Lesson 8 - Anatomy Lab

Agonists

prime movers, primarily responsible for producing a particular movement

Antagonists

oppose, restrict, or reverse a movement

Synergists

aid the action of agonists

Fixators

Specialized synergists that immobilize the origin of the agonist muscle so all tension is exerted at the insertion

Muscles are named on the basis of:

1. Direction of the muscle fiber

2. relative size of muscle

3. location of muscle

4. number of origins

5. location of muscle origin/insertion

6. Shape of muscle

7. Action of muscle

Convergent

Circular

Multipennate

Fusiform

Bipennate

Unipennate

Parallel

(a)

Circular (Orbicularis oris)

(b)

Convergent (Pectoralis major)

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Parallel (Sartorius)

(d)

Unipennate (Extensor digitorum longus)

(e)

Multipennate (Deltoid)

(f)

Fusiform (Biceps brachii)

(g)

Bipennate (Rectus femoris)

Orbicularis oculi

Orbicularis oris

Masseter

Temporalis

Occipital belly

Frontal belly

Epicranial aponeurosis

Epicranius

Epicranius frontalis (Epicranius frontal belly) function:

Raise eyebrows

o - epicranial aponeurosis

i - skin of eyebrows and root of nose

Epicranius occipitalis (Epicranius occipital belly) function:

Pulls scalp posteriorly

o - occipital and temporal bones

i - epicranial aponeurosis

Orbicularis oculi function:

close eye/pull eyebrow down

Orbicularis oris function:

close/protrude lips

Masseter function:

Close jaw

o - zygomatic arch and maxilla

i - angle and ramus of mandible

Temporalis function:

Close jaw

Platysma function:

open jaw/pull lower lip down

o - over pectoral muscles

i - lower margin of mandible, skin, muscle at mouth corner

Sternocleidomastoid function:

neck flexion/head rotation towards shoulder

o - manubrium of sternum and medial portion of clavicle

i - mastoid process of temporal bone and superior nuchal line of occipital bone

Sternocleidomastoid

Platysma

Masseter

Temporalis

Orbicularis oris

Digastric anterior belly and Digastric posterior belly function:

Open jaw/elevate hyoid bone

o - lower margin of mandible and mastoid process

i - connective tissue loop to hyoid bone

Mylohyoid function:

elevate hyoid bone and base of tongue

Sternohyoid function:

Depress larynx and hyoid bone

Mylohyoid

Hyoid Bone

Sternohyoid

Sternocleidomastoid

Anterior belly

Posterior belly

Digastric

Sternocleidomastoid

Deltoid function:

abduct arm; flex/extend/rotate humerus

Pectoralis major function:

adduct/rotate medially arm; pulls chest upward (inhalation)

o - clavicle, sternum, cartilage of ribs 1-6, and aponeurosis of external obliques

i - short tendons into intertubercular sulcus of humerus

Pectoralis minor function:

move scapula anterior/inferior; raise ribs (inhalation)

Serratus anterior function:

fixes scapula for arm abduction (essential for raising arm); pulls scapula anterior/inferior

Deltoid

Pectoralis major

Pectoralis minor

Serratus anterior

Rectus abdominis function:

flex vertebral column; depress ribs; compress abdomen (exhalation)

o - pubic crest and symphysis

i - xiphoid process and costal cartilage of ribs 5-7

External oblique function:

flex vertebral column; depress ribs; rotate trunk, compress abdomen (exhalation)

Internal oblique function:

Flex vertebral column; depress ribs; rotate trunk; compress abdomen (exhalation)

Transverse abdominis function:

compress abdomen (exhalation)

Rectus abdominis

Transverse abdominis

Internal oblique

External oblique

Trapezius function:

extends head; adduct scapula and lateral clavicle

Latissimus dorsi function:

extend, adduct, and medial rotate arm

Trapezius

Latissimus dorsi

Triceps brachii function:

extend forearm

Biceps brachii function:

flex forearm

o - short head - coracoid process; long head - intertubercular sulcus and within capsule of shoulder joint

i - radial tuberosity

Brachioradialis function:

flex forearm

Brachialis function:

Flex forearm

Deltoid

Pectoralis major

Triceps brachii

Lateral head

Long head

Medial head

Biceps brachii

Brachialis

Brachioradialis

Triceps brachii

Lateral head

Long head

Latissimus dorsi

Pronator teres function:

pronate and weakly flex arm

Flexor carpi radialis function:

flex and abduct hand at wrist

Palmaris longus function:

flex hand at wrist

o - medial epicondyle of humerus

i - palmar aponeurosis, skin and fascia of palm

Flexor carpi ulnaris function:

Flex and adduct hand at wrist

Pronator teres

Flexor carpi radialis

Palmaris longus

Flexor carpi ulnaris

Extensor carpi radialis function:

extend and abduct hand at wrist

Extensor digitorum function:

extends fingers and hand at wrist

o - lateral epicondyle of humerus

i - by tendons into distal phalanges of fingers 2-5

Extensor carpi ulnaris function:

extend and adduct hand at wrist

Extensor carpi ulnaris