Muscle System

Ch. 10

 Four functional groups of muscle: 1- prime movers (agonists): Muscle that bears the prime responsibility for effecting a movement 2- antagonist: Muscle that opposes the action of another muscle.

3- synergists: these muscles act as stabilizers to the prime movers. They may also contribute extra force to the prime mover as well.

4- fixator: muscle that immobilizes one or more bones (scapula)

 Muscle are classified according to their fascicular arrangement or attachment. Parallel - long axis of fascicle runs with longitudinal axis of muscle: sartorius muscle Pennate - fascicle branch form central tendon diagonally   Unipennate - extensor muscles Bipennate - rectus femoris  Multipennate - deltoid Convergent - fascicle converge toward a single tendon: pectoralis major Circular - fascicle are arranged in concentric rings Orbicularis oris and oculi

 Types of muscle attachments: direct and indirect Direct (tendon) - epimysium of muscle fused to periosteum of bone or perichondrium of cartilage. Indirect (aponeurosis) - muscle fascia extends beyond the muscle to bone or another muscle. Latissimus dorsi or galea aponeurotica

Muscle have points of attachment on the skeleton via tendons or aponeurosis Origin and insertion Origin: end of the muscle attaches to the stationary bone (non-moveable) Insertion: end of muscle attaches to the moving bone Biceps (two heads) have two origins on the scapula Biceps inserts on the radius (crosses elbow joint)

 Muscle list 1- Frontalis: O: galea aponeurotica I: skin of eyebrows N: Facial nerve (CN VII) A: raises eyebrows 2- Orbicularis oculi: O: frontal bone I: tissues of eyelid N: Facial nerve A: closes eyes

3- Temporalis: O: temporal fossa I: coronoid process of mandible N: Trigeminal nerve (CN V) A: closes jaw (muscle of mastication) 4- Orbicularis oris O: indirectly from maxilla and mandible I: encircles mouth N: Facial nerve A: puckers lips (kissing and whistling)

5- Platysma: O: subcutaneous skin over delto-pectoral region I: skin widely over the mandible A: depress mandible and lower lip tenses the skin over the lower neck N: facial nerve 6- Scalenes: located deep in the neck anterior middle posterior

7- Sternohyoid: O: manubrium I: hyoid bone A: depresses hyoid and larynx 8- Digastric: consists of two bellies that are connected by an intermediate tendon 9- Sternocleidomastoid: O: manubrium and medial portion of clavicle I: mastoid process A: together they flex head forward; separately they rotate head opposite to muscle contracting N: Spinal accessory (CN XI)

10- Deltoid: O: lateral 1/3 of clavicle, acromion and spine of scapula I: deltoid tuberosity A: arm abduction N: axillary nerve 11: Pectoralis minor: Thin muscle located underneath pectoralis major O: ribs 3-5 I: coracoid process

12- Pectoralis major O: medial 1/3 of clavicle I: lateral lip of bicipital groove to the crest of the greater tubercle A: arm flexion, rotates arm medially N: lateral and median pectoral nerves 13- Serratus anterior O: ribs 1-8 I: vertebral border of scapula A: protract and hold scapula N: long thoracic nerve 14- Intercostals: accessory muscle to respiration

15- Rectus abdominis: O: pubic symphysis I: xiphoid process and costal cartilage A: flex lumbar spine N: intercostal nerves 16- Diaphragm: O: inferior surface of rib cage I: central tendon A: primary muscle of respiration N: phrenic nerve (C3,4,5)

17- Triceps brachii: O: long head: infraglenoid tubercle of scapula medial head: posterior humeral shaft lateral head: posterior humeral shaft I: olecranon process of ulna A: forearm extension N: radial nerve 18- Biceps brachii : O: short head: coracoid process long head: supraglenoid tubercle I: radial tuberosity A: forearm flexor N: musculocutaneous nerve

19- Brachialis: Forearm flexor (lifts ulna) 20- Brachioradialis: “drinking muscle” O: distal end of humerus I: styloid process of radius A: forearm flexor N: radial nerve 21- Flexor carpi radialis: A: wrist flexor N: median nerve

