The next few chapters (scalp and face, anterior triangle, posterior triangle, and posterior neck) complete the superficial dissection of the head and neck. The head and neck section begins with a description of the bones of the region - the cervical vertebrae and the skull.
Introduction
The typical cervical vertebrae
Anterior to the foramen is a bony bar - the costal process - which projects laterally from the body to the end of the anterior tubercle. A bony bar—the costotransverse bar—unites the anterior and posterior tubercles and completes the foramen transversarium.
The atypical cervical vertebrae
The superior and inferior articular processes are short bony rods at the junction of the pedicle and lamina on each side [Fig. The costal process corresponds to the rib and gives attachment to two muscles - scalenus anterior and longus capitis.
C. 1 (atlas)
The superior and inferior aspects of the process are cut at an angle to form the joint facets. The transverse process of the atlas is long and thick and lacks an anterior tubercle.
C. 2 (the axis)
The superior and inferior articular facets lie on the lateral masses for the first and second cervical nerves, respectively. An inward projection of each lateral mass gives attachment to the transverse ligament of the atlas, which divides the vertebral foramen into a small anterior compartment for the dens, and a larger, oval posterior compartment for the spinal cord and its coverings.
Surface projections of cervical vertebrae
On examination, he had pain and tenderness in the neck with pain radiating from the neck to the shoulder. Answer: fractures of cervical vertebrae can cause damage to the spinal cord, leading to spinal shock, quadriplegia, or even death.).
General architecture of the skull
External features of the skull
Frontal or anterior view of the skull
The lower edge of the body extends laterally to the angle of the lower jaw. The two halves of the mandible are fused in the adult at the symphysis menti.
Superior view of the skull
Below the nasal opening, the two maxillae are firmly connected in the median plane by the articulation of the alveolar processes. Identify the horizontal body of the mandible that carries the alveolar sockets for the lower teeth.
Posterior view of the skull
The upper edge is formed by the two nasal bones, which articulate with each other in the midline. The mental foramen lies approximately 4 cm lateral to the midline between the alveolar border and the lower edge of the mandible.
Lateral view of the skull
The squamous part of the temporal bone lies below the lower edge of the parietal bone. The zygomatic process of the temporal bone arises from the postero-inferior side of the squamosal part.
Inferior view of the skull
On the inferior aspect of the petrous part of the temporal bone is the carotid canal. Between the infratemporal crest on the greater wing of the sphenoid and the lateral pterygoid lamina is the infratemporal fossa.
Internal features of the base of the cranial cavity
Note the coronal suture between the frontal and parietal bones, the sagittal suture between the two parietal bones, and the lambdoid suture between the occipital and parietal bones [Fig.
Internal features of the skull
Internal features of the vault
The apex of the petrous temporal bone is directed toward the body of the sphenoid bone. The posterior surface of the petrous part of the temporal bone laterally forms the anterior border of the posterior cranial fossa.
Surface anatomy
We begin the study of the head with dissection of the scalp, including the temple and face.
Auricle
Back and side of the head
Face
The free edge of the eyelids is rounded medially and has a small elevation - the lacrimal papilla. The skin of the lower part of the auricle is supplied by the great auricular nerve.
Occipitofrontalis muscle
Epicranial aponeurosis
Nerves of the scalp and temple General features of the nerves
The scalp
The scalp Objectives
Make a coronal incision from the center of the first incision to the root of each auricle. Small branches of the superficial temporal artery supply the temple and anterior part of the scalp.
Arteries of the scalp and temple
It starts behind the neck of the mandible, or deep to the parotid gland. The superficial temporal vein joins the middle temporal vein at the root of the zygomatic arch to form the retromandibular vein.
Veins of the scalp and temple
The supratrochlear and supra-orbital veins unite at the medial angle of the eye to form the facial vein. The occipital veins run with the scalp artery but allow it to join the suboccipital plexus, deep to the semispinalis capitis muscle at the back of the neck.
Lymph vessels of the scalp and temple
Superficial dissection of the face
Facial muscles
Face Objectives
Make a horizontal incision from the corner of the mouth to the posterior border of the mandible. It is in continuity with the lateral part of the orbicularis oris and will be cut later.).
Vessels and nerves of the face Objectives
The fibers of the various muscles converging on the mouth mingle and sweep in curves through the lips. The upper and lower fibers enter the corresponding lip and interdigitate with fibers of the opposite muscle in the midline.
Arteries of the face
Transverse facial artery
Facial artery
Veins of the face
Facial vein
The facial vein receives branches that correspond to the branches of the facial artery. On the surface of the buccinator, it gives off the deep facial vein, which passes medially to the masseter to join the pterygoid plexus of veins.
