Chapter 11: The Muscular System Muscle Organization & Function (Interactive pgs ) The Muscular System Consists only of skeletal muscles Muscle Organization and Function Muscle organization affects power, range, and speed of muscle movement Fascicles Muscle cells (fibers) are organized in bundles (fascicles) Classification of Skeletal Muscles By the way fascicles are organized By relationships of fascicles to tendons Organization of Skeletal Muscle Fibers 4 patterns of fascicle organization: parallel convergent pennate circular Parallel Muscles Figure 111a Parallel Muscles Fibers parallel to the long axis of muscle e.g., biceps brachii Parallel Muscle Body The center or body of the muscle thickens when parallel muscle contracts Parallel muscles contract about 30% Parallel Muscle Tension Depends on total number of myofibrils Directly relates to cross section of muscle 1 in. 2 (6.45 cm 2 ) of cross section develops 50 lb (23 kg) of tension Convergent Muscles Figure 111b Convergent Muscles A broad area converges on attachment site (tendon, aponeurosis, or raphe) Muscle fibers pull in different directions, depending on stimulation e.g., pectoralis muscles Pennate Muscles Figure 111c, d, e Pennate Muscles Unipennate: fibers on 1 side of tendon e.g., extensor digitorum Bipennate: fibers on both sides of tendon e.g., rectus femoris Pennate Muscles Multipennate: tendon branches within muscle e.g., deltoid Pennate Muscles Form an angle with the tendon Do not move as far as parallel muscles Contain more myofibrils than parallel muscles Develop more tension than parallel muscles Circular Muscles Figure 111f Circular Muscles Also called sphincters Open and close to guard entrances of body e.g., obicularis oris Skeletal Motion Skeletal muscles attach to skeleton, produce motion Type of muscle attachment affects power, range, and speed of muscle movement Levers Mechanically, each bone is a lever (a rigid, moving structure): and each joint a fulcrum (a fixed point) Muscles provide applied force (AF): required to overcome resistance (R) Functions of a Lever To change: direction of an AF distance and speed of movement produced by an AF effective strength of an AF 3 Classes of Levers Depend on the relationship between applied force, fulcrum, and resistance: first class second class third class First, Second, and Third-Class Levers PLAY First-Class Levers Figure 112a First-Class Levers Seesaw is an example Center fulcrum between applied force and resistance Force and resistance are balanced SecondClass Levers Figure 112b Second-Class Levers Wheelbarrow is an example Center resistance between applied force and fulcrum A small force moves a large weight Third-Class Levers Figure 112c Third-Class Levers Most common levers in the body Center applied force between resistance and fulcrum Greater force moves smaller resistance Maximizes speed and distance traveled KEY CONCEPT Skeletal muscles can shorten to 70% of resting length Power, speed, and range of movement Depend on positions of muscle attachment Relative to joints How are actions of a muscle based on the relative positions of its origin and insertion? Origins and Insertions Muscles have 1 fixed point of attachment (origin) and 1 moving point of attachment (insertion) Most muscles originate or insert on the skeleton Origin is usually proximal to insertion Actions Movements produced by muscle contraction Body movements e.g., flexion, extension, adduction, etc. Described in terms of bone, joint, or region How do muscles interact to produce or oppose movements? Muscle Interactions Muscles work in groups to maximize efficiency Smaller muscles reach maximum tension first, followed by larger, primary muscles Muscle Terminology Based on Function Agonist (prime mover): produces a particular movement Antagonist: opposes movement of a particular agonist Muscle Terminology Based on Function Synergist: a smaller muscle that assists a larger agonist helps start motion or stabilize origin of agonist (fixator) Muscle Opposition Agonists and antagonists work in pairs: when 1 contracts, the other stretches