Unit 2-face Flashcards
Why do lacerations on the scalp tend to gape open
because the face has not distinct deep fascia and the subcutaneous tissue between the cutaneous attachments of the facial muscles is loose, facial lacerations tend to gape (part widely). The skin must be carefully sutured to prevent scarring. The looseness the the subcutaneous tissue also enables fluid and blood to accumulate in the loose connective tissue following bruising of the face.
Facial inflammation causes considerable swelling
Why can a partially detached scalp be replaced with a reasonable chance of healing
as long as one of the vessels supplying the scalp remains intact ,because the scalp arteries arising at the sides of the head are well protected by dense connective tissue and anastomose freely, there is a reasonably good chance of healing.
The first 3 layers of the scalp remain together when the scalp becomes detached, (scalp proper) and nerves and vessels of the scalp enter inferiorly and ascend through the layer two to the skin. The arteries of the scalp supply little blood to the calvaria, which is supplied by the middle meningeal arteries. Therefore, loss of the scalp does not produce necrosis or death of the calvarial bones.
Why do superficial scalp wounds not gape
The strength of the epicranial aponeurosis is able to hold the margins of the wound together. Deep sutures are not necessary when suturing superficial wounds because the epicranial aponeurosis does not allow wide separation of the skin. Deep scalp wounds gape widely when the epicranial aponeurosis is lacerated in the coronal plane because of the pull of the frontal and occipital bellies of the occipitofrontalis muscle in opposite directions.
Why is the loose connective tissue layer of the scalp the “danger layer” of the scalp?
vecayse pus or blood spreads easily in it. Infection in this layr can also pass into the cranial cavity through small emissary veins, which pass through parietal foramina in the calvaria and reach the intracranial structures such as the meningies. An infection cannot pass into the neck becase the occipital bellies of the occipitofrontalis muscle attach to the occipital bone and mastoid parts of the temporal bones. Neither can a scalp infection spread laterally beyond the zygomatic arches becayse the epicranial aponeurosis is continuous with the temporal fascia that attaches to these arches.
An infection or fluid (pus or blood) can enter the eyelids and the root of the nose because the occipitofrontalis muscle inserts into the skin and subcutaneos tissue and does not attach to the bone.
A pt presents with sagging of one side of the face with a distorted facial expression, making it appear passive or sad. What is this condition, cause and complications?
Bell Palsy- CN VII facial nerve.
Injury to the facial nerve CN VII or its branches produces paralysis of some or all of the facial muscles on the affected side- affected area sags, facial expression distorted.
There is loss of tonus of the obicularis oculi causing the inferior eyelid to evert, and as a result, lacrimal fluid is not spread over the cornea preventing adeqyate lubrivaton, hydration and flushing of the cornea. Prone to corneal ulceration and a corneal scar can impair vision. If injury or weakness paralyzes the buccinator and obicularis oris, food will accumulate in the ral vestibule and require removal with a finger. When the spincters of the dilateors of the mouth are affected, displacement f the mouth (drooping of the corner) is produced by contraction of unoppposed contralateral facial muscles and gravity resulting in food and salvia dribbling out te side of the mouth. Weakened lip muscles affect speach. Affected individuals cannot whistle or blow an instrument.
Why can a fx to the pterion be life threatening
it overlies the frontal branches of the middle meningeal vessels, which lie in grroves on the internal aspect of the lateral walll of the calvaria. A hard blow to the side of the head may fx the thin bones forming the pterion producing a rupture of the frontal branch of hte middle meningeal artery or vein crossing hte pterion. The restulting hematoma exerts pressure on the underlying cerebral cortex and an utreated middle meningeal vessel hemorrhage may cause death within a few hours .
Why is the danger triangle of the face particularly dangerous in regards to infection?
the facial vein makes clinically important connections with the cavernous sinus through the superior opthalmic vein and the pterygoid venous plexus through the inferior opthalmic and deep facial veins. Because of these connections, an infection of the face may spread to the cavernous sinus and pterygoid venous plexus.
Blood from the medial angle of the eye, nose and lips usually drains inferiorly through the facial vein, especially when a person is erect. Because the facial vein has no valves, blood may pss through it in the opposite direction. Consequently, venous blood from the face may enter the cavernous sinus/
In individuals with thromboplebitis of the facial vein, inflammation of the facial vein with secondary thrombus, peices of an infected clot may extend intot the intracranial venous system and produce thromboplehbitis of the cavernous sinus.
Infection of the facial veins spreading to the dural venous sinuses may result from lacerations of the nose or be initiated by squeezing pimples on the side f the nose and upper lip. Consequently, the triangular area from the upper lip to the bridge ofo the nose is considered the danger triangle of the face.