Nerves of the face
Sensory nerves of the face
In the neck it crosses the carotid arteries and drains into the internal jugular vein.
Motor nerves of the face
Structures in the cheek and lips
Buccinator
Buccopharyngeal fascia
Buccinator Objective
Molar glands and buccal lymph nodes
Buccal pad of fat
Levator anguli oris
Mentalis
Labial and buccal glands
Eyelids
Tarsal plates
Palpebral fascia and tarsi Objective
Palpebral ligaments
Levator palpebrae superioris
Vessels and nerves of eyelids
Lacrimal gland
Conjunctiva
The lacrimal apparatus
The space bounded by the bulbar and palpebral conjunctivae is known as the conjunctival sac. It opens outward through the palpebral fissure and empties into the lacrimal sac through the canaliculi [Fig.
Lacrimal canaliculi
Lacrimal sac
Nasolacrimal duct
Cartilages of the nose
Inferior alveolar nerve block to anesthetize all mandibular teeth is done by infiltrating the nerve in the lingula of the mandible. Lingual nerve block to anesthetize the anterior two-thirds of the tongue is done by infiltrating the nerve near the mandibular second molar.
Introduction to the neck
Surface anatomy of the posterior triangle of the neck
The lesser supraclavicular fossa is a shallow depression between the sternal and clavicular parts of the sternocleidomastoid. It is above the medial part of the clavicle and overlaps the internal jugular vein.
General arrangement of neck structures
The posterior triangle
Boundaries and contents of the posterior triangle
Deep fascia of the posterior triangle
Skin reflection and cutaneous nerves and veins of the posterior triangle-1 Objectives
Locate the three cutaneous nerves that pierce the deep fascia in the middle of the posterior border of the sternocleidomastoid. The prevertebral fascia covers the muscles on the floor of the posterior triangle—the levator scapulae, scalenus anterior, medius, and posterior.
Cutaneous branches of the cervical plexus
Cutaneous nerves and veins of the posterior triangle-2 Objectives
The accessory nerve enters the triangle at the posterior border of the sternocleidomastoid muscle and passes postero-inferiorly over the triangle, which is embedded in the fascia [fig. The nerves pass over the corresponding thirds of the clavicle and supply the skin on the front of the chest, up to the level of the sternum and over the upper half of the deltoid muscle [Fig.
External jugular vein
Accessory nerve (eleventh cranial)
Posterior triangle Objectives
To trace the accessory nerve and branches of the third and fourth cervical nerves to the trapezius. Expose the top of the brachial plexus and trace it back to its roots.
Deep dissection of the posterior triangle
Locate the accessory nerve [Fig. 5.4] at the posterior border of the sternocleidomastoid, and follow it and the branches from the third and fourth cervical nerves near it, to the trapezius. Remove the fascia from the inferior belly of the omohyoid and turn the muscle forward to expose the nerve that enters its deep surface near the sternocleidomastoid.
Scalenus anterior
Locate the long thoracic nerve in the axilla and follow it to the three roots of origin. Follow it across the posterior triangle and back toward the origin, removing the deeper layer of the fascia.
Omohyoid, inferior belly
To clear the brachial plexus and identify and trace the branches in the posterior triangle. It joins the tendon which connects it with the superior belly of the omohyoid, deep to the sterno-cleidomastoid.
Subclavian artery, third part
Subclavian vein
Suprascapular and superficial cervical vessels
The fifth and sixth cervical ventral rami (with a small contribution from the fourth) unite to form the upper trunk. It joins the suprascapular nerve at the postero-inferior angle of the posterior triangle and descends with it to the scapular notch [see fig.
The brachial plexus
Supraclavicular part of the brachial plexus Objective
All the roots of the brachial plexus receive gray rami communicantes from the sympathetic trunk. Most of the branches in the neck are muscular and pass to the upper limb.
Skin reflection of the anterior triangle Objectives
Note that it ends in a projection—the superior horn—immediately anterior to the sternocleidomastoid. Only the transverse process of the first cervical vertebra, immediately antero-inferior to the tip of the mastoid process, can be clearly palpated.
Superficial fascia
Platysma
Cervical branch of the facial nerve
Anterior jugular vein
Sternocleidomastoid
Cleaning the sternocleidomas- toid and tracing the accessory nerve
The thick, anterior border of the sternocleidomastoid muscle inserts into the anterior surface of the mastoid process. Damage to the spinal portion of the accessory nerve paralyzes the sternocleidomastoid, causing the neck to bend to the opposite side and the face to rotate to the paralyzed side through the unopposed action of the normal sternocleidomastoid.