i.e., flexorsextensors, abductors adductors, etc. How does the name of a muscle help identify its location, appearance, or function? Names of Skeletal Muscles Correct names of muscles include the term muscle Exceptions: platysma diaphragm Naming Skeletal Muscles Table 111 (1 of 2) Naming Skeletal Muscles Table 111 (2 of 2) Descriptive Names for Skeletal Muscles 1.Location in the body 2.Origin and insertion 3.Fascicle organization 4.Relative position 5.Structural characteristics 6.Action Location in the Body Identifies body regions: e.g., temporalis muscle Origin and Insertion First part of name indicates origin Second part of name indicates insertion: e.g., genioglossus muscle Fascicle Organization Describes fascicle orientation within muscle: i.e., rectus (straight), transversus, oblique Relative Position Externus (superficialis): visible at body surface Internus (profundus): deep muscles Extrinsic: muscles outside an organ Intrinsic: muscles inside an organ Structural Characteristics Number of tendons: bi = 2, tri = 3 Shape: trapezius, deltoid, rhomboid Size Names for Muscle Size (1 of 2) Longus = long Longissimus = longest Teres = long and round Brevis = short Magnus = large Names For Muscle Size (2 of 2) Major = larger Maximus = largest Minor = small Minimus = smallest Action Movements: e.g., flexor, extensor, retractor Occupations or habits: e.g., risor = laughter Ch. 11 Notes Axial and Appendicular Muscles Part I: Face and Neck Figure 113a Axial and Appendicular Muscles Figure 113b Divisions of the Muscular System 1.Axial muscles: position head and spinal column move rib cage 60% of skeletal muscles 2.Appendicular muscles: support pectoral and pelvic girdles support limbs 40% of skeletal muscles The Axial Muscles Divisions based on location and function: muscles of head and neck muscles of vertebral column oblique and rectus muscles muscles of pelvic floor 6 Muscle Groups of the Head and Neck Muscles of facial expression: originate on skull Extrinsic eye muscles: originate on surface of orbit control position of eye 6 Muscle Groups of the Head and Neck Muscles of mastication: move the mandible Muscles of the tongue: names end in glossus Muscles of the pharynx: begin swallowing process 6 Muscle Groups of the Head and Neck Anterior muscles of the neck: control position of larynx depress the mandible support tongue and pharynx Muscles of Facial Expression Orbicularis oris: constricts the mouth opening Buccinator: moves food around the cheeks Muscles of the epicranium (scalp) Muscles of Facial Expression Figure 114b Muscles of the Epicranium (Scalp) Temporoparietalis Occipitofrontalis: frontal and occipital bellies separated by epicranial aponeurosis Platysma: covers anterior surface of neck Muscles of Facial Expression Figure 114a Extrinsic Eye Muscles Also called extra-ocular muscles Figure 115a, b 6 Extrinsic Eye Muscles Inferior rectus Medial rectus Superior rectus Lateral rectus Inferior oblique Superior oblique 3 Muscles of Mastication Masseter: the strongest jaw muscle Temporalis: helps lift the mandible Pterygoid muscles: position mandible for chewing Muscles of Mastication Figure 116 4 Muscles of the Tongue Palatoglossus: originates at palate Styloglossus: originates at styloid process Genioglossus: originates at chin Hypoglossus: originates at hyoid bone Muscles of the Tongue Figure 117 3 Muscles of the Pharynx Pharyngeal constrictor muscles: move food into esophagus Laryngeal elevator muscles: elevate the larynx Palatal muscles: lift the soft palate Muscles of the Pharynx Figure 118 6 Anterior Muscles of the Neck Digastric: from chin to hyoid and hyoid to mastoid Mylohyoid: floor of the mouth Geniohyoid: between hyoid and chin 6 Anterior Muscles of the Neck Stylohyoid: between hyloid and styloid Sternocleidomastoid: from clavicle and sternum to mastoid Omohyoid: attaches scapula, clavicle, first rib, and hyoid Anterior Muscles of the Neck Figure 119 Ch.11 Axial/Appendicular Muscles Part II: Muscles of the Vertebral Column Figure 1110a Muscles of the Vertebral Column Spinal extensors or erector spinae muscles (superficial