal sphincter 10-54 Muscles of the Pelvic Floor

Figure 10.20c

• Pelvic diaphragm: deepest compartment of the perineum – Levator ani: supports viscera and defecation – Coccygeus muscle(s)

10-55 Hernias • Hernia—any condition in which the viscera protrudes through a weak point in the muscular wall of Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. the abdominopelvic cavity Aponeurosis of external abdominal oblique muscle • Inguinal hernia Inguinal canal

– Most common type of hernia (rare External inguinal ring

in women) Herniated loop of small intestine – Viscera enter inguinal canal or Upper scrotum even the scrotum • Hiatal hernia – Stomach protrudes through diaphragm into thorax Figure 10.21 – Overweight people over 40 • Umbilical hernia – Viscera protrude through the navel 10-56 Muscles Acting on the Shoulder and Upper Limb

• Expected Learning Outcomes – Name and locate the muscles that act on the pectoral girdle, shoulder, elbow, wrist, and hand. – Relate the actions of these muscles to the joint movements described in chapter 9. – Describe the origin, insertion, and innervation of each muscle.

10-57 Muscles Acting on the Shoulder and Upper Limb

• Compartments—spaces where muscles are separated by fibrous connective tissue sheets (fasciae) – Each compartment contains one or more functionally related muscles along with their nerve and blood supplies • Muscles of upper limbs divided into anterior and posterior compartments • Intermuscular septa (thick fascia) separates compartments • Compartment syndrome—one of the muscles or blood vessels in a compartment is injured

10-58 Compartment Syndrome • If a blood vessel in a compartment is damaged, blood and tissue fluid accumulate • Fasciae enclose muscle compartments snugly and prevent expansion • Compartment syndrome—mounting pressure triggers a sequence of degenerative events – Blood flow to compartment is obstructed by pressure – If ischemia (poor blood flow) persists for more than 2 to 4 hours, nerves begin to die – After 6 hours, muscles begin to die • Nerves can regenerate after pressure relieved, but muscle damage is permanent • Myoglobin in urine indicates compartment syndrome • Treatment: immobilization of limb and fasciotomy (incision to relieve compartment pressure)

10-59 Muscles Acting on the Shoulder and Upper Limb

• Upper limb is used for a broad range of powerful and subtle actions – Climbing, grasping, throwing, writing, playing musical instruments, and manipulating small objects • Muscles that act on the scapula • Muscles that act on the humerus and shoulder joint • Muscles that act on the forearm and elbow joint • Muscles that act on the wrist, hand, and fingers

10-60 Muscles Acting on the Shoulder

• A group of muscles originate on the axial skeleton and insert on clavicle or scapula • Scapula loosely attached to thoracic cage – Capable of great movement – Rotation, elevation, depression, protraction, retraction • Clavicle braces the shoulder and moderates movements

10-61 Muscles Acting on the Scapula

Figure 10.22 10-62 Muscles Acting on the Shoulder • Anterior group of muscles of pectoral girdle • Pectoralis minor • Serratus anterior – Ribs 3–5 to coracoid – All ribs to medial process of scapula border of scapula – Draws scapula laterally – Draws scapula laterally Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. and forward; prime

Subclavius mover for reaching and

Pectoralis minor (cut) pushing

Pectoralis minor Internal intercostals

Serratus anterior

External intercostals Rectus abdominis (cut)

Rectus sheath

External abdominal oblique (cut)

Internal abdominal Internal abdominal oblique oblique (cut)

Posterior wall of rectus sheath (rectus abdominis removed) Inguinal ligament Transverse abdominal (cut)

(b) Deep Figure 10.15b 10-63 Muscles Acting on the Shoulder • Posterior group of muscles of pectoral girdle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Superficial Deep

• Four muscles of posterior group

Semispinalis capitis – Trapezius: superficial Sternocleidomastoid Splenius capitis Trapezius Levator scapulae – Levator scapulae, Rhomboid Rhomboid minor Rhomboid major minor, and Rhomboid major: Supraspinatus Infraspinatus Deltoid Teres minor deep Teres major

Erector spinae Serratus anterior Serratus posterior inferior

Latissimus External abdominal • Trapezius dorsi oblique External abdominal Internal abdominal oblique oblique – Stabilizes scapula and shoulder Thoracolumbar fascia – Elevates and depresses shoulder Gluteus medius Gluteus minimus Gluteus maximus apex Lateral rotators

Figure 10.17

10-64 Muscles Acting on the Shoulder

(Continued from slide 170) • Levator scapulae – Elevates scapula – Flexes neck laterally

