The Scalp: Anatomy, Lecture Notes PDF

The Scalp Lecture 1 Structure The scalp consists of five layers, the first three of which are intimately bound together and move as a unit. To assist one in memorizing the na...

The Scalp Lecture 1 Structure The scalp consists of five layers, the first three of which are intimately bound together and move as a unit. To assist one in memorizing the names of the five layers of the scalp, use each letter of the word SCALP to denote the layer of the scalp. Layers of the scalp 1- Skin, which is thick and hair bearing and contains numerous sebaceous glands 2- Connective tissue beneath the skin, which is fibrofatty, the fibrous septa uniting the skin to the underlying aponeurosis of the occipitofrontalis muscle. Numerous arteries and veins are found in this layer. The arteries are branches of the external and internal carotid arteries, and a free anastomosis takes place between them. 3- Aponeurosis (epicranial), which is a thin, tendinous sheet that unites the occipital and frontal bellies of the occipitofrontalis muscle. The lateral margins of the aponeurosis are attached to the temporal fascia. The subaponeurotic space is the potential space beneath the epicranial aponeurosis. It is limited in front and behind by the origins of the occipitofrontalis muscle, and it extends laterally as far as the attachment of the aponeurosis to the temporal fascia. 4- Loose areolar tissue, which occupies the subaponeurotic space and loosely connects the epicranial aponeurosis to the periosteum of the skull (the pericranium). The areolar tissue contains a few small arteries, but it also contains some important emissary veins. The emissary veins are valveless and connect the superficial veins of the scalp with the diploic veins of the skull bones and with the intracranial venous sinuses. 5- Pericranium, which is the periosteum covering the outer surface of the skull bones. It is important to remember that at the sutures between individual skull bones, the periosteum on the outer surface of the bones becomes continuous with the periosteum on the inner surface of the skull bones.  Muscles of the scalp Occipitofrontalis muscle Origin Frontal belly (frontalis): Skin of eyebrow, muscles of forehead Occipital belly (occipitalis): (Lateral 2/3 of) superior nuchal line Insertion Epicranial aponeurosis Action Frontal belly: Elevates eyebrows, wrinkles skin of forehead Occipital belly: Retracts scalp Innervation Frontal belly: Temporal branches of facial nerve Occipital belly: Posterior auricular nerve (branch of facial nerve) Blood supply Superficial temporal, ophthalmic, posterior auricular and occipital arteries Relations Occipitofrontalis is found deep to the subcutaneous tissue of the skin of the scalp and superficial to the periosteum of the skull. Once they leave the orbits, supraorbital and supratrochlear arteries and nerves travel over the anterior surface of the frontal belly. The anterior surface of the occipital belly is crossed by the greater occipital nerve and occipital artery. Action: When its aponeurotic attachment is fixed, the frontal belly elevates the eyebrows and skin of the forehead, producing a facial expression of shock or surprise. When its forehead attachment is fixed, the frontal belly aids the procerus, orbicularis oculi and corrugator supercilii muscles to frown the eyebrows by pulling the scalp forwards and wrinkling the forehead. Since the muscle heads of the frontal belly are separated, it is possible to perform these movements on only one of the halves of the face. Occipital belly retracts the scalp when its nuchal part is fixed and moves it forwards when the aponeurotic attachment is fixed.  The scalp Lecture 2 Sensory Nerve Supply of the Scalp Sensory Nerve Supply of the Scalp The main trunks of the sensory nerves lie in the superficial fascia. Moving laterally from the midline anteriorly, the following nerves are present: 1- The supratrochlear nerve, a branch of the ophthalmic division of the trigeminal nerve, winds around the superior orbital margin and supplies the scalp. It passes backward close to the median plane and reaches nearly as far as the vertex of the skull. 2- The supraorbital nerve, a branch of the ophthalmic division of the trigeminal nerve, winds around the superior orbital margin and ascends over the forehead. It supplies the scalp as far backward as the vertex. 3- The zygomaticotemporal nerve, a branch of the maxillary division of the trigeminal nerve, supplies the scalp over the temple. 4- The auriculotemporal nerve, a branch of the mandibular division of the trigeminal nerve, ascends over the side of the head from in front of the auricle. Its terminal branches supply the skin over the temporal region. 5- The lesser occipital nerve, a branch of the cervical plexus (C2), supplies the scalp over the lateral part of the occipital region and the skin over the medial surface of the auricle. 6- The greater occipital nerve, a branch of the posterior ramus of the second cervical nerve, ascends over the back of the scalp and supplies the skin as far forward as the vertex of the skull.  Arterial Supply of the Scalp Arterial Supply of the Scalp The scalp has a rich supply of blood to nourish the hair follicles, and, for this reason, the smallest cut bleeds profusely. The arteries lie in the superficial fascia. Moving laterally from the midline anteriorly, the following arteries are present: 1- The supratrochlear and the supraorbital arteries, branches of the ophthalmic artery, ascend over the forehead in company with the supratrochlear and supraorbital nerves. 2- The superficial temporal artery, the smaller terminal branch of the external carotid artery, ascends in front of the auricle in company with the auriculotemporal nerve. It divides into anterior and posterior branches, which supply the skin over the frontal and temporal regions. 3- The posterior auricular artery, a branch of the external carotid artery, ascends behind the auricle to supply the scalp above and behind the auricle. 4- The occipital artery, a branch of the external carotid artery, ascends from the apex of the posterior triangle, in company with the greater occipital nerve. It supplies the skin over the back of the scalp and reaches as high as the vertex of the skull.  Venous Drainage of the Scalp 1- The supratrochlear and supraorbital veins unite at the medial margin of the orbit to form the facial vein. 2- The superficial temporal vein unites with the maxillary vein in the substance of the parotid gland to form the retromandibular vein. 3- The posterior auricular vein unites with the posterior division of the retromandibular vein, just below the parotid gland, to form the external jugular vein. 4- The occipital vein drains into the suboccipital venous plexus, which lies beneath the floor of the upper part of the posterior triangle; the plexus in turn drains into the vertebral veins or the internal jugular vein. The veins of the scalp freely anastomose with one another and are connected to the diploic veins of the skull bones and the intracranial venous sinuses by the valveless emissary veins. Lymph Drainage of the Scalp 1- Lymph vessels in the anterior part of the scalp and forehead drain into the submandibular lymph nodes. 2- Lymph vessels from the lateral part of the scalp above the ear is into the superficial parotid (preauricular) nodes. 