11 Muscles of the Body.

11 Muscles of the Body

Muscles act with or against each other Criteria used in naming muscles
Muscles of the Body Skeletal muscles Produce movements Blinking of eye, standing on tiptoe, swallowing food, etc. Muscles act with or against each other Criteria used in naming muscles

Arrangement of Fascicles in Muscles
Skeletal muscles—consist of fascicles Fascicles—arranged in different patterns Fascicle arrangement—tells about action of a muscle

Types of fascicle arrangement Parallel—fascicles run parallel to the long axis of the muscle Strap-like—sternocleidomastoid Fusiform—biceps brachii

Types of fascicle arrangement Convergent Origin of the muscle is broad Fascicles converge toward the tendon of insertion Example—pectoralis major

Types of fascicle arrangement Pennate Unipennate—fascicles insert into one side of the tendon Bipennate—fascicles insert into the tendon from both sides Multipennate—fascicles insert into one large tendon from all sides

Circular Fascicles are arranged in concentric rings Surround external body openings Sphincter—general name for a circular muscle Examples Orbicularis oris and orbicularis oculi

(b) (a) Circular (orbicularis oris) (c) (b) Convergent (pectoralis major) (d) (f) (g) (c) Fusiform (biceps brachii) (d) Parallel (sartorius) (e) Multipennate (deltoid) (f) Bipennate (rectus femoris) (g) Unipennate (extensor digitorum longus) Figure 11.1

Muscle Actions and Interactions
A muscle cannot reverse the movement it produces Another muscle must undo the action Muscles with opposite actions lie on opposite sides of a joint

Prime mover (agonist) Has major responsibility for a certain movement Antagonist Opposes or reverses a movement Synergist—helps the prime mover By adding extra force By reducing undesirable movements Fixator A type of synergist that holds a bone firmly in place

Example: Pectoralis major (anterior view) (a) A muscle that crosses on the anterior side of a joint produces flexion* *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. Example: Latissimus dorsi (posterior view) (b) A muscle that crosses on the posterior side of a joint produces extension* *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. Figure 11.5a, b

Example: Medial deltoid (anterolateral view) (c) A muscle that crosses on the lateral side of a joint produces abduction Example: Teres major (posterolateral view) (d) A muscle that crosses on the medial side of a joint produces adduction Figure 11.5c, d

Muscle Compartments of the Limbs
Dense fibrous connective tissue divides limb muscles into compartments Muscles in opposing compartments are Agonist and antagonist pairs Each compartment is innervated by a single nerve

Muscle Compartments of Arm and Forearm
The upper limb has anterior and posterior compartments Anterior arm compartment muscles Flex the shoulder or arm Innervation is the musculocutaneous nerve Anterior forearm compartment muscles Flex the wrist and digits Innervation is the median or ulnar nerve

Muscle Compartments of the Arm and Forearm
Triceps brachii Lateral head Humerus Posterior compartment of arm (extends elbow); innervation: radial nerve Anterior compartment of arm (flexes elbow); innervation: musculocutaneous nerve Long Medial (a) Brachialis Short head Long head Biceps brachii (a) Muscles of the arm Extensors Flexors Figure 11.6a

Muscle Compartments of the Arm and Forearm
Anterior compartment of forearm (flexes wrist and fingers); innervation: median or ulnar nerve Posterior compartment of forearm (extends wrist and fingers); innervation: radial nerve (b) Flexors Extensors Radius Pronator teres Brachioradialis (elbow flexor) Abductor pollicis longus Ulna (b) Muscles of the forearm Figure 11.6b

Muscle Compartments of the Thigh
Posterior compartment muscles Extend the hip and flex the knee Innervation is the tibial branch of the sciatic nerve Anterior compartment muscles Flex the hip and extend the knee Innervation is the femoral nerve Medial compartment Adduct the thigh Innervation is the obturator nerve

Muscle Compartments of the Thigh and Leg
Adductors Vastus lateralis Hamstrings Posterior compartment of thigh (flexes leg and extends thigh); innervation: tibial nerve (portion of sciatic nerve) Medial compartment (adducts thigh); innervation: obturator nerve Anterior compartment (extends leg); innervated by femoral nerve intermedius Rectus femoris Femur Vastus medialis (a) (a) Muscles of the thigh Posterior compartment muscles Anterior compartment muscles of thigh and lateral compartment muscles of leg Figure 11.7a

