Head and Neck Lecture for Dentistry Students PDF

Scalp & Meninges SCALP:  The skin & connective tissue that covers the cranial vault.  Extent:  sup. Nuchal lines (post.)  gives an attachment for occipitalis m. or occipital belly of occipitofrontalis.  Supraorbital margins (ant.)  Zygomatic arches (lat.)  NOTE: The highest nuchal lines give...

Scalp & Meninges SCALP:  The skin & connective tissue that covers the cranial vault.  Extent:  sup. Nuchal lines (post.)  gives an attachment for occipitalis m. or occipital belly of occipitofrontalis.  Supraorbital margins (ant.)  Zygomatic arches (lat.)  NOTE: The highest nuchal lines gives an attachment for Galea Apneurotica(intermediate tendon of occipitofrontalis).  5 layer: indicated by its letters SCALP (from outward to inward). SCALP Layers S: Skin  Many hair follicles & sebaceous glands (are the glands associated with the hair follicles that secrete oily substance that lubricate the hair (sebum).  Consist of:  stratified sequamas epithelium, epidermis, and dermis.  Rich in blood Supply. C: Connective tissue  Thick, dens C.T. with septa & fat lobules (fibrofatty).  Rich in blood Supply.  Very important clinical importance  in that injuries or laceration in the scalp will result in profuse bleeding because of its attachment to the walls of blood vessels.  Blood vessels and nerves of scalp are running within this layer A: Aponeurosis (flat tendon)  Epicranial aponeurosis= Galea Aponeurotica.  Strong tendinous sheet that extends between the frontal belly and occipital belly of occipitofrontalis m.  Provides attachment for:  occipitofrontalis m. 1  1st 3 layers move together as one unit & called: Scalp proper. L: Loose C.T. (areolar C.T.)  Has many potential spaces:  The space does not exist normally (it is not a real space) but can develop into a real space in pathological condition (infection, injury).  Sponge like layer.  Allows free movement of scalp proper over bone.  The contraction of the occipitalis m. will pull the scalp proper posteriorly. P: Periosteum (pericranium)  Outer C.T. layer that surrounds the bones of calvaria (cranial vault).  Firmly attached to the bone at the sutures. Innervations to The Scalp Anteriorly: (2 nerves)  Supratrochlear & Supraorbital n. (from V1)  V1 ophthalmic division of trigeminal n. , that is located inside the orbit.  They will leave the orbit and go upward (directly above the orbital margin passing through the supraorbital notch or supraorbital foramen (Supraorbital n.).  supplying the forehead and the scalp as far as the vertex and more medially above the trochlea (Supratrochlear n.) supplying the forehead and the scalp.  The supraorbital n. extends toward the vertex more than the Supratrochlear n. Laterally:( 2 nerves)  Zygomaticotemporal n.:  fromV2 branch of maxillary division of trigeminal n.  supplying very small area over the temple region of the scalp.  Auriculotemporal n.:  (from v3 branch mandibular division from trigeminal n.)  supplying the auricle and large area over the temple region of the scalp. 2 Posteriorly.: (2 nerves)  lesser occipital n.:  supplying the skin of the temple region (Opposite to auricle).  Greater occipital n.:  supplying the posterior occipital region as far up as the vertex. Arteries of The Scalp  In Which Layer? C: Connective tissue. Anteriorly.:  Supratrochlear & Supraorbital a. (indirect branches from ICA)  The ICA:  located inside the cranial cavity.  It will give the ophthalmic a. that will enter the orbit through the optic foramen.  Inside the optic foramen will give many branches.  two of them will leave the orbit (Supratrochlear & Supraorbital a.)  the Supratrochlear is located more medially. (nerve or artery). Laterally:  Superficial temporal a. (from ECA) that pass between the external auditory meatus and the neck of the mandible.  Here you can feel the pulse of this artery. Posteriorly:  Post. Auricular a.  Occipital a. Both of them supply the scalp posteriorly. (From ECA)  NOTE: Scalp is an area of anastomosis(Connection) between branches of ICA & ECA. Summary:  Supratrochlear & Supraorbital a. with Supratrochlear & Supraorbital n.  Superficial temporal a. with Auriculotemporal n.  Post. Auricular a. with lesser occipital n.  Occipital a. with Greater occipital n. 3 Veins of The Scalp  Supratrochlear + Supraorbital veins unite:  To form the Facial vein that will pass diagonally in the face.  Superficial temporal vein:  Join Maxillary unites to form the Retromandibular vein that will divide into ant. And post. Division  Posterior auricular vein:  Join Posterior division of the retromandibular to form the External jugular vein. That will drain into subclavian vein.  Occipital vein:  Posteriorly will drain into occipital venous plexus that will drain into vertebral vein or can also drain into internal jugular vein.  