Introduction to the Muscular System.docx

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Anatomy and Cell Biology
Anatomy and Cell Biology 3319
Kem Rogers

Introduction to the Muscular System: Muscles of the Head Arrangement of Fascicles • Skeletal muscles consist of fascicles (bundles of fibres) which are large enough to be seen with naked eye • Alignment is different in different muscles • Arragement influences amount of movement produced when muscle shortens (range of motion) & amount of force the muscle produces (power) • Skeletal muscles can shorten by up to 1/3 of their resting length • More nearly parallel fibres are to long axis of muscle - more muscle can shorten – larger movement distance o Parallel muscles - usually not that powerful • Power of muscle depends on # of fibres o Bipennate & multipennate muscles contain the most fibres but shorten very little Circular • Concentric ring arrangement • Surround external body openings • Close openings by contracting • General name: sphincter (squeezer) • Ex. orbicularis oris muscle around mouth & orbicularis oculi around eyes Convergent • Origin is broad • Fascicles converge toward the tendon of insertion • Triangle or fan-shaped • Muscle fibres extend the length of muscle – from origin to insertion • Ex. pectoralis major muscle in anterior thorax Parallel • Long axes of fascicles run parallel to long axis of muscle • Muscle fibres extend from origin to insertion • Muscles are either fusiform, with expanded central belly (Ex. biceps brachii of arm) or strap-like (Ex. satorius muscle of lower limb) Pennate • Fascicles are short & attach obliquely to a tendon hat runs the whole length of muscle • Pattern makes muscle look like a feather • Multipennate o Looks like many feathers side by side, with all their quills inserting into one large tendon o Ex. deltoid muscle (forms roundness of shoulder) • Bipennate o Fascicles insert into tendon from both sides o Ex. rectus femoris muscle of thigh • Unipennate o Fascicles insert into only one side of the tendon o Ex. Extensor digitorum longus muscle on anterior leg Muscle Attachments • Prime mover o Major action (agonist) • Antagonist o Muscle which opposes action • Synergist o Muscle that assists prime mover Muscles of Facial Expression Occipitofrontalis (Epicranius) 1. Occipitalis 2. Frontalis Eye 3. Obicularis Oculi a. Palprebal b. Orbital 4. Corrugator Supercilii Face 5. Levator Labi Superioris 6. Zygomaticus a. Major b. Minor 7. Risorius 8. Orbicularis Oris 9. Depressor Labii Inferioris 10. Depressor Angui Oris 11. Mentalis 12. Buccinator Neck 13. Platysma Bell’s Palsy • Facial nerve is most commonly damaged cranial nerve • Bell’s palsy is the most common cause of acute facial paralysis • Usually only involves one side • Condition can be transient with no known cause • Patients usually fully recover Muscles of Mastication Muscle Description Origin (O) & Insertion (I) Action Nerve Supply Muscles of the Scalp Occipitalis/Occipital Overlies posterior O – occipital and temporal Fixes aponeurosis Facial nerve Belly occiput; by pulling (mastoid) bones and pulls scalp galea (tendon) I – epicranial aponeurosis posteriorly Fixes origin of frontalis Frontalis/Frontal Covers forehead & O – epicranial aponeurosis With aponeurosis Facial nerve Belly dome of skull I – skin of eyebrows & root fixed, elevates No body attachments of nose eyebrows (surprise) Wrinkles forehead skin horizontally Muscles of the Eye Corrugator Small muscle to O – arch of frontal bone Draws eyebrows Facial nerve Supercilli eyebrow above nasal bone medially & inferiorly Acts with orbicularis I – skin of eyebrow Wrinkles skin of oculi forehead vertically Orbicularis Oculi Thin, flat sphincter O – frontal & maxillary bones Closes eye Facial nerve muscle of eyelid & ligaments around orbit Produces: blinking, Surrounds rim of orbit I – tissue of eyelid squinting & draws eyebrows inferiorly Muscles of the Face Zygomaticus Muscle pair O – zygomatic bone Raises lateral Facial nerve extending diagonally I – skin & muscle at corner corners of mouth from cheekbone to of mouth (smiling muscle) corner of mouth Risorius Slender muscle O – lateral fascia associated Draws corner of lip Facial nerve inferior to lateral to with masseter muscle laterally (tenses lip) zygomaticus I – skin at angle of mouth Synergist of zygomaticus Orbicularis Oris Multilayered muscle O – arises indirectly from Closes lips Facial nerve of lips with fibers that maxilla & mandible – fibres Purses & protrudes run in many different blended with fibres of other lips directions; most run facial muscles associated Kissing & whistling circularly with lips muscle I – encircles mouth, inserts into muscle & skin at angles of mouth Levator Labi Thin muscle between O – zygomatic bone and Opens lips Facial nerve Superioris orbicularis oris & infraorbital margin of maxilla Elevates & furrows inferior eye ma
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