Muscular System: Muscles of Head, Neck, and Trunk

1. The muscular system I“Muscles of the head neck and trunk” Dr. NabilKhouri 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. Third class lever: the effort is applied between the fulcrum and the load Figure 10.3c

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

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

17. 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. 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. 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: • http://www.docstoc.com/docs/108855590/Muscles-of-Mastication-Muscles-of-the-Neck-Muscles-of-the-Thoracic Dr. Nabil Khouri MD MsC, PhD

31. Muscles of the Anterior Neck: Supra-hyoid Supra-hyoid

32. Muscles of the Anterior Neck : infra-hyoid 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. Latissimusdorsi