I.    General Considerations

      A. Ex 18: General Principles

Label major muscles of head, and ant./post trunk on figs18-4 a,b.

• Most skeletal muscles extend from one bone to another and cross at least one joint. (note: in the face some muscles attach to bone and the connective tissue of the skin)
• Tendons - (dense fibrous connective tissue) - attach muscles to bones and to other muscles. An aponeurosis is a broad flat expanse of tendon.
• Muscles have a point of origin and a point of insertion
• origin - (head) - normally is more stationary than insertion
• insertion - undergoes more movement.
•  Synergists and Antagonists
• Synergists - are groups of muscles working together to cause movement
• Prime Mover - One muscle in a group of synergists that accomplishes the major desired movement.
• Fixators - are muscles that stabilize joints so that one type of action can take place without another happening as well.
•  Antagonists - groups or individual muscles working in opposition to one another.

• Location - pectoralis, femoris
• Size - maximus-minimus, longus-brevis
• Shape - deltoid, trapezius
• Orientation - Rectus, transversus, oblique
• Origin and Insertion - Sternocleidomastoid, Brachioradialis
• Number of Heads - biceps, triceps
• Function - flexor-extensor, adductor-abductor, opponens

    A. Facial Expression, Scalp Movement - Fig. 19.2

• platysma - remnant of panniculus carnosum, embedded in superficial fascia
• Orbicularis Oris - surrounds mouth
• Orbicularis oculi - surrounds eyes
• Epicranial - Occipitalis and Frontalis - move scalp
• Zygomaticus major and minor - raise corners of mouth

• Temporalis m
• O= temporal line on skull.
• I = coronoid process on mandible
• A = raises mandible, incisor biting
•  Massester m.
• O = zygomatic arch
• I = angle of mandible
• A = raises mandible, molar chewing

• Sternocleidomastoid m.
• O = sternum, clavicle
• I = mastoid process
• A = Both sides = flexion, one side = rotation of head to opposite. side.
•  Trapezuius m. - diamond shaped muscle with 3 heads
• O = nuchal line & ligament, Spinous Processes of C7-T12
• I = lateral clavicle, acromion, scapula
• A = elevates and rotates scapula, retracts scapula, depresses scapula
•  Splenius Capitis m
• O = C7-T3
• I = superior nuchal line and mastoid
• A = extend head and rotate
•  Semispinalis Capitis m.
• O = C7-T4
• I = mastoid process and superior nuchal line
• A = extend and slightly rotate neck.
• Others
• Suboccipital muscles - found deep in neck, under semispinalis
• Digastric m - lowers mandible
• mylohyoid m - floor of oral cavity

• Trapezuius m. - diamond shaped muscle with 3 heads
• O = nuchal line & ligament, SP of C7-T12
• I = lateral clavicle, acromion, scapula
• A = elevates and rotates scapula, retracts scapula,depresses scapula
•  Latissimus Dorsi m
• O = iliac crest, Thoracolumbar fascia
• I = medial edge of bicipital groove on humerus
• A = adduction and medial rotation

• Levator Scapulae m.
• O = transverse processes of C1-4
• I = Superior angle of scapula
• A = raises rotates and retracts the scapula
•  Rhomboid minor m.
• O = SP of C7-T1
• I = upper ¼ of medial scapular border
• A = retracts scapula
•  Rhomboid Major m.
• O = SP of T2-5
• I = Lower ¾ of medial border of scapula
• A= retraction and depression of scapula

• iliocostalis group
• longissimus group
• spinalis group
• all function to extend back and extend neck

• Pectoralis Major m.
• O = clavicle, sternum
• I = lateral edge of bicipital groove on humerus
• A= adduction and medial rotation

• Pectoralis Minor m
• O = ribs 3,4,5
• I = coracoid process of scapula
• A = protraction and depression of the scapula

• others
• Serratus anterior - depresses the scapula
• External Intercostal m. - hands in pockets = inspiration
• Internal intercostal m. - perpendicular to externals = expiration

• domed sheet of skeletal muscle that separates thoracic and abdominal cavities
• when it contracts it increases the size of the thoracic cavity, i.e. inspiration

• Rectus Abdominus m
• runs superior-inferiorly
• six pack - separated by tendinous inserts
• Flexes trunk, maintains posture
•  External and Internal Oblique
• external = hands in pockets
• internal = perpendicular to external
• love handles
• trunk flexion and rotation
•  Transversus abdominus m.
• under all others
• compresses abdomen

• Collectively called the Iliopsoas
• Psoas Major
• O = lumbar vertebrae
• I = lesser trochanter of femur
• A = Mainly flexion of the hip
• Iliacus
• O = Inner surface of ilium
• I = lesser trochanter of femur
• A = Mainly hip flexion