3- Lymph vessels in the part of the scalp above and behind the ear drain into the mastoid nodes. 4- Lymph vessels in the back of the scalp drain into the occipital nodes.  Clinical Notes Clinical Significance of the Scalp Structure It is important to realize that the skin, the subcutaneous tissue, and the epicranial aponeurosis are closely united to one another and are separated from the periosteum by loose areolar tissue. The skin of the scalp possesses numerous sebaceous glands, the ducts of which are prone to infection and damage by combs. For this reason, sebaceous cysts of the scalp are common. Lacerations of the Scalp The scalp has a profuse blood supply to nourish the hair follicles. Even a small laceration of the scalp can cause severe blood loss. It is often difficult to stop the bleeding of a scalp wound because the arterial walls are attached to fibrous septa in the subcutaneous tissue and are unable to contract or retract to allow blood clotting to take place. Local pressure applied to the scalp is the only satisfactory method of stopping the bleeding (see below). In automobile accidents, it is common for large areas of the scalp to be cut off the head as a person is projected forward through the windshield. Because of the profuse blood supply, it is often possible to replace large areas of scalp that are only hanging to the skull by a narrow pedicle. Suture them in place, and necrosis will not occur. The tension of the epicranial aponeurosis, produced by the tone of the occipitofrontalis muscles, is important in all deep wounds of the scalp. If the aponeurosis has been divided, the wound will gape open. For satisfactory healing to take place, the opening in the aponeurosis must be closed with sutures. Often a wound caused by a blunt object such as a baseball bat closely resembles an incised wound. This is because the scalp is split against the unyielding skull, and the pull of the occipitofrontalis muscles causes a gaping wound. This anatomic fact may be of considerable forensic importance. Life-Threatening Scalp Hemorrhage Anatomically, it is useful to remember in an emergency that all the superficial arteries supplying the scalp ascend from the face and the neck. Thus, in an emergency situation, encircle the head just above the ears and eyebrows with a tie, shoelaces, or even a piece of string and tie it tight. Then insert a pen, pencil, or stick into the loop and rotate it so that the tourniquet exerts pressure on the arteries. Scalp Infections Infections of the scalp tend to remain localized and are usually painful because of the abundant fibrous tissue in the subcutaneous layer. Occasionally, an infection of the scalp spreads by the emissary veins, which are valveless, to the skull bones, causing osteomyelitis. Infected blood in the diploic veins may travel by the emissary veins farther into the venous sinuses and produce venous sinus thrombosis. Blood or pus may collect in the potential space beneath the epicranial aponeurosis. It tends to spread over the skull, being limited in front by the orbital margin, behind by the nuchal lines, and laterally by the temporal lines. On the other hand, subperiosteal blood or pus is limited to one bone because of the attachment of the periosteum to the sutural ligaments.  The orbital region Lecture 3 Eyelids The eyelids protect the eye from injury and excessive light by their closure. The upper eyelid is larger and more mobile than the lower, and they meet each other at the medial and lateral angles. The palpebral fissure is the elliptical opening between the eyelids and is the entrance into the conjunctival sac. When the eye is closed, the upper eyelid completely covers the cornea of the eye. When the eye is open and looking straight ahead, the upper lid just covers the upper margin of the cornea. The lower lid lies just below the cornea when the eye is open and rises only slightly when the eye is closed. The superficial surface of the eyelids is covered by skin, and the deep surface is covered by a mucous membrane, called the conjunctiva. The eyelashes are short, curved hairs on the free edges of the eyelids. They are arranged in double or triple rows at the mucocutaneous junction. The sebaceous glands (glands of Zeis) open directly into the eyelash follicles. The ciliary glands (glands of Moll) are modified sweat glands that open separately between adjacent lashes. The tarsal glands are long, modified sebaceous glands that pour their oily secretion onto the margin of the lid; their openings lie behind the eyelashes. This oily material prevents the overflow of tears and helps make the closed eyelids airtight. The more rounded medial angle is separated from the eyeball by a small space, the lacus lacrimalis, in the center of which is a small, reddish yellow elevation, the caruncula lacrimalis. A reddish semilunar fold, called the plica semilunaris, lies on the lateral side of the caruncle. Near the medial angle of the eye a small elevation, the papilla lacrimalis, is present. On the summit of the papilla is a small hole, the punctum lacrimale, which leads into the canaliculus lacrimalis. The papilla lacrimalis projects into the lacus, and the punctum and canaliculus carry tears down into the nose. The conjunctiva is a thin mucous membrane that lines the eyelids and is reflected at the superior and inferior fornices onto the anterior surface of the eyeball. Its epithelium is continuous with that of the cornea. The upper lateral part of the superior fornix is pierced by the ducts of the lacrimal gland (see below). The conjunctiva thus forms a potential space, the conjunctival sac, which is open at the palpebral fissure. Beneath the eyelid is a groove, the subtarsal sulcus, which runs close to and parallel with the margin of the lid. The sulcus tends to trap small foreign particles introduced into the conjunctival sac and is thus clinically important. The framework of the eyelids is formed by a fibrous sheet, the orbital septum. This is attached to the periosteum at the orbital margins. The orbital septum is thickened at the margins of the lids to form the superior and inferior tarsal plates. The lateral ends of the plates are attached by a band, the lateral palpebral ligament, to a bony tubercle just within the orbital margin. The medial ends of the plates are attached by a band, the medial palpebral ligament, to the crest of the lacrimal bone. The tarsal glands are embedded in the posterior surface of the tarsal plates. The superficial surface of the tarsal plates and the orbital septum are covered by the palpebral fibers of the orbicularis oculi muscle. The aponeurosis of insertion of the levator palpebrae superioris muscle pierces the orbital septum to reach the anterior surface of the superior tarsal plate and the skin. Movements of the Eyelids The position of the eyelids at rest depends on the tone of the orbicularis oculi and the levator palpebrae superioris muscles and the position of the eyeball. The eyelids are closed by the contraction of the orbicularis oculi and the relaxation of the levator palpebrae superioris muscles. The eye is opened by the levator palpebrae superioris raising the upper lid. On looking upward, the levator palpebrae superioris contracts, and the upper lid moves with the eyeball. On looking downward, both lids move, the upper lid continues to cover the upper