1. The Muscular System Part B08
The Muscular System
Part B

2. Interactions of Skeletal Muscles
Skeletal muscles work together or in opposition
Muscles only pull (never push)
As muscles shorten, the insertion generally moves toward the origin
Whatever a muscle (or group of muscles) does, another muscle (or group) “undoes”

3. Muscle Classification: Functional Groups
Prime movers – provide the major force for producing a specific movement
Antagonists – oppose or reverse a particular movement
Synergists
Add force to a movement
Reduce undesirable or unnecessary movement
Fixators – synergists that immobilize a bone or muscle’s origin

4. Naming Skeletal Muscles
Location of muscle – bone or body region associated with the muscle
Shape of muscle – e.g., the deltoid muscle (deltoid = triangle)
Relative size – e.g., maximus (largest), minimus (smallest), longus (long)
Direction of fibers – e.g., rectus (fibers run straight), transversus, and oblique (fibers run at angles to an imaginary defined axis)

5. Naming Skeletal Muscles
Number of origins – e.g., biceps (two origins) and triceps (three origins)
Location of attachments – named according to point of origin or insertion
Action – e.g., flexor or extensor, as in the names of muscles that flex or extend, respectively

6. Arrangement of Fascicles
Parallel – fascicles run parallel to the long axis of the muscle (e.g., sartorius)
Fusiform – spindle-shaped muscles (e.g., biceps brachii)
Pennate – short fascicles that attach obliquely to a central tendon running the length of the muscle (e.g., rectus femoris)
Convergent – fascicles converge from a broad origin to a single tendon insertion (e.g., pectoralis major)
Circular – fascicles are arranged in concentric rings (e.g., orbicularis oris)

7. Arrangement of Fascicles
Figure 10.1

8. Bone-Muscle Relationships: Lever Systems
Lever – a rigid bar that moves on a fulcrum, or fixed point
Effort – force applied to a lever
Load – resistance moved by the effort

9. Bone-Muscle Relationships: Lever Systems
Figure 10.2a

10. Bone-Muscle Relationships: Lever Systems
Figure 10.2b

11. Lever Systems: Classes
First class – the fulcrum is between the load and the effort
Second class – the load is between the fulcrum and the effort
Third class – the effort is applied between the fulcrum and the load

12. Lever Systems: First Class
Figure 10.3a

13. Lever Systems: Second Class
Figure 10.3b

14. Lever Systems: Third Class
Figure 10.3c

15. Major Skeletal Muscles: Anterior View
The 40 superficial muscles here are divided into 10 regional areas of the body
Figure 10.4b

16. Major Skeletal Muscles: Posterior View
The 27 superficial muscles here are divided into seven regional areas of the body
Figure 10.5b

17. Muscles: Name, Action, and Innervation
Name and description of the muscle – be alert to information given in the name
Origin and insertion – there is always a joint between the origin and insertion
Action – best learned by acting out a muscle’s movement on one’s own body
Nerve supply – name of major nerve that innervates the muscle

18. Epicranius (occipitofrontalis) – bipartite muscle consisting of the:
Muscles of the Scalp
Epicranius (occipitofrontalis) – bipartite muscle consisting of the:
Frontalis
Occipitalis
Galea aponeurotica – cranial aponeurosis connecting above muscles
These two muscles have alternate actions of pulling the scalp forward and backward

19. Origin: Insertion: Primary Action(s): Frontalis cranial aponeurosis
skin of eyebrows
Primary Action(s):
Raises eyebrows

20. Origin: Occipital bone Insertion: galea aponeurosis Primary Action(s):
wrinkles brow
Occipitalis

21. All are innervated by cranial nerve VII (facial nerve)
Muscles of the Face
11 muscles are involved in lifting the eyebrows, flaring the nostrils, opening and closing the eyes and mouth, and smiling
All are innervated by cranial nerve VII (facial nerve)
Usually insert in skin (rather than bone), and adjacent muscles often fuse

22. Origin: Insertion: Primary Action(s): Orbicularis Oculi
Frontal bone and maxilla
Insertion:
Tissue around eyes
Primary Action(s):
Blinks and closes eyes

