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The Muscular System: Revised by Dr. Par Mohammadian
10 The Muscular System: Revised by Dr. Par Mohammadian
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Naming Skeletal Muscles
Muscle location—bone or body region with which muscle associated (intercostal=between the ribs) Muscle shape—e.g., deltoid muscle (deltoid = triangle) Muscle size—e.g., maximus (largest), minimus (smallest), longus (long), brevis (short) 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)
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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
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Arrangement of Fascicles (bundles of fibers)
Circular (Fascicles arranged in concentric rings) (orbicularis oris) Convergent (Broad origin; fascicles converge toward single insertion (pectoralis major) Fusiform (Spindle-shaped with parallel fibers) (biceps brachii) (a) (e) (b) (c) (d) (f) Parallel (sartorius) Fascicles parallel to long axis Pennate (feather) Unipennate – fascicles attach only to one side of tendon Bipennate – fascicles insert from opposite sides of tendon Multipennate –appears as feathers inserting into one tendon (g) Bipennate (rectus femoris) Multipennate (deltoid) Unipennate (extensor digitorum longus)
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Major Skeletal Muscles: Anterior View
Facial The 40 superficial muscles here are divided into 10 regional areas of the body 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 Abdomen Pronator teres 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
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Major Skeletal Muscles: 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 The 27 superficial muscles here are divided into seven regional areas of the body Extensor carpi ulnaris Gluteus maximus Thigh Iliotibial tract Adductor magnus Hamstrings: Biceps femoris Semitendinosus Leg Semimembranosus Gastrocnemius Soleus Fibularis longus Calcaneal (Achilles) tendon
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Overview of muscles Head Facial Expression (Face & Scalp)
Mastication & Tongue movement Neck & Throat (swallowing) Neck & Vertebral Column Head movement Trunk extension Deep thorax muscles (Breathing) Abdominal Wall Superficial muscles of thorax (movement of scapula & Arm) Anterior & posterior Muscles crossing the shoulder joint (movement of arm) Muscles crossing the elbow (Flexion & extension of the forearm) Muscles of the forearm (movements of the wrist, hand & fingers) Muscles crossing the hip & knee joints (movements of the thigh & leg) Muscles of the leg (movement of the ankle & toes)
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Muscles of the Head Two groups
Muscles of facial expression (Scalp & face) Insert into skin Important in nonverbal communication All innervated by cranial nerve VII (facial nerve) Muscles of mastication and tongue movement
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Muscles of Facial Expression: The Scalp
Epicranius (occipitofrontalis) Bipartite muscle consisting of Galea aponeurotica—cranial aponeurosis connecting two bellies a) Frontal belly O: epicranial aponeurosis I: skin of eyebrows & root of nose Action: raises eyebrows b) occipital belly O: Occipital & temporal bones I: epicranial aponeurosis Action: fixes aponeurosis & pulls scalp posteriorly a) b)
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Muscles of Facial Expression: The Face
Epicranial aponeurosis Frontal belly Epicranius Corrugator supercilii Occipital belly *Orbicularis oculi Levator labii superioris Temporalis ***Zygomaticus minor and major Buccinator Masseter Risorius Sternocleidomastoid **Orbicularis oris Trapezius Mentalis Depressor labii inferioris Splenius capitis Depressor anguli oris (draws corners of mouth down - tragedy mask!) Platysma (tenses the skin of neck as during shaving) *closes eyes **closes mouth ***smiling muscle - raises lateral corners of the mouth upward
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Muscles of the head: 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 Temporalis O: temporal fossa I: coronoid process of mandible Orbicularis oris Masseters (chewer) O: Zygomatic bone I: angle &ramus of mandible) Buccinator (compresses cheek – as in whistling and sucking- facial nerve)
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Muscles of the Anterior Neck and Throat - Swallowing
Mylohyoid Two groups Suprahyoid muscles (pulls the hyoid bone toward the mandible => widens the pharynx to receive food) Infrahyoid muscles (pulls hyoid to the inferior position as swallowing ends) Stylohyoid Hyoid bone Omohyoid (superior belly) Sternohyoid Sternocleido- mastoid Omohyoid (inferior belly)
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Muscles of the Neck and Vertebral Column: Head Movement
Sternocleidomastoid and scalenes—lateral head movements Splenius capitis and cervicis portions - head extension, rotation, and lateral bending Semispinalis capitis—synergist with sternocleidomastoid