part of the cornea, and the lower lid is pulled downward slightly by the conjunctiva, which is attached to the sclera and the lower lid. Muscle Origin Insertion Nerve Supply Action Extrinsic Muscles of Eyeball (Striated Skeletal Muscle) Superior Tendinous ring Superior surface of eyeball Oculomotor Raises cornea rectus on posterior wall just posterior to nerve (third upward and of orbital cavity corneoscleral junction cranial nerve) medially Inferior Tendinous ring Inferior surface of eyeball Oculomotor Depresses cornea rectus on posterior wall just posterior to nerve (third downward and of orbital cavity corneoscleral junction cranial nerve) medially Medial Tendinous ring Medial surface of eyeball Oculomotor Rotates eyeball so rectus on posterior wall just posterior to nerve (third that cornea looks of orbital cavity corneoscleral junction cranial nerve) medially Lateral Tendinous ring Lateral surface of eyeball Abducent nerve Rotates eyeball so rectus on posterior wall just posterior to (sixth cranial that cornea looks of orbital cavity corneoscleral junction nerve) laterally Superior Posterior wall of Passes through pulley and Trochlear nerve Rotates eyeball so oblique orbital cavity is attached to superior (fourth cranial that cornea looks surface of eyeball beneath nerve) downward and superior rectus laterally Inferior Floor of orbital Lateral surface of eyeball Oculomotor Rotates eyeball so oblique cavity deep to lateral rectus nerve (third that cornea looks cranial nerve) upward and laterally Intrinsic Muscles of Eyeball (Smooth Muscle) Sphincter pupillae of Parasympathetic via Constricts pupil iris oculomotor nerve Dilator pupillae of iris Sympathetic Dilates pupil Ciliary muscle Parasympathetic via Controls shape of lens; in oculomotor nerve accommodation, makes lens more globular Orbicularis oculi Palpebral part Medial lateral facial nerve closes eyelids & Palpebral palpebral dilates lacrimal ligament raphe sac Orbital part Medial loops facial nerve throws skin palpebral return to around orbit ligament & origin into folds to adjoining bone Levator palpebrae Back of orbital Anterior surface & Striated muscle Raises upper lid superioris cavity upper margin of oculomotor nerve, superior tarsal plate smooth muscle sympathetic Lacrimal Apparatus Lacrimal Gland The lacrimal gland consists of a large orbital part and a small palpebral part, which are continuous with each other around the lateral edge of the aponeurosis of the levator palpebrae superioris. It is situated above the eyeball in the anterior and upper part of the orbit posterior to the orbital septum. The gland opens into the lateral part of the superior fornix of the conjunctiva by 12 ducts. The parasympathetic secretomotor nerve supply is derived from the lacrimal nucleus of the facial nerve. The preganglionic fibers reach the pterygopalatine ganglion (sphenopalatine ganglion) via the nervus intermedius and its great petrosal branch and via the nerve of the pterygoid canal. The postganglionic fibers leave the ganglion and join the maxillary nerve. They then pass into its zygomatic branch and the zygomaticotemporal nerve. They reach the lacrimal gland within the lacrimal nerve. The sympathetic postganglionic nerve supply is from the internal carotid plexus and travels in the deep petrosal nerve, the nerve of the pterygoid canal, the maxillary nerve, the zygomatic nerve, the zygomaticotemporal nerve, and finally the lacrimal nerve. Lacrimal Ducts The tears circulate across the cornea and accumulate in the lacus lacrimalis. From here, the tears enter the canaliculi lacrimales through the puncta lacrimalis. The canaliculi lacrimales pass medially and open into the lacrimal sac, which lies in the lacrimal groove behind the medial palpebral ligament and is the upper blind end of the nasolacrimal duct. The nasolacrimal duct is about 0.5 in. (1.3 cm) long and emerges from the lower end of the lacrimal sac. The duct descends downward, backward, and laterally in a bony canal and opens into the inferior meatus of the nose. The opening is guarded by a fold of mucous membrane known as the lacrimal fold. This prevents air from being forced up the duct into the lacrimal sac on blowing the nose. Openings into the Orbital Cavity 1- Orbital opening: Lies anteriorly. About one-sixth of the eye is exposed; the remainder is protected by the walls of the orbit. 2- Supraorbital notch (Foramen): The supraorbital notch is situated on the superior orbital margin. It transmits the supraorbital nerve and blood vessels. 3- Infraorbital groove and canal: Situated on the floor of the orbit in the orbital plate of the maxilla; they transmit the infraorbital nerve (a continuation of the maxillary nerve) and blood vessels. 4- Nasolacrimal canal: Located anteriorly on the medial wall; it communicates with the inferior meatus of the nose. It transmits the nasolacrimal duct. 5- Inferior orbital fissure: Located posteriorly between the maxilla and the greater wing of the sphenoid; it communicates with the pterygopalatine fossa. It transmits the maxillary nerve and its zygomatic branch, the inferior ophthalmic vein, and sympathetic nerves. 6- Superior orbital fissure: Located posteriorly between the greater and lesser wings of the sphenoid; it communicates with the middle cranial fossa. It transmits the lacrimal nerve, the frontal nerve, the trochlear nerve, the oculomotor nerve (upper and lower divisions), the abducent nerve, the nasociliary nerve, and the superior ophthalmic vein. 7- Optic canal: Located posteriorly in the lesser wing of the sphenoid; it communicates with the middle cranial fossa. It transmits the optic nerve and the ophthalmic artery.  Nerves of the Orbit 1-Optic Nerve The optic nerve enters the orbit from the middle cranial fossa by passing through the optic canal. It is accompanied by the ophthalmic artery, which lies on its lower lateral side. The nerve is surrounded by sheaths of pia mater, arachnoid mater, and dura mater. It runs forward and laterally within the cone of the recti muscles and pierces the sclera at a point medial to the posterior pole of the eyeball. Here, the meninges fuse with the sclera so that the subarachnoid space with its contained cerebrospinal fluid extends forward from the middle cranial fossa, around the optic nerve, and through the optic canal, as far as the eyeball. A rise in pressure of the cerebrospinal fluid within the cranial cavity therefore is transmitted to the back of the eyeball. 2-Lacrimal Nerve The lacrimal nerve arises from the ophthalmic division of the trigeminal nerve. It enters the orbit through the upper part of the superior orbital fissure and passes forward along the upper border of the lateral rectus muscle. It is joined by a branch of the zygomaticotemporal nerve, which later leaves it to enter the lacrimal gland (parasympathetic secretomotor fibers). The lacrimal nerve ends by supplying the skin of the lateral part of the upper lid. 3-Frontal Nerve The frontal nerve arises from the ophthalmic division of the trigeminal nerve. It enters the orbit through the upper part of the superior orbital fissure and passes forward on the upper surface of the levator palpebrae superioris beneath the roof of the orbit. It divides into the supratrochlear and supraorbital nerves that wind around the upper margin of the orbital cavity to supply the skin of the forehead; the supraorbital nerve also supplies the mucous membrane of the frontal air sinus. 