this lecture covered the bones, muscles, and nerves of the face. the bones related to the face are the maxilla (front teeth), mandible (jaw), frontal bone (forehead), nasal bone (bridge of nose), and zygomas (cheeks). the muscles involved in facial expression: for the eyes, the orbicularis oculi acts as a sphincter around the eye, while the frontalis is above the eye. the orbicularis oris is a sphincter muscle around the mouth, while the zygomaticus, labii, anguli, and platymas act as dilators of the lips.
the face muscles are innervated by the facial nerve, cranial nerve V, which is separated into three divisions: the opthamalic division is the topmost division, from the supraorbital nerve to the forehead and scalp area, contains the supraorbital foramen, and the supratrochlear, infratrochlear, external nasal, and lacrimal nerves. below this is the maxillary division, which runs from the infraorbital nerve to the bottom of the eyes, contains the infraorbital foramen, and the zygomaticofacial and zygomaticotemporal nerves.
the lowest division is the mandibular division, which is the mental nerve and chin area, and contains the mental foramen, as well as the mental nerve, inferior alveolar nerve, and the auriculotemporal nerve, which innervates the lateral scalp, temporomandibular junction (TMJ), and the tympanic membrane of the ear-- this is why injury to the TMJ area can potentially cause hearing loss. these nerves branch out from the mandibular nerve, which branches from the facial nerve, passes through the foramen ovale, into the inferotemporal fossa, and branches into the auriculotemporal and inferior alveolar nerve, which then passes through the mental foramen and becomes the mental nerve.
the facial muscles with respect to their actions on the mandible: the medial and lateral pterygoid both protrude and move the mandible from side to side, but the medial pterygoid elevates while the lateral pterygoid depresses the mandible. the temporalis and masseter both elevate the mandible but the temporalis retracts it as well, while the masseter protrudes it. finally, the digastric muscle runs from the mastoid processes to the digastric fossa and depresses the mandible.
the temporal mandibular joint is the connection between the condylar processes of the mandible and the mandibular fossa and articular tubercle of the temporal bone. in between the two bones are the articular disks, which allows the condylar process to move forward smoothly, allowing the lower mandible to rotate back and open the mouth- this motion is restricted by the temporomandibular ligament. the TMJ "click" is an abrupt movement of the condylar process against the articular tubercle which can be caused by a deformed articular tubercle or an articular plate with low compliance.
the last topic covered was the pterygoid venous plexus, which lies in and around the lateral pterygoid. it pools blood from local structures and the cavernous sinus, which collects blood from the deep facial and opthamalic vein. opening the mouth compresses the lateral pterygoid, which drains blood from the cavernous sinus, allowing for arterial blood to flow upwards-- this is one of the hypotheses for why we open our mouths so wide when we yawn.
questions
bones and muscles...
1. what are the bones of the face?
2. where are the "mental foramen"?
3. what are the muscles around the eyes?
4. what is the sphincter muscle around the mouth called?
5. what are the dilator muscles of the face?
6. what are the five layers to the scalp?
7. what is the nerve that innervates the facial muscles? describe its path.
8. what is bell's palsy?
innervation...
9. what is the trigeminal nerve and what are its divisions?
10. what are the boundaries of the opthamalic division and what are some nerves contained in it?
11. what are the boundaries of the maxillary division and what are some nerves contained in it?
12. what are the boundaries of the mandibular division and what are some nerves contained in it?
13. what are the foramen contained in each division of the trigeminal nerve?
14. how can damage to the TMJ cause hearing loss?
15. what are the nerves that innervate the back of the head? where do the nerves exit?
facial muscles: origins, insertions, innervations, actions:
16. temporalis...
17. masseter...
18. medial pterygoid...
19. lateral pterygoid...
20. digastric...
temporal mandibular joint...
21. describe the point of articulation for the TMJ.
22. what is the function of the articular disc in the TMJ?
23. which ligament of the TMJ restricts posterior motion of mandible?