• Rhomboid minor – Retracts scapula and braces shoulder

• Rhomboid major – Same as Rhomboid minor

10-65 Muscles Acting on the Shoulder • Posterior scapular muscles

Superficial Deep

Semispinalis capitis Sternocleidomastoid Splenius capitis Trapezius Levator scapulae Rhomboid minor Rhomboid major Supraspinatus Infraspinatus Deltoid Teres minor

Teres major

Erector spinae Serratus anterior Serratus posterior inferior

External abdominal Latissimus oblique dorsi

External abdominal Internal abdominal oblique oblique Thoracolumbar fascia

Gluteus medius Gluteus minimus

Gluteus maximus Lateral rotators

Figure 10.17 10-66 Muscles Acting on the Arm • Nine muscles cross the shoulder joint and insert on humerus • Two are axial muscles originating on axial skeleton – Pectoralis major: flexes, adducts, and medially rotates humerus – Latissimus dorsi: adducts and medially rotates humerus

Supraspinatus

Clavicle Spine of scapula Greater tubercle Sternum of humerus Infraspinatus Deltoid Pectoralis major Humerus Teres minor Teres major

Triceps brachii: Coracobrachialis Triceps brachii: Lateral head Lateral head Long head Long head Medial head Biceps brachii Latissimus dorsi Brachialis Brachioradialis

(a) Anterior view (b) Posterior view Figure 10.23b Figure 10.23a 10-67 Anterior View of Cadaver Chest

Figure 10.24a 10-68 Back Muscles of Cadaver

Figure 10.24b 10-69 Muscles Acting on the Arm

scapular origin Sternum Deltoid Pectoralis major – Deltoid

Triceps brachii: Coracobrachialis • Rotates and abducts arm Lateral head Long head Medial head • Intramuscular injection site Biceps brachii Brachialis – Teres major Brachioradialis • Extension and medial Figure 10.23a rotation of humerus (a) Anterior view Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. – Coracobrachialis Supraspinatus Spine of scapula • Flexes and medially rotates Greater tubercle of humerus Infraspinatus arm Humerus Teres minor Teres major

– Remaining four form the Triceps brachii: Lateral head rotator cuff that reinforce Long head the shoulder joint Latissimus dorsi

Figure 10.23b 10-70 (b) Posterior view Muscles Acting on the Arm • Rotator cuff muscles • Tendons of the remaining four scapular muscles form the rotator cuff

• Acronym “SITS muscles” – Supraspinatus – Infraspinatus – Teres minor – Subscapularis

• Tendons of these muscles merge with the joint capsule of the shoulder as they cross it in route to the humerus

• Holds head of humerus into glenoid cavity

• Supraspinatus tendon easily damaged 10-71 Rotator Cuff Muscles

Anterior Posterior

Clavicle Rotator cuff (SITS) muscles: Acromion Supraspinatus Coracoid Infraspinatus process Glenoid cavity Teres minor Subscapularis

Inferior angle

Figure 10.25

10-72 Muscles Acting on the Forearm

• Elbow and forearm capable of flexion, extension, pronation, and supination – Carried out by muscles in both brachium (arm) and antebrachium (forearm)

• Muscles with bellies in the arm (brachium) – Principal elbow flexors: anterior compartment • Brachialis and biceps brachii – Brachialis produces 50% more power than biceps brachii – Brachialis is prime mover of elbow flexion – Principal elbow extensor: posterior compartment • Triceps brachii – Prime mover of elbow extension

10-73 Muscles Acting on the Forearm

Figure 10.23c • Principal flexor

Biceps brachii: – Brachialis Long head Short head

Clavicle • Synergistic Sternum Deltoid Pectoralis major flexors Triceps brachii: Coracobrachialis (c) Anterior view Lateral head Long head Medial head – Biceps brachii Biceps brachii Brachialis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Brachioradialis

Supraspinatus – Brachioradialis Spine of scapula Greater tubercle of humerus Infraspinatus Humerus (a) Anterior view Teres minor Teres major

Triceps brachii: Figure 10.23a Lateral head • Principal extensor Long head – Triceps brachii Latissimus dorsi Figure 10.23b

(b) Posterior view 10-74 Muscles Acting on the Forearm

• Muscles with bellies in the forearm (antebrachium) – Brachioradialis: flexes elbow – Anconeus: extends elbow – Pronator quadratus: prime mover in forearm pronation – Pronator teres: assists pronator quadratus in pronation – Supinator: supinates the forearm

10-75 Muscles Acting on the Forearm

Lateral epicondyle Lateral epicondyle Medial epicondyle Medial epicondyle Supinator Supinator Pronator teres Pronator teres