4-Trochlear Nerve The trochlear nerve enters the orbit through the upper part of the superior orbital fissure. It runs forward and supplies the superior oblique muscle. 5-Oculomotor Nerve The superior ramus of the oculomotor nerve e nters the orbit through the lower part of the superior orbital fissure. It supplies the superior rectus muscle, then pierces it, and supplies the levator palpebrae superioris muscle. The inferior ramus of the oculomotor nerve enters the orbit in a similar manner and supplies the inferior rectus, the medial rectus, and the inferior oblique muscles. The nerve to the inferior oblique gives off a branch that passes to the ciliary ganglion and carries parasympathetic fibers to the sphincter pupillae and the ciliary muscle. 6-Nasociliary Nerve The nasociliary nerve arises from the ophthalmic division of the trigeminal nerve. It enters the orbit through the lower part of the superior orbital fissure. It crosses above the optic nerve, runs forward along the upper margin of the medial rectus muscle, and ends by dividing into the anterior ethmoidal and infratrochlear nerves. Branches of the Nasociliary Nerve a)The communicating branch to the ciliary ganglion is a sensory nerve. The sensory fibers from the eyeball pass to the ciliary ganglion via the short ciliary nerves, pass through the ganglion without interruption, and then join the nasociliary nerve by means of the communicating branch. b)The long ciliary nerves, two or three in number, arise from the nasociliary nerve as it crosses the optic nerve. They contain sympathetic fibers for the dilator pupillae muscle. The nerves pass forward with the short ciliary nerves and pierce the sclera of the eyeball. They continue forward between the sclera and the choroid to reach the iris. c)The posterior ethmoidal nerve supplies the ethmoidal and sphenoidal air sinuses. d)The infratrochlear nerve passes forward below the pulley of the superior oblique muscle and supplies the skin of the medial part of the upper eyelid and the adjacent part of the nose. e)The anterior ethmoidal nerve passes through the anterior ethmoidal foramen and enters the anterior cranial fossa on the upper surface of the cribriform plate of the ethmoid. It enters the nasal cavity through a slitlike opening alongside the crista galli. After supplying an area of mucous membrane, it appears on the face as the external nasal branch at the lower border of the nasal bone, and supplies the skin of the nose down as far as the tip. 7-Abducent Nerve The abducent nerve enters the orbit through the lower part of the superior orbital fissure, It supplies the lateral rectus muscle. 8-Ciliary Ganglion The ciliary ganglion is a parasympathetic ganglion about the size of a pinhead and situated in the posterior part of the orbit. It receives its preganglionic parasympathetic fibers from the oculomotor nerve via the nerve to the inferior oblique. The postganglionic fibers leave the ganglion in the short ciliary nerves, which enter the back of the eyeball and supply the sphincter pupillae and the ciliary muscle. A number of sympathetic fibers pass from the internal carotid plexus into the orbit and run through the ganglion without interruption.  The Orbit Lecture 4 Blood and Lymph Vessels of the Orbit Ophthalmic Artery The ophthalmic artery is a branch of the internal carotid artery after that vessel emerges from the cavernous sinus. It enters the orbit through the optic canal with the optic nerve. It runs forward and crosses the optic nerve to reach the medial wall of the orbit. It gives off numerous branches, which accompany the nerves in the orbital cavity. Branches of the Ophthalmic Artery 1-The central artery of the retina is a small branch that pierces the meningeal sheaths of the optic nerve to gain entrance to the nerve. It runs in the substance of the optic nerve and enters the eyeball at the center of the optic disc. Here, it divides into branches, which may be studied in a patient through an ophthalmoscope. The branches are end arteries. 2-The muscular branches 3-The ciliary arteries can be divided into anterior and posterior groups. The former group enters the eyeball near the corneoscleral junction; the latter group enters near the optic nerve. 4-The lacrimal artery to the lacrimal gland 5-The supratrochlear and supraorbital arteries are distributed to the skin of the forehead. Ophthalmic Veins The superior ophthalmic vein communicates in front with the facial vein. The inferior ophthalmic vein communicates through the inferior orbital fissure with the pterygoid venous plexus. Both veins pass backward through the superior orbital fissure and drain into the cavernous sinus. Lymph Vessels No lymph vessels or nodes are present in the orbital cavity. Structure of the Eye The eyeball is embedded in orbital fat but is separated from it by the fascial sheath of the eyeball. The eyeball consists of three coats, which, from without inward, are 1) the fibrous coat, 2) the vascular pigmented coat, and 3) the nervous coat. Coats of the Eyeball 1) Fibrous Coat The fibrous coat is made up of a posterior opaque part (the sclera) and an anterior transparent part (the cornea). a-The Sclera The opaque sclera is composed of dense fibrous tissue and is white. Posteriorly, it is pierced by the optic nerve and is fused with the dural sheath of that nerve. The lamina cribrosa is the area of the sclera that is pierced by the nerve fibers of the optic nerve. The sclera is also pierced by the ciliary arteries and nerves and their associated veins, the venae vorticosae. The sclera is directly continuous in front with the cornea at the corneoscleral junction, or limbus. b-The Cornea The transparent cornea is largely responsible for the refraction of the light entering the eye. It is in contact posteriorly with the aqueous humor. Blood Supply The cornea is avascular and devoid of lymphatic drainage. It is nourished by diffusion from the aqueous humor and from the capillaries at its edge. Nerve Supply Long ciliary nerves from the ophthalmic division of the trigeminal nerve Function of the Cornea The cornea is the most important refractive medium of the eye. This refractive power occurs on the anterior surface of the cornea, where the refractive index of the cornea (1.38) differs greatly from that of the air. The importance of the tear film in maintaining the normal environment for the corneal epithelial cells should be stressed. 2) Vascular Pigmented Coat The vascular pigmented coat consists, from behind forward, of the choroid, the ciliary body, and the iris. a-The Choroid The choroid is composed of, highly vascular layer. b-The Ciliary Body an outer pigmented layer and an inner The ciliary body is continuous posteriorly with the choroid, and anteriorly it lies behind the peripheral margin of the iris. It is composed of the ciliary ring, the ciliary processes, and the ciliary muscle. 1)The ciliary ring is the posterior part of the body, and its surface has shallow grooves, the ciliary striae. 