Although veins and venous sinuses may be torn, most bleeding is usually from what?
torn arteries
Becaused the internal periosteum is firmly attached to calvaria, when bleeding occurs what happens?
there is a slow, localized accumulation of blood forming an extradural hematoma
What happens as the hematoma increases in size?
compression of brain occurs
When a hematoma comprsses the brain it necessitates what?
evacuation of fluid and occlusion of bleeding vessels
The formation of an extradural hematoma, superior to the tentorium cerebelli causes a rise in what?
supratentorial pressure
What happens if supratentorial pressure rises very high?
part of cerebellum may be forced through foramen magnum, compressing medulla
Fatal effects owing to interference with respiratory and cardiovascular centers may be caused by what?
part of cerebellum passing through foramen magnum because of supratentorial pressure
subdural (intradural) hemorrhage:
bleeding within the dura following blow to head that jerks brain inside the skull
Subdural hemorrhage is greastest in whom?
elderly people in whom some shrinkage of the brain has occured
Subdural hemorrhage commonly results from tearing which vein as it enters the superio sagittal sinus?
superir cerebral vein
Subarachnoid hemorrhage:
bleeding into subarachnoid space following rupture of aneurysm or intracranial artery
also associated ith skull fractures and cerebral lacerations
What do subarachnoid hemorrhages look like?
thin-walled outpouchings or evaginations
Where do subarachnoid hemorrhages occur?
at bifurcations of arteries at base of brain
What is the result of subarachnoid hemorrhages?
meningeal irritation
severe hadache
stiff neck
loss of consciousness
Intracerebral hemorrhage:
bleeding into brain from one of branches of middle cerebral artery
Intracerebral hemorrhage is common in persons with what?
hypertension
Why does paralysis occur with intracerebral hemorrhage?
because of interruption of motor pathways from motor cortex to brain stem and spinal cord
What color is the bulbar conjunctiva?
colorless
When would the bulbar conjuntiva not be colorless?
when vessels are dilated and congested (bloodshot eyes)
What causes hyperemia of conjunctiva?
local irritations and infections
Subconjunctival hemorrhages are common and manifested by:
bright or dark red patches deep to and in the bulbarconjunctiva
Subcnjunctival hemorrhages are a result from what?
injury or inflammation
Conjunctivitis:
conjunctiva inflamed owing to infection
What happens in third nerve palsy?
upper eyelid droops (ptosis) and cannot be voluntarily raised
Third nerve palsy is a result of what?
damage to superior division of oculomotor nerve (CN III)
What does CN III supply?
levator palpebrae superioris muscle
What happens to the eyelids when the facial nerve is damaged?
eyelids can't be closed owing to paralysis of the orbicularis oculi muscles which closes the eyelids
What does irritation of the unprotected eyeball result in?
excessive lacrimation (tear formation)
What does obstruction of the lacrimal drainage apparatus cause when lower eyelid is lax and everted?
excessive tearing
What causes glands inthe eyelid to become inflamed and swollen?
infection or obstruction of ducts
What happens if ducts of the ciliary glands become obstructed or inflamed?
painful red swelling known as a 'sty' develops on eyelid
What are cysts of the sebaceous glands of the eyelid called?
chalazia
What does an obstruction of the tarsal gland produce?
inflammation called tarsal chalazion
What happens with tarsal chalazion?
protrudes toward eyeball and rubs against it as eyelids blink
Which are more painful? Chalazia or sties?
chalazia
Where does the pigment epithelium of the retina develop from?
outer layer of optic cup
What is the outer layer of the optic cup?
derivative of embryonic optic vesicle
Where does the neural layer of the retina develop?
from inner layer of optic cup
When do the 2 layers of the retina fuse?
during early fetal period
What are the 2 layers of the retina suparated by?
poential intraretinal space
The pigment layer becomes fixed to what?
choroid
Is the neural layer attached firmly?
no
What may cause detachment of the retina?
blow to the eye
What is affected in third (cranial) nerve palsy?
levator palpebrae superioris muscle
upper eyelid can't be raised voluntarily
What happens if the cervical sympathetic trunk is interrupted?
superior tarsal muscle is paralyzed
causing drooping of eyelid (ptosis)
What is ptosis a sign of?
cervical sympathetic trunk injury and is part of Horner's syndrome
Paralysis of one or more extraocular muscles owing to injury of nerves supplying them results in what?
diplopia
What is diplopia?
double vision
Limitation of eye movement in the field of action of the paralyzed muscle and production of two images when an attempt is made to use the paralyzed muscle notes what?
paralysis of a muscle of the eyeball
What happens when the abducent nerve (CN VI) is paralyzed?
patient is unabel to abduct the eye on the affected side
usually double vision (diplopia)
The patient is asked to look superolaterally (upward and outward) to test which muscle?
superior rectus
The patient is asked to look inferolaterally (downward and outward) to test which muscle?
inferior rectus
The patient is asked to look superomedially (upward and inward) to test which muscle?
inferior oblique
The patient is aked to look inferomedially (downward and inward) to test which muscle?
superior oblique
The patient is asked to look medially (inward) to test which muscle?
medial rectus
The patient is asked to look laterally (outward) to test which muscle?