The veins of the scalp freely anastomose with one another and are connected to the diploic veins and the Dural venous sinuses by Emissary veins. Emissary Veins & Diploic Veins Clinical: Injuries to The Scalp  The scalp is one of the richest areas of blood Supply in the body.  2 Sources: ECA & ICA.  Small injuries to the scalp can result in severe prolonged bleeding Due to:  rich blood supply  separation of vessel ends by C.T. Septa & the aponeurosis.  Remember that: the aponeurotic layer is attached to two m. (ant. Frontalis and post. Occipitalis)  when the scalp is injured  the frontal belly will pull anteriorly and the occipital will pull posteriorly will result in opening of the injury more and that will result in increased bleeding. ) ‫(الحل‬: suturing the injury. 4 Scalp Infections  Pus or blood spreads easily in the loose connective tissue layer of SCALP.  Danger area of scalp: This is because there are not many fibers in it, so Infection and pus spread easily.  Infection or fluid in this layer (pus or bld.) cannot pass posteriorly or laterally, WHY??  Posteriorly.: because of the firm attachment of occipitalis m. to the bone.  Laterally: because of the attachment of temporal fascia.  instead, Infection or fluid in this layer (pus or bld.) can spread either:  Anteriorly  eyelids (resulting in black eye or Ecchymosis of the eye) & root of nose because the frontal belly is not attached to bone.  Into the cranial cavity through emissary veins. The Cranial Meninges  Three layers of connective tissue that protect and surround the brain and spinal cord. (CNS).  Meninges  (singular : meninx)  Function:  Protect the brain.  Provide supporting framework for (a. & v.) the arteries of the brain (cerebral arteries) will pass between the second and third layer in what is known as the subarachnoid space.  Enclose fluid-filled cavity (CSF).  Three layers: (from outer to inner one)  Dura mater )‫(األم الجافية‬: tough membrane covering the brain and spinal cord.  Arachnoid mater )‫ ألنه الها امتدادات‬، ‫ (األم العنكبوتية‬inside the dura mater, there are projections extend from the arachnoid into the subarachnoid space, below the arachnoid.  between the arachnoid and pia mater, we have a space filled with a fluid known as cerebrospinal fluid, inside it have strand of C.T that resembles the spider web (Hence the name) and we have cerebral arteries in subarachnoid space.  Pia mater (‫ )األم الحنون‬the inner most layer that is closely adherent to the brain structure and it follows the sulci or the grooves of the brain and the Arachnoid & dura are not.  NOTE: Mater not matter, mater means mother. 5 1.Dura Mater:  Most external part.  Double layered membrane.  2 layers:  External periosteal or endosteal layer.  Internal meningeal layer (known as dura mater proper).  These two layers are adherent except at dural venous sinuses.  Brain Venous Sinuses are located between periosteal & meningeal layers of dura.  In the picture (doctor’s video 26:58 -30:00): ‫شوفوا شرح الدكتور‬  We can see the two layer of the Dura mater in each side.  These layers are strongly connected to each other and then Split from each other.  When they Split from each other, they form a gap called sinus (superior sagittal sinus) on of the Dural venous sinus of the brain.  we have Arachnoid mater consist of:  subarachnoid space: contains from 1.cerebral vessels. 2. Cerebrospinal fluid. 3.arachnoid trabeculae: are strand of the connective tissue that extend between arachnoid mater and the pia mater.  The pia mater is vascularized so we can see it in the red color and it follows the brain contours into the sulci and up to the gyri.  Note:  The cerebral vessels are located in the subarachnoid space and the meningeal vessels are located epidural. (either between two layers of dura or between outer layer of dura and bone) and any injury in (meningeal artery) will lead to epidural hemorrhage like middle meningeal artery. 6  The meninges extend to cover the spinal cord and are therefore called spinal meninges.  The outer layer will not extend to cover spinal cord but it will reflect at the side of foramen magnum to become continues with outer periosteal layer while the inner meningeal layer will extend downward and cover the spinal cord.  We have also:  Dura mater  Arachnoid mater: subarachnoid space.  Pia mater. Dural Reflections  Folds of internal meningeal layer between brain compartments, and these compartments are subdivisions of the cranial cavity by these reflections of inner layer of dura.  4 main reflections:  falx cerebri.  falx cerebelli.  tentorium cerebelli.  sellar diaphragm.  Function:  They restrict rotary movement or rotary displacement. ) ‫دوارة‬ ّ ‫( حركة‬  Falx cerebri  between two cerebral hemispheres and attach ant. To the crista Galli and frontal crest.  Falx cerebelli superior sagittal sinus  between two cerebellar hemispheres.  Sellar diaphragm: (diaphragma sellae)  above pituitary gland except for the pituitary stalk.  