|Lecture: 9 Head and neck Dr. Omar Riadh
1-11-2017 عددالاوراق ( 3 )
Blood supply of submandibular salivary gland:-
-facial artery and submental artery.
-venous drainage by facial vein and submental vein.
Nerve supply of submandibular salivary gland:-
-sympathetic:- from sympathetic plexus around facial artery.
-parasympathetic:- by postganglionic parasympathetic fibers from submandibular ganglia through chorda tympani which is branch of facial nerve. Chorda tympani arises from superior salivatory nucleus of facial nerve in pons, it leaves the petrous bone through petrotympanic fissure, then passes to infratemporal fossa where it joins the posterior part of lingual nerve. This nerve supplies parasympathetic to submandibular, sublingual gland and special taste sensation to the anterior 2/3 of the tongue.
It is triangular parasympathetic ganglia suspended from the lingual nerve by two short roots, it lies on the hyoglossus muscle, one of its root is preganglionic parasympathetic from chorda tympani and the other is postganglionic parasympathetic to the submandibular and sublingual glands. Some sensory fibers may pass through the ganglia and distributed with its branches.
Sublingual salivary gland:-
This gland lies on mylohyiod muscle between the mandible and genioglossus muscle, it raises the mucus membrane which covers its superior surface to form sublingual fold. It gives 8-20 small ducts open in the summit of sublingual fold.
Blood supply:- lingual and facial arteries.
Nerve supply:- same as submandibular salivary gland i.e sympathetic, parasympathetic and sensory.
the orbital region:-
these are bilateral bony cavities which contain the eyeball and their associated muscles, nerves, vessels, fat and most of the lacrimal apparatus.
The palpebral fissure:- an elliptical opening between the eyelids and conjunctiva. The eyelid is a movable fold, the upper eyelid is larger and more movable than the lower eyelid, it contains levator palpebrae superioris muscle.
Layers of the eyelid:-
Skin which is very thin.
Subcutaneous tissue which contain eyelashes, sebaceous gland (gland of Zeis) and modified sweat gland (cilliary gland of Moll).
Muscular layer:- orbicularis oculi muscle.
Tarsofacial layer:- the tarsal plate is dense fibrous plate, it is semilunar in shape and gives support and form to the eyelid, it contains modified sebaceous tarsal gland with their ducts open in the free margin of the lids.
Conjunctiva:- this membrane lines the inner surface of the eyelid (palpebral conjunctiva) and reflected over the anterior portion of the sclera and cornea (bulbur conjunctiva). The line of reflection is the superior and inferior fornices.
Lacrimal fluid produced by lacrimal gland. It passes to the medial angle of the eye aided by contraction of orbicularis oculi muscle and enters through the lacrimal punctum to the lacrimal canaliculi, these canaliculi discharge into the nose through the nasolacrimal duct.
Located in the lacrimal fossa in the orbital plate of the frontal bone behind the superolateral margin of the orbit. It has a superior large (orbital) and inferior small (palpebral) portion. It have ten or less ducts open into the conjunctiva near the superior fornix.
Nerve supply of the lacrimal gland:-
Sensory:- by lacrimal branch of ophthalmic division of trigeminal nerve.
Sympathetic:- by deep petrosal nerve.
Parasympathetic:- by greater petrosal nerve.
These are two slender tubes about 1 cm in length begin as lacrimal punctum located in the summit of lacrimal papilla, it runs medially in the margin of the eyelid and open in lacrimal sac.
It lies behind the medial palpebral ligament, it is the upper dilated portion of the nasolacrimal duct situated in the lacrimal fossa.
it is about 1.5 cm long and it is continuation of the lacrimal sac, it passes downward to opens in the inferior meatus of the nasal cavity.
Lacrimal lake (lacus lacrimalis):- is a shallow triangular space in the medial angle of the eye bounded by semilunar fold of conjunctiva.
Semilunar fold (plica semilunaris):- as a small fold of bulbar conjunctiva at the medial angle of the eye.
Lacrimal caruncle:- small rounded elevation in the middle of lacrimal lake contain few sweat and sebaceous gland.
Is a pyramid shaped space with its base directed anteriorly and the apex directed posteriorly, it has four walls and it is formed by seven bones of the skull, the space between the two orbit occupies by the sphenoid and ethmoid air sinuses.
The walls of the orbit:-
Roof:- formed by orbital plate of frontal bone and lesser wing of sphenoid.
Lateral wall:- formed by zygomatic bone and greater wing of sphenoid.
Floor:- formed by the orbital plate of maxilla and palatine bone.
Medial wall:- formed by frontal process of maxilla, lacrimal bone, ethmoid bone and body of sphenoid.
In the orbit there are three main opening:-
Superior orbital fissure:- which leads to middle cranial fossa.
Inferior orbital fissure:- which leads to temporal and infratemporal fossa.
Also the orbit is in relation with the paranasal sinuses:-
Medially:- with the ethmoidal air sinus.
Inferiorly:- with the maxillary air sinus.
Superiorly:- with the frontal air sinus.
Forms a funnel shape sheath which is loosely attached to the bony wall. It encloses all the contents of the orbit and it is continuous with the periosteum of the bone of the cranial cavity through the optic canal and superior orbital fissure.
The ocular muscles:-
These are six muscles 4 recti and 2 oblique muscles in addition to the levator palpebrae superioris muscle which passes to the upper eyelid.
The four recti are superior, inferior, medial and lateral rectus all arise from a common ring tendon which surround the margin of optic canal and encircle the optic nerve, each muscle inserted into the sclera 6mm behind the cornea.
The oblique muscles are superior and inferior oblique. All these muscles are supplied by oculomotor nerve except superior oblique which is supplied by trochlear nerve and lateral rectus which is supplied by abducent nerve. The levator palpebrae superioris is supplied by oculomotor nerve and cervical sympathetic trunk.
Action of ocular muscles:-
Superior rectus:- turns sclera superiorly and medially.
Inferior rectus:- turns sclera inferiorly and medially.
Medial rectus:- turns sclera medially.
Lateral rectus:- turns sclera laterally.
Superior oblique:- turns sclera inferiorly and laterally.
Inferior oblique:- turns sclera superiorly and laterally.
Superior rectus and inferior oblique:- turns sclera superiorly.
Inferior rectus and superior oblique:- turns sclera inferiorly.
Oculomotor nerve (3rd cranial nerve):-
Consist of three components:-
General somatic efferent:- motor to the superior, medial and inferior rectus muscles, inferior oblique and levator palpebrae superioris muscle.
General somatic afferent:- proprioception from the same muscles.
Special visceral efferent:- parasympathetic to the muscle of the iris and ciliary body.
The oculomotor nerve emerges from the anterior surface of the midbrain on the medial side of cerebral peduncles, it enters the lateral wall of cavernous sinus superior to trochlear and ophthalmic and maxillary division of trigeminal nerve, then it enters the superior orbital fissure between the two head of lateral rectus muscle where it is divided into upper and lower branches. The upper branch is small and crosses the optic nerve and supplies superior rectus muscle and terminates into levator palpebrae superioris muscle.
The lower branch is large runs under the optic nerve supplies medial rectus, inferior rectus and inferior oblique muscles, from nerve to inferior oblique branch passes to ciliary ganglia.