Deep fascia of the neck
The posterior part is thin and aponeurotic and is attached to the lateral surface of the mastoid process and the lateral half of the upper neck line. During forced inspiration, the two muscles work together and raise the sternum when neck flexion is prevented by the extensors.
Suprahyoid region
Actions: acting alone, the sternocleidomastoid tilts the head to its own side and rotates the head, so that the face is turned to the opposite side.
Infrahyoid region
Subdivisions of the anterior triangle
Digastric triangle
Digastric triangle Objective
Follow the facial vein posteroinferiorly, superficial to the gland and posterior abdomen of the digastric. The mylohyoid nerve lies on the lower surface of the mylohyoid nerve near the lower jaw.
Carotid triangle
Carotid triangle Objective
The inferior root of the ansa cervicalis arises from the second and third cervical ventral rami. Expose the part of the hyoglossus that lies in the carotid triangle immediately above the hyoid bone.
Muscular triangle
Muscular triangle Objective
It extends from the oblique line on the thyroid cartilage to the lower edge of the greater horn of the hyoid bone [Fig. The lower abdomen of the omohyoid extends from the intermediate tendon to the scapular notch [see Fig.
Introduction to the back
Back of the neck
General arrangement of muscles of the back
Skin reflection and identification of cutaneous nerves of the back Objectives
The intrinsic back muscles are limited to the back and are supplied by the dorsal branches of the spinal nerves. A detailed dissection and description of all the muscles of the back is beyond the scope of this book.
Extrinsic muscles
Superficial dissection of the back of the neck
Reflect the trapezius laterally by separating it from the superior neck line and dividing it vertically 1 cm from the vertebral spines. Locate the accessory nerve on its deep surface with the branches of the third and fourth cervical nerves.
Intrinsic muscles
Actions: both muscles are inspiratory muscles; the superior raises the upper ribs, and the inferior holds down the lower ribs against the pull of the diaphragm.
Superficial layer—splenius
Intermediate layer—erector spinae and thoracolumbar fascia
Intrinsic muscles of the back-1 Objective
Deep layer
Intrinsic muscles of the back-2 Objectives
Occipital artery
Ligamentum nuchae
Deep cervical artery
Suboccipital triangle
Dorsal ramus of the first cervical (suboccipital) nerve
Vertebral artery
Suboccipital plexus of veins
Suboccipital muscles
Suboccipital triangle Objectives
Dorsal rami of spinal nerves
It anastomoses with the descending branch of the occipital artery deep to the semispinalis capitis, and with the superficial cervical artery. In the thorax, the posterior branches of the intercostal arteries supply the muscles and skin of the back, together with branches of the deep cervical artery.
Veins of the back
Greater occipital nerve
Third occipital nerve
Arteries of the back
Arteries of the cervical region
In this chapter, the soft tissue structures seen inside the skull after brain removal are described. Begin the study of this region by removing the skull cap, as described in Dissection 8.1.
Skull cap or calvaria
Sutural ligaments
Removal of the skull cap Objective
From the third to the fourth decade of life, the adjacent cranial bones are united by ossification of the su.
The meninges
Dura mater
The arachnoid and subarachnoid space
The brain has been removed to show the folds of dura mater which incompletely divide the cranial cavity. At the tip of the arachnoid villi are perforations through which the subarachnoid space communicates with the venous sinus [p.
Pia mater
In a few places, notably at the superior sagittal sinus, the arachnoid pierces the dura like a finger or cauliflower. The finger-like projections are arachnoid villi; the more spherical ones are arachnoid granulations [Fig.
Cerebrospinal fluid
The dural venous sinuses also drain the CSF through the arachnoid villi and granulations in the superior sagittal sinus and its lateral lacunae.
Arachnoid villi and granulations
Superior cerebral veins
Structure of dural venous sinuses
Exploration of the superior sagittal sinus
Reflection of the dura Objective
Falx cerebri
Superior sagittal sinus
Lateral lacunae
Exposure of the falx cerebri Objective
A deep depression behind the tip of the temporal lobe of the brain, posterolateral to the orbit. Middle meningeal vessels visible through the dural floor of the lateral part of the fossa.
Removal of the brain
It adapts closely to the irregularities of or. the bital surface of the frontal lobe which separates it from the orbit. The diaphragma sellae is the raised central area formed by the dura lying between the four cli. noid processes of the sphenoid bone. i) Infundibulum as it passes into hy.
