1. The muscular system I “Muscles of the head neck and trunk”
Dr. Nabil Khouri
Dr. Nabil Khouri MD MSc, PhD

2. Interactions of Skeletal Muscles
Skeletal muscles work together or in opposition
Muscles only pull (never push)
All muscles have an Origin and Insertion
Origin of a muscle is close to body center
Insertion is far from body center.
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)

7. Arrangement of Fascicles
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)

8. Arrangement of Fascicles
Circular – fascicles are arranged in concentric rings
(e.g., orbicularis oris)

9. Bone-Muscle Relationships: The 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

10. Lever Systems: Classes

11. First class – the fulcrum is between the load and the effort

12. Lever Systems: Second class lever
Figure 10.3b

13. Third class lever

14. the effort is applied between the fulcrum and the load
Third class lever:
the effort is applied between the fulcrum and the load
Figure 10.3c

15. Axial Muscles Appendicular muscles Muscles of the head and Neck
Thoracic wall
Abdominal wall
Diaphragm
Muscles of the trunk:
Back
Appendicular muscles
Muscles of the upper limb
Muscles of the lower limb

16. Muscles of the head and neck Dr. Nabil Khouri MD MSc, PhD

17. Dr. Nabil Khouri MD MsC, PhD
Muscles of the Scalp
Occipito-frontalis
Epicranius (occipitofrontalis) – this muscle consists of two:
The Frontalis
The Occipitalis
Galea aponeurotica – cranial aponeurosis connecting the two muscles
These two muscles have alternate actions of pulling the scalp forward and backward
Dr. Nabil Khouri MD MsC, PhD

19. Dr. Nabil Khouri MD MsC, PhD
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
Dr. Nabil Khouri MD MsC, PhD

20. Muscles of facial expression:
Change shape of eyes and mouth
Innervated by the 7th cranial nerve (facial nerve)
Bell,s palsy
Examples: Orbicularis oris muscle
Orbicularis oculi muscle
Frontalis muscle
Zygomatic muscle
Buccinator muscle

22. Dr. Nabil Khouri MD MsC, PhD

23. Muscles of mastication:
Move the mandible (insertion): open and close (chewing)
Innervation by the 5th cranial nerve (trigeminal nerve)
Masseter muscle: closes
Temporalis muscle: closes
Lateral Pterygoid muscle: opens

24. Muscles of Mastication

25. Muscles Of mastication

27. Platysma muscle Origin : from deep fascia of pect. Major M Insertion
lower mandible margin
Muscles of mouth angle
Anterior fibers cross to the opposite side

28. Muscles of the neck Sternocleidomastoid muscle Suprahyoid muscles
Infrahyoid muscles
Scalene muscles

29. Dr. Nabil Khouri MD MSc, PhD
Muscles of the Neck
Dr. Nabil Khouri MD MSc, PhD

30. Muscles of the Anterior Neck : Supra-hyoid
These deep throat muscles form the floor of the oral cavity, anchor the tongue, elevate the hyoid, and move the larynx superiorly during swallowing
For full discribtion regarding the origin and insetion and action of this groups of muscle:
Muscles-of-the-Neck-Muscles-of-the-Thoracic
Dr. Nabil Khouri MD MsC, PhD

31. Muscles of the Anterior Neck: Supra-hyoid

32. Muscles of the Anterior Neck : infra-hyoid
Dr. Nabil Khouri MD MSc, PhD

33. Muscles of the Neck: Head Movements
Major head flexor is the sternocleidomastoid muscle
Synergists to head flexion are the suprahyoid and infrahyoid
Lateral head movements are accomplished by the sternocleidomastoid and the scalene muscles
Head extension is accomplished by the deep splenius muscles and aided by the superficial trapezius
Dr. Nabil Khouri MD MsC, PhD

35. Muscles of the Neck: Head Movements
Dr. Nabil Khouri MD MsC, PhD

36. Muscles of the Trunk Thoracic wall Muscles: Intercostal muscles
Diaphragm
Abdominal wall muscles

37. Muscles of the Thorax: Respiratory muscles
Internal intercostals – deeper layer that aids in forced expiration
The primary function of deep thoracic muscles is to promote movement for breathing
External intercostals – more superficial layer that lifts the rib cage and increases thoracic volume to allow inspiration

39. Muscles of the Thorax: Resp. Muscles
Diaphragm – most important muscle in inspiration

41. Muscles of the Abdominal Wall

42. Muscles of the Abdominal Wall

45. Muscles of the back

46. Stabilization of the Scapulae
Elevators
Trapezius (upper)
Levator scapulae
Rotators
Rhomboid minor
Rhomboid major
Serratus anterior
Depressors
Trapezius (lower)
Pectoralis minor
(next slide)

48. Latissimus dorsi

52. Teres major

53. Trunk Movements: Deep Back Muscles
The prime mover of back extension is the erector spinae
Erector spinae, or sacrospinalis, muscles consist of three columns on each side of the vertebrae – iliocostalis, longissimus, and spinalis
Lateral bending of the back is accomplished by unilateral contraction of these muscles
Other deep back extensors include the semispinalis muscles and the quadratus lumborum

54. Trunk Movements: Deep Back Muscles