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The Muscular System: Part A
10 The Muscular System: Part A
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Muscle tissue – all contractile tissues Focus on skeletal muscle
The Muscular System Muscle tissue – all contractile tissues Skeletal, cardiac, smooth muscle Focus on skeletal muscle How muscles interact to movement Criteria for naming muscles Principles of leverage © 2013 Pearson Education, Inc.
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Actions and Interactions of Skeletal Muscles
Muscles can only pull; never push What one muscle group "does", another "undoes" © 2013 Pearson Education, Inc.
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Actions and Interactions of Skeletal Muscles
Functional Groups Prime mover (agonist) Major responsibility for producing specific movement Antagonist Opposes or reverses particular movement Prime mover and antagonist on opposite sides of joint across which they act © 2013 Pearson Education, Inc.
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Skeletal Muscles: Functional Groups
Synergist helps prime movers Adds extra force to same movement Reduces undesirable or unnecessary movement Fixator Synergist that immobilizes bone or muscle's origin Gives prime mover stable base on which to act © 2013 Pearson Education, Inc.
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Figure The action of a muscle can be inferred by the position of the muscle relative to the joint it crosses. (Examples given relate to the shoulder joint.) A muscle that crosses on the anterior side of a joint produces flexion* Example: Pectoralis major (anterior view) A muscle that crosses on the posterior side of a joint produces extension* Example: Latissimus dorsi (posterior view) The latissimus dorsi is the antagonist of the pectoralis major. A muscle that crosses on the lateral side of a joint produces abduction Example: Deltoid middle fibers (anterolateral view). A muscle that crosses on the medial side of a joint produces adduction Example: Teres major (posterolateral view) The teres major is the antagonist of the deltoid. *These generalities do not apply to the knee and ankle because the lower limb is rotated during development. The muscles that cross these joints posteriorly produce flexion, and those that cross anteriorly produce extension. © 2013 Pearson Education, Inc.
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Skeletal Muscles: Functional Groups
Same muscle may be Prime mover of one movement Antagonist for different movement Synergist for third movement © 2013 Pearson Education, Inc.
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Naming Skeletal Muscles
Muscle location—bone or body region with which muscle associated Muscle shape—e.g., deltoid muscle (deltoid = triangle) Muscle size—e.g., maximus (largest), minimus (smallest), longus (long) Direction of muscle fibers or fascicles—e.g., rectus (fibers run straight), transversus (fibers run at right angles), and oblique (fibers run at angles to imaginary defined axis) © 2013 Pearson Education, Inc.
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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 © 2013 Pearson Education, Inc.
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Muscle Mechanics: Importance of Fascicle Arrangement and Leverage
Additional factors contributing to muscle force and speed Fascicle arrangement Lever systems © 2013 Pearson Education, Inc.
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Arrangement of Fascicles
Most common patterns – circular, convergent, parallel, fusiform, pennate Circular Fascicles arranged in concentric rings (e.g., orbicularis oris) Convergent Broad origin; fascicles converge toward single tendon insertion (e.g., pectoralis major) © 2013 Pearson Education, Inc.
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Muscle Mechanics: Arrangement of Fascicles
Parallel Fascicles parallel to long axis of straplike muscle (e.g., sartorius) Fusiform Spindle-shaped muscles with parallel fibers (e.g., biceps brachii) © 2013 Pearson Education, Inc.
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Muscle Mechanics: Arrangement of Fascicles
Pennate Short fascicles attach obliquely to central tendon running length of muscle (e.g., rectus femoris) Three forms Unipennate – fascicles attach only to one side of tendon (e.g., extensor digitorum longus) Bipennate – fascicles insert from opposite sides of tendon (e.g., rectus femoris) Multipennate –appears as feathers inserting into one tendon (e.g., deltoid) © 2013 Pearson Education, Inc.
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Figure 10.2 Patterns of fascicle arrangement in muscles.
Convergent (pectoralis major) Circular (orbicularis oris) (a) (e) (b) (c) Fusiform (biceps brachii) (d) (f) (g) Parallel (sartorius) Multipennate (deltoid) Bipennate (rectus femoris) Unipennate (extensor digitorum longus) © 2013 Pearson Education, Inc.
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Arrangement of Fascicles
Determines muscle's range of motion Amount of movement when muscle shortens Determines muscle's power Long fibers more parallel to long axis shorten more; usually not powerful Power depends on number of muscle fibers Bipennate, multipennate muscles have most fibers shorten little but powerful © 2013 Pearson Education, Inc.