Structures seen after removal of the cerebrum
The diaphragm sellae is the raised central area formed by the dura stretched between the four cli. noid processes of the sphenoid bone. i) Infundibulum when it passes into hy. ii). The oculomotor nerves as they pierce the dura, medial to the free border of.
Tentorium cerebelli
Remove the brain from the cranial cavity, dividing any roots of the accessory nerve still attached to the spinal cord. Removing the brain in this way, without complete separation of the tentorium from the skull, tears the great cerebral vein.
Paranasal air sinuses
Dural venous sinuses Inferior sagittal sinus
Straight, transverse, and sigmoid sinuses Objective
It arises in the orbit and enters the cranial cavity with the anterior ethmoidal artery between the frontal and ethmoid bones [Fig. The nerve and artery supply the mucous membrane of the upper anterior part of the nasal cavity and terminate as the external nasal artery and nerve.
Middle cranial fossa
Hypophysis or pituitary gland
Frontal air sinuses
Anterior cranial fossa
Anterior ethmoidal nerve
Frontal air sinus Objective
Anterior cranial fossa Objective
Cavernous sinus
Pituitary gland Objective
Back pressure in the ophthalmic veins can cause the eyeball to protrude and even blink. Using the instructions in dissection 8.10, expose the structures at the base of the middle cranial fossa.
Trigeminal nerve
Middle cranial fossa Objectives
Follow the ophthalmic nerve into the lateral wall of the cavernous sinus, where it divides into three branches that can be traced to the superior orbital fissure [Fig. Raise the trigeminal ganglion and try to identify the motor root of the trigeminal nerve on its lower surface.
Trigeminal ganglion
Oculomotor nerve
Trochlear nerve
Abducens nerve
Intracranial part of the internal carotid artery
The tortuous course of the internal carotid artery produces a tortuous groove on the side of the body of the sphenoid [Fig. The internal carotid artery gives off the following branches at the base of the brain: (1) the ophthalmic artery to the orbit; (2) small twigs on the pi.
Meningeal vessels of the middle cranial fossa
At the root of the lesser wing of the sphenoid, the artery becomes sharp again. It then runs obliquely upward and posteriorly, parallel to and slightly posterior to the coronal suture, often sending a large branch posteriorly on the deep surface of the parietal bone [Fig.
Petrosal nerves
The ophthalmic and lacrimal arteries from the orbit also send branches through the superior orbital fissure to the middle cranial fossa. Its fibers synapse with the cells of the otic ganglion on the medial side of the man.
Posterior cranial fossa
Structures seen in the posterior cranial fossa
Dura mater of the base of the skull
Dural venous sinuses in the posterior cranial fossa
Venous sinuses of the posterior cranial fossa
Diploic veins
Emissary veins
Meningeal veins
Other symptoms of CST arise due to the close relationship between the cavernous sinus and the third, fourth, fifth - ophthalmic and maxillary divisions -. Deep to the covering formed by the pre-tracheal fascia is the fibrous capsule of the gland.
Lobes of the thyroid gland
It extends from the oblique line on the thyroid cartilage down to the fifth or sixth tracheal ring. It is surrounded by a sheath of pretracheal fascia, which is attached above to the oblique line of the thyroid cartilage and to the arch of the cricoid cartilage.
Thymus
This attachment to the thyroid cartilage means that the thyroid gland moves with the larynx when swallowing and speaking – a feature that helps differentiate thyroid swellings from swellings of adjacent structures. The gland varies widely in size and is relatively larger in women and children than in men.
Thyroid gland
Isthmus of the thyroid gland
Arteries of the thyroid gland
Thyroid gland, trachea, oesophagus, and related structures Objectives
Remove the fascia from the lobes of the thyroid gland and expose the arteries and veins that feed it. Pull the upper part of the thyroid gland laterally and follow the external laryngeal branch of the superior laryngeal nerve to the cricothyroid muscle.
Veins of the thyroid gland
Lymph vessels of the thyroid gland
Parathyroid glands
Trachea and oesophagus
Thyroid and parathyroid glands Objective
Examine the posterior surface of the thyroid lobe and identify blood vessels and parathyroid glands. Make an incision through the thyroid lobe and examine the surface with a hand lens.
Trachea and oesophagus Objective
Locate the anastomotic vessel between the superior and inferior thyroid arteries on the medial part of the posterior surface. The best guide to the parathyroids is the small parathyroid artery which arises from the inferior thyroid artery.