2)The ciliary processes are radially arranged folds, or ridges, to the posterior surfaces of which are connected the suspensory ligaments of the lens. 3)The ciliary muscle is composed of meridianal and circular fibers of smooth muscle. a-The meridianal fibers run backward from the region of the corneoscleral junction to the ciliary processes. b-The circular fibers are fewer in number and lie internal to the meridianal fibers. Nerve supply of the ciliary muscle is supplied by the parasympathetic fibers from the oculomotor nerve. After synapsing in the ciliary ganglion, the postganglionic fibers pass forward to the eyeball in the short ciliary nerves. Nerve supply of the ciliary muscle is contraction of the ciliary muscle, especially the meridianal fibers, pulls the ciliary body forward. This relieves the tension in the suspensory ligament, and the elastic lens becomes more convex. This increases the refractive power of the lens. c-The Iris and Pupil The iris is a thin, contractile, pigmented diaphragm with a central aperture, the pupil. It is suspended in the aqueous humor between the cornea and the lens. The periphery of the iris is attached to the anterior surface of the ciliary body. It divides the space between the lens and the cornea into an anterior and a posterior chamber. The muscle fibers of the iris are involuntary and consist of circular and radiating fibers. 1)The circular fibers form the sphincter pupillae and are arranged around the margin of the pupil. 2)The radial fibers form the dilator pupillae and consist of a thin sheet of radial fibers that lie close to the posterior surface. Nerve supply of the sphincter pupillae by parasympathetic fibers from the oculomotor nerve. After synapsing in the ciliary ganglion, the postganglionic fibers pass forward to the eyeball in the short ciliary nerves. Nerve supply of The dilator pupillae by sympathetic fibers, which pass forward to the eyeball in the long ciliary nerves. Action of the sphincter pupillae constricts the pupil in the presence of bright light and during accommodation. Action of the dilator pupillae dilates the pupil in the presence of light of low intensity or in the presence of excessive sympathetic activity such as occurs in fright. 3) Nervous Coat: The Retina The retina consists of an outer pigmented layer and an inner nervous layer. Its outer surface is in contact with the choroid, and its inner surface is in contact with the vitreous body. The posterior three fourths of the retina is the receptor organ. Its anterior edge forms a wavy ring, the ora serrata, and the nervous tissues end here. The anterior part of the retina is nonreceptive and consists merely of pigment cells, with a deeper layer of columnar epithelium. This anterior part of the retina covers the ciliary processes and the back of the iris. At the center of the posterior part of the retina is an oval, yellowish area, the macula lutea, which is the area of the retina for the most distinct vision. It has a central depression, the fovea centralis. The optic nerve leaves the retina about 3 mm to the medial side of the macula lutea by the optic disc. The optic disc is slightly depressed at its center, where it is pierced by the central artery of the retina. At the optic disc is a complete absence of rods and cones so that it is insensitive to light and is referred to as the blind spot. On ophthalmoscopic examination, the optic disc is seen to be pale pink in color, much paler than the surrounding retina. Contents of the Eyeball The contents of the eyeball consist of the refractive media, the aqueous humor, the vitreous body, and the lens. 1) Aqueous Humor The aqueous humor is a clear fluid that fills the anterior and posterior chambers of the eyeball. It is believed to be a secretion from the ciliary processes, from which it enters the posterior chamber. It then flows into the anterior chamber through the pupil and is drained away through the spaces at the iridocorneal angle into the canal of Schlemm. Obstruction to the draining of the aqueous humor results in a rise in intraocular pressure called glaucoma. This can produce degenerative changes in the retina, with consequent blindness. The function of the aqueous humor is to support the wall of the eyeball by exerting internal pressure and thus maintaining its optical shape. It also nourishes the cornea and the lens and removes the products of metabolism; these functions are important because the cornea and the lens do not possess a blood supply. 2) Vitreous Body The vitreous body fills the eyeball behind the lens and is a transparent gel. The hyaloid canal is a narrow channel that runs through the vitreous body from the optic disc to the posterior surface of the lens; in the fetus, it is filled by the hyaloid artery, which disappears before birth. The function of the vitreous body is to contribute slightly to the magnifying power of the eye. It supports the posterior surface of the lens and assists in holding the neural part of the retina against the pigmented part of the retina. 3) The Lens The lens is a transparent, biconvex structure enclosed in a transparent capsule. It is situated behind the iris and in front of the vitreous body and is encircled by the ciliary processes. The lens consists of an elastic capsule, which envelops the structure; a cuboidal epithelium, which is confined to the anterior surface of the lens; and lens fibers, which are formed from the cuboidal epithelium at the equator of the lens. The lens fibers make up the bulk of the lens. The elastic lens capsule is under tension, causing the lens constantly to endeavor to assume a globular rather than a disc shape. The equatorial region, or circumference, of the lens is attached to the ciliary processes of the ciliary body by the suspensory ligament. The pull of the radiating fibers of the suspensory ligament tends to keep the elastic lens flattened so that the eye can be focused on distant objects. Accommodation of the Eye To accommodate the eye for close objects, the ciliary muscle contracts and pulls the ciliary body forward and inward so that the radiating fibers of the suspensory ligament are relaxed. This allows the elastic lens to assume a more globular shape. With advancing age, the lens becomes denser and less elastic, and, as a result, the ability to accommodate is lessened (presbyopia). This disability can be overcome by the use of an additional lens in the form of glasses to assist the eye in focusing on nearby objects. Constriction of the Pupil During Accommodation of the Eye To ensure that the light rays pass through the central part of the lens so spherical aberration is diminished during accommodation for near objects, the sphincter pupillae muscle contracts so the pupil becomes smaller Convergence of the Eyes During Accommodation of the Lens In humans, the retinae of both eyes focus on only one set of objects (single binocular vision). When an object moves from a distance toward an individual, the eyes converge so that a single object, not two, is seen. Convergence of the eyes results from the coordinated contraction of the medial rectus muscles. Clinical Notes Eye Trauma Although the eyeball is well protected by the surrounding bony orbit, it is protected anteriorly only from large objects, such as tennis balls, which tend to strike the orbital margin but not the globe. The bony orbit provides no protection from small objects, such as golf balls, which can cause severe damage to the eye. Careful examination of the eyeball relative to the orbital margins shows that it is least protected from the lateral side. Blowout fractures of the orbital floor involving the