and deep) Spinal flexors (transversospinalis) Muscles of the Vertebral Column Figure 1110b, c Superficial Spinal Extensors Spinalis group Longissimus group Iliocostalis group Deep Spinal Extensors Semispinalis group Multifidus muscle Interspinalis muscles Intertransversarii muscles Rotatores muscles Spinal Flexors Neck: longus capitis and longus colli rotate and flex the neck Lumbar: quadratus lumborum muscles flex spine and depress ribs Oblique and Rectus Muscles Lie within the body wall Figure 1111a, b Oblique and Rectus Muscles Oblique muscles: compress underlying structures rotate vertebral column Rectus muscles: flex vertebral column oppose erector spinae Oblique Muscles Cervical region: scalene muscles flex the neck Oblique Muscles Thoracic region: intercostal muscles (external and internal intercostals): respiratory movements of ribs transversus thoracis: cross inner surface of ribs Oblique Muscles Abdominopelvic region (same pattern as thoracic): external oblique muscles internal oblique muscles Transversus abdominis Oblique and Rectus Muscles Figure 1111a, c Rectus Group Rectus abdominis: between xiphoid process and pubic symphysis divided longitudinally by linea alba divided transversely by tendinous inscriptions Rectus Group Diaphragmatic muscle or diaphragm: divides thoracic and abdominal cavities performs respiration Functions of Pelvic Floor Muscles 1.Support organs of pelvic cavity 2.Flex sacrum and coccyx 3.Control movement of materials through urethra and anus Perineum Muscular sheet forming the pelvic floor, divided into: anterior urogenital triangle posterior anal triangle Muscles of the Pelvic Floor Figure 1112a Urogenital Diaphragm Deep muscular layer between pubic bones: supports the pelvic floor and muscles of the urethra Superficial muscles of the urogenital triangle: support external genitalia Pelvic Diaphragm Deep muscular layer extending to pubis: supports anal triangle Muscles of the Pelvic Floor Figure 1112b What are the principal appendicular muscles of the body and their origins, insertions, actions, and innervations? Ch.11 Muscle Notes: Part III The Appendicular Muscles Figure 1113a The Appendicular Muscles Figure 1113b The Appendicular Muscles Position and stabilize pectoral and pelvic girdles Move upper and lower limbs Muscles of the Shoulders and Upper Limbs Position the pectoral girdle Move the arm Move the forearm and hand Move the hand and fingers 3D Peel-Away of Muscles of the Pectoral Girdle PLAY Muscles that Position the Pectoral Girdle Figure 1114a Muscles that Position the Pectoral Girdle Figure 1114b 6 Muscles that Position the Pectoral Girdle (1 of 4) Trapezius: superficial covers back and neck to base of skull inserts on clavicles and scapular spines 6 Muscles that Position the Pectoral Girdle (2 of 4) Rhomboid and levator scapulae: deep to trapezius attach to cervical and thoracic vertebrae insert on scapular border 6 Muscles that Position the Pectoral Girdle (3 of 4) Serratus anterior: on the chest originates along ribs inserts on anterior scapular margin 6 Muscles that Position the Pectoral Girdle (4 of 4) Subclavius: originates on ribs inserts on clavicle Pectoralis minor: attaches to scapula Muscles that Move the Arm Figure 1115a Muscles that Move the Arm Figure 1115b 9 Muscles that Move the Arm (1 of 3) Deltoid: the major abductor Supraspinatus: assists deltoid Subscapularis and teres major: produce medial rotation at shoulder 3D Rotation: Muscles of the Arm PLAY 9 Muscles that Move the Arm (2 of 3) Infraspinatus and teres minor: produce lateral rotation at shoulder Coracobrachialis: attaches to scapula produces flexion and adduction at shoulder 9 Muscles that Move the Arm (3 of 3) Pectoralis major: between anterior chest and greater tubercle of humerus produces flexion at shoulder joint Latissimus dorsi: between thoracic vertebrae and humerus produces extension at shoulder joint The Rotator Cuff Muscles involved in shoulder rotation supraspinatus, subscapularis, infraspinatus, teres minor,and their tendons Muscles that Move the Forearm and Hand Figure 1116a Muscles that