Unit 2 Flashcards
how many layers does the scalp consist of?
5
name the 5 layers the scalp consist of
Skin
Connective tissue
Aponeurosis
Loose connective tissue
periosteum
in the scalp: describe the relationship between the superifcial connective tissue and the underlying aponeurosis
superficial connective tissue is fibrous and tighly bound to both the skin and underlying aponeurosis
= no movement between the two
if theres no movement between the superficial connective tissue and underlying aponeurosis, howcome the scalp can move over the cranium?
because of the very loose areolar connective tissue tissue between the aponeurosis and the pericranium
give an important clinical implication of the density of the subcutaneous scalp tissue
its dense = and tends to hold superficial blood vessels open even when theyre cut = profuse bleeding often requiring sutures
regarding cuts in the scalp:
transver tear vs sagittal tear
If a wound penetrates the aponeurosis, a transverse tear will gape due to the pull of the occipitalis and frontalis muscles across the defect,
whereas a sagittal tear is more easily sutured
danger regarding infection in wounds penetrating the aponeurosis?
Any wound that penetrates the aponeurosis is serious as infection can enter the subaponeurotic space and spread over the entire surface of the cranial vault with little obstruction.
in the scalp where do the vessels and nerves run?
between the aponeurosis and skin
which blood vessels supply the scalp - describe how these interact?
The scalp is supplied by branches of the external and internal carotid arteries: superficial temporal and posterior auricular arteries (ECA); supraorbital and supratrochlear arteries (ICA).
All these vessels anastomose freely with each other.
in the scalp; Cutaneous nerves follow the……
Cutaneous nerves follow the blood vessels
which nerves supply the posterior of the scalp
Posteriorly, the scalp is supplied by the greater occipital and third occipital nerves, branches of the posterior rami of C2 and C3 respectively and laterally by the lesser occipital (C2) and auriculotemporal (branch of Vc) nerves
which nerves supply the anterior of the scalp
Anteriorly and up to the vertex, it is supplied by the zygomaticotemporal (branch of Vb) nerve, and the supratrochlear and supraorbital nerves (branches of Va).
heres another picture
The facial nerve (CN ___) is the ____ paired cranial nerve.
The facial nerve (CN VII) is the seventh paired cranial nerve.
The facial nerve is associated with the derivatives of the ____ pharyngeal arch:
The facial nerve is associated with the derivatives of the second pharyngeal arch:
describe the following in relation to the facial nerve
motor function
sensory fuction
special sensory function
parasympathetics
The facial nerve is the source of branchiomotor innervation to all the muscles that are derived from the ______ pharyngeal arch
The facial nerve is the source of branchiomotor innervation to all the muscles that are derived from the second pharyngeal arch
the facial nerve it carries preganglionic parasympathetic fibres destined for the ……….., and taste fibres from the……………of the tongue via its ………….. branch
it carries preganglionic parasympathetic fibres destined for the lacrimal, submandibular, sublingual and nasal mucous glands, and taste fibres from the anterior two-thirds of the tongue via its chorda tympani branch
T or F
the facial nerve is also partially responsible for general sensation of the skin lining the external auditory meatus.
T
describe where the facial nerve originates?
pons of the brainstem
can you visualise the path of the facial nerve?
describe how the facial nerve begins
2 roots:
larger motor root
and a smaller nervus intermedius containing parasympathetic and sensory fibres
describe the intracranial path of the facial nerve
2 roots enter the internal acoustic meatus with the vestibulocochlear nerve (CN VIII), and join to form the facial nerve, which enters the narrow facial canal which lies within the petrous temporal bone.
On the medial wall of the middle ear, the facial nerve bends posteriorly.
At the end, there is a swelling, the facial (geniculate) ganglion
On reaching the posterior wall of the tympanic cavity, the nerve runs inferiorly to emerge from the skull at the stylomastoid foramen.
can you remember the hole the facial nerve leaves teh skull from?
stylomastoid foramen
describe the extracranial path of the facial nerve
After exiting the skull, the facial nerve turns superiorly to run just anterior to the outer ear.
the main trunk of the facial nerve now termes the motor root of the facial nerve, enters the parotid gland and divides into upper and lower divisions.
The upper division gives the temporal, zygomatic and buccal branches,
while the lower division gives the mandibular and cervical branches.
the branches given off by the facial nerve in the paroti gland do what?
These branches are responsible for innervating the muscles of facial expression.
what are the 5 branches the facial nerve gives in the parotid gland?
