The muscular system I “Muscles of the 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