24. what are the muscles that rotate the mandible around the TMJ axis?
25. describe what occurs in dislocation of the TMJ.
26. what does the "click" come from in the TMJ?
mandibular nerve...
27. describe the location and path of the mandibular nerve.
28. what nerves branch off of the mandibular nerve and what do they innervate?
pterygoid venous plexus...
29. what is the pterygoid venous plexus?
30. cavernous sinus connects with...
31. describe the potential for infection of the cavernous sinus.
32. what is a possible role of the pterygoid venous plexus in yawning?
33. what are the three actions that propel venous blood to the heart upon waking?
answers
1. frontal bones, zygomas, nasal, maxilla, mandible
2. in the body of the mandible.
3. frontalis, orbicularis oculi
4. orbicularis oris
5. the zygomaticus, labii, anguli, and platysma
6. SCALP: Skin, Connective tissue (dense), Aponeurosis, Loose connective tissue, Periosteum
7. cranial nerve VII, exits stylomastoid foramen, goes through the parotid duct.
8. a lesion of the facial nerve which leads to paralysis or weakness of facial muscles on one side of face.
9. cranial nerve 5, the nerve that receives sensory input from the face and scalp; has opthamalic, maxillary, mandibular divisions.
10. from the supraorbital nerve to the forehead and scalp. nerves are supra and infratrochlear, lacrimal, external nasal nerves
11. from the infraorbital nerve to the bottom of the eyes, zygomaticofacial and zygomaticotemporal nerves.
12. from the mental nerve to the chin area, contains auriculotemporal nerve.
13. opthamalic: supraorbital foramen, maxillary: infraorbital foramen, mandibular: mental foramen.
14. by damage to the auriculotemporal nerve, which innervates the tympanic membrane in the ear.
15. the greater and lesser occipital nerves, exit at the C2 level.
16. O: temporal fossa, I: coronoid processes, N: mandibular division of trigeminal nerve, A: elevate, retract mandible
17. O: zygomatic arch, I: ramus, angle, coronoid process of mandible, N: V3, A: elevate, protrude mandible
18. O: maxilla, lateral pterygoid plates, I: medial surface of angle of mandible, N: V3, A: elevate, protrude, side to side motion of mandible
19. O: pterygoid process, I: condylar process, articular disc of TMJ, N: V3, A: protrude, depress, side to side motion of mandible
20. O: mastoid process, I: digastric fossa, N: facial nerve (posterior belly), mylohyoid branch of V3 (anterior belly), A: depress mandible
21. the TMJ is a joint between the condylar processes of the mandible and the mandibular fossa / articular tubercle of the temporal bone.
22. allows for the upper portion of condylar processes to move anteriorly, and lower portion to rotate
23. temporomandibular ligament.
24. lateral pterygoid and digastric
25. excess anterior movement of mandible places condylar process anterior to articular tubercle.
26. a distorted articular tubercle or an articular disk with less compliance, which can cause abrupt movement of condylar process.
27. comes from facial nerve mandibular division, through foramen ovale, into inferotemporal fossa, innervates masticating muscles.
28. the auriculotemporal nerve, which innervates the lateral scalp, TMJ, and tympanic membrane. the inferior alveolar nerve, which innervates the lower teeth and goes through the mental foramen and turns into the mental nerve.
29. valveless veins near and around the lateral pterygoids which drains blood from cavernous sinus and other local structures.
30. deep facial and opthamalic veins.
31. infection of the nose or cheek area (via an infected pimple, for example) can carry from the opthamalic vein or deep facial vein into the cavernous sinus, which might carry into the brain, causing serious illnesses such as meningitis or even death.
32. compression of the pterygoid venous plexus by contraction of the lateral pterygoid will drain the blood from the cavernous sinus and allow for arterial blood flow, which will increase O2 flow to the brain.
33. the yawning action described above, extending limbs engages the extensor muscles which propel venous blood back to the heart, and taking a deep breath pushes down on the abdominal area, which pushes venous blood up into the thorax.
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