The upper division gives the temporal, zygomatic and buccal branches, while the lower division gives the mandibular and cervical branches.
does the facial nerve innervate the parotid gland?
the facial nerve does not contribute towards the innervation of the parotid gland, which is innervated by the glossopharyngeal nerve).
give the branches the facial nerve gives before it exits the skull
3:
greater petrosal nerve
nerve to stapedius
chorda tympani
describe the greater petrosal branch of the facial nerve
greater petrosal nerve, arising at the geniculate ganglion and carrying parasympathetic fibres to the lacrimal gland via the pterygopalatine ganglion;
describe the nerve to stapedius branch of the facial nerve
nerve to stapedius, a muscle which dampens over-vibration of the tympanic membrane and ossicles; and the
describe the chorda tympani branch of the facial nerve
chorda tympani, which joins the lingual nerve. It mediates taste from the anterior two thirds of the tongue, and also carries preganglionic parasympathetic secretomotor fibres to the submandibular and sublingual glands.
give the branches given by the facial nerve outside of the skull
muscular branches to the posterior belly of digastric, stylohyoid and occipitalis;
branches to the muscles of facial expression, namely:
- *temporal**, to orbicularis oculi and frontalis;
- *zygomatic**, to the muscles of the eyelid;
- *buccal**, to buccinator, orbicularis oris and muscles of the external nose;
mandibular, to the muscles of the lower lip and chin; and cervical, to platysma.
facial nerve
just for fun
parasympathetic fibres of the facial nerve are carried by?
The parasympathetic fibres of the facial nerve are carried by the greater petrosal and chorda tympani branches.
describe the shape of the bony orbit
It is cone- shaped, with the apex pointing posteromedially
bony orbit:
the two medial walls are almost ________ to each other, while the two lateral walls are virtually at….
the two medial walls are almost parallel to each other, while the two lateral walls are virtually at right angles.
the roof of the orbit is…. which bone?
orbital plate of the frontal bone, which separates the frontal lobes of the brain from the orbital contents
what bones forms the floor of the orbit
The floor is formed almost entirely by the maxilla with its air sinus
whart bone forms the lateral wall of the orbit
The lateral wall is formed by the zygomatic bone and greater wing of the sphenoid, and separates the temporalis muscle from the eye.
whart bone forms the medial wall of the orbit
The medial wall is formed mainly by the labyrinth of the ethmoid.
anteriorly 2 more bones contricute to the orbit - what are they
Anteriorly, both the lacrimal bone and the frontal process of the maxilla contribute to the orbit.
describe the lacrimal fossa and what it houses
Posterior to the inferomedial angle of the orbital rim is a depression, the lacrimal fossa, which houses the lacrimal sac
describe teh nasolacrimal duct
The duct begins in the eye socket between the maxillary and lacrimal bones, from where it passes downwards and backwards. The opening of the nasolacrimal duct into the inferior nasal meatus of the nasal cavity is partially covered by a mucosal fold (valve of Hasner)
carries excess tears into the nasal cavity
give the 3 groups of muscles which are involved in the eye
intraocular muscles and pupillary dilators and constrictors
6 extraocular muscles which move the eye ball
levator palpebrae superioris which elevates the upper eyelid
which muscle lifts the eye lid
levator palpebrae superioris
describe the 6 extraocular muscles which move the eye
small skeletal muscles
4 straight - recti
2 oblique (superior and inferior)
where do the recti of the eye arise from?
tendinous ring at the back of the bony orbit
where do the recti attach to the eye
just behind the junction of the cornea and sclera, i.e. just anterior to the equator of the eyeball
which muscles of the eye are supplied by the oculomotor nerve (CNIII)
Three recti (superior, inferior and medial) and inferior oblique are supplied by the oculomotor nerve
superior oblique is supplied by what?
(muscles of the eye)
trochlear nerve (CN IV)
what supplied the eye muscle - lateral rectus
abducent nerve (CN VI)
The medial rectus ______ the eyeball, and lateral rectus _______ it
The medial rectus adducts the eyeball, and lateral rectus abducts it
superior rectus has 2 actions. what are they
can you think why? its visually quite simple
Due to the different long axes of the orbit and eyeball, superior rectus elevates and adducts the eyeball
inferior rectus has 2 actions on the eye - what are they
inferior rectus depresses and adducts it
superior oblique has 2 actions on the eye - what are they
so does inferior oblique - what are they
Due to their attachments posterior to the equator of the eyeball,
superior oblique depresses and abducts the eyeball,
and inferior oblique elevates and abducts it.
Any coordinated movement of the eyeballs involves at least ____ muscles.
3
list the 7 extraocular muscles
the levator palpebrae superioris, superior rectus, inferior rectus, medial rectus, lateral rectus, inferior oblique and superior oblique
whats special about the levator palpebrae superioris
A small portion of this muscle contains a collection of smooth muscle fibres – known as the superior tarsal muscle. In contrast to the LPS, the superior tarsal muscle is innervated by the sympathetic nervous system.
attachments of levator palpebrae superioris
Originates from the lesser wing of the sphenoid bone, immediately above the optic foramen.