Trachea
Oesophagus
Vessels and nerves of the neck Objectives
On the left, find the thoracic duct that enters the junction of the internal jugular and subclavian. On both sides, expose the small cervical part of the brachiocephalic vein and its side branches.
Brachiocephalic trunk
Subclavian artery
First part of the subclavian artery
Second part of the subclavian artery
The deep cervical artery passes in the back of the neck above the neck of the first rib. None of the veins corresponding to the branches of the subclavian artery drain into the subclavian vein.
Brachiocephalic veins
It arches posteriorly over the pleura and divides at the neck of the first rib into the deep cervical and superior intercostal arteries. The internal thoracic vein joins the brachiocephalic vein near the upper opening of the thorax.
Tributaries in the neck
If the lung has been removed, these are examined from the interior of the thorax [Fig. The subclavian vein is a continuation of the axillary vein at the outer border of the first rib.
Thoracic duct
In the neck, the anterior pleura lies behind the medial part of the clavicle [Fig. The mode of termination of the three lymphatic trunks changes the territory drained by the thoracic duct.
Cervical pleura
Vertical neurovascular bundles of the neck
Neurovascular structures of the neck Objectives
Make a midsagittal saw cut through the anterior part of the skull to the foramen magnum. Find the glossopharyngeal, accessory and hypoglossal nerves in the upper part of the nose.
Common carotid artery
Carotid sinus and carotid body
External carotid artery
The posterior auricular artery is a small branch which extends along the upper border of the posterior belly of the digastric [Fig. The ascending pharyngeal artery is the first and smallest branch of the external carotid artery.
Internal carotid artery
The rest of the neck - mainly muscle and bone - is supplied by the subclavian artery [Fig. The rest of the structures in the head are supplied by the external carotid arteries.
Internal jugular vein
Of the common, internal, and external carotid arteries on each side, only the external carotid artery provides branches to structures in the neck (primarily to the parts of the respiratory and digestive systems). The internal carotid arteries supply a significant portion of the brain, orbital contents, forehead, anterior portion of the scalp, and parts of the external nose and walls of the nasal cavities.
Nerves of the neck
Glossopharyngeal nerve
It receives taste and general sensation from the posterior third of the tongue, vallate papillae [see Fig. 18.1], palatine tonsil, part of the soft palate and adjacent pharynx, and the anterior surface of the epiglottis.
Branches of the glossopharyngeal nerve
It has two small sensory ganglia at the base of the skull - superior and inferior ganglia. It descends between the internal jugular vein and the internal carotid artery, wraps around the lateral surface of the stylopharynx, between the internal and external carotid arteries, and together with this muscle passes into the pharynx [see Figure 1].
Vagus nerve course
At the root of the neck, each vagus crosses the anterior surface of the corresponding subclavian artery. The right vagus then descends posterior to the brachiocephalic vein to the right side of the trachea in the thorax.
Branches of the vagus nerve
Accessory nerve
Branches to all the internal and external muscles of the tongue except the palatoglossus [Fig.
Cervical sympathethic trunk
Hypoglossal nerve
Branches of the hypoglossal nerve
On the right, it passes before or behind the subclavian artery and descends behind the brachiocephalic trunk to end in the deep cardiac plexus. It creates: (1) the gray rami communicates with the fifth and sixth cervical nerves; (2) branches of the thyroid forming a plexus in the inferior thyroid artery and communicating with the recurrent and external laryngeal nerves; (3) middle cervical cardiac nerves in the deep cardiac plexus;.
Sympathetic ganglia and rami communicantes
Cervical sympathetic ganglion Objective
When the inferior cervical ganglion is not fused with the first thoracic ganglion, it is small and lies posterior to the common carotid and vertebral arteries, anterior to the eighth ventral cervical ramus. The inferior cervical ganglion has the following branches, which arise from the cervicothoracic ganglion when they unite: (1) the gray rami communicates with the seventh and eighth cervical rami; (2) fine filaments from the ansa subclavia to form the subclavian plexus in the subclavian artery; (3) larger filaments to form the vertebral plexus in the vertebral artery; and (4) the inferior cervical nerves passing with the median cervical nerve in the deep cardiac plexus.
Branches of the cervical plexus
Scalene muscles
Cervical plexus
Ventral rami of cervical spinal nerves
The scalenus medius is innervated by the dorsal scapular nerve and by the upper two roots of the long thoracic nerve [see Fig.
Scalenus posterior
Cervical fascia
Investing fascia
Scalenus medius
The buccopharyngeal fascia is a delicate, decomposable fascial layer that covers the constrictor muscles of the pharynx and buccinator.