maxillary sinus commonly occur as a result of blunt force to the face. If the force is applied to the eye, the orbital fat explodes inferiorly into the maxillary sinus, fracturing the orbital floor. Not only can blowout fractures cause displacement of the eyeball, with resulting symptoms of double vision (diplopia), but also the fracture can injure the infraorbital nerve, producing loss of sensation of the skin of the cheek and the gum on that side. Entrapment of the inferior rectus muscle in the fracture may limit upward gaze. Strabismus Many cases of strabismus are nonparalytic and are caused by an imbalance in the action of opposing muscles. This type of strabismus is known as concomitant strabismus and is common in infancy. Pupillary Reflexes The pupillary reflexes that is, the reaction of the pupils to light and accommodation depend on the integrity of nervous pathways. In the direct light reflex, the normal pupil reflexly contracts when a light is shone into the patient's eye. The nervous impulses pass from the retina along the optic nerve to the optic chiasma and then along the optic tract. Before reaching the lateral geniculate body, the fibers concerned with this reflex leave the tract and pass to the oculomotor nuclei on both sides via the pretectal nuclei. From the parasympathetic part of the nucleus, efferent fibers leave the midbrain in the oculomotor nerve and reach the ciliary ganglion via the nerve to the inferior oblique. Postganglionic fibers pass to the constrictor pupillae muscles via the short ciliary nerves. The consensual light reflex is tested by shining the light in one eye and noting the contraction of the pupil in the opposite eye. This reflex is possible because the afferent pathway just described travels to the parasympathetic nuclei of both oculomotor nerves. The accommodation reflex is the contraction of the pupil that occurs when a person suddenly focuses on a near object after having focused on a distant object. The nervous impulses pass from the retina via the optic nerve, the optic chiasma, the optic tract, the lateral geniculate body, the optic radiation, and the cerebral cortex of the occipital lobe of the brain. The visual cortex is connected to the eye field of the frontal cortex. From here, efferent pathways pass to the parasympathetic nucleus of the oculomotor nerve. From there, the efferent impulses reach the constrictor pupillae via the oculomotor nerve, the ciliary ganglion, and the short ciliary nerves.  THE FACE Dr. Assist prof. Imad Tamimi Clinical & applied anatomist Lecture 7 Skin of the Face The skin of the face contains two types of glands (sweat & sebaceous glands). The skin of the face is connected to the underlying bones by loose connective tissue. The muscles of facial expression are embedded in the loose connective tissue. There is No deep fascia in the face. The wrinkle lines of the face result from 1) the repeated folding of the skin which is caused by the underlying contracting muscles in a perpendicular direction to the long axis of the muscles. 2) the loss of youthful skin elasticity. Surgical scars of the face are less obvious if they follow the wrinkle lines. Muscles of the Face (Muscles of Facial Expression) The muscles of the face are embedded in the superficial fascia & most of them arise from the bones of the skull & are inserted into the skin. The orifices of the face are a) the orbit ( it is guarded by the eyelids). b) the nose ( is guarded by the nostrils). c) the mouth ( is guarded by the lips). The function of the facial muscles: 1) They serve as sphincters or dilators for the orifices of the face. 2) they change the expression of the face. Muscles of Facial Expression Muscle origin insertion Nerve action supply Orbicularis oculi Facial Orbital part Medial Lateral palpebral nerve Closes eyelid palpebral raphe & dilate ligament lacrimal sac Palpebral part Loops return to Medial origin Throws skin palpebral around orbit ligament & into folds to adjoining protect bone eyeball Corrugator supercilii Superciliary Skin of eyebrow === Vertical arch wrinkles of forehead as in frowning Compressor nasi Frontal Aponeuorosis of === Compresses process of bridge of nose mobile nasal maxilla cartilages Dilator naris maxilla Ala of nose ==== Widen nasal aperture Procerus Nasal bone Skin between ==== Wrinkle skin eyebrows of nose Orbicularis oris Maxilla, Compresses mandible & ==== lips together skin Levator labii From Into substance of Separate lips superioris alaeque bones & lips === nasi fascia Levator labii around the superioris oral zygomaticus minor aperture zygomaticus major levator anguli oris risorius depressor anguli oris depressor labii inferioris mentalis From Into substance of === Separate lips bones & lips fascia around the oral aperture Buccinator Outer Pterygomandibular === Compresses surface of ligament cheecks & alveolar lips against margins of teeth maxilla & mandible platysma Deep fascia Body of mandible Facial Depresses over and angle of nerve mandible pectoralis mouth & and angle of major and cervical mouth deltoid branch  THE FACE Dr. Assist prof. Imad Tamimi Clinical & applied anatomist Lecture 8 Sensory Nerves of the Face The skin of the face is supplied by branches of the three divisions of the trigeminal nerve, except for the small area over the angle of the mandible and the parotid gland, which is supplied by the great auricular nerve (C2 and 3). The overlap of the three divisions of the trigeminal nerve is slight compared with the considerable overlap of dermatomes of the trunk and limbs. The ophthalmic nerve supplies the region developed from the frontonasal process; the maxillary nerve serves the region developed from the maxillary process of the first pharyngeal arch; and the mandibular nerve serves the region developed from the mandibular process of the first pharyngeal arch. These nerves not only supply the skin of the face, but also supply proprioceptive fibers to the underlying muscles of facial expression. They are, in addition, the sensory nerve supply to the mouth, teeth, nasal cavities, and paranasal air sinuses. Ophthalmic Nerve The ophthalmic nerve supplies the skin of the forehead, the upper eyelid, the conjunctiva, and the side of the nose down to and including the tip. Five branches of the nerve pass to the skin. 1- The lacrimal nerve supplies the skin and conjunctiva of the lateral part of the upper eyelid. 2- The supraorbital nerve winds around the upper margin of the orbit at the supraorbital notch. It divides into branches that supply the skin and conjunctiva on the central part of the upper eyelid; it also supplies the skin of the forehead. 3- The supratrochlear nerve winds around the upper margin of the orbit medial to the supraorbital nerve. It divides into branches that supply the skin and conjunctiva on the medial part of the upper eyelid and the skin over the lower part of the forehead, close to the median plane. 