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Muscle Mechanics: Lever Systems
Components of lever system Lever—rigid bar (bone) that moves on a fixed point called fulcrum (joint) Effort—force (supplied by muscle contraction) applied to lever to move resistance (load) Load—resistance (bone + tissues + any added weight) moved by the effort © 2013 Pearson Education, Inc.
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Levers: Power Versus Speed
Levers allow given effort to move heavier load; move load farther or faster Depends on fulcrum position relative to load and effort Mechanical advantage (power lever) – load close to fulcrum; effort far from fulcrum Small effort can move large load Mechanical disadvantage (speed lever) – load far from fulcrum; effort close to fulcrum Load moved rapidly over large distance; wide range of motion © 2013 Pearson Education, Inc.
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Effort x length of effort arm = load x length of load arm
Figure 10.3a Lever systems operating at a mechanical advantage and a mechanical disadvantage. Effort x length of effort arm = load x length of load arm (force x distance) = (resistance x distance) Effort 10 kg Effort 0.25 cm 25 cm Fulcrum Load 1000 kg 10 x 25 = 1000 x 0.25 250 = 250 Load Fulcrum Mechanical advantage with a power lever © 2013 Pearson Education, Inc.
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Mechanical disadvantage with a speed lever
Figure 10.3b Lever systems operating at a mechanical advantage and a mechanical disadvantage. Effort 100 kg Effort Load 25 cm 50 cm Fulcrum Fulcrum 50 kg 100 x 25 = 50 x 50 2500 = 2500 Load Mechanical disadvantage with a speed lever © 2013 Pearson Education, Inc.
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Classes of Lever Systems
Basic principle of levers Effort farther than load from fulcrum = lever operates at mechanical advantage Effort nearer than load to fulcrum = lever operates at mechanical disadvantage Three classes of levers Depends on relative position of effort, fulcrum, load © 2013 Pearson Education, Inc.
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Classes of Lever Systems
First-class lever Fulcrum between load and effort E.g., seesaw, scissors © 2013 Pearson Education, Inc.
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Figure 10.4a Lever systems. (1 of 2)
First-class lever Arrangement of the elements is load-fulcrum-effort Load Effort L Fulcrum Load L Effort Fulcrum © 2013 Pearson Education, Inc.
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Figure 10.4a Lever systems. (2 of 2)
First-class lever Example: scissors Fulcrum Load Effort In the body: A first-class lever system raises your head off your chest. The posterior neck muscles provide the effort, the atlanto-occipital joint is the fulcrum, and the weight to be lifted is the facial skeleton. © 2013 Pearson Education, Inc.
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Classes of Lever Systems
Second-class lever Load between fulcrum and effort E.g., Wheelbarrow, standing on toes © 2013 Pearson Education, Inc.
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Figure 10.4b Lever systems. (1 of 2)
Second-class lever Arrangement of the elements is fulcrum-load-effort Load L Fulcrum Effort Load L Effort Fulcrum © 2013 Pearson Education, Inc.
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Figure 10.4b Lever systems. (2 of 2)
Second-class lever Example: wheelbarrow Effort Load Fulcrum In the body: Second-class leverage is exerted when you stand on tip-toe. The effort is exerted by the calf muscles pulling upward on the heel; the joints of the ball of the foot are the fulcrum; and the weight of the body is the load. © 2013 Pearson Education, Inc.
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Classes of Lever Systems
Third-class lever Effort applied between fulcrum and load E.g., tweezers, forceps, most skeletal muscles Speed levers – force lost; speed, range of movement gained Power levers – slower, more stable, used where strength priority © 2013 Pearson Education, Inc.
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Figure 10.4c Lever systems. (1 of 2)
Third-class lever Arrangement of the elements is load-effort-fulcrum Load Effort L Fulcrum Load L Fulcrum Effort © 2013 Pearson Education, Inc.
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Figure 10.4c Lever systems. (2 of 2)
Third-class lever Example: tweezers or forceps Effort Load Fulcrum In the body: Flexing the forearm by the biceps brachii muscle exemplifies third-class leverage. The effort is exerted on the proximal radius of the forearm, the fulcrum is the elbow joint, and the load is the hand and distal end of the forearm. © 2013 Pearson Education, Inc.
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Major Skeletal Muscles of the Body
> 600 in body; grouped by function and location Information for each muscle Shape Location relative to other muscles Origin and insertion—usually a joint between origin and insertion Actions—insertion moves toward origin Innervation—name of major nerve that supplies muscle © 2013 Pearson Education, Inc.