Compartments of the Leg
Posterior compartment muscles Contains digital and plantar flexors Innervation is the tibial nerve Anterior compartment muscles Contains digital extensors and dorsiflexors Innervation is the deep fibular nerve Lateral compartment muscles Plantar flex and evert the foot Innervation is the superficial fibular nerve

Muscle Compartments of the Thigh and Leg
Posterior compartment of leg (plantar flexes foot, flexes toes); innervated by tibial nerve Anterior compartment of leg (dorsiflexes foot, extends toes); innervated by deep fibular nerve Lateral compartment of leg (plantar flexes and everts foot); innervation: superficial fibular nerve Triceps surae Fibula Tibialis anterior Tibia Fibularis muscles (b) Muscles of the leg (b) Posterior compartment muscles Anterior compartment muscles Medial compartment muscles of thigh and lateral compartment muscles of leg Figure 11.7b

Naming the Skeletal Muscles
Location Example—the brachialis is located on the arm Shape Example—the deltoid is triangular Relative size Maximus, minimus, and longus indicate size Example—gluteus maximus and gluteus minimus

Direction of fascicles and muscle fibers Name tells direction in which fibers run Example—rectus abdominis and transversus abdominis Location of attachments—name reveals point of origin and insertion Example—brachioradialis

Number of origins Two, three, or four origins Indicated by the words biceps, triceps, and quadriceps Action The action is part of the muscle’s name Indicates type of muscle movement Flexor, extensor, adductor, or abductor

Superficial Muscles of the Body—Anterior View
Trapezius Shoulder Deltoid Arm Triceps brachii Biceps brachii Brachialis Forearm Pronator teres Brachioradialis Flexor carpi radialis Palmaris longus Pelvis/thigh Iliopsoas Pectineus Thigh Rectus femoris Vastus lateralis Vastus medialis Leg Fibularis longus Extensor digitorum longus Tibialis anterior Head Facial Temporalis Epicranius, frontal belly Orbicularis oculi Zygomaticus Orbicularis oris Neck Sternohyoid Sternocleidomastoid Thorax Pectoralis major Pectoralis minor Serratus anterior Intercostals Abdomen External oblique Rectus abdominis Internal oblique Transversus abdominis Sartorius Tensor fasciae latae Adductor longus Gracilis Gastrocnemius Soleus Masseter Platysma (a) Figure 11.8a

Superficial Muscles of the Body—Posterior View
Neck Epicranius, occipital belly Arm Sternocleidomastoid Triceps brachii Trapezius Brachialis Shoulder Deltoid Forearm Infraspinatus Brachioradialis Teres major Extensor carpi radialis longus Rhomboid major Triangle of auscultation Flexor carpi ulnaris Latissimus dorsi Extensor carpi ulnaris Hip Extensor digitorum Gluteus medius Gluteus maximus Iliotibial tract Thigh Adductor magnus Gracilis Hamstrings: Biceps femoris Leg Semitendinosus Gastrocnemius Semimembranosus Soleus Fibularis longus Calcaneal (Achilles) tendon (b) Figure 11.8b

Muscles of the Head—Facial Expression
Muscles of facial expression Lie in the face and scalp Thin and variable in shape Often insert in the skin—not on bones Innervated by cranial nerve VII—the facial nerve

Muscles of the Head—Facial Expression
Corrugator supercilii Orbicularis oculi Levator labii superioris Zygomaticus minor and major Buccinator Risorius Orbicularis oris Mentalis Depressor labii inferioris Depressor anguli oris Platysma Galea aponeurotica Frontal belly Occipital Temporalis Masseter Sternocleidomastoid Trapezius Splenius capitis Epicranius Figure 11.9

Muscles Mastication and Tongue Movement
Four main pairs of muscles involved in mastication Innervated by mandibular division of the trigeminal nerve (cranial nerve V) Prime movers of jaw closure Masseter and temporalis Side-to-side movement Pterygoid muscles Compression of cheeks Buccinator muscles PLAY PLAY PLAY A&P Flix: Buccinator A&P Flix: Masseter A&P Flix: Temporalis

