Axial Muscles

Front 1

Back 1

Myofibers:

Muscle cells containing various organelles and contractile proteins that are used for contraction

Front 2

Back 2

Striations:

Alternating light and dark bands caused by the overlap of the motor proteins myosin and actin (thick and thin filaments)

Front 3

Back 3

Skeletal Muscle:

Appearance: long striated (striped) fibers with multiple nuclei;

striations caused by the overlap of thick and thin filaments

Functions: body movements, facial expression, posture, breathing, speech, swallowing,; VOLUNTARY

Locations: skeletal muscle, tongue, encircling the lips, eyelids, urethra, and anus

Front 4

Back 4

Cardiac Muscle:

Appearance: short myocytes (muscle cells) with slightly beached ends; striations caused by the overlap of thick and thin filaments; intercalated discs (a complex of adherens, gap junctions, and desmosomes that join cardiac cells; uninucleated

Functions: pumping of blood; INVOLUNTARY

Location: heart

Front 5

Back 5

Smooth Muscle:

Appearance: short fusiform (tapered at ends) cells overlapping each other; non-striated; uninucleated

Functions: swallowing; contractions of gastrointestinal tract; expulsion of urine/feces; labor contractions; blood pressure; pupil diameter; erection of hairs; INVOLUNTARY

Locations: sheets of tissue in walls of blood vessels and viscera; Iris; associated with hair follicles; involuntary sphincters of urethra and anus

Front 6

Agonist

Back 6

Also called prime mover; the muscle that produces most of the force during a particular joint action

Front 7

Antagonist

Back 7

A muscle that opposes the prime mover (agonist); maintains some tension on a joint and thus limits the speed of range of the prime mover

Front 8

Fixator

Back 8

A muscle that prevents a bone from moving, allowing other muscles attached to pull on a different bone

Front 9

Synergist

Back 9

A muscle that aids the prime mover (agonist); actions between the prime mover and synergists are not necessarily identical

(If the prime mover worked alone, it may cause rotation or other undesirable movement. A synergist may stabilize the joint.)

Front 10

Extension

Back 10

Movement that increases the angle of a joint

Front 11

Flexion

Back 11

Movement that decreases the angle of a joint

Front 12

Dorsiflexion

Back 12

Movement of the ankle that reduces the joint angle and raises the toes

Front 13

Plantar Flexion

Back 13

Movement of the ankle that increases the joint angle and curls the toes

Front 14

Abduction

Back 14

Movement of a body part away from the midline

Front 15

Adduction

Back 15

Movement of a body part towards the midline

Front 16

Circumduction

Back 16

Movement in which one end of appendage remains stationary while the other moves in a circular motion

Front 17

Hyperextension

Back 17

Movement that increases the joint angle beyond 180 degrees

Front 18

Inversion

Back 18

Foot movement in which the plantar region faces the median plane

Front 19

Eversion

Back 19

Foot movement in which the plantar regions faces laterally

Front 20

Pronation

Back 20

A rotational movement of the forearm that turns the palm downward or posteriorly

Front 21

Supination

Back 21

A rotational movement of the forearm that turns the palm so that it faces upward or forward

Front 22

Rotation

Back 22

Turning of a joint along its axis

Front 23

Back 23

Temporalis:

Action: Elevation of mandible during mastication (chewing)

Front 24

Back 24

Masseter:

Action: Elevation of the mandible, with smaller roles in protraction, retraction, and lateral and medial excursion (mastication)

Front 25

Back 25

Orbicularis Oculi:

Action: Sphincter of the eyelids; closes eye in blinking, squinting, and sleep; aids in flow of tears across eye

Front 26

Back 26

Levator Palpabrae Superioris:

Action: Elevates upper eyelid; opens eye

Front 27

Back 27

Orbicularis Oris:

Action: Encircles mouth, closes lips, protrudes lips as in kissing; uniquely developed in humans for speech

Front 28

Back 28

Platysma:

Action: Draws lower lip and angle of mouth downward in expressions of horror or surprise; may aid in opening mouth widely

Front 29

Back 29

Sternocleidomastoid:

Origin: Manubrium of sternum; medial one-third of clavicle

Insertion: Mastoid process of temporal bone

Action: Unilateral action tilts head slightly upward and toward the opposite, as in looking over one's contralateral should. Rotating head left or right. Bilateral action draws head straightforward and down.

Front 30

Back 30

Scalenes (Anterior, Middle, and Posterior):

Action: Bilateral contration flexes neck. If spine is fixed, scalenes elevate ribs 1-2 and aid in breathing.

Front 31

Back 31

Digastric:

Action: Depresses mandible when hyoid is fixed; opens mouth widely, as when ingesting food or yawning; elevates hyoid when mandible is fixed

Front 32

Back 32

Stylohyoid:

Origin: Styloid process of temporal bone

Insertion: Hyoid bone

Action: Elevates and retracts hyoid

Front 33

Back 33

Mylohyoid:

Origin: Inferior margin of mandible

Insertion: Hyoid bone

Action: Spans mandible from side to side and forms floor of mouth; elevates floor of mouth in initial stage of swallowing

Front 34

Back 34

Sternohyoid:

Origin: Manubrium of sternum; medial end of clavicle

Insertion: Hyoid bone

Action: Depresses hyoid after it has been elevated

Front 35

Back 35

Sternothyroid:

Action: Depresses larynx after it has been elevated in swallowing and vocalization

Front 36

Back 36

Omohyoid:

Action: Depresses hyoid after it has been elevated

Front 37

Back 37

Thyrohyoid:

Action: Depresses hyoid

Front 38

Back 38

External Intercostals:

Action: When scalenes fix rib 1, external intercostals elevate and protract ribs 2-12, expanding the thoracic cavity and creating a partial vacuum causing inflow of air

Front 39

Back 39

Internal Intercostals:

Action: In inspiration, the inter cartilaginous part aids in elevating the ribs and expanding the thoracic cavity; in expiration, the interosseous part depresses and retracts the ribs, compressing the thoracic cavity and expelling air

Front 40

Back 40

Diaphragm:

Action: prime mover of inspiration; contraction compresses abdominal viscera and aids in childbirth and expulsion of urine and feces

Front 41

Back 41

Rectus Abdominis:

Action: Flexes trunk, stabilizes pelvic region during walking; and compresses abdominal viscera

Front 42

Back 42

External Abdominal Oblique:

Action: Support viscera; stabilizes vertebral column; maintains posture

Front 43

Back 43

Internal Abdominal Oblique:

Action: Support viscera; stabilizes vertebral column; maintains posture; unilateral contraction causes ipsilateral rotation of waist

Front 44

Back 44

Transverse Abdominis:

Action: Compresses abdominal contents; does not contribute to vertebral column movements

Front 45

Back 45

Linea Alba:

Non-muscular, fibrous structure running between the xiphoid process and pubic symphysis

Insertion site for transverse abdominis

Front 46

Back 46

Iliocostalis:

Action: Lateral flexion of vertebral column; extension of vertebral column; depression of ribs

"Antigravity" muscle

Front 47

Back 47

Longissimus:

Action: Unilateral: lateral flexion of vertebral column and rotation of head

Action: Bilateral: extension of vertebral column and head

Depresses ribs; "Antigravity" muscle

Front 48

Back 48

Spinalis:

Action: Unilateral: Lateral flexion of vertebral column

Action: Bilateral: Extension of vertebral column

"Antigravity" muscle