Ulna Ulna Radius Radius Pronator quadratus Pronator quadratus Biceps Biceps brachii brachii

Radius Radius Bursa Bursa Supinator Supinator Ulna Ulna

(b) Muscle actions (b) Muscle actions in supination in supination

(a) Supination (c) Pronation Figure 10.26a Figure 10.26c • Supination • Pronation – Supinator muscle – Pronator quadratus and – Palm facing anteriorly pronator teres or superiorly – Palm faces posteriorly or inferiorly 10-76 Muscles Acting on the Wrist and Hand • Anterior group • Extrinsic muscles of the forearm • Intrinsic muscles in the hand itself • Extrinsic muscle actions – Flexion and extension of wrist and digits – Radial and ulnar flexion – Finger abduction and adduction Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

– Thumb opposition Biceps brachii Triceps brachii Brachialis Common flexor tendon Common flexor tendon Pronator teres Supinator Aponeurosis of biceps Anterior view Interosseous brachii Brachioradialis membrane Flexor carpi radialis Flexor Flexor Palmaris longus digitorum digitorum Flexor carpi ulnaris superficialis profundus

Extensor carpi radialis Flexor longus and brevis Flexor pollicis longus pollicis Flexor digitorum longus superficialis

Flexor retinaculum Flexor Flexor digitorum digitorum Palmar superficialis superficialis aponeurosis tendons tendons

Flexor Flexor Figure 10.28a,b,c digitorum digitorum profundus profundus tendons tendons (a) Superficial flexors (b) Intermediate flexor (c) Deep flexors 10-77 Muscles Acting on the Wrist and Hand

• Anterior (flexor) compartment—superficial layer – Flexor carpi radialis – Flexor carpi ulnaris – Flexor digitorum superficialis – Palmaris longus

• Anterior (flexor) compartment—deep layer – Flexor digitorum profundus – Flexor pollicis longus

10-78 Cross Section of Upper Limb

Biceps brachii: Short head Long head

(a) Coracobrachialis Humerus

(b) Latissimus dorsi tendon Teres major

(a)

Anterior Biceps brachii Lateral Medial

Brachialis

Posterior Triceps brachii: Key Medial head Anterior (flexor) Long head compartment, superficial Lateral head Anterior (flexor) compartment, deep (b) Posterior (extensor) compartment Other muscles

Pronator teres Brachioradialis Flexor carpi radialis Supinator Palmaris longus Radius Flexor digitorum superficialis Extensor carpi radialis longus Flexor pollicis longus Figure 10.27a,b,c Extensor carpi radialis brevis Flexor carpi ulnaris Extensor digitorum Flexor digitorum profundus Extensor digiti minimi Ulna Anconeus Extensor carpi ulnaris 10-79 (c) Muscles Acting on the Wrist and Hand • Posterior group • Extension of wrist and fingers, adduct/abduct wrist • Extension and abduction of thumb (pollicis) • Brevis means “short,” ulnaris indicates “on ulna side of forearm”

Triceps brachii Brachioradialis Olecranon Anconeus Extensor carpi radialis longus Anconeus Supinator Posterior view Extensor carpi Flexor carpi radialis brevis ulnaris Abductor pollicis longus Extensor carpi Extensor digitorum ulnaris Abductor pollicis Extensor digiti Extensor pollicis longus Extensor pollicis brevis minimi longus Extensor pollicis Extensor indicis brevis

Tendon of Extensor pollicis extensor indicis longus Tendons of extensor carpi radialis longus Tendons of extensor and brevis digitorum Figure 10.29a,b

(a) Superficial extensors (b) Deep extensors 10-80 Muscles Acting on the Wrist and Hand

• Posterior (extensor) compartment—superficial layer – Extensor carpi radialis longus – Extensor carpi radialis brevis – Extensor digitorum – Extensor digiti minimi – Extensor carpi ulnaris • Posterior (extensor) compartment—deep layer – Abductor pollicis longus – Extensor pollicis brevis – Extensor pollicis longus – Extensor indicis

10-81 Carpal Tunnel Syndrome

• Flexor retinaculum—bracelet-like fibrous sheet, passed under by flexor tendons crossing the wrist

• Carpal tunnel—tight space between the flexor retinaculum and the carpal bones – Flexor tendons passing through the tunnel are enclosed in tendon sheaths • Enable tendons to slide back and forth quite easily

10-82 Carpal Tunnel Syndrome

• Carpal tunnel syndrome—prolonged, repetitive motions of wrist and fingers cause tissues in the carpal tunnel to become inflamed, swollen, or fibrotic – Puts pressure on median nerve of wrist that passes through the carpal tunnel along with flexor tendons – Tingling and muscular weakness in the palm and medial side of the hand – Pain may radiate to arm and shoulder – Treatment: anti-inflammatory drugs, immobilization of the wrist, and sometimes surgery to remove part or all of flexor retinaculum