Muscles of Mastication and Tongue Movement
Lateral pterygoid Medial Masseter pulled away (b) Orbicularis oris Temporalis Masseter Buccinator (a) Figure 11.10a, b

Muscles Mastication and Tongue Movement
Extrinsic muscles of the tongue Move tongue Laterally Anteriorly Posteriorly All innervated by cranial nerve XII—the hypoglossal nerve

Muscles of Mastication and Tongue Movement
Styloid process Styloglossus Genioglossus Hyoglossus Stylohyoid Mandibular symphysis Stylopharyngeus Geniohyoid Hyoid bone Thyroid cartilage Thyrohyoid (c) Figure 11.10c

Muscles of the Anterior Neck and Throat—Swallowing
The neck is divided into anterior and posterior triangles Anterior triangle Divided into suprahyoid and infrahyoid muscles Participate in swallowing Pharyngeal constrictors Squeeze food into the esophagus

belly Mylohyoid Stylohyoid Digastric Posterior belly Hyoid bone Omohyoid (superior belly) Stylohyoid (cut) Thyrohyoid Sternohyoid Thyroid cartilage of the larynx Sternocleido- mastoid Thyroid gland Sternothyroid Omohyoid (inferior belly) (a) Figure 11.11a

(b) Platysma (cut) Sternocleidomastoid (cut) Internal jugular vein Hyoid bone Omohyoid Sternohyoid Sternothyroid Pectoralis major Figure 11.11b

Muscles of the Neck and Vertebral Column
Head movement Sternocleidomastoid Splenius capitis and splenius cervicis Base of occipital bone 1st cervical vertebra Mastoid process Middle scalene Sternocleido- mastoid Anterior scalene Posterior scalene (a) Anterior Figure 11.12a

Mastoid process Splenius capitis Spinous processes of the vertebrae Splenius cervicis (b) Posterior Figure 11.12b

Trunk extension Deep muscles of the back Maintain normal curvatures of the spine Form a column from sacrum to the skull Erector spinae group Largest of the deep back muscles

Mastoid process of temporal bone Semispinalis capitis cervicis Multifidus Quadratus lumborum thoracis Longissimus capitis Iliocostalis cervicis Longissimus cervicis Iliocostalis thoracis Longissimus thoracis Spinalis thoracis Iliocostalis lumborum External oblique Iliocostalis Longissimus Erector spinae Spinalis Ligamentum nuchae (c) O = origin I = insertion Intertransversarius Rotatores Multifidus Interspinales PLAY PLAY A&P Flix: Iliocostalis A&P Flix: Spinalis PLAY A&P Flix: Longissimus (d)

Deep Muscles of the Thorax—Breathing
Deep muscles provide movements for breathing External intercostal muscles Lift the rib cage Internal intercostal muscles Aid expiration during heavy breathing

Diaphragm Most important muscle of respiration Flattens as it contracts Increases the volume of the thoracic cavity

External intercostal Internal intercostal (a) PLAY PLAY A&P Flix: External intercostal muscles A&P Flix: Internal intercostal muscles Figure 11.13a

Foramen for esophagus Costal cartilage Lumbar vertebra Diaphragm Quadratus lumborum Psoas major Xiphoid process of sternum Foramen for inferior vena cava Central tendon of diaphragm Foramen for aorta 12th rib (b) Figure 11.13b

Muscles of the Abdominal Wall
Lateral and anterior abdominal wall Formed from three flat muscle sheets External oblique Internal oblique Transversus abdominis Fourth muscle pair Rectus abdominis Inserts at the linea alba

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 (a) PLAY PLAY A&P Flix: Internal obliques A&P Flix: External obliques Figure 11.14a

Rectus abdomini Internal oblique External oblique Transversus abdominis PLAY PLAY A&P Flix: Transverse abdominis A&P Flix: Rectus abdominis Figure 11.14c

Muscles of the Pelvic Floor
Pelvic floor (pelvic diaphragm) Sheet of two muscles Both support pelvic organs Levator ani Formed from iliococcygeus, puborectalis, and pubococcygeus Coccygeus