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Major Skeletal Muscles of the Body
To learn Be aware of information learned from muscle name Read description; identify on figure; relate location and description Relate attachments to actions Act out movements on yourself © 2013 Pearson Education, Inc.
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Figure 10.5 Superficial muscles of the body: Anterior view.
Facial Epicranius, frontal belly Orbicularis oculi Head Zygomaticus Temporalis Orbicularis oris Masseter Neck Shoulder Platysma Trapezius Sternohyoid Sternocleidomastoid Deltoid Arm Thorax Pectoralis minor Triceps brachii Pectoralis major Biceps brachii Serratus anterior Brachialis Intercostals Forearm Pronator teres Abdomen Brachioradialis Rectus abdominis Flexor carpi radialis External oblique Internal oblique Palmaris longus Transversus abdominis Pelvis/thigh Iliopsoas Thigh Pectineus Tensor fasciae latae Thigh Sartorius Rectus femoris Adductor longus Gracilis Vastus lateralis Vastus medialis Leg Leg Fibularis longus Gastrocnemius Extensor digitorum longus Soleus Tibialis anterior © 2013 Pearson Education, Inc.
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Figure 10.6 Superficial muscles of the body: Posterior view.
Neck Epicranius, occipital belly Sternocleidomastoid Trapezius Arm Shoulder Triceps brachii Deltoid Brachialis Infraspinatus Forearm Teres major Brachioradialis Rhomboid major Extensor carpi radialis longus Latissimus dorsi Flexor carpi ulnaris Hip Extensor digitorum Gluteus medius Extensor carpi ulnaris Gluteus maximus Thigh Iliotibial tract Adductor magnus Hamstrings: Biceps femoris Semitendinosus Leg Semimembranosus Gastrocnemius Soleus Fibularis longus Calcaneal (Achilles) tendon © 2013 Pearson Education, Inc.
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Muscles of the Head Two groups Muscles of facial expression
Muscles of mastication and tongue movement © 2013 Pearson Education, Inc.
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Muscles of Facial Expression
Insert into skin Important in nonverbal communication All innervated by cranial nerve VII (facial nerve) © 2013 Pearson Education, Inc.
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Muscles of Facial Expression: The Scalp
Epicranius (occipitofrontalis) Bipartite muscle consisting of Galea aponeurotica—cranial aponeurosis connecting two bellys Frontal belly; occipital belly Have alternate actions; pull scalp forward and backward © 2013 Pearson Education, Inc.
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Muscles of Facial Expression: The Face
Corrugator supercilii Zygomaticus Risorius Levator labii superioris Depressor labii inferioris Depressor anguli oris Orbicularis oris Mentalis Buccinator Platysma © 2013 Pearson Education, Inc.
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Figure 10.7b Lateral view of muscles of the scalp, face, and neck.
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 Platysma © 2013 Pearson Education, Inc.
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Muscles of Mastication
Four pairs involved in mastication; all innervated by cranial nerve V (trigeminal nerve) Prime movers of jaw closure Temporalis and masseter Grinding movements Medial and lateral pterygoids Chewing role - holds food between teeth Buccinator © 2013 Pearson Education, Inc.
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Figure 10.8a Muscles promoting mastication and tongue movements.
Temporalis Orbicularis oris Masseters Buccinator © 2013 Pearson Education, Inc.
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Figure 10.8b Muscles promoting mastication and tongue movements.
Lateral pterygoid Medial pterygoid Masseter pulled away © 2013 Pearson Education, Inc.
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Muscles of Mastication and Tongue Movement
PLAY A&P Flix™: Temporalis PLAY A&P Flix™: Masseter PLAY A&P Flix™: Buccinator © 2013 Pearson Education, Inc.
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Muscles of Tongue Movement
Three muscles anchor and move tongue Genioglossus Hyoglossus Styloglossus All innervated by cranial nerve XII - hypoglossal nerve © 2013 Pearson Education, Inc.
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Figure 10.8c Muscles promoting mastication and tongue movements.
Styloid process Styloglossus Genioglossus Hyoglossus Mandibular symphysis Stylohyoid Hyoid bone Geniohyoid Thyroid cartilage Thyrohyoid © 2013 Pearson Education, Inc.
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Muscles of the Anterior Neck and Throat
Two groups Suprahyoid muscles Infrahyoid muscles Most involved in swallowing © 2013 Pearson Education, Inc.
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Suprahyoid Muscles of the Anterior Neck and Throat
Four deep muscles involved in swallowing (move hyoid bone and larynx) Form floor of oral cavity Anchor tongue Move hyoid bone and larynx © 2013 Pearson Education, Inc.
