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In fetal and infant skulls, what separates the bones of the calvaria?
dense connectiv tissue membranes at fibrous joints called sutures
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What are fontanelles?
large fibrous area where several sutures meet
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The softness of the bones and the looseness of their connections at these sutures enable the calvaria to do what?
undergo changes of shape during birth called molding
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When does the shape of the infant's calvaria return to normal?
within a day or so after birth
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What allows the newborn's skullto enlarge and undergo remodeling during infancy and childhood?
loose construction of calvaria
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When is the increase in the size of the cranium the greatest?
during first 2 years of life (the period of most rapid postnatal growth of the brain
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The cranium normally increases in capacity until what age?
15 or 16
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After age 15/16 what happens to the size of the cranium?
usually increases only slightly in size as its bones thicken for 3-4 years
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What makes the widest parts of the face?
zygomatic arches
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Because the zygomatic arches are the widest parts of the face and are such prominent facial features, they are commonly:
fractured and depressed
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A fracture of the temporal process of the zygomatic bone would likely involve what other structure?
the lateral wall of the orbit and could injure the eye
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Why are studies of the sella turcica and hypophyseal fossa in radiographs or other imaging techniques important?
may reflect pathological changes such as pituitary tumor or aneurysm of internal carotid artery
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Decalcification of the dorsum sellae is one of the signs of a generalized increase in what?
intracranial prssure
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What is the importance of the mobility of the anteriorinferior portion of the nose (supported only by cartilages)?
partial protection against injury (punch in nose)
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What could fracture the nasal bones (broken nose)?
hard blow to anterosuperior bony portion of the nose
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Which direction are bones often displaced?
sideways and/or posteriorly
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In places where the bone is very thin what function does the overlyin muscles perform?
affords some assistance in cushioning blows
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What causes fractures of the skull?
external violence
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What are the most frequent types of skull fractures?
linear skull fractures
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Where does the fracture usually occur?
at point of impact, but fracture lines may radiate away from it in two or more directions
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What determines the directions of the radiating fracture lines?
the thick and thin areas of the skull
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contrecoup fracture ("counterblow")
no fracture at point of impact, but one occurs at the opposite side of the skull
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Why do facial lacerations tend to gape?
because face has no distinct deep fascia and the superficial fascia between the cutaneous attachments of the facial muscle is loose
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Why must the skin of facial lacerations be sutured with great care?
to prevent scarring
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What enabels fluid and blood to accumulate in the loose connective tissue following bruising of the face ("black eye")?
looseness of superficial fascia
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What allows facial inflammation to cause considerable swelling?
looseness of superficial fascia
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Injury to facial nerve or some of its branches produces what?
paresis (weakness) or paralysis o all or some of the facial muscles on the affected side
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Bell's Palsy
paralysis of facial nerve for no obvious reason
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Causes of Bell's palsy:
- exposure to cold draft
- inflammation of facial nerve near stylomastoid foramen
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What does inflammation of facial nerve near stylomastoid foramen cause?
edema and swelling of facial nerve and compression of its fibers in the facial canal or stylomastoid foramen
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What are symptoms of facial paralysis?
- unable to close lips and eyelids on affected side
- eye on affected side is not lubricated
- unable to whistle, blow a wind instrument, or chew effectively
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Why does food and saliva dribble out or collect in te oral vestibule on side affected by facial nerve palsy?
because buccinator muscle is weakened or paralyzed
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What nerve is used for local anesthesia of the inferior part of the face?
infraorbital nerve
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Where is the infraorbital nerve infiltrated with anesthetic agent for anesthesia of the inferior part of the face?
infraorbital foramen or in infraorbital canal
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How can the site of emergence of the infrorbital nerve be determined?
- by exerting pressure on the maxilla in the region of infraorbital foramen and nerve
- pressure on nerve causes considerable pain
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Why is care exercised when performing an infraorbital nerve block?
because companion infraorbitalvessels leave the infraorbital foramen with the nerve
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What prevents inadvertent injection of anesthetic fluid into a blood vessel?
careful aspiration of the syringe during injection
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A careless injection of anesthesia into the infraorbital nerve could result in the passage of anesthetic fluid into the orbit, causing:
temporary paralysis of extraocular muscles that move the eyeball
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Which nerve do dentists anesthetize before repairing or removing mandibular teeth?
inferior alveolar nerve
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Why does a person's chin and lower lip on the affected side of inferior alveolar nerve block also lose sensation?
because mental and incisive nerves are the inferior alveolar nerve's terminal branches
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How can the mental nerve be blocked?
by injecing anesthetic fluid around the nerve as it emerges from themental foramen
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What is another name for trigeminal neuralgia?
tic douloureux
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What is trigeminal neuralgia?
condition characterized by sudden attacks of excruciated pain initiated by mere touch in area of distribution of one of the divisions of the trigeminal nerve
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Which branch of the trigeminal nerve is usually involved in trigeminalneuralgia?
CN V2
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What is the cause of trigeminal neuralgia?
unknown
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In some cases of trigeminal neralgia, the symptoms are removed if what happens?
a small aberrant artery is moved away from the sensory root of CN V
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Which nerve is commonly injured in fractures of the maxilla?
infaorbital nerve
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Why is the infraorbital nerve commonly injured in fractures of the maxilla?
because such fractures often pass through or cose to infraorbital foramen where the nerve exits the skull
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Which nerve may be damaged by a fracture of the ramus of the madible?
inferior alveolar nerve
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A lesion of the entire trigeminal nerve causes widespread anesthesia involving:
- 1. corresponding anterior half of scalp
- 2. face, except for area around angle of mandible
- 3. cornea and conjunctiva
- 4. mucous membranes of nose, moth, and tongue (anterior 2/3)
- paralysis/atrophy of muscls of mastication (w/ mouth open, mandible moves to paralyzed side)
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What is Herpes zoster ophthalmicus?
infectin of face that involves region supplied by ophthalmic nerve
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What is another name for Herpes zoster ophthalmicus?
shingles
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Which part of the eye is involved in Herpes zoster ophthalmicus?
cornea
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In some cases of herpes zoster ophthalmicus, there is partial paralysis or paresis of ocular muscles indicated that the infection has also invlved which nerves?
CN III, IV, VI, or a combination of these nerves which supply the extraocular muscles that move the eye
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