Muscles of the Pelvic Floor
Anterior Pubococcygeus Symphysis pubis Levator ani IIiococcygeus Urogenital diaphragm Urethra Vagina Anal canal Obturator internus Coccyx Piriformis Levator ani Pelvic diaphragm Coccygeus (a) Posterior Figure 11.15a

Muscles of the Perineum
Inferior to the muscles of the pelvic floor Urogenital diaphragm formed from: Sphincter urethrae and the deep transverse perineus Inferior pubic ramus External urethral sphincter Urethral opening Vaginal Deep transverse perineal muscle Central tendon Anus anal sphincter Male (b) Female Figure 11.15b

Muscles of the superficial perineal space Ischiocavernosus Bulbospongiosus Superficial transverse perineus

Male Female Penis Midline raphe Ischiocavernosus Clitoris Urethral opening Anus Vaginal Bulbospongiosus Superficial transverse perineal muscle Levator ani (c) Gluteus maximus Figure 11.15c

Superficial Muscles of the Anterior Thorax
Movements of the scapula Pectoralis major Pectoralis minor Serratus anterior Subclavius PLAY PLAY A&P Flix: Pectoralis major A&P Flix: Serratus anterior PLAY A&P Flix: Pectoralis minor

Superficial Muscles of the Anterior Thorax
Sternocleidomastoid Deltoid Pectoralis major Sternum Biceps brachii (a) Subclavius Clavicle Subscapularis minor Coracobrachialis Serratus anterior Humerus Figure 11.16a

Superficial Muscles of the Posterior Thorax
Movements of the scapula Trapezius Levator scapulae Rhomboid major Rhomboid minor PLAY PLAY A&P Flix: Trapezius A&P Flix: Levator scapulae PLAY PLAY A&P Flix: Rhomboid major A&P Flix: Rhomboid minor

Trapezius (c) Levator scapulae Supraspinatus Clavicle Spine of scapula Infraspinatus Teres minor Humerus Deltoid Teres major Latissimus dorsi Rhomboid minor Figure 11.16c

Levator scapulae (d) Rhomboid minor major Infraspinatus Teres major Teres minor Latissimus dorsi Trapezius Deltoid Triceps brachii Triangle of auscultation Figure 11.16d

Muscles Crossing the Shoulder Joint
Movements of the arm Deltoid Pectoralis major Clavicle Deltoid Sternum Pectoralis major Lateral head Long head Medial head Coracobrachialis Triceps brachii Biceps brachii Brachialis Brachio- radialis (a) Anterior view PLAY A&P Flix: Deltoid Figure 11.17a

Movements of the arm A&P Flix: Latissimus dorsi A&P Flix: Supraspinatus A&P Flix: Infraspinatus Supraspinatus Spine of scapula (b) Posterior view Deltoid (cut) Greater tubercle of humerus Infraspinatus Teres minor Teres major Triceps brachii Latissimus dorsi Humerus Olecranon process of ulna Lateral head Long head Anconeus PLAY PLAY PLAY Figure 11.17b

Movements of the arm A&P Flix: Teres minor A&P Flix: Teres major A&P Flix: Subscapularis Supraspinatus Spine of scapula (b) Posterior view Deltoid (cut) Greater tubercle of humerus Infraspinatus Teres minor Teres major Triceps brachii Latissimus dorsi Humerus Olecranon process of ulna Lateral head Long head Anconeus PLAY PLAY PLAY Figure 11.17b

Muscles Crossing the Elbow Joint
Clavicle Deltoid Sternum Pectoralis major Coracobrachialis Triceps brachii Lateral head Long head Medial head PLAY Biceps brachii A&P Flix: Biceps brachii Brachialis PLAY A&P Flix: Brachialis Brachio- radialis PLAY A&P Flix: Brachioradialis (a) Anterior view Figure 11.17a

Muscles Crossing the Elbow Joint
Posterior muscles—extensors of the forearm Triceps brachii Anconeus Anterior muscles—flexors of the forearm Biceps brachii—also supinates the forearm Brachialis Brachioradialis PLAY A&P Flix: Triceps brachii

Movements of the wrist, hand, and fingers
Muscles of the Forearm Movements of the wrist, hand, and fingers Tendons are anchored by Flexor and extensor retinacula Most forearm muscles arise from the distal humerus Movements at the wrist include Flexion, extension, abduction, and adduction Wrist and fingers are “operated” by muscles in the forearm