10-83 Carpal Tunnel Syndrome

Repetitive motions cause inflammation and pressure on median nerve

Tendon sheath First dorsal interosseous

Tendon of flexor Adductor digitorum profundus pollicis Tendon of flexor digitorum superficialis Tendon of flexor Lumbricals pollicis longus Opponens digiti minimi Flexor pollicis brevis Flexor digiti minimi brevis Abductor pollicis brevis Abductor digiti minimi Opponens pollicis Flexor retinaculum Tendons of: Tendons of: Abductor pollicis Flexor carpi ulnaris longus Flexor carpi Flexor digitorum radialis superficialis Figure 10.31b Flexor pollicis Palmaris longus longus

(a) Palmar aspect, superficial

Figure 10.31a 10-84 Intrinsic Muscles of the Hand • Thenar group—form thick, fleshy mass at base of thumb – Adductor pollicis – Abductor pollicis brevis – Flexor pollicis brevis – Opponens pollicis • Hypothenar group—fleshy base of the little finger – Abductor digiti minimi – Flexor digiti minimi brevis – Opponens digiti minimi • Midpalmar group—hollow of palm – Dorsal interosseous muscles (4) – Palmar interosseous muscles (3) – Lumbricals (4 muscles) 10-85 Muscles Acting on the Hip and Lower Limb

• Expected Learning Outcomes – Name and locate the muscles that act on the hip, knee, ankle, and toe joints. – Relate the actions of these muscles to the joint movements described in chapter 9. – Describe the origin, insertion, and innervation of each muscle.

10-86 Muscles Acting on the Hip and Lower Limb

• Body’s largest muscles found in lower limb • Less for precision, more for strength needed to stand, maintain balance, walk, and run • Several cross and act on two or more joints • Leg—the part of the limb between the knee and ankle • Foot—includes tarsal region (ankle), metatarsal region, and the toes

10-87 Muscles Acting on the Hip and Femur

• Anterior muscles of the hip Iliopsoas: Iliacus Psoas – Iliacus major Piriformis • Flexes thigh at hip

• Iliacus portion arises from iliac Pectineus Adductor Obturator crest and fossa magnus externus Adductor brevis – Psoas major Adductor • Flexes thigh at hip longus

• Arises from lumbar vertebrae Gracilis – They share a common tendon on the femur

Insertion of gracilis on tibia Figure 10.32 10-88 Muscles Acting on the Hip and Femur

• Lateral and posterior muscles of the hip – Tensor fasciae latae • Extends knee, laterally rotates knee – Gluteus maximus • Forms mass of the buttock • Prime hip extensor • Provides most of lift when you climb stairs – Gluteus medius and minimus • Abduct and medially rotate thigh Figure 10.33 10-89 Muscles Acting on the Hip and Femur

• Posterior group • Lateral rotators—six muscles inferior to gluteus minimus • Deep to the two other gluteal muscles – Gemellus superior – Gemellus inferior – Obturator externus – Obturator internus – Piriformis – Quadratus femoris

10-90 Muscles Acting on the Hip and Femur

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • Medial (adductor) Iliopsoas: compartment of thigh Iliacus Psoas major Piriformis • Five muscles act as Pectineus primary adductors of the Adductor Obturator magnus externus Adductor thigh brevis Adductor – Adductor brevis longus

– Adductor longus Gracilis – Adductor magnus – Gracilis

Insertion of – Pectineus gracilis on tibia

Figure 10.32 10-91 Muscles Acting on the Knee and Leg

• Anterior (extensor) compartment of the thigh – Contains large quadriceps femoris muscle • Prime mover of knee extension • Most powerful muscle in the body • Has four heads—rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius – All converge on single quadriceps (patellar) tendon – Extends to patella – Then continues as patellar ligament – Inserts on tibial tuberosity – Sartorius: longest muscle in the body • “Tailor’s muscle”

10-92 Anterior Thigh Cadaver Muscles

Figure 10.34 10-93 Muscles Acting on the Knee and Leg

Figure 10.35a,b 10-94 Muscles Acting on the Knee and Leg

• Posterior (flexor) compartment of the thigh – Contains hamstring muscles – From lateral to medial: Biceps femoris Semitendinosus Semimembranosus

Figure 10.33 10-95 Muscles Acting on the Foot

(a)

