Lecture: 10 Head and neck Dr. Omar Riadh
1-11-2017عددالاوراق ( 3 )
Ciliary ganglia:-
Small pin-head parasympathetic ganglia presents between the lateral rectus and the optic nerve. It has the following components:-
Sensory fibers from nasociliary nerve which is branch of ophthalmic division of trigeminal nerve.
Sympathetic fibers which are postganglionic fibers inter the ophthalmic nerve from internal carotid plexus.
Parasympathetic fibers which are preganglionic parasympathetic fibers from oculomotor nerve.
The sensory and sympathetic fibers pass through the ganglia without synapses, while the parasympathetic relay in the ganglia then about six short ciliary nerve arise from the ganglia and run around the optic nerve and pierce the sclera to supply the eyeball. Sympathetic fibers supply the dilator papillae and parasympathetic supply the sphincter papillae of pupil and also supply ciliary muscle of the lens.
Trochlear nerve (4th cranial nerve):-
This nerve is the only cranial nerve which arises from the dorsal surface of the brainstem just inferior to the midbrain, it passes in the lateral wall of cavernous sinus inferior to oculomotor nerve, it enters the superior orbital fissure then enters the superolateral border of the superior oblique muscle and supplies it, so it is supplies only one muscle.
Abducent nerve (6th cranial nerve):-
This nerve supplies only one muscle which is the lateral rectus. It arises from the ventral surface of the brain stem in groove between pones and medulla oblongata, it passes through the cavernous sinus lateral to internal carotid artery, it enters the orbit through the superior orbital fissure between the two head of lateral rectus and continues forward closely applied to the medial surface of lateral rectus.
Ophthalmic division of trigeminal nerve:-
this is the first and the smallest division of trigeminal nerve, arises from the upper portion of trigeminal ganglia and runs forward in the lateral wall of cavernous sinus inferior to trochlear nerve, befor reaching the superior orbital fissure it divides into three branches:-
Frontal nerve:- this is the direct continuation of the ophthalmic nerve, it enters the orbit through superior orbital fissure and runs forward under the roof of the orbit and on the levator palpebrae superioris muscle then about the midway of the orbit it divides into supraorbital and supratrochlear nerve.
Lacrimal nerve:- this is the smallest branch of ophthalmic nerve enters through the superior orbital fissure and runs forward above the lateral rectus, it receives postganglionic parasympathetic fibers from zygomaticotemporal nerve which supply the lacrimal gland. This nerve supplies lacrimal gland, conjunctiva and the skin on the lateral part of the upper eyelid.
Nasociliary nerve:- it passes through superior orbital fissure between the two head of lateral rectus, then it runs anteromedially above the optic nerve and below the superior rectus and superior oblique muscles and divides into:-
Communicating sensory branch to the ciliary ganglia.
Long ciliary nerves:- these are usually two passes along the medial side of the optic nerve to the sclera and supply sensory fibers to the eyeball except retina and also carry sympathetic fibers from the internal carotid plexus to the dilator papillae muscle.
Posterior ethmoidal nerve:- passes through posterior ethmoidal foramen and supplies the mucus membrane of ethmoid and sphenoid sinus.
Infratrochlear nerve:- it runs forward and appears on the face above the medial angle of the eye and supplies the skin of the eyelid and upper half of external nose.
Anterior ethmoidal nerve:- it is a terminal portion of nasociliary nerve leaves the orbit through anterior ethmoidal foramen to appears on the lateral margin of cribriform plate of ethmoid, here it turns forwards and descends into the wall of nasal cavity through a slit like aperture at the side of crista galli. It gives internal nasal branch to the nasal septum and lateral nasal wall, and terminates as external nasal branch to the skin of lower half of the nose.
Optic nerve (2nd cranial nerve):-
It is a sensory nerve, it enters the orbit through the optic canal carries with it sheath of dura mater, arachnoids and pea mater with extension of subdural and subarachnoid spaces. It runs anterolaterally and slightly downward, pierces the sclera just medial to the centre of its posterior surface. The nasociliary nerve, ophthalmic artery and vein cross above it, and the ciliary nerves and vessels surround it near the eyeball. The nerve is slightly longer than the distance it has to run, so that it doesn`t restricts the movements of the eyeball.
Ophthalmic artery:-
Arises from the internal carotid artery, it passes forward and enters the orbit through the optic canal, at first it lies below the optic nerve, but gradually winding round the lateral side of the optic nerve crosses above it to reaches the medial wall of the orbit, then the artery runs forwards below the superior oblique muscle and then divides into supratrochlear and dorsal nasal arteries near the front of the orbit.
Branches:-
Palpebral artery.
Supraorbital artery.
Supratrochlear artery.
Anterior and posterior ethmoidal artery.
Dorsal and external nasal artery.
Central artery of the retina.
Short and long ciliary arteries.
Muscular arteries.
Ophthalmic vein:-
Superior ophthalmic vein:- begins in the anterior part of the orbit close to the artery, and communicates with supraorbital and supratrochlear tributaries of the facial vein. It runs with the ophthalmic artery in the orbit.
Inferior ophthalmic vein:- it is smaller and lies below the optic nerve.
Both veins receive numerous tributaries in the orbit and passing through superior orbital fissure to open into the cavernous sinus either separately or by common trunk.
The ear:-
The ear divided into three parts:-
External ear.
Middle ear.
Inner ear.
External ear:-
Which collects the sound wave to tympanic membrane. It consist of two parts:-
The auricle.
External acoustic meatus.
The auricle composed of cartilage covered with thin skin which adheres to the cartilage and contain fine hair and sebaceous glands. The auricle attached to the skull by ligaments and muscles, the external muscle are anterior, posterior and superior auricular muscles.
Nerve supply:-
Lesser occipital nerve.
Great auricular nerve.
Auriculotemporal nerve.
Auricular branch of vagus.
Facial nerve (motor).
External acoustic meatus:-
The canal about 2.4 cm long, consist of two part outer 1/3 is cartilaginous and inner 2/3 which is bony. The tympanic membrane lies obliquely in the meatus so that the anterior wall and the floor are longer than the posterior wall and roof. The meatus lined with skin which is firmly attached to the cartilage and the bone and also covers the tympanic membrane, the skin of the cartilaginous part contains many ceruminous glands and hair. The external meatus runs medially and is slightly curved with an upward convexity then inclines downwards and forwards. The meatus is straight viewed for examination by pulling the auricle upward, outward and backward.
Middle ear:-
Is a small cavity in petrous temporal bone, it lies medial to tympanic membrane and connected to the pharynx by auditory tube, it also connected to the mastoid air sinus. It includes the tympanic cavity proper ( space directly internal to the membrane) and epitympanic recess (space above the tympanic membrane), its lined with mucous membrane.
Contents:-
Bones:- three ossicles (malleus, incus and stapes).
Two muscles (stapedius and tensor tympani muscle).
Two nerves (chorda tympani and tympanic plexus of nerves).
It has roof, floor and four walls.
Roof:- composed of tegmen tympani which separates the middle ear from the middle cranial fossa.
Floor:- (jugular wall) is thin bone separates the middle ear from jugular fossa and its contained superior bulb of jugular vein.