Originate from a common tendon
Muscles of the Forearm Flexors Anterior flexor compartment Innervated by median and ulnar nerves Originate from a common tendon Medial epicondyle of the humerus

Superficial Anterior Muscles of the Forearm
Biceps brachii Medial head of triceps brachii Tendon of biceps brachii Pronator teres Brachioradialis Extensor carpi radialis longus Flexor pollicis longus Pronator quadratus Flexor retinaculum (a) Medial epicondyle of humerus Flexor carpi radialis Palmar aponeurosis Superficial transverse ligament of palm Palmaris longus Flexor carpi ulnaris Flexor digitorum superficialis Pronator teres Flexor carpi radialis Palmaris longus Flexor carpi ulnaris Flexor digitorum superficialis PLAY A&P Flix: Flexor carpi radialis PLAY A&P Flix: Flexor carpi ulnaris PLAY A&P Flix: Flexor digitorum superficialis Figure 11.18a

Deep Anterior Muscles of the Forearm
Flexor pollicis longus Flexor digitorum profundus Pronator quadratus

Deep Anterior Muscles of the Forearm
Tendon of flexor digitorum profundus Tendon of flexor digitorum superficialis Tendon of flexor digitorum superficialis (cut) Lumbricals Tendon of flexor pollicis longus Tendon of brachioradialis (cut) Thenar muscles of thumb Tendon of flexor carpi ulnaris (cut) Tendon of flexor carpi ulnaris (cut) Pronator quadratus Pronator quadratus Tendon of flexor carpi radialis (cut) Flexor pollicis longus Flexor pollicis longus Flexor digitorum superficialis Extensor carpi radialis longus Flexor digitorum profundus Supinator Supinator Tendon of biceps brachii (cut) (b) (c) Figure 11.18b, c

Muscles of the Forearm Extensors Posterior compartment of the forearm
Innervated by the radial nerve Originate at a common tendon Lateral epicondyle of the humerus

Superficial Posterior Muscles of the Forearm
Insertion of triceps brachii Anconeus Flexor carpi ulnaris Extensor carpi ulnaris Extensor digiti minimi Extensor indicis Tendons of extensor carpi radialis brevis and longus Extensor expansion (a) Extensor pollicis longus brevis Abductor pollicis longus Extensor digitorum radialis brevis radialis longus Brachioradialis Tendons of extensor digitorum Brachioradialis— flexes forearm Extensor carpi radialis longus Extensor carpi radialis brevis Extensor digitorum Extensor carpi ulnaris PLAY PLAY A&P Flix: Extensor carpi radialis longus A&P Flix: Extensor digitorum PLAY PLAY A&P Flix: Extensor carpi radialis brevis A&P Flix: Extensor carpi ulnaris Figure 11.19a

Deep Posterior Muscles of the Forearm
Supinator Abductor pollicis longus Extensor pollicis brevis and longus Extensor indicus Interossei Extensor indicis Extensor pollicis brevis Extensor pollicis longus Abductor pollicis longus Supinator Anconeus PLAY A&P Flix: Supinator Olecranon process of ulna (b) Figure 11.19b

Intrinsic Muscles of the Hand
Fine movement of the fingers All located in the palm Control precise movements Include muscles of Adduction, abduction, and opposition

Thenar muscles—ball of thumb Abductor pollicis brevis Flexor pollicis brevis Opponens pollicis Adductor pollicis Hypothenar muscles Abductor digiti minimi Flexor digiti minimi

Flexor digitorum profundus Tendons of superficialis Third lumbrical Fourth Opponens digiti minimi Flexor digiti minimi brevis Abductor Pisiform bone Flexor carpi ulnaris tendon tendons Flexor pollicis longus Flexor carpi radialis Palmaris longus Flexor retinaculum Abductor pollicis longus pollicis brevis Flexor pollicis Adductor pollicis Dorsal interossei First lumbrical Second lumbrical Fibrous sheath (a) Superficial layer Figure 11.21a

Midpalmar muscles Lumbricals Palmar interossei Dorsal interossei Flexor digitorum profundus tendon superficialis tendon Palmar interossei Opponens digiti minimi Flexor digiti minimi brevis (cut) Abductor digiti minimi (cut) Flexor pollicis longus tendon Opponens pollicis Abductor pollicis brevis Adductor pollicis Dorsal (b) Second layer Figure 11.21b