23. Origin: Insertion: Primary Action(s): Orbicularis Oris
Mandible and maxilla
Insertion:
Skin and muscle around mouth
Primary Action(s):
Closes and protrudes lips

24. Origin: Insertion: Primary Action(s): Zygomaticus Zygomatic bone
Skin and muscle at corner of lips
Primary Action(s):
Raises corner of mouth

25. Origin: Insertion: Primary Action(s): Platysma
Connective tissue covering of superior chest muscles
Insertion:
Tissue around mouth
Primary Action(s):
Pulls corners of mouth inferiorly

26. Muscles of the Face
Figure 10.6

27. Muscles of Mastication
There are four pairs of muscles involved in mastication
Prime movers – temporalis and masseter
Grinding movements – pterygoids and buccinators
All are innervated by cranial nerve V (trigeminal nerve)

28. Muscles of Mastication
Figure 10.7a

29. Origin: Insertion: Primary Action(s): Temporalis Temporal bone
Mandible
Primary Action(s):
Closes jaw

30. Origin: Insertion: Primary Action(s): Masseter
zygomatic arch and maxilla
Insertion:
Mandible
Primary Action(s):
Closes jaw
Protraction

31. Origin: Insertion: Primary Action(s): Buccinator
Maxilla and mandible near molars
Insertion:
Orbicularis oris
Primary Action(s):
Compresses cheeks
Whistling
Holds food between teeth during chewing

32. Muscles of Mastication
Figure 10.7b

33. Origin: Insertion: Mandible Primary Action(s): Depresses mandible
sphenoid
Insertion:
Mandible
Primary Action(s):
Depresses mandible
Protrude mandible
Pterygoid

34. Extrinsic Tongue Muscles
Three major muscles that anchor and move the tongue
All are innervated by cranial nerve XII (hypoglossal nerve)

35. Extrinsic Tongue Muscles
Figure 10.7c

36. Protrude, depress, draw back and down
Origin:
mandible
Insertion:
tongue
Primary Action(s):
Protrude, depress, draw back and down
Genioglossus

37. Retracts & elevates tongue
Origin:
Temporal bone
Insertion:
Tip and side of tongue
Primary Action(s):
Retracts & elevates tongue
Styloglossus

38. Depresses & retracts tongue
Origin:
hyoid
Insertion:
Side of tongue
Primary Action(s):
Depresses & retracts tongue
Hyoglossus

39. Muscles of the Neck: Head Movements
Major head flexor is the sternocleidomastoid
Synergists to head flexion are the suprahyoid and infrahyoid
Lateral head movements are accomplished by the sternocleidomastoid and scalene muscles
Head extension is accomplished by the deep splenius muscles and aided by the superficial trapezius

40. Muscles of the Neck: Head Movements
Figure 10.9a

41. Muscles of the Neck: Head Movements
Figure 10.9b

42. Origin: Insertion: Primary Action(s): Sternocleidomastoid
Sternum and clavicle
Insertion:
Temporal bone
Primary Action(s):
Flexes neck; rotates neck

43. Consists of four muscles
digastric, stylohyoid, geniohyoid, and mylohyoid
Primary Action(s):
Elevates hyoid and widens esophagus during swallowing
Suprahyoid

44. Group of four pairs of muscles in the anterior part of the neck
Primary Action(s):
depress the hyoid bone and larynx during swallowing and speaking.
Infrahyoid

45. Scalenes (anterior, posterior, medius)
Origin:
C2-C7
Insertion:
1st & 2nd ribs
Primary Action(s):
Lateral head movement
Scalenes (anterior, posterior, medius)

46. temporal and occipital bone Primary Action(s):
Origin:
C7-T6
Insertion:
temporal and occipital bone
Primary Action(s):
Extend, rotate, and laterally flex the head
Splenius capitus

47. Rotation, retraction, elevation, and depression of scapula
Primary Action(s):
Head extension
Rotation, retraction, elevation, and depression of scapula
Trapezius