It attaches to the superior tarsal plate of the upper eyelid (a thick plate of connective tissue).
innervation of Levator palpebrae superioris
Oculomotor nerve (CN III)
The superior tarsal muscle (located within the LPS) is innervated by the sympathetic nervous system.
picture of levator palpebrae superioris
recti muscles characteristically originate from ….
recti muscles characteristically originate from the common tendinous ring
describe the common tendinous ring
ring of fibrous tissue, which surrounds the optic canal at the back of the orbit
the recti muscles attach to where on the eye ball
to the sclera
(behind the junction of the cornea and sclera)
recti muscles have a ______ path from origin to attachment
recti muscles have a direct path from origin to attachment
innervation of lateral rectus muscle
abducens nerve (CN VI)
attachments of the superior oblique muscle
body of sphenoid.
Its tendon passes through a trochlea and then attaches to the sclera of the eye, posterior to the superior rectus.
actions of superior oblique muscle of the eye
Depresses, abducts and medially rotates the eyeball.
innervation of superior oblique
trochlear nerve (CN IV)
attachements of inferior oblique
Originates from the anterior aspect of the orbital floor.
Attaches to the sclera of the eye, posterior to the lateral rectus
actions of inferior oblique muscle
Elevates, abducts and laterally rotates the eyeball.
inenervation of the inferior oblique muscle
oculomotor nerve (CN III)
3 eye characteristics of horners syndrome
horners syndrome - damamge to sympathetic trunk in the neck
Partial ptosis (drooping of the upper eyelid) – Due to denervation of the superior tarsal muscle.
Miosis (pupillary constriction) – Due to denervation of the dilator pupillae muscle.
Anhidrosis (absence of sweating) on the ipsilateral side of the face – Due to denervation of the sweat glands.
give some possible pathologies horners syndrome can represent
Horner’s syndrome can represent serious pathology, such as a tumour of the apex of the lung (Pancoast tumour), aortic aneurysm or thryoid carcinoma.
is the optic nerve purely sensory?
yep
where do the axons of the optic nerve originate?
in the retinal cells
describe the path of the optic nerve
The two nerves partially decussate to form the optic chiasma, where the optic tracts continue posteriorly to the lateral geniculate body inferior to the thalamus.
what surrounds the optiv nerve
As an outgrowth of the brain, the optic nerve is surrounded by pia, arachnoid, and dura up to the point where it pierces the sclera
is there a subarachnoid space surrounding the optic nerve
a small but definite one
describe the effect on an increase in intracranial pressure on the optic nerve - and how this can be seen
any increase in intracranial pressure is transmitted around the nerve via the cerebrospinal fluid, leading to the appearance of papilloedema, i.e. swelling of the optic nerve disc.
describe the path of the oculomotor nerve
After exiting the midbrain, the oculomotor nerve pierces the roof of the cavernous sinus and runs in its lateral wall.
Emerging from the sinus, it divides into superior and inferior divisions, which pass into the orbit through the superior orbital fissure and the tendinous ring.
what do the superior and inferior divisions of the oculomotor nerve supply
The superior division supplies levator palpebrae superioris and superior rectus.
The inferior division supplies the inferior rectus, medial rectus and inferior oblique muscles, and also carries parasympathetic axons for the ciliary muscle and sphincter pupillae.
describe how the oculomotor nerve innervates the ciliary and sphincter pupillae muscles.
Preganglionic parasympathetic fibres leave the inferior division to reach the ciliary ganglion.
Postsynaptic postganglionic axons leave the ganglion via 10-12 short ciliary nerves. These run forwards in the eyeball to reach the ciliary and sphincter pupillae muscles.
describe the location of the ciliary ganglion
between the lateral surface of the optic nerve and the lateral rectus muscle.
describe the path of the trochlear nerve
arises from tochlear nucleus of the brain
emerges from the posterior aspect of the midbrain
It runs anteriorly and inferiorly within the subarachnoid space before piercing the dura mater adjacent to the posterior clinoid process of the sphenoid bone.
The nerve then moves along the lateral wall of the cavernous sinus (along with the oculomotor nerve, the abducens nerve, the ophthalmic and maxillary branches of the trigeminal nerve and the internal carotid artery) before entering the orbit of the eye via the superior orbital fissure.
whats the smallest cranial nerve by number of axons
trochlear nerve
does the trochlear nerve have purely somatic function
yep
does the trohlear nerve innervate the contralateral side?
yep.
As the fibres from the trochlear nucleus cross in the midbrain before they exit, the trochlear neurones innervate the contralateral superior oblique.
how does trochlear nerve palsy present?
head tilt away from the affected side.
patients have difficulty looking downwards “verticle diplopia”
abducens nerve: somatic motor or sensory function
purely somatic motor function
abducens nerve innervates what muscle
path of the abducens nerve (CN VI)
arises from the abducens nucleus in the pons of the brainstem.
exits the brainstem at the junction of the pons and the medulla.
