1. 8.7 Skeletal Muscle Action

2. Skeletal Muscle Actions
Skeletal muscles provide a variety of body movements
The movements largely depend on the origin and insertion of the muscle

3. Skeletal Muscle Actions
The origin in the muscle attachment at the immovable end
For the biceps brachii, this is two places on the scapula

4. Skeletal Muscle Actions
The insertion is the movable end, it is pulled towards the origin
The insertion on the biceps brachii is on the radius

5. Skeletal Muscle Actions
Skeletal muscles almost always function in groups.
For a body movement to occur, more than one muscle must contract.

6. Skeletal Muscle Actions
The main muscle that is responsible for a movement is called the prime mover (agonist)
Muscles that contract to assist the prime mover are called synergists

7. Skeletal Muscle Actions
Some muscles can resist the prime mover, these are called antagonists
If both a prime mover and antagonist contract, then the part they act on is rigid

8. Skeletal Muscle Actions
For a motion to happen, the prime mover contracts and the antagonists relaxes

9. Muscles of Facial expression

10. Muscles of Facial Expression
Facial muscles
Enable us to communicate feelings through facial expression

11. Muscles of Facial Expression
Epicranius
Frontalis
Epicranial aponeurosis
Occipitalis

12. Muscles of Facial Expression
Epicranius
Origin – occipital bone
Insertion – skin and muscle around superior portion of eyes
Action: raises eyebrows

13. Muscles of Facial Expression
Orbicularis oculi
Muscle around the eye
Origin: maxillary/frontal bones
Insertion: skin around the eye
Action: closes eye

14. Muscles of Facial Expression
Orbicularis oris
The kissing muscle
Origin: muscles near the mouth
Insertion: skin of lips
Action: closes and protrudes lips

15. Muscles of Facial Expression
Buccinator
Cheek muscle
Means “trumpet”
Origin: outer surface of maxilla/mandible
Insertion: orbicularis oris
Action: compresses cheeks inward
Helps you keep food between teeth

16. Muscles of Facial Expression
Zygomaticus
“smiling” muscle
Origin: zygomatic arch
Insertion: orbicularis oris
Action: raises corner of mouth

17. Muscles of mastication (chewing)

18. Muscles of mastication
Masseter
Origin: Lower part of zygomatic arch
Insertion: Lateral surface of the mandible
Action:
elevates mandible

19. Muscles of mastication
Temporalis
Origin: temporal bone
Insertion: Lateral surface of mandible
Action: Elevates mandible

20. Muscles of Mastication movements