lecture 6: skeletal muscles – muscles of the head and neck...
TRANSCRIPT
Lecture 6: Skeletal Muscles – Muscles of the Head and Neck 10/24/2013
Muscle Architecture
Muscles in the same compartments typically have same function (originate from same cell)Sartorius crosses the thigh (due to tailors)Pectoralis major = major is describing the largest muscle of that regionPectoralis minor is underneath pectoralis major and is smallerRectus Femoris = straight muscle of the femoral region Rectus = straight
Muscle FunctionOnly one nerve innervates facial expressions = facial nerve (CRANIAL VII)Muscles of facial expressionMuscles of chewingMuscles of the tongue, eye and throatAnterior and posterior neck muscles
Facial Expressions
Tend not to organize by attachments – some with fascia, sometimes boneOccipitofrontalis muscle:
Two bellies and one central tendonDifferent function depending on which belly is contractedFrontalis(close to frontal bone) – causes you to raise eyebrowsOccipitalis (close to occipital bone) – draws the scalp backwardsOrbicularis OculiGoes around the eyeSoft tissue, eyelid is a big attachment for this muscle,functionally know as the winking muscleZygomatic Major & Minororiginates from zygomatic process and to corners of the mouth and soft tissue around the lipsAllows you to smile “smiling muscle”Orbicularis OrisKissing muscleAround the mouthDraws lips to closed postionDepressor Anguli OrisOrigin: Center of the chin @ mandibular angle and attaches on the corner of the mouthKnown as the “frowning muscle”PlatysmaOriginates from pectoralis major: Reaches superiorly to the mandibleLarge muscles
Called the shaving muscleBuccinatorDoesn’t fit in a compartment – no common functionUnder zygomatic major Look at as a muscle involved in chewingWhistling muscle – draws corner of lips inwardsOne on each side – not usually contracted at the same time – usually contracted in a pattern (one side then other side)Common innervation to all: facial nerve – cranial VII
Facial nerveThere is 2 parotid glands: one on left side one on rightParotid glandSalivary glandSecretes juices into the oral cavity – helps moisten the food as we mechanically break it downSometimes this gland can become infected it swellsThe swelling of this gland puts a lot of pressure on the facial nerveMore often than not it is just one of the glands that is affectedLeaves droopiness on one side of the faceInteracoustic metusNot a true foramen but somewhatLeads into a temporal bone
Specific in that it carries the facial nerve – exits out of the skull through the styloid masto foramen
Temporal: running up towards temporal boneZygomatic: running from zygomatic process to zygomatic boneBuccal: cheekMandibular jawCervical: neck/throat
Permanent damage = won’t be able to perform certain facial movements associated with that nerve
Muscles of Mastication aka chewing
Massetersuperficialoriginates from the zygomatic process on the temporal bone and attaches down to the angle of the mandibleContraction of this muscle closes the jawAgonist is the temporalis muscleIsn’t positioned in the best position to close the jawWe sacrifice some of the position of masseter, but it over compensates with strength that provides maximal power for closing the jaw
Temporalis
Originates off of the temporal boneMoves underneath the zygomatic process Inserts onto the coronoid process of the mandible Has maximal pull on the jaw
BuccinatorLargely responsible for moving our cheeks inwardsMoving the jaw from side to sideAllows us to put food between our molars so we can mechanically break it down (chewing)Impediment in this muscle will strongly affect chewing ability
^ these two are primary movers of the jaw – very strong
* Aside from the buccinators all of the muscles that are involved in chewing innervated by the third branch of the trigeminal nerve
Trigeminal Nerve: 3rd branch = mandibular nerveMandibular nerve – innervates temporalis and masseterhas sensory nerves and picks up sensory info from mandibular region
2nd branch of trigeminal nerve = maxillary nerve
above jaw can be picked up
1st branch of trigeminal nerve =
Insertion: point of attachment that is being pulledOrigin: where its being pulled from
Deeper layers
Pterygoid process (or plate)Both pterygoid medial and lateral both arise from each pterygoid process (medial lateral from each side)
Lateral Pterygoid:Moves laterally from sphenoid temporal mandibular joints and attachesWhen it contracts it pulls the joint forward in effect causes you to bring your jaw forward (protraction)Delicate movements
Medial Pterygoid:Moves downwards towards the angle of the mandible (on the inside of the jaw) Moves jaw to side to side – assist in keeping food between molars
More to do with speech Delicate movements
Innervation of these muscles is via the mandibular nerve
Muscles of the Tongue or Glossus
Not prime movers of the jawUse it in speech x sounds
StyloglossusMoves from the styloid process down to the glossus (attachment is underneath the tongue)Contraction will move tongue towards the styloid processes (brings the tongue backwards or retracts the tongue and ELEVATES the tongue slightly
HyloglossusRuns form the hyoid bone to the underside of the glossusContraction will draw the muscle downwards (draws sides of tongue downwards)
GenioglossusInner side of the mandible (chin region) to the underside of the tongueWhen contracts bring the tongue forwards