It then enters the subarachnoid space and pierces the dura mater to travel in an area known as Dorello’s canal.
At the tip of petrous temporal bone, the abducens nerve leaves Dorello’s canal and enters the cavernous sinus (a dural venous sinus).
It travels through the cavernous sinus (lying just lateral to the internal carotid artery)
enters the bony orbit via the superior orbital fissure.
whats diplopia?
double vision
the ophthalmic nerve is a branch of what>
its V1 branch of the trigeminal nerve (CN V)
describe the path of the ophthalic nerve
arises from the trigeminal ganglion
travels laterally to the cavernous sinus
gives off the recurrent tentorial branch .
picks up postganglionic sympathetic fibres from the internal carotid plexus.
exits the cranium via the superior orbital fissure, where it divides into 3 main branches
3 main branches of the ophthalmic nerve
frontal nerve
lacrimal nerve
nasociliary nerve
The ophthalmic division of trigeminal nerve provides sensory innervation to the following structures:
Forehead and scalp
Frontal, ethmoid and sphenoid sinuses
Upper eyelid and its conjunctiva
Cornea
Dorsum of the nose
Lacrimal gland
Parts of the meninges and tentorium cerebelli (recurrent tentorial branch)
do you know which part of the skull the ophthalmic nerve gives cutaneous innervation to
cutaneous innervation to the face and scalp by the three branches of the trigeminal nerve have sharp borders and little overlap
outline the corneal reflex
ophthalmic nerve acts as the afferent limb
what artery primarily supplies the eye?
ophthalmic artery - arising as a branch of the internal carotid artery immediatly distal to the cavernous sinus
give the branches of the ophthalmic artery
After entering the orbit, ophthalmic artery gives the central artery of the retina and branches to the extraocular muscles.
It ascends on the lateral surface of the optic nerve and gives the lacrimal artery
what does the central artery of the retina supply
internal surface of the retina
occulsion of this artery. = blindness
whats special about the lacrimal artery
Not infrequently it is given off before the artery enters the orbit.
It accompanies the lacrimal nerve along the upper border of the lateral rectus and supplies the lacrimal gland.
has a recurrent meningeal branch that anastomoses with the anterior branch of the middle meningeal artery, creating an anastomosis between the internal and external carotid arteries.
describe the superior ophthalmic vein
and the inferior ophthalmic vein
leaves the orbit through the superior orbital fissure to enter the cavernous sinus
The inferior ophthalmic vein may join the superior vein, pass separately through the superior orbital fissure to join the cavernous sinus, or pass through the inferior orbital fissure to join with the pterygoid venous plexus in the infratemporal fossa.
what are the medial and lateral canthi
The eyelids are two movable folds which protect the eye. When they are open, the angles of junction of the upper and lower lids are known as the medial and lateral canthi.
whats the palpebral fissure.
The opening between the eyelids is the palpebral fissure.
what are the tarsal plates
The tarsal plates are laminae of condensed connective tissue in each lid.
what does the superior tarsal plate receive
the main insertion of levator palpebrae superioris
describe the
tarsal or Meibomian glands
Modified sebaceous glands, along rims of eye lid - produce meibum - an oily secretion to make the lid margins waterproof when closed and prevents evaporation of the eye’s tear film.
There are about 25 such glands on the upper eyelid, and 20 on the lower eyelid
what do lacrimal glands do
secrete lacrimal fluid onto the surfaces of the conjunctiva and cornea of the eye
describe the location fo the lacrimal gland
anteriorly in the superolateral aspect of the orbit, within the lacrimal fossa – a depression in the orbital plate of the frontal bone.
anatomical relations=:
Superior – zygomatic process of frontal bone
Anterior – orbital septum
Posterior – orbital fat
Inferolateral – lateral rectus muscle
where do the lacrimal glands open?
Closing the lids creates a conjunctival sac, with the lines of reflection known as the superior and inferior conjunctival fornices
The ducts (12-14) open into the lateral part of the superior conjunctival fornix.
The lacrimal fluid produced by the gland is secreted into excretory ducts, which empty into the ,……
The lacrimal fluid produced by the gland is secreted into excretory ducts, which empty into the superior conjunctival fornix.
describe the lacrimal apparatus
responsible for the drainage of lacrimal fluid from the orbit.
After secretion, lacrimal fluid circulates across the eye, and accumulates in the lacrimal lake – located in the medial canthus of the eye. From here, it drains into the lacrimal sac via a series of canals.
The lacrimal sac is the dilated end of the nasolacrimal duct, and is located in a groove formed by the lacrimal bone and frontal process of the maxilla. Lacrimal fluid drains down the nasolacrimal duct and empties into the inferior meatus of the nasal cavity.
done
yay