Palmar interossei (c) Palmar interossei (isolated) Dorsal interossei (d) Dorsal interossei (isolated) Figure 11.21c, d

Muscles Crossing the Hip and Knee Joints
Thigh and leg movements Anterior muscles Flex the thigh and extend the leg at the knee Posterior muscles Extend the thigh and flex the leg

Thigh and leg movements Adductor muscles—on medial aspect of thigh Adduct the thigh only Deep fascia of the thigh Surrounds and encloses all three groups

Movements at the hip joint Muscles that flex the thigh Originate on vertebral column or pelvis Muscles that extend the thigh Arise posterior to the hip joint Adductors originate medial to the hip joint Abductors originate lateral to the hip joint

Anterior and Medial Muscles
Origin on pelvis or vertebral column Iliacus Psoas major Sartorius Muscles of the medial compartment Adductor longus Adductor brevis Adductor magnus Pectineus Gracilis PLAY A&P Flix: Iliopsoas PLAY A&P Flix: Sartorius

Anterior and Medial Muscles
12th rib Quadratus lumborum 12th thoracic vertebra 5th lumbar vertebra Adductor longus Gracilis Adductor magnus Patella Patellar ligament Psoas minor Iliac crest Psoas major Iliacus Anterior superior iliac spine Tensor fasciae latae Pectineus Sartorius Tendon of quadriceps femoris Quadriceps femoris Rectus femoris Vastus lateralis Vastus medialis Iliopsoas (a) Figure 11.22a

Muscles of the Anterior Compartment of the Thigh
Quadriceps femoris Has four separate heads Has a common insertion at the quadriceps tendon Powerful knee extensors Rectus femoris Vastus lateralis Vastus medialis Vastus intermedius Tensor fasciae latae PLAY A&P Flix: Rectus femoris PLAY A&P Flix: Vastus lateralis PLAY A&P Flix: Vastus medialis PLAY A&P Flix: Vastus intermedius

Muscles of the Anterior Compartment of the Thigh
(b) Patella Tensor fasciae latae Iliopsoas Sartorius Rectus femoris Vastus lateralis medialis Pectineus Adductor magnus Gracilis longus 12th rib Quadratus lumborum 12th thoracic vertebra 5th lumbar vertebra Adductor longus Gracilis Adductor magnus Patella Patellar ligament Psoas minor Iliac crest Psoas major Iliacus Anterior superior iliac spine Tensor fasciae latae Pectineus Sartorius Tendon of quadriceps femoris Quadriceps femoris Rectus femoris Vastus lateralis Vastus medialis Iliopsoas (a) Figure 11.22a, b

Posterior Muscles Origin on pelvis or sacrum Gluteus maximus
Gluteus medius Gluteus minimus Lateral rotators Piriformis Obturator externus Obturator internus Superior and inferior gemellus Quadratus femoris PLAY A&P Flix: Gluteus maximus PLAY A&P Flix: Gluteus medius

Posterior Muscles Gluteus medius Gluteus maximus Adductor magnus
Gracilis Iliotibial tract Long head Semitendinosus Semimembranosus Short head Biceps femoris (c) Figure 11.23c

Muscles of the Posterior Compartment of the Thigh
Hamstrings Biceps femoris Semitendinosus Semimembranosus Gluteus medius (cut) Gluteus minimus Superior gemellus PLAY A&P Flix: Biceps femoris Piriformis Obturator internus Obturator externus PLAY A&P Flix: Semimembranosus Inferior gemellus Quadratus femoris PLAY A&P Flix: Semitendinosus Gluteus maximus (cut) (a) Figure 11.23a

Fascia lata of the leg surrounds muscles
Muscles of the Leg Fascia lata of the leg surrounds muscles Tightly binds muscles Prevents swelling during exercise Aids venous return Divides leg into three compartments Tendons are held in place by Extensor, fibular, and flexor retinacula Muscle movement at ankle and intertarsal joints