Lymph nodes and lymph vessels of the head and neck
Superficial lymph nodes of the head Occipital lymph nodes
Pre-tracheal fascia
Carotid sheath
Prevertebral fascia
They receive lymph from a wedge-shaped area, including the lower incisors, gums, and front of the floor of the mouth. The submandibular lymph nodes lie along the submandibular gland, mostly under the mandible.
Superficial cervical lymph nodes
Two of the nodes are particularly large: the jugulo-gastric nodes that drain the palatine tonsil and tongue, and the jugulo-omohyoid nodes. See Clinical Applications 9.1, 9.2, and 9.3 for the practical implications of the anatomy discussed in this chapter.
Deep cervical lymph nodes
The external branch of the superior laryngeal nerve runs with the superior thyroid vessel to the superior pole of the thyroid gland. Elevation of the hyoid bone and the thyroid gland and cricoid cartilage during swallowing causes the thyroid gland to rise.).
Muscles
Longus colli
Longus capitis
Rectus capitis anterior
Rectus capitis lateralis
This chapter describes the muscles and vessels that lie in front of the cervical vertebrae.
First part of the vertebral artery
Second part of the vertebral artery
It is anterior to the ventral branches of the cervical nerves between the transverse processes. The artery passes vertically upwards through the foramen transversaria of the sixth to the second cervical vertebra.
Third part of the vertebral artery
In the transverse foramen of the axis, the artery turns laterally below the superior articular facet, bends upward and enters the foramen transversary of the atlas, which is laterally more distant than the others [see Fig.
Fourth part of the vertebral artery
Branches of vertebral artery
Vertebral vein
The orbit contains the eyeball, optic nerve, extraocular muscles that move the eye, associated vessels and nerves, orbital fat, and fascia. It also contains the lacrimal gland and the levator palpebrae superioris, the muscle that raises the upper eyelid.
Bony orbit
Ethmoidal sinuses
Roof of the orbit Objectives
The anterior and middle ethmoidal sinuses open into the middle nasal cavity [see Fig. Examine them with a blunt probe, trying to find their openings in the nasal cavity.
Orbital periosteum
Frontal nerve
Supratrochlear nerve
Supra-orbital nerve
Orbit Objectives
Lacrimal nerve
The concave medial surface of the gland rests on the levator palpebrae superioris and lateral rectus. It comes from the roof of the orbit, immediately in front of the optic canal.
Extraocular muscles of the eyeball
Nine to ten thin tubes of the gland open on the deep surface of the upper eyelid near the superior conjunctival fornix [see Fig. Parasympathetic secretomotor nerve fibers to the gland originate in the pterygopalatine ganglion and reach the gland through a branch of the zygomatic nerve.
Superior rectus
Superior oblique
Fascial sheath of the eyeball Objective
Optic nerve
Parasympathetic ganglia
Nasociliary nerve
Post-ganglionic sympathetic and sensory fibers of the trigeminal nerve frequently pass through this ganglia, but have no functional connection with it. The post-ganglionic sympathetic nerves reach the ganglia through plexuses on the arteries that supply them.
Ciliary ganglion
Connections of the ciliary ganglion
-Sympathetic and sensory ganglionic fibers of the trigeminal nerve often pass through these ganglia, but have no functional connection with them. They divide into 12-20 nerves which pierce the sclera around the entrance of the optic nerve.
Ophthalmic artery
They carry post-ganglionic fibers to the eyeball and innervate the sphincter pupillae and the ciliary muscle.
Course
Branches of the ophthalmic artery
Ophthalmic veins
The recti superior and inferior cause simple elevation and depression of the cornea only when the eye is abducted. When the eye is turned medially, the visual axis moves closer to the axis of the oblique muscles.
Extraocular muscles of the eyeball (continued)
Elevation and depression of the cornea is caused by different groups of muscles, depending on whether the eye is abducted or adducted. In addition to the four main movements of adduction, abduction, elevation, and depression of the eyeball, the eyeball also rotates about an anteroposterior axis.
Origin of the extraocular muscles
The medial rectus rotates the cornea medially (adduction of the eye) and the lateral rectus rotates it laterally (abduction of the eye). As the cornea is rotated medially, the superior and inferior recti become progressively less effective in elevating and depressing the cornea, but tend to rotate it further medially [Fig.
Insertions of the extraocular muscles
In the medially turned eye, the inferior oblique produces elevation and the superior oblique produces depression. Both superior and inferior ophthalmic veins receive numerous orbital tributaries, pass through the superior orbital fissure, and empty into the cavernous sinus either separately or through a common trunk.