What can be a consequence of blunt trauma to the head
A blow to the head can detach the periosteal layer of dural mater from the calvaria without fracturing the cranial bones. In the cranial base, the two dural layers are firmly attached and difficult to searate from the bones, but a fx of the cranial base usually tears the dura and results in leakage of CSF. The innermose part of the dura, the dural border cell layer, is composed of flattened fibroblasts that are separated by large extracellular spaces. This layer constitutes a plane of structural weakness at the dura-arachnoid junction.
What causes a tentorial herniation, what are the complications of this type of herniation
The tentorial notch is the opening in the tentorium cerebelli for the brainstem which is slightly larger than is necessary to accomodate the midbrain. Space occupying lesions , such as tumors in the supratentorial compartment, produce increased intracranial pressure and may cause part of the adjacent temporal lobe of the brain to herniate through the tentorial notich. During tentorial herniation, the temporal lobe may be lacerated by the tough tentorium cerebelli and the oculomotor nerve (CN III) may be stretched, compressed or both. Oculomotor lesions may produce paralysis of the extrinsic eye muscles supplied by CN III.
Which structure do pituitary tumors often push onto and what disturbances do they cause
may extend superiorly through the aperture in teh diaphragm sellae or cause it to bulge. Tumors often expand the diaphragma selae producing disturbances in endocrine function early or late (before or after enlargement of the diaphgrama sellae). Superior extension of a tumor may cause visual sx owing to pressure on the optic chiasm, where the optic nerve fibers cross.
Which dural sinuses are most frequently thrombosed and what are the consequences of this
Occlusion of the cerebral veins and dural venous sinuses may result from thrombi (clots), thrombnophlebitis (venous inflammation) or tumors (meningiomas). The dural venous sinuses most frequently thrombosed are the transverse, cavernous and superior sagittal sinuses. The facial veins make clinically important connections with the cavernous sinus through the superior opthalmic veins. Cavernous sinus thrombus usually results from infections in the orbit, nasal sinuses and superior part of the face (the danger triangle). In persons with thromboplebitis of the cavernous sinus, pieces of an infected thrombus may extend into the cavernous sinus producing thrombophelbitis of the cavernous sinus. The infection usually involves only one sinus initially, but it may spread to the opposite sie through the intercavernous sinuses. Thromboplebitis of the cavernous sinus may affect the nerves embedded within the lateral wall of the sinus. Septic thrombosis of the cavernous sinus often results in the development of acute meningitis.
What is the danger about fx in the cranial base?
In fx of the cranial base, the internal carotid artery can be torn, producing an arteriovenous fistula within the cavernous sinus. Arterial blood rushes into the cavernous sinus, enlarging it and forcing retrograde blood flow into its venous tributaries, especially the opthalmic veins. As a result, the eyeball protrudes (exopthalmos) and the conjunctiva becomes engorged (chemosis). The protruding eyeball pulstates in synchrony with the radial pulse, known as pulsating exopthalmos. Because CN III, ,CN IV, CN V1, CN V2, and CNVI lie in or close to the lateral wall of the cavernous sinus, these nerves may also be affected when the sinus is injured.
What is leptomeningitis
Inflammation of the leptomeninges (arachnoid and pia) reulting from pathogenic microorganisms. Infection and inflammation are usually confined to the subarachnoid space and the arachnoid pia. The bacteria may enter the subarachnoid space through the blood (septicemia) or spread from an infection of the hear, lungs or other viscera.
Microorganisms may also enter the subarachnoid space from a compound cranial fx or a fx of the nasal sinuses. Acute purulent meningitis can result from infection with almost any pathogenic bacteria.
What is the source and most common mechanism for an epidura hemorrhage?
Arterial in origin. Blood from torn branches of a middle meningeal artery collects between the external periosteal layer of the dura and teh calvaria. The extravasated blood strops the dura from the cranium Usually this follows a hard blow to the head and forms and extradural (epidural) hematoma. Typically a brief concussion (LOC) occurs followed by a lucid interval for some hours. Later, drowsiness and coma (profound unconsciousness) occur. Compression of the brain occurs as the blood mass increases necessitating evacuation of the blood and occlusion of the bleeding vessels.
What is the mechanism of a subdural hematoma
A dural border hematoma, commonly called a subdural hematoma, are usually called by extravasated blood that splits open the dural brder cell layer. The blood does not collect within a preexisting space, but rather creates a space at the dura-arachnoid junction. Dural border hemorrhage uslally follows a hard blow to the head that jeres the brain inside the cranium and injues it The precipitating trauma may be trivial or forgotten. Dural border heomrrhage is typically venous in orgin and commonly result from tearing a superior cerebral vein as it enters the superior sagitta sinus.