Tentorium cerebelli:  between cerebellum and occipital lobe of cerebrum (between cerebellum in the post. Cranial fossa and the occipital lobe forming a tent above the cerebellum).  Each Dural reflection has attached border and free border within the attached border run the Dural venous sinuses. (except inferior sagittal sinus that is located at the free border of the falx cerebri ) 7 Dural Reflections  Falx Cerebri & Falx Cerebelli Sickle –shaped.  Tentorium cerebelli  Crescent-shaped (half a moon( This is called longitudinal fissure of the brain, separates the two cerebral hemispheres , and longitudinal fissure is occupied by the falx cerebri. 2.Arachnoid Mater:  Thin Intermediate layer that attaches to pia mater through web-like arachnoid trabeculae.  Avascular layer.  CSF nourishes this layer  The arachnoid mater attached to dura,  and There is no real space between  them, there is potential space WHY?  Because it is always held against dura (by pressure of CSF (cerebrospinal fluid).  Subarachnoid space: (the real space)  between arachnoid & pia.  contains: arachnoid trabeculae & Cerebrospinal fluid (CSF).  We have a structures called arachnoid granulations, that are projections from the arachnoid mater into the dural vinous sinus, and these structures and arachnoid villi will return the CSF to the blood to the venous sinus.  The CSF is formed by blood and it will return to the blood. 3.Pia Mater:  Very thin & delicate membrane that is highly vascularized.  Adheres to brain surface & follows its contours. Meningeal Spaces  Three spaces.  Epidural Space: (potential space)  between dura & bone.  not present normally.  happens pathologically (as hemorrhage). 8  Recall  pterion.  Subdural Space: (potential space)  between dura and arachnoid  not present normally, occurs only in pathological conditions (subdural hematoma)  Subarachnoid Space:  A real space.  Contains CSF.  Spaces that are not present normally are called potential spaces (but can develop in injury or in infection). Arterial Supply to Meninges (Dura & Calvaria)  Middle Meningeal artery & Accessory Meningeal artery:  From the maxillary artery.  Middle Meningeal a. will pass to the skull through foramen spinosum.  Accessory Meningeal a. through foramen ovale.  2 Anterior meningeal arteries:  From the ethmoidal artery.  They are branches of the ophthalmic a. of the ICA.  Four Post. Meningeal arteries:  Two will come From the ascending pharyngeal a.  pass through jugular foramen and hypoglossal canal.  One will come from vertebral a.  pass through foramen magnum.  One will come from occipital apass through mastoid foramen. Clinical: Epidural Hemorrhage  Type of the “Intracranial Hemorrhage”.  Due to injury to a meningeal artery  Middle meningeal a. (pterion)  Blood Collects between:  bones of calvaria & periosteal layer or  or between the two layers of dura periosteum & meningeal layers (more common). 9  Complications:  blood. Mass  compress the brain loss of consciousness & coma death.  Rx.: )‫(الحل‬ (Drill hole) draining blood & closure of the artery (ligation). Dural Venous Sinuses  Blood filled spaces within dura matter that are lined with endothelium and drain all blood from brain and meninges.  Without smooth muscles so it not like veins.  Location: Between the periosteal and meningeal layers of dura, where Dural foldings attach.  Main(‫)مهم‬:  Sup. Sagittal sinus: the blood Runs through it from front to back.  Inf. Sagittal sinus: the blood Runs through it from front to back.  Straight sinus: The Inf. Sagittal sinus will join the great cerebral vein to form straight sinus that will run between falx cerebri and tentorium cerebelli.  In the internal occipital protuberance area  connecting point of sinuses called confluence of sinuses.  Transverse sinus (2): the blood will pass transversely in the right and left Transverse sinuses.  Sigmoid sinus (2):S shaped sinus that will end at the jugular foramen  IJV.  Cavernous sinus (2): two venous sinuses located at each side of Sella turcica, connecting them what is known as the inter cavernous sinuses and they are attached to the pterygoid venous plexus by Emissary veins. 10 Cavernous sinus  At sides of Sella turcica.  Connected to each other by intercavernous sinus.  Communicate with facial vein through (superior & inferior) ophthalmic v. also indirectly through the deep facial vein  the pterygoid venous plexus emissary vein cavernous sinus.  Recall : Danger triangle of face  Structure that pass in the cavernous sinus:  Abducent nerve (VI).  ICA.  Structures that pass in the lateral wall of cavernous sinus:  Oculomotor n (III).  Trochlear n. (IV).  Ophthalmic n. (V1).  Maxillary n. (V2). Spread of infection  Can occur:  Through emissary veins: from superficial veins of scalp to Dural venous sinuses.  Through connection from facial vein to cavernous sinus. If you have any questions don’t hesitate to contact us The End 11