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Base of occipital bone 1st cervical vertebra Mastoid process Middle scalene Sternocleido- mastoid Anterior scalene Posterior scalene Anterior
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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 (when touching fingertips to floor…) Iliocostalis Longissimus Spinalis Semispinalis and quadratus lumborum—synergists in extension and rotation
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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
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Deep Muscles of the Thorax: Breathing
Muscles of respiration (inspiration & expiration) External intercostals—more superficial muscles; elevate ribs for inspiration Internal intercostals—deeper muscles; aid forced expiration Diaphragm Partition between thoracic and abdominal cavities – dome shaped Most important muscle in inspiration (contraction => flattens => increase the volume of the thoracic cavity) Innervated by phrenic nerves
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Muscles of Respiration
The primary function of deep thoracic muscles is to promote movement for breathing External intercostals – more superficial layer that lifts the rib cage and increases thoracic volume to allow inspiration
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Muscles of Respiration
Internal intercostals – deeper layer that aids in forced expiration
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Diaphragm – most important muscle in inspiration
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
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Central tendon of diaphragm
Body of thoracic vertebra Pericardium (cut) Aorta Diaphragm (muscular part) Inferior vena cava Esophagus Pericardial sac
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Muscles of the Abdominal Wall: 4 paired muscles
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)
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Muscles of the Abdominal Wall
Fascicles 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 Relaxed during inspiration allowing the descending diaphragm to push the abdominal viscera inferiorly Rectus abdominis Lumbar fascia External oblique Internal oblique Lumbar fascia Iliac crest Transversus abdominis Inguinal ligament Pubic tubercle
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Superficial Muscles of the Thorax: Movement of scapula & arm
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
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Muscles of anterior thorax
Sternocleidomastoid Subclavius Clavicle Subscapularis Deltoid Pectoralis minor Pectoralis major Coracobrachialis Sternum Serratus anterior Biceps brachii Humerus Muscles of anterior thorax Pectoralis minor (O: ribs, I: coracoid process of scapula, A: draws scapula forward) Serratus anterior (O: ribs, I: anterior surface of vertebral border of scapula, A: rotates scapula) Subclavius (O: rib 1, I: Clavicle, A: stabilizes pectoral girdle)
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Posterior shoulder muscles
Levator scapulae Trapezius Supraspinatus Clavicle Deltoid Spine of scapula Rhomboid minor Infraspinatus Rhomboid major Teres minor Teres major Humerus Latissimus dorsi Posterior shoulder muscles Trapezius (O: occipital bone, spinous process of C7 and T; I: acromion, spine of scapula, clavicle; A: rotates, stabilizes, raises scapula) Levator scapulae (O: transverse process of C1-C4; I: medial border of scapula; A: elevates/adducts scapula) Rhomboids (major and minor): (O: spinous process of C7 & T; I: medial boarder of scapula; A: stabilizes scapula)
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Muscles Crossing the Shoulder Joint: Movement of the Arm – Humerus)
Nine muscles cross shoulder joint; insert on and move humerus Some originate from scapula; others from axial skeleton Actions include flexion, extension, adduction
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Muscles Crossing the Shoulder Joint
Three prime movers of arm Pectoralis major (flexion, adduction) Latissimus dorsi (extension, adductor) Deltoid (abduction) Rotator cuff muscles: synergists and fixators; originate on scapula; reinforce shoulder capsule; prevent dislocation Supraspinatus & Infraspinatus Teres minor Subscapularis Coracobrachialis and teres major - synergists
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Deltoid: O: clavicle, acromion, scapula I: deltoid tuberosity of humerus Clavicle Deltoid Sternum Pectoralis major: O: sternal end of clavicle, sternum I: greater tubercle of humerus Pectoralis major Coracobrachialis Triceps brachii: Lateral head Long head Medial head Biceps brachii Brachialis Brachio- radialis Anterior view (muscles that originate anterior to the shoulder flex the arm)
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Supraspinatus* Spine of scapula Deltoid (cut) Greater tubercle of humerus Latissimus dorsi: O: iliac crest, lumbar & thoracic vertebrae I: spirals around teres major to insert in intertubercular sulcus of humerus Infraspinatus* Teres minor* Teres major Triceps brachii: Lateral head Long head (Latissimus & pectoralis: antagonistic) Latissimus dorsi Humerus Olecranon of ulna Anconeus Posterior view (muscles originating from posterior to the shoulder extend the arm: latissimus & teres major)