4- The infratrochlear nerve leaves the orbit below the pulley of the superior oblique muscle. It supplies the skin and conjunctiva on the medial part of the upper eyelid and the adjoining part of the side of the nose. 5- The external nasal nerve leaves the nose by emerging between the nasal bone and the upper nasal cartilage. It supplies the skin on the side of the nose down as far as the tip. Maxillary Nerve The maxillary nerve supplies the skin on the posterior part of the side of the nose, the lower eyelid, the cheek, the upper lip, and the lateral side of the orbital opening. Three branches of the nerve pass to the skin. 1- The infraorbital nerve is a direct continuation of the maxillary nerve. It enters the orbit and appears on the face through the infraorbital foramen. It immediately divides into numerous small branches, which radiate out from the foramen and supply the skin of the lower eyelid and cheek, the side of the nose, and the upper lip. 2- The zygomaticofacial nerve passes onto the face through a small foramen on the lateral side of the zygomatic bone. It supplies the skin over the prominence of the cheek. 3- The zygomaticotemporal nerve emerges in the temporal fossa through a small foramen on the posterior surface of the zygomatic bone. It supplies the skin over the temple. Mandibular Nerve The mandibular nerve supplies the skin of the lower lip, the lower part of the face, the temporal region, and part of the auricle. It then passes upward to the side of the scalp. Three branches of the nerve pass to the skin. 1- The mental nerve emerges from the mental foramen of the mandible and supplies the skin of the lower lip and chin. 2- The buccal nerve emerges from beneath the anterior border of the masseter muscle and supplies the skin over a small area of the cheek. 3- The auriculotemporal nerve ascends from the upper border of the parotid gland between the superficial temporal vessels and the auricle. It supplies the skin of the auricle, the external auditory meatus, the outer surface of the tympanic membrane, and the skin of the scalp above the auricle. Arterial Supply of the Face The face receives a rich blood supply from two main vessels: the facial and superficial temporal arteries, which are supplemented by several small arteries that accompany the sensory nerves of the face. The facial artery arises from the external carotid artery. Having arched upward and over the submandibular salivary gland,it curves around the inferior margin of the body of the mandible at the anterior border of the masseter muscle. It is here that the pulse can be easily felt. It runs upward in a tortuous course toward the angle of the mouth and is covered by the platysma and the risorius muscles. It then ascends deep to the zygomaticus muscles and the levator labii superioris muscle and runs along the side of the nose to the medial angle of the eye, where it anastomoses with the terminal branches of the ophthalmic artery. Branches 1- The submental artery arises from the facial artery at the lower border of the body of the mandible. It supplies the skin of the chin and lower lip. 2- The inferior labial artery arises near the angle of the mouth. It runs medially in the lower lip and anastomoses with its fellow of the opposite side. 3- The superior labial artery arises near the angle of the mouth. It runs medially in the upper lip and gives branches to the septum and ala of the nose. 4- The lateral nasal artery arises from the facial artery alongside the nose. It supplies the skin on the side and dorsum of the nose. 5- The superficial temporal artery, the smaller terminal branch of the external carotid artery,commences in the parotid gland. It ascends in front of the auricle to supply the scalp. 6- The transverse facial artery, a branch of the superficial temporal artery, arises within the parotid gland. It runs forward across the cheek just above the parotid duct. 7- The supraorbital and supratrochlear arteries, branches of the ophthalmic artery, supply the skin of the forehead.  venous driange of the Face The facial vein is formed at the medial angle of the eye by the union of the supraorbital and supratrochlear vein. It is connected to the superior ophthalmic vein directly through the supraorbital vein. By means of the superior ophthalmic vein, the facial vein is connected to the cavernous sinus; this connection is of great clinical importance because it provides a pathway for the spread of infection from the face to the cavernous sinus. The facial vein descends behind the facial artery to the lower margin of the body of the mandible. It crosses superficial to the submandibular gland and is joined by the anterior division of the retromandibular vein. The facial vein ends by draining into the internal jugular vein. Tributaries The facial vein receives tributaries that correspond to the branches of the facial artery. It is joined to the pterygoid venous plexus by the deep facial vein and to the cavernous sinus by the superior ophthalmic vein. Lymphatic driange of the face Lymph from the forehead and the anterior part of the face drains into the submandibular lymph nodes. A few buccal lymph nodes may be present along the course of these lymph vessels. The lateral part of the face, including the lateral parts of the eyelids, is drained by lymph vessels that end in the parotid lymph nodes. The central part of the lower lip and the skin of the chin are drained into the submental lymph nodes.  Facial nerve As the facial nerve runs forward within the substance of the parotid salivary gland. It divides into its five terminal branches. 1) The temporal branch emerges from the upper border of the gland and supplies the anterior and superior auricular muscles, the frontal belly of the occipitofrontalis, the orbicularis oculi, and the corrugator supercilii. 2) The zygomatic branch emerges from the anterior border of the gland and supplies the orbicularis oculi. 3) The buccal branch emerges from the anterior border of the gland below the parotid duct and supplies the buccinator muscle and the muscles of the upper lip and nostril. 4) The mandibular branch emerges from the anterior border of the gland and supplies the muscles of the lower lip. 5) The cervical branch emerges from the lower border of the gland and passes forward in the neck below the mandible to supply the platysma muscle; it may cross the lower margin of the body of the mandible to supply the depressor anguli oris muscle. The facial nerve is the nerve of the second pharyngeal arch and supplies all the muscles of facial expression. It does not supply the skin, but its branches communicate with branches of the trigeminal nerve. It is believed that the proprioceptive nerve fibers of the facial muscles leave the facial nerve in these communicating branches and pass to the central nervous system via the trigeminal nerve.  