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Infrahyoid Muscles of the Anterior Neck and Throat
Straplike muscles; depress hyoid and larynx as swallowing ends and during speaking © 2013 Pearson Education, Inc.
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Median raphe Anterior belly Mylohyoid Digastric Stylohyoid Posterior
Figure 10.9a Muscles of the anterior neck and throat used in swallowing. Median raphe Anterior belly Mylohyoid Digastric Stylohyoid Posterior belly Hyoid bone Stylohyoid (cut) Omohyoid (superior belly) Thyrohyoid Sternohyoid Thyroid cartilage of the larynx Sternocleido- mastoid Thyroid gland Sternothyroid Omohyoid (inferior belly) © 2013 Pearson Education, Inc.
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Platysma (cut) Mylohyoid Omohyoid (superior belly) Sternohyoid
Figure 10.9b Muscles of the anterior neck and throat used in swallowing. Platysma (cut) Mylohyoid Omohyoid (superior belly) Sternohyoid Sternocleido- mastoid © 2013 Pearson Education, Inc.
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Tensor veli palatini Levator veli palatini Styloid process Buccinator
Figure 10.9c Muscles of the anterior neck and throat used in swallowing. Tensor veli palatini Levator veli palatini Styloid process Buccinator Superior pharyngeal constrictor Mandible Middle pharyngeal constrictor Mylohyoid (cut) Hyoid bone Thyrohyoid membrane Geniohyoid Hyoglossus Inferior pharyngeal constrictor Thyroid Cartilage of larynx Esophagus Trachea © 2013 Pearson Education, Inc.
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Infrahyoid Muscles of the Anterior Neck and Throat
PLAY Animation: Rotating head PLAY Animation: Rotating face © 2013 Pearson Education, Inc.
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Muscles of the Neck and Vertebral Column
Two functional groups Muscles that move head Muscles that extend trunk and maintain posture © 2013 Pearson Education, Inc.
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Muscles of the Neck and Vertebral Column: Head Movement
Sternocleidomastoid—major head flexor Suprahyoid and infrahyoid—synergists to head flexion Sternocleidomastoid and scalenes—lateral head movements Splenius capitis and cervicis portions - head extension, rotation, and lateral bending Semispinalis capitis—synergist with sternocleidomastoid © 2013 Pearson Education, Inc.
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Base of occipital bone 1st cervical vertebra Mastoid process Middle
Figure 10.10a Muscles of the neck and vertebral column that move the head and trunk. Base of occipital bone 1st cervical vertebra Mastoid process Middle scalene Sternocleido- mastoid Anterior scalene Posterior scalene Anterior © 2013 Pearson Education, Inc.
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Mastoid process Splenius capitis Spinous processes of the vertebrae
Figure 10.10b Muscles of the neck and vertebral column that move the head and trunk. Mastoid process Splenius capitis Spinous processes of the vertebrae Splenius cervicis Posterior © 2013 Pearson Education, Inc.
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Platysma (cut) Sternocleidomastoid (cut) Internal jugular vein
Figure 10.10c Muscles of the neck and vertebral column that move the head and trunk. Platysma (cut) Sternocleidomastoid (cut) Internal jugular vein Omohyoid Sternohyoid Sternothyroid Sternocleidomastoid Pectoralis major © 2013 Pearson Education, Inc.
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Muscles of the Neck and Vertebral Column: Head Movement
PLAY A&P Flix™: Splenius capitis PLAY A&P Flix™: Semispinalis capitis © 2013 Pearson Education, Inc.
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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 Iliocostalis Longissimus Spinalis Semispinalis and quadratus lumborum—synergists in extension and rotation © 2013 Pearson Education, Inc.
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Iliocostalis cervicis Longissimus cervicis
Figure 10.10d Muscles of the neck and vertebral column that move the head and trunk. Ligamentum nuchae Mastoid process of temporal bone Semispinalis capitis Longissimus capitis Semispinalis cervicis Iliocostalis cervicis Longissimus cervicis Semispinalis thoracis Iliocostalis thoracis Longissimus thoracis Spinalis thoracis Iliocostalis Erector spinae Longissimus Spinalis Multifidus Iliocostalis lumborum Quadratus lumborum External oblique © 2013 Pearson Education, Inc.
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Muscles of the Neck and Vertebral Column: Trunk Extension
PLAY A&P Flix™: Iliocostalis PLAY A&P Flix™: Longissimus PLAY A&P Flix™: Spinalis © 2013 Pearson Education, Inc.
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