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Muscles Crossing the Shoulder
Chief medial rotator Flexes & adducts humerus
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Muscles Crossing the Elbow Joint: Flexion & Extension of the forearm
Clavicle Anterior flexor muscles Brachialis and biceps brachii __ chief forearm flexors Brachioradialis —synergist and stabilizer Deltoid Sternum Pectoralis major Coracobrachialis Triceps brachii: Lateral head Long head Medial head Biceps brachii Brachialis Brachio- radialis Anterior view
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Muscles Crossing the Elbow Joint: Flexion & Extension of the forearm
Supraspinatus* Spine of scapula Posterior extensor muscles Triceps brachii—prime mover of forearm extension Anconeus—weak synergist Deltoid (cut) Greater tubercle of humerus Infraspinatus* Teres minor* Teres major Triceps brachii: Lateral head Long head Latissimus dorsi Humerus Olecranon of ulna Anconeus Posterior view
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Muscles of the Forearm: Movements of the wrist, hand, and fingers
The two functional forearm muscle groups: wrist movement move the fingers & the thumb These muscles insert via strong ligaments (“wrist bands”: = flexor retinacula & extensor retinacula) Two main compartments: Anterior flexors Posterior extensors
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Superficial anterior view
transverse ligament of palm The pronator teres & pronator quadratus are not flexors, but pronate the forearm. Pronation – one of the important movements of forearm. Palmar aponeurosis Flexor retinaculum Flexor digitorum superficialis Pronator quadratus Flexor pollicis longus Flexor carpi ulnaris Palmaris longus Extensor carpi radialis longus Flexor carpi radialis Brachio- radialis Medial epicondyle of humerus Pronator teres Tendon of biceps brachii Medial head of triceps brachii Biceps brachii
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Forearm: Deeper Anterior Compartment
The supinator muscle is synergist with the biceps brachii in supinating the forearm 1 2 6 3 4 Deep Deepest 5
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Forearm: Superficial Posterior Compartment
1 9 2 8 3 These muscles are primarily extensors of the wrist and fingers 4 7 5 6
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Forearm: Deep Posterior Compartment
1 2 3 These muscles are primarily extensors of the wrist and fingers and the supinator 4 5
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Muscles Crossing Hip and Knee Joints: Movements of the thigh and leg
The most important thigh flexors: iliopsoas (prime mover) tensor fasciae latae rectus femoris The medially located adductor muscles sartorius (straplike) assist in flexion
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1 2 3 4 5 6 10 11 7 12 8 9
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Muscles Crossing Hip and Knee Joints: Movements of the thigh and leg
Thigh extension primarily effected by: hamstrings (biceps femoris, semitendinosus, & semimembranosus) Forceful extension is aided by gluteus maximus
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Movements of the Thigh at the Hip: Other Movements
Abduction and rotation: gluteus medius gluteus minimus, and are antagonized by the lateral rotators Thigh adduction is the role of five adductor muscles adductor magnus adductor longus adductor brevis pectineus gracilis
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1 2 * * 3 4 5 6
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Movements of the Thigh at the Hip: Other Movements
1 2 7 4 8 5 6 9 3
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Movements: Knee Joint sole extensor of the knee
quadriceps femoris flex the knee, and are antagonists to the quadriceps femoris hamstrings
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Muscles of the leg: Movements of the ankle & toes - Anterior Compartment
primary toe extensors and ankle dorsiflexors tibialis anterior extensor digitorum longus extensor hallucis longus fibularis (peroneus) tertius 1 2 3 4 5 6 7
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Muscles of the Anterior Compartment ISOLATED
Figure 10.21b-d
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Muscles of the Lateral Compartment
plantar flex and evert the foot fibularis longus fibularis brevis 1 2 3 4 5 6 8 7 9
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Muscles of the Lateral Compartment - ISOLATED
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Muscles of the Posterior Compartment
1 primarily flex the foot and the toes gastrocnemius soleus tibialis posterior flexor digitorum longus flexor hallucis longus 2 3 4
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Muscles of the Posterior Compartment
1 * 2 * * 3 1 2 4 3 4 7 5 Deep 5 Deepest 6 6
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Muscles of the Posterior Compartment - ISOLATED
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