Actions of the extraocular muscles
Origin of the extraocular muscles
Both divisions enter the orbit between the two heads of the lateral rectus muscle [Fig. It is in this position that the oblique muscles become effective elevators (inferior oblique) and depressors (superior oblique) of the cornea.
Ligaments in the orbit
Each of the extrinsic muscles of the eyeball pierces the fascial sheath at the equator of the eyeball and receives a covering sleeve from it. Each of these sleeves is attached by fibrous tissue to the bony wall of the orbit and acts as a pulley to prevent the muscle from compressing the eyeball when it contracts.
Fascial sheath of the eyeball
Any downward gaze that a patient can achieve is only by superior oblique action. CLINICAL APPLICATION 11.1 Conjugate eye movements Eye and pupil movements occur continuously to bring.
General structure of the eyeball
The eyeball lies in the anterior part of the orbit, surrounded by a fascial sheath that separates it from the orbital muscles and fat. The front bright part - the cornea - has a smaller radius of curvature than the rest of the globe and protrudes from the front surface of the eyeball.
Fibrous coat
For a satisfactory dissection of the eyeball, use one that has been fixed for several days in formaldehyde.
Sclera
Sectioning of the eyeball Objectives
Pick up the conjunctiva and fascial sheath close to the corneal margin and cut through these layers around the corneal edge. Identify the posterior ciliary arteries and ciliary nerves as they enter the sclera around the attachment of the optic nerve [Fig.
Cornea
Continue to remove these soft parts from the surface of the white part of the eye (sclera), working steadily back towards the entrance of the optic nerve. To get a general idea of the parts of the eyeball, make sections of the hardened specimens in different planes: (1) through the equator; (2) horizontal section.
Middle (vascular) coat choroid
Iris
Pectinate ligament of the iris
Blockage of this system is associated with a serious condition called glaucoma, in which the intraocular tension increases sharply.
Ciliary body
Choroid
Ciliary nerves
Choroid Objective
Iris and ciliary processes Objective
Ciliary arteries
Venae vorticosae
Retina
Retina Objective
The nerve fibers coming from the ganglion cell run across the inner surface of the retina and converge on the optic nerve. In the center of the visual axis is a small yellow spot on the retina: the macula lutea.
Central retinal arteries and veins
At the beginning of the optic nerve, the retina has a circular elevation, with a slight central depression on it. At the fovea, the inner layers of the nerve layer of the retina are swept aside to expose the cones.
Vitreous body
Ciliary zonule and lens Objective
Lens
Ciliary zonule and suspensory ligament of the lens
Lens Objective
This will remove the lens body and allow the capsule to be studied separately. Stimulus of the cornea of one side elicits a direct (ipsilateral) and consensual (opposite side) blink response.
The external ear
It can be easily distinguished into three parts: the outer ear, the middle ear, and the inner ear.
External acoustic meatus
In the bony part of the canal, the skin is thin and adheres tightly to the periosteum. It has no hairs and few or no glands and continues as a very delicate layer over the lateral surface of the eardrum.
Tympanic membrane
External acoustic meatus Objective
Middle ear
Introduction to middle ear cavity
The part of the upper cavity to the tympanic membrane is called epitympanic incision [Fig.
Boundaries of the middle ear cavity
Middle ear cavity Objectives
The upper part of the back wall (mastoid) of the middle ear cavity has an opening - aditus. Identify the thin tendon that runs from the malleus to the medial wall of the middle ear.
Mucous membrane of the middle ear cavity
Movements of the stapes generate pressure waves to the fluid in the bony labyrinth (perilymph). The tympanic cavity and the cavity of the ear canal can become blocked when the lining swells during inflammation.
Auditory ossicles
The middle ear cavity contains: (1) the ossicles - malleus, anvil, and stirrup; (2) the tendon of the stapedius and tensor tympani muscles; and (3) the chorda tympani nerve and the tympanic plexus of nerves. Once blocked, the air in the cavity is absorbed by surrounding blood vessels, leading to a drop in pressure and hearing loss because the eardrum cannot vibrate freely.
Tympanic muscles
The chorda tympani carries taste fibers from the anterior two-thirds of the tongue, and preganglionic parasympathetic fibers to the submandibular ganglion. The parasympathetic fibers innervate the submandibular and sublingual salivary glands and the glands in the anterior two-thirds of the tongue.
Mastoid antrum and mastoid air cells
15.8], runs antero-inferiorly, medially to the spine of the sphenoid, and joins the lingual nerve a short distance below the skull [Fig.