Posterior

Lateral Medial (b) Figure 10.40b

Anterior Gastrocnemius Gastrocnemius (lateral head) (medial head) Soleus

Key b Fibula Flexor hallucis longus Anterior (extensor) Flexor digitorum longus compartment Fibularis longus Tibialis posterior Lateral (fibular) compartment Fibularis brevis Posterior (flexor) Extensor hallucis longus Tibia compartment, superficial Extensor digitorum longus Posterior (flexor Tibialis anterior compartment, deep) (b)

• Crural muscles, acting on the foot, are separated into three compartments – Anterior compartment (red) – Fibular (lateral) compartment (green) – Posterior compartments (superficial = pink) (deep = purple) 10-96 Muscles Acting on the Foot Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Patella Patellar ligament

Tibia Fibularis Gastrocnemius longus

Soleus Fibularis Tibialis brevis anterior Extensor digitorum longus Tibialis Extensor Extensor anterior hallucis digitorum longus longus Extensor retinacula Fibularis tertius Extensor hallucis brevis Figure 10.38a–d Extensor digitorum brevis (a) (b) (c) (d) • Anterior (extensor) compartment of the leg – Dorsiflex the ankle – Prevent toes from scuffing ground when walking – Fibularis (peroneus) tertius – Extensor digitorum longus – Extensor hallucis longus

– Tibialis anterior 10-97 Muscles Acting on the Foot

Heads of Plantaris gastrocnemius (cut) Popliteus Fibularis longus Gastrocnemius: Soleus Medial head Lateral head Tendon of plantaris

Gastrocnemius (cut) Fibularis Tendon of longus gastrocnemius Fibularis Flexor brevis digitorum longus Flexor hallucis Figure 10.38a,b longus

Calcaneal tendon

(a) Calcaneus (b) • Posterior compartment—three muscles of the superficial group – Gastrocnemius: plantar flexes foot, flexes knee – Soleus: plantar flexes foot – Plantaris: weak synergist of triceps surae • Triceps surae—collective name for gastrocnemius and soleus – Inserts on calcaneus by way of the calcaneal (Achilles) tendon – Strongest tendon in the body 10-98 Muscles Acting on the Foot

Tibialis Flexor posterior digitorum Plantaris (cut) longus

Gastrocne Popliteus -mius (cut)

Soleus (cut)

Fibula (b) (c)

Tibialis posterior Fibularis Flexor digitorum Popliteus longus longus

Flexor hallucis longus

Flexor Fibularis hallucis brevis longus Figure 10.39 Calcaneal tendon Plantar surface (cut) of the foot (a) Calcaneus (d)

• Posterior compartment—four muscles in the deep group – Flexor digitorum longus: flexes phalanges – Flexor hallucis longus: flexes great toe – Tibialis posterior: inverts foot – Popliteus: acts on knee 10-99 Muscles Acting on the Foot

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. • Lateral (fibular) compartment—two muscles – Fibularis longus Plantaris (cut) – Fibularis brevis Gastrocnemius (cut) Popliteus

Soleus (cut) • Both plantar flex and Fibula

Tibialis evert the foot posterior Fibularis Flexor digitorum longus longus

Flexor hallucis longus • Provide lift and

Fibularis forward thrust brevis

Calcaneal tendon (cut) Figure 10.39a Calcaneus

(a) 10-100 Intrinsic Muscles of Foot

– Extensor Lumbricals

Flexor digiti Flexor hallucis digitorum minimi brevis longus tendon Flexor digitorum Abductor digiti Abductor hallucis longus tendon minimi Abductor hallucis brevis extends Flexor digitorum (cut) Quadratus plantae toes brevis Plantar aponeurosis Flexor digitorum (cut) brevis (cut)

Calcaneus

(a) Layer 1, plantar view (b) Layer 2, plantar view • Four ventral Figure 10.41a–e muscle layers – Support arches Adductor hallucis – Abduct and Plantar Flexor hallucis brevis interosseous Flexor digiti Dorsal minimi brevis Flexor hallucis interosseous adduct the toes longus tendon (cut) Abductor hallucis (cut) Quadratus plantae – Flex the toes (cut) Flexor digitorum longus tendon (cut) Dorsal view

(c) Layer 3, plantar view (d) Layer 4, plantar view (e) Layer 4, dorsal view 10-101 Common Athletic Injuries • Muscles and tendons are vulnerable to sudden and intense stress • Proper conditioning and warm-up needed • Common injuries include: – Compartment syndrome – Shin splints – Pulled hamstrings – Tennis elbow – Pulled groin – Rotator cuff injury • Treat with rest, ice, compression, and elevation • “No pain, no gain” is a dangerous misconception

10-102