Chapter 11 The Muscular System

1. Chapter 11The Muscular System • Skeletal muscle major groupings • How movements occur at specific joints • Learn the origin, insertion, function and innervation of all major muscles • Important to allied health care and physical rehabilitation students

2. Muscle Attachment Sites:Origin and Insertion • Skeletal muscles shorten & pull on the bones they are attached to • Origin is the bone that does not move when muscle shortens (normally proximal) • Insertion is the movable bone (some 2 joint muscles) • Fleshy portion of the muscle in between attachment sites = belly

3. Fascicle Arrangements • A contracting muscle shortens to about 70% of its length • Fascicular arrangement represents a compromise between force of contraction (power) and range of motion • muscles with longer fibers have a greater range of motion • a short fiber can contract as forcefully as a long one.

4. Coordination Within Muscle Groups • Most movement is the result of several muscle working at the same time • Most muscles are arranged in opposing pairs at joints • prime mover or agonist contracts to cause the desired action • antagonist stretches and yields to prime mover • synergists contract to stabilize nearby joints • fixators stabilize the origin of the prime mover • scapula held steady so deltoid can raise arm

5. How Skeletal Muscle are Named • Direction the muscle fibers run • Size, shape, action, number of origins or locations • Examples triceps brachii -- 3 sites of origin • quadratus femoris -- square shape • serratus anterior -- saw-toothed edge

6. Muscles of Facial Expression • Arise from skull & insert onto skin • Encircle eyes, nose & mouth • Express emotions • Facial Nerve (VII) • Bell’s palsy = facial paralysis due

7. Muscles of Facial Expression

9. Muscles of facial expression • lie within layers of superficial fascia • originate in the fascia or bones of the skull • insert into the skin • move the skin rather than a joint • several act as sphincters • orbicularis oris – closes the eye • levator palpebrae superioris – opens the eye

10. -sometimes called the occipitofrontalis -dual belly -innervation by VII -two bellies held together by the epicranial aponeurosis Scalp Muscles

11. Mouth muscles • Orbicularis oris • zygomaticus major & minor • levator labii superioris • depressor labii superioris • depressor anguli oris • levator anguli oris • buccinator • risorius • mentalis

12. -ZMj: smiling (angle of mouth superiorly and laterally) -ZMr: “snarl” (raises upper lip to expose maxillary teeth)

13. -risorius: grimace (draws angle laterally)

14. -DAO: opens the mouth -DLI: depresses lower lip -LLS: raises upper lip -LAO: angle of mouth superiorly & laterally

15. -pouting muscle

16. -buccinator forms the major muscular portion of the cheek -duct of the parotid passes through to reach the oral cavity -compresses the cheeks during blowing

17. Orbit and Eyebrow Muscles -orbicularis oculi – closes eye -corrugator superioris – frowing -levator palpebrae superioris – opens eye

18. Extrinsic Muscles of the Eyeballs • Extrinsic muscles insert onto white of eye • Fastest contracting & most precisely controlled • Cranial nerves 3, 4 & 6 innervate the six muscles • 4 Rectus muscles & 2 obliques • Intrinsic muscles are found within the eyeball • strabismus – eyes are unaligned -lazy eye – brain ignores the message sent by one eye and the ignored eye becomes weaker = “amblyopia” -origin of the rectus muscles = common tendinous ring (attached to orbit around the optic foramen) -insert onto the sclera (white) -origin of superior rectus: sphenoid -origin of inferior rectus: maxilla (floor of orbit)

19. Muscles that Move the Mandible • Masseter, temporalis & pterygoids • Arise from skull & insert on mandible • form part of the TMJ structure • Cranial nerve V (trigeminal nerve) • Protracts, elevates or retracts mandible • Temporalis & Masseter elevate the mandible (biting) • temporalis retracts

20. -masseter elevates mandible -mandibular division of V -temporalis elevates and retracts mandible -mandibular division of V

21. Jaw Muscles -- Deep Dissection • Lateral pterygoid protracts mandible • sphenoid bone to condyle of mandible • Medial pterygoid elevates & protracts mandible • sphenoid bone to angle of mandible • Together move jaw side to side to grind food.

23. Muscles that Move the Tongue • 4 extrinsic muscles ariseelsewhere, but insertinto tongue • Genioglossus • from inside tip of mandible • Styloglossus • from styloid process • Palatoglossus • from hard palate • Hyoglossus • from hyoid bone • Together move tongue in various directions • Intubation is necessary during anesthesia since Genioglossus relaxes & tongue falls posteriorly blocking airway

25. Muscles of the Floor of the Oral Cavity • Suprahyoid muscles lie superior to hyoid bone. • Digastric m. extends from mandible to mastoid process • used to open the mouth • Mylohyoid m. extends from hyoid to mandible • supports floor of mouth & elevates hyoid bone during swallowing • Stylohyoid & Geniohyoid elevate the hyoid during swallowing

26. innervated by V and VII – diagastric innervated by V – mylohyoid innervated by VII – stylohyoid innervated by C1 - geniohyoid

27. innervated by branched of C1-C3

29. Neck muscles • platysma: draws outer part of lower lip inferiorly and pulls skin of chin up as in pouting

30. Muscles that Move the Head • Sternocleidomastoid muscle • arises from sternum & clavicle & inserts onto mastoid process of skull • innervated by cranial nerve XI (spinal accessory) • contraction of both flexes the cervical vertebrae & extends head • contraction of one, laterally flexes the neck and rotates face in opposite direction

31. -SCM divides the neck into two triangles 1. anterior triangle: bordered by mandible, sternum, cervical midline & anterior border of SCM -contains the submandibular gland, part of the parotid, the facial artery and vein, common carotids, internal jugular and nerves IX, X, XI and XII -contains three paired sub-triangles + unpaired submental a. submandibular b. carotid c. muscular 2. posterior triangle: bordered by clavicle, SCM and anteriorly by the trapezius -subdivided into: a. occipital b. supraclavicular -contains part of external jugular, subclavian artery, brachial plexus and nerve XI

32. Muscles that Move the Vertebrae • Quite complex due to overlap • Erector spinae fibers run longitudinally • 3 groupings • spinalis • iliocostalis • longissimus • extend vertebral column • Smaller, deeper muscles • transversospinalis group • semispinalis, multifidis & rotatores • run from transverse process to dorsal spine of vertebrae above & help rotate vertebrae

33. Scalene Muscle Group • Attach cervical vertebrae to uppermost ribs • Flex, laterally flex & rotate the head