Chorda tympani nerve
It is widest at its junction with the middle ear cavity and narrowest where it joins the cartilaginous part, posteromedial to the spine of the sphenoid bone. The bony part lies between the petrous and tympanic parts of the temporal bone, below the semicanal in front of the tensor tympani, lateral to the internal carotid artery in the carotid artery [Fig.
Intrapetrous parts of the facial and vestibulocochlear nerves
Using the instructions given in dissection 13.3, dissect the mastoid antrum, mastoid air cells, and middle ear cavity.
Auditory tube
In the vertical part of its course the facial nerve gives off: (1) the nerve to the stapedius; (2) the chorda tympani; and (3) small branches to the over branch of the vagus [Fig.
Vestibulocochlear nerve
Facial nerve
Mastoid antrum, mastoid air cells, and middle ear cavity Objectives
Remove all soft parts, including the periosteum, from the lateral surface of the temporal bone of the mastoid and identify the suprameatal triangle and supramastoid crest. Extend the bone removal anteromedially, parallel to the posterior wall of the external acoustic meatus, until the mastoid antrum is opened.
The internal ear
Facial nerve Objective
It is separated from the walls of the bony labyrinth by a space that contains a similar fluid - the perilymph - and some delicate connective tissue. It registers the direction of gravity acting on the head and the rotational movements of the head.
Bony labyrinth
The scala vestibuli continues with the vestibule at the base of the cochlea. The scala tympani also extends into the aqueduct of the cochlea, which passes through a canal in the bone - the cochlear canaliculus [Fig.
Membranous labyrinth
The saccule is continuous with the base of the cochlear duct through the ductus reu. Answer: the mucosa of the nasopharynx is continuous with that of the middle ear cavity through hearing.
Parotid gland
Shape and position of the parotid gland
The part of the gland deep to the ramus of the mandible is the deep lobe. Part of the cervical fascia is thickened, deep to the gland, to form the stylomandibular ligament.
Parotid duct
The deep surface of the parotid gland is very irregular and is divided into anteromedial and posteromedial surfaces. The anteromedial surface is related to the posterior border of the ramus of the mandible, the masseter and the medial pterygoid [Fig.
Structures within the parotid gland
The canal pierces the buccal fat pad, buccopharyngeal fascia, and buccinator muscle to open into the vestibule of the mouth, in front of the upper second molar [see Fig. See Clinical Applications 14.1 and 14.2 for the practical implications of the anatomy discussed in this chapter.
Vessels and nerves of the parotid gland
Structures in the parotid gland Objectives
Auriculotemporal syndrome, or gustatory sweating, is redness and sweating on the side of the face in response to a salivary stimulus of either the smell or taste of food. It may follow surgery on the parotid gland (or other surgery involving the capsule of the parotid gland) and is said to be the result of aberrant connections that occur between the secretomotor fibers destined for the parotid gland and the facial sweat glands.
Introduction to the temporal region
Temporal fascia
Muscles of mastication
Masseter
Alternately, the two muscles (right and left) move the chin back and forth, creating a grinding movement of the teeth.
Temporalis
Introduction to the infratemporal region
Temporalis Objective
Superficial contents of the infratemporal fossa
Lateral pterygoid muscle
Superficial dissection of the infratemporal fossa Objectives
1 = first part of maxillary artery; 2 = second part of maxillary artery; 3 = third part of maxillary artery. The two medial pterygoid muscles acting alternately produce a grinding movement, similar to the action of the superficial fibers of the masseter.
Maxillary artery
Pterygoid venous plexus and maxillary vein
Temporomandibular joint
When the mouth is wide open, the head of the mandible swings forward and downward. In protraction, the head of the mandible and the articular plate slide forward on the temporal articular surface on both sides, but the mouth does not open.
Deeper contents of the infratemporal fossa
The opposite movement to extension is traction which is caused by the posterior or temporalis fibers. When these movements are alternated on both sides by the muscles of opposite sides acting alternately, a grinding motion is produced as the chin swings from side to side.
Middle meningeal artery
Mandibular nerve
Deep dissection of the infratemporal fossa Objectives
The nerve to the lateral pterygoid runs with the buccal nerve and enters the muscle as it passes between the heads of the lateral pterygoid. Introduction to the infratemporal region.. by the lesser petrosal branch of the glossopharyngeal nerve.).
Chorda tympani
It is joined in the triangle by the submental artery and supplies the mylohyoid muscle and the anterior belly of the digastric bone [see fig. It runs between the mandible and the mucous membrane that covers it, just below the last molar and above the last fiber of the mylohyoid muscle [fig.
Otic ganglion