Muscles of the Anterior Compartment
Fibularis longus Gastrocnemius Tibia Tibialis anterior Extensor digitorum longus Soleus Extensor hallucis longus Fibularis tertius Extensor hallucis brevis Extensor digitorum Superior and inferior extensor retinacula (a) Tibialis anterior Extensor digitorum longus Fibularis tertius Extensor hallucis longus PLAY A&P Flix: Tibialis anterior PLAY A&P Flix: Extensor digitorum longus PLAY A&P Flix: Extensor hallucis longus Figure 11.25a

Muscles of the Lateral Compartment
Fibularis longus Fibularis brevis Flexor hallucis longus Extensor hallucis longus Fibularis tertius Patella Head of fibula Gastrocnemius Soleus Fibularis longus Extensor digitorum longus Tibialis anterior Extensor hallucis longus Fibularis tertius Fibularis brevis Flexor hallucis longus Fibular retinaculum Lateral malleolus Superior and inferior extensor retinacula Extensor digitorum brevis 5th metatarsal Extensor hallucis brevis (a) PLAY A&P Flix: Fibularis longus PLAY A&P Flix: Flexor hallucis longus Figure 11.26a

Muscles of the Lateral Compartment
Tendon of fibularis longus O = origin I = insertion (b) Fibularis longus Fibularis brevis (c) Figure 11.26b, c

Muscles of the Posterior Compartment
Superficial muscles Triceps surae Gastrocnemius Soleus Plantaris PLAY A&P Flix: Gastrocnemius PLAY A&P Flix: Soleus

Plantaris Tendon of gastrocnemius Calcaneal tendon Medial malleolus Medial head Gastroc- nemius Lateral head Lateral Calcaneus (a) Soleus Tendon of tibialis posterior Tendon of plantaris Fibularis brevis Head of fibula Popliteus Plantaris Gastroc- nemius Lateral head (cut) Medial head Fibularis longus (b) Figure 11.27a, b

Deep muscles Popliteus Flexor digitorum longus Flexor hallucis longus Tibialis posterior Plantaris (cut) Gastrocnemius lateral head (cut) Gastrocnemius medial head (cut) Popliteus Soleus (cut) Tibialis posterior Fibula Fibularis longus Flexor digitorum longus Flexor hallucis longus PLAY A&P Flix: Tibialis posterior Tendon of tibialis posterior Fibularis brevis PLAY A&P Flix: Flexor digitorum longus Medial malleolus Calcaneal tendon (cut) PLAY A&P Flix: Flexor hallucis longus Calcaneus (c) Figure 11.27c

Intrinsic Muscles of the Foot
Toe movement and foot support Help to flex, extend, abduct, and adduct the toes Support the arches of the foot Single muscle on dorsal aspect of the foot Many muscles on the plantar aspect

Muscles of the Foot Muscle on the dorsum of the foot
Extensor digitorum brevis Muscles on the sole of the foot First layer Flexor digitorum brevis Abductor hallucis Abductor digiti minimi Tendon of flexor hallucis longus Lumbricals Flexor hallucis brevis Flexor digiti minimi brevis Abductor hallucis Flexor digitorum Flexor accessorius Abductor digiti minimi Calcaneal tuberosity (a) First layer Figure 11.28a

Muscles of the Foot Second layer Flexor accessorius Lumbricals
Flexor hallucis brevis Tendon of flexor hallucis longus Flexor digitorum longus (tendon) Flexor digiti minimi brevis Abductor digiti minimi Flexor accessorius Fibularis longus (b) Second layer Figure 11.28b

Muscles of the Foot Third layer Fourth layer Flexor hallucis brevis
Adductor hallucis Flexor digiti minimi brevis Fourth layer Plantar and dorsal interossei Adductor hallucis (transverse head) (oblique head) Interosseous muscles Flexor hallucis brevis Flexor digiti minimi brevis Fibularis longus (tendon) Flexor accessorius Flexor digitorum longus (tendon) (c) Third layer Figure 11.28c

Muscles of the Foot Plantar interossei Adductor hallucis
(d) Fourth layer: plantar Adductor hallucis (transverse head) (oblique head) Interosseous muscles Flexor hallucis brevis Flexor digiti minimi brevis Fibularis longus (tendon) Flexor accessorius Flexor digitorum longus (tendon) (c) Third layer Figure 11.28c, d

11 Muscles of the Body.

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