PalatoglossusRuns from the soft pallet down to the underside of the tonguePushes the tongue up against the soft palletInnervated by the vagus nerveIs involved in swallowing and speech and less to do with chewingGag reflex! – helps in throwing up food (CONTROLLED BY VAGUS NERVE)A way to elicit the gag reflex is to put pressure on the soft pallet thus eliciting the gag reflex which is controlled by the vagus nerve
BLUE muscles are innervated by the hypoglossus nerve
Extrinsic Muscles of the EyeInnervated by oculomotor nerve (CN III)
Oculomotor muscles = move the eye
Optic NerveExists the skull through the optic foramen (optic canal)Around the optic nerve we have the common tenuous ring
Medial rectusContraction = eye to move towards the nose (adduction)
Lateral Rectus à abducens nerve (CN VI)Movement of eye away from the nose (Abduction)
Superior Rectus:Contraction = elevation of the eye (raising the eye)
Inferior RectusDepression of the eye
*all rolling of the eye
Oblique eye muscles – come at them at an oblique angle and cause twisting
Superior oblique à trochlear nerve (CN IV)First moves through a trochlea (pulling device situated on the medial side, inside the eye orbit) and then abruptly turns to the superior attachment of the eyeContraction = medial rotation of the eye
Inferior Oblique Originates off of bone in the interior eye orbit and inserts itself on the eye inferiorly coming across the eye at an oblique angleContraction = lateral rotation of the eye
Abducens nerve (CN VI)Lateral rectus
Trochlear nerve (CN IV)Superior oblique
Oculomotor nerve (CN III)All others
*These nerves exit through the phisher EXCEPT optic nerve which runs through optic foramen or optic canal
Muscles of the pharynx (aka Throat)
Pharyngeal constrictors Group of muscles Constrict throat/pharynx to push food down into esophagusinnervated by VAGUS nerve (CN X)
Stylopharyngeus innervated by glossopharyngeal nerve!!stretches between styloid process and pharynx
elevates pharynx
PalatopharyngeusEither longitudinal (straight like) or a circle around the pharynx work to push food down into esophagus.Elevates pharynx to help with swallowingVagus nerve is heavily involved in digestion (part of autonomic NS – parasympathetic nervous system – rest and digest)
When you constrict these muscles it opens the entrance into the nasal pharynxWhen you swallow you here a popping sound and are constricting muscles you close the entranceEustachian tube: running from middle ear to nasal pharynx which opens
**Attachments to cartilage, bone and ligaments
Anterior Neck Muscles
Hyoid bone:Attached to thyroid cartilage through band like ligament (thyroid membrane)When you move hyoid you move larynx (voice box)
Sternocleidomastoid
Multiple attachments: Sternum x clavicle to mastoid process Two heads (sternal and clavicular)Superiorly attaches to mastoid processOne on each sideIf you contract both you will have flexion of the neckIf you contract just one your head will move to the opposite side
StylohyoidSlender muscles, lying anterior and superior to the posterior belly of the digastric muscleDraws hyoid bone backwards and elevates the tongue
MylohyoidActually one of the more superficial ones appearance of a millPaired muscle running from mandible to hyoid bone
Digastric muscle (ANTERIOR AND POSTERIOR BELLY):Utilizes a trochlea located on the hyoid (or stirrup)Doesn’t attach to the hyoid!!Means 2 belly’s and in the center is where it attaches (anterior bigger than posterior)First attachment is on inner side of the mandible (anterior belly)
From the inner side of the mandible through the stirrup and its lateral attachment is to the mastoid process (posterior belly)2 bellys for multiple functions increase in the strength of the muscle as a result of the 2 bellys!
Suprahyoid: (mylohyoid, stylohyoid, digastric, geniohyoid) ^1. push larynx up (elevate)2. depress mandible (lowering the jaw)3. most attached to the hyoid (all except digastric)4. OPEN MOUTH
infrahyoid: (thyrohyoid, sternothyroid, sternohyoid, omohyoid)muscles that attach to the hyoidcollectively these work to lower (depress) the larynx and hyoid bone during speaking and swallowing(after its raised its brought back down using these infrahyoid muscles to basal/no swallowing position)
omohyoid:2 bellys separated by trochlea/stirrup that’s attached to the claviclescapula attachment
if we contract both at same time what we get is the origin and the suprahyoid muscles contract and they pull down the jaw (RELAX TEMPORALIS MASSETER AND TERI..)
Supra and infra – participate in opening of the mouthSuprahyoid muscle – attached to the jaw, and lower the jaw
Hyoid doesn’t move, so with contraction of this muscle the jaw has to go down à raising of the larynx
Sternocleidomastoid and lateral musculature
Anterior
• Bordering muscle for anterior and posterior component is the sternocleidomastoid (indicating its attachment on the mastoid process on the temporal bone)
o Borders anterior compartment from posterioro when BOTH(sides) are contracting = flexion of the necko if just one contracts = rotation of the head to the opposite sideo innervated by accessory nerve (cranial nerve 11) and cervical roots
• scalene muscles (group of muscles that..o their superior attachment is the transverse processes of the cervical vertebraeo attach posteriorly to ribs 1 and 2
• cervical rootso root fibers coming off the spinal chord
PosteriorExtension of the head and neckSplenius Capitis = rounded headSplenius Cervicis = attaches to cervical vertebrae (moves behind capitus)Super spinous ligament = keeps spines of vertebrae close together so there is no fish tailingThis thickening of super spinous ligament serves a prominent attachment for muscles of the backInnervation by cervical roots