Move the Forearm and Hand Figure 1116b Muscles that Move the Forearm and Hand Originate on humerus and insert on forearm Exceptions: the major flexor (biceps brachii) the major extensor (triceps brachii) 3D Rotation: Muscles of the Forearm and Hand PLAY Extensors and Flexors Extensors: mainly on posterior and lateral surfaces of arm Flexors: mainly on anterior and medial surfaces 13 Muscles that Move the Forearm and Hand (1 of 8) Biceps brachii: flexes elbow stabilizes shoulder joint originates on scapula inserts on radial tuberosity 13 Muscles that Move the Forearm and Hand (2 of 8) Triceps brachii: extends elbow originates on scapula inserts on olecranon Brachialis and brachioradialis: flex elbow 13 Muscles that Move the Forearm and Hand (3 of 8) Anconeus: opposes brachialis Palmaris longus: superficial flexes wrist 13 Muscles that Move the Forearm and Hand (4 of 8) Flexor carpi ulnaris: superficial flexes wrist adducts wrist 13 Muscles that Move the Forearm and Hand (5 of 8) Flexor carpi radialis: superficial flexes wrist abducts wrist 13 Muscles that Move the Forearm and Hand (6 of 8) Extensor carpi radialis: superficial extends wrist abducts wrist 13 Muscles that Move the Forearm and Hand (7 of 8) Extensor carpi ulnaris: superficial extends wrist adducts wrist 13 Muscles that Move the Forearm and Hand (8 of 8) Pronator teres and supinator: originate on humerus and ulna rotate radius Pronator quadratus: originates on ulna assists pronator teres Muscles that Move the Hand and Fingers Figure 1117a, b Muscles that Move the Hand and Fingers Figure 1117c, d Muscles of the Pelvis and Lower Limbs Pelvic girdle is tightly bound to axial skeleton: permits little movement has few muscles Muscles that Position the Lower Limbs 1.Muscles that move the thigh 2.Muscles that move the leg 3.Muscles that move the foot and toes Muscles that Move the Thigh Figure 1119a, b Muscles that Move the Thigh Figure 1119c, d Muscles that Move the Thigh Gluteal muscles Lateral rotators Adductors Iliopsoas 3D Peel-Away of Muscles of the Thigh PLAY 3D Peel-Away of Rectus Muscle PLAY Gluteal Muscles (1 of 2) Cover lateral surfaces of ilia Gluteus maximus: largest, most posterior gluteal muscle produces extension and lateral rotation at hip Gluteal Muscles (2 of 2) Tensor fasciae latae: works with gluteus maximus stabilizes iliotibial tract Gluteus medius and gluteus minimus: originate anterior to gluteus maximus insert on trochanter Lateral Rotators Group of 6 muscles, including: piriformis obturator Adductors (1 of 2) Adductor magnus: produces adduction, extension, and flexion Adductor brevis: hip flexion and adduction Adductor longus: hip flexion and adduction Adductors (2 of 2) Pectineus: hip flexion and adduction Gracilis: hip flexion and adduction Iliopsoas 2 hip flexors insert on the same tendon: psoas major iliacus Muscles that Move the Leg Figure 1120a Muscles that Move the Leg Figure 1120b, c Muscles that Move the Leg Flexors of the knee: originate on the pelvic girdle Extensors of the knee: originate on the femoral surface insert on the patella Flexors of the Knee Biceps femoris Semimembranosus Semitendinosus Sartorius: originates superior to the acetabulum Popliteus: rotates the tibia to unlock the knee Hamstrings Made up of: biceps femoris semimembranosus semitendinosus Extensors of the Knee 4 muscles of the quadriceps femoris: 3 vastus muscles rectus femoris muscle Muscles that Move the Foot and Toes Figure 1121a, b Muscles that Move the Foot and Toes Figure 1121c, d Muscles that Move the Foot and Toes Extrinsic muscles that move the foot and toes include: muscles that produce extension at the ankle muscles that produce flexion at the ankle muscles that produce extension at the toes muscles that produce flexion at the toes 4 Muscles that Produce Extension at the Ankle Gastrocnemius Soleus Fibularis Tibialis posterior 3D Peelaway of Muscles of the Leg and Foot PLAY The Achilles Tendon The calcaneal tendon (Achilles tendon): shared by the gastrocnemius and soleus Muscles that Produce Flexion at the Ankle Tibialis anterior: opposes the gastrocnemius