22- Palmaris longus: O: medial epicondyle of humerus I: palmar aponeurosis A: weak wrist flexor N: median nerve Absent in 15% of the population (More females than males) 23- Lumbricals: 4 worm shaped muscles A: flex fingers at MCP joint

24- Iliopsoas: combination iliacus and psoas muscle A: primary hip and trunk flexor 25- Pectineus: Short flat muscle that adducts thigh O: pubis I: lesser trochanter 26- Tensor fasciae latae: O: ASIS I: Iliotibial tract (Gerdy’s tubercle) A: thigh abduction

27- Sartorius: “tailor’s muscle” O: anterior superior iliac spine (ASIS) I: upper medial surface of body of tibia A: Flexes, abducts and laterally rotates thigh N: Obturator nerve 28: Adductor longus Common thigh adductor 29: Gracilis: O: pubis I: tibia A: adducts thigh

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Quadriceps:

30: Rectus femoris O: ASIS I: patella by way of quadriceps tendon and tibial tuberosity by way of patellar ligament   A: hip flexor and knee extension N: femoral nerve 31: Vastus lateralis medius knee extension intermedius

32: Tibialis anterior: O: lateral condyle of tibia I: medial cuneiform and 1 st A: dorsiflexion of foot N: deep fibular nerve MTP.

33: Flexor hallucis longus: flexes great toe “push off” while taking a step

 Posterior 1- Occipitalis: O: occipital bone I: galea aponeurotica A: pulls scalp posteriorly I: facial nerve 2- Trapezius O: Occipital bone, vertebra of cervical and thoracic spinous processes I: acromion, spine of scapula and lateral 1/3 of clavicle A: extends head and raises scapula. “shrugging shoulders” N: Spinal Accessory nerve (CNXI)

Rotator cuff of shoulder: Holds humerus tight to glenoid fossa (S.I.T.S.) 3- Supraspinatus: O: supraspinous fossa of scapula I: greater tubercle of humerus A: assists in abduction 4- Infraspinatus O: infraspinous fossa of scapula I: greater tubercle of humerus A: rotates humerus laterally

5- Subscapularis O: subscapular fossa I: lesser tubercle of humerus A: medial rotation of humerus 6- Teres minor: A: Arm adductor

7- Teres major: A: posteromedial extension of humerus 8- Rhomboid major and minor O: spinous processes of C7-T1 (minor) I: medial border of scapula A: retract scapula “standing up straight” N: dorsal scapular nerve

9- Erector Spinae: Iliocostalis Longissimus Spinalis A: prime muscles for back extension 10- Latissimus dorsi O: Thoracolumbar fascia (aponeurosis) - T6-T12 and L1-L5 and iliac crest I: intertubercular groove of humerus A: arm extension and adductor N: thoracodorsal nerve

11- Extensor carpi ulnaris: Extension of the wrist 12- Extensor carpi radialis Extends and abducts wrist 13- Flexor carpi ulnaris Powerful wrist flexor N: ulnar nerve 14- Extensor digitorum Prime mover of finger extension

15- Gluteus medius A: abducts and medial rotates thigh N: superior gluteal nerve 16- Gluteus maximus O: dorsal ilium, sacrum and coccyx I: gluteal tuberosity of femur A: powerful thigh extender N: inferior gluteal nerve

Hamstrings (crosses knee joint- popliteal) 17- Biceps femoris: O: ischial tuberosity I: head of fibula and lateral condyle of tibia A: thigh extension and knee flexion N: Sciatic nerve 18- Semitendinosus: A: extends thigh and knee flexion 19- Semimembranosus A: extends thigh and flexes knee

20- Gastrocnemius O: medial and lateral condyles of femur I: posterior calcaneus (achilles tendon) A: plantar flexes foot (raise up on toes) N: Tibial nerve 21- Soleus A: plantar flexes foot and raise up on toes while seated N: Tibial nerve