The Tongue Lecture 11 The tongue is a mass of striated muscle covered with mucous membrane. The muscles attach the tongue to the styloid process and the soft palate above and to the mandible and the hyoid bone below. The tongue is divided into right and left halves by a median fibrous septum. Mucous Membrane of the Tongue The mucous membrane of the upper surface of the tongue can be divided into anterior and posterior parts by a V-shaped sulcus, the sulcus terminalis. The apex of the sulcus projects backward and is marked by a small pit, the foramen cecum. The sulcus serves to divide the tongue into the anterior two thirds, or oral part, and the posterior third, or pharyngeal part. The foramen cecum is an embryologic remnant and marks the site of the upper end of the thyroglossal duct. Three types of papillae are present on the upper surface of the anterior two thirds of the tongue: the filiform papillae, the fungiform papillae, and the vallate papillae. The mucous membrane covering the posterior third of the tongue is devoid of papillae but has an irregular surface, caused by the presence of underlying lymph nodules, the lingual tonsil. The mucous membrane on the inferior surface of the tongue is reflected from the tongue to the floor of the mouth. In the midline anteriorly, the undersurface of the tongue is connected to the floor of the mouth by a fold of mucous membrane, the frenulum of the tongue. On the lateral side of the frenulum, the deep lingual vein can be seen through the mucous membrane. Lateral to the lingual vein, the mucous membrane forms a fringed fold called the plica fimbriata. Muscles of the Tongue The muscles of the tongue are divided into two types: intrinsic and extrinsic. Intrinsic Muscles These muscles are confined to the tongue and are not attached to bone. They consist of longitudinal, transverse, and vertical fibers. Nerve supply: Hypoglossal nerve Action: Alter the shape of the tongue Extrinsic Muscles These muscles are attached to bones and the soft palate. They are the genioglossus, the hyoglossus, the styloglossus, and the palatoglossus. Nerve supply: Hypoglossal nerve Blood Supply The lingual artery, the tonsillar branch of the facial artery, and the ascending pharyngeal artery supply the tongue. The veins drain into the internal jugular vein. Lymph Drainage Tip: Submental lymph nodes Sides of the anterior two thirds: Submandibular and deep cervical lymph nodes Posterior third: Deep cervical lymph nodes Sensory Innervation Anterior two thirds: Lingual nerve branch of mandibular division of trigeminal nerve (general sensation) and chorda tympani branch of the facial nerve (taste) Posterior third: Glossopharyngeal nerve (general sensation and taste) Movements of the Tongue Protrusion: The genioglossus muscles on both sides acting together Retraction: Styloglossus and hyoglossus muscles on both sides acting together Depression: Hyoglossus muscles on both sides acting together Retraction and elevation of the posterior third: Styloglossus and palatoglossus muscles on both sides acting together Shape changes: Intrinsic muscles  Nerve Muscle Origin Insertion Supply Action Intrinsic Muscles Longitudinal Median septum Mucous Hypoglossal Alters shape of tongue and submucosa membrane nerve Transverse Vertical Extrinsic Muscles Genioglossus Superior genial Blends with Hypoglossal Protrudes apex of tongue spine of mandible other muscles of nerve through mouth tongue Hyoglossus Body and greater Blends with Hypoglossal Depresses tongue cornu of hyoid other muscles of nerve bone tongue Styloglossus Styloid process of Blends with Hypoglossal Draws tongue upward and temporal bone other muscles of nerve backward tongue Palatoglossu Palatine Side of tongue Pharyngeal Pulls roots of tongue upward s aponeurosis plexus and backward, narrows oropharyngeal isthmus  The neck Lecture 18 Skin of the Neck The natural lines of cleavage of the skin are constant and run almost horizontally around the neck. This is important clinically because an incision along a cleavage line will heal as a narrow scar, whereas one that crosses the lines will heal as a wide or heaped-up scar. Fasciae of the Neck Superficial Cervical Fascia The superficial fascia of the neck forms a thin layer that encloses the platysma muscle. Also embedded in it are the cutaneous nerves referred to in the previous section, the superficial veins, and the superficial lymph nodes. The platysma muscleis a thin but clinically important muscular sheet embedded in the superficial fascia. The platysma muscle is a thin but clinically important muscular sheet embedded in the superficial fascia. Muscle Origin Insertion Nerve Supply Action PlatysmaDeep fascia over Body of mandible Facial nerve Depresses mandible pectoralis major and and angle of mouth cervical branch and angle of mouth deltoid. Deep Cervical Fascia The deep cervical fascia supports the muscles, the vessels, and the viscera of the neck. In certain areas, it is condensed to form well-defined, fibrous sheets called the investing layer, the pretracheal layer, and the prevertebral layer. It is also condensed to form the carotid sheath. Investing Layer The investing layer is a thick layer that encircles the neck. It splits to enclose the trapezius and the sternocleidomastoid muscles. Pretracheal Layer The pretracheal layer is a thin layer that is attached above to the laryngeal cartilages. It surrounds the thyroid and the parathyroid glands, forming a sheath for them, and encloses the infrahyoid muscles. Prevertebral Layer The prevertebral layer is a thick layer that passes like a septum across the neck behind the pharynx and the esophagus and in front of the prevertebral muscles and the vertebral column. It forms the fascial floor of the posterior triangle, and it extends laterally over the first rib into the axilla to form the important axillary sheath. Carotid Sheath The carotid sheath is a local condensation of the prevertebral, the pretracheal, and the investing layers of the deep fascia that surround the common and internal carotid arteries, the internal jugular vein, the vagus nerve, and the deep cervical lymph nodes. Axillary Sheath All the anterior rami of the cervical nerves that emerge in the interval between the scalenus anterior and scalenus medius muscles lie at first deep to the prevertebral fascia. As the subclavian artery and the brachial plexus emerge in the interval between the scalenus anterior and the scalenus medius muscles, they carry with them a sheath of the fascia, which extends into the axilla and is called the axillary sheath. Cervical Ligaments Stylohyoid ligament: Connects the styloid process to the lesser cornu of the hyoid bone. Stylomandibular ligament: Connects the styloid process to the angle of the mandible. Sphenomandibular ligament: Connects the spine of the sphenoid bone to the lingula of the mandible. Pterygomandibular ligament: Connects the hamular process of the medial pterygoid plate to the posterior end of the mylohyoid line of the mandible. It gives attachment to the superior constrictor and the buccinator muscles.  Muscles of the Neck Digastric Posterior Mastoid process of Intermediate Facial nerve Depresses mandible belly temporal bone tendon is held to or elevates hyoid hyoid by fascial sling bone Anterior Body of mandible Nerve to belly mylohyoid Stylohyoid Styloid process Body of hyoid bone Facial nerve Elevates hyoid bone Sternohyoid Manubrium sterni Body of hyoid bone Ansa Depresses hyoid and clavicle cervicalis; C1, bone 2, and 3 Sternothyroid Manubrium sterni Oblique line on Ansa Depresses larynx lamina of thyroid cervicalis; C1, cartilage 2, and 3 Thyrohyoid Oblique line on Lower border of First cervical Depresses hyoid lamina of thyroid body of hyoid bone nerve bone or elevates cartilage larynx Omohyoid Inferior Upper margin of Intermediate Ansa Depresses hyoid belly scapula and tendon is held to cervicalis; C1, bone suprascapular clavicle and first rib 2, and 3 ligament by fascial sling Superior Lower border of body belly of hyoid bone Scalenus Transverse processes First rib C4, 5, and 6 Elevates first rib; anterior of third, fourth, fifth, laterally flexes and and sixth cervical rotates cervical part vertebrae of vertebral column Scalenus Transverse processes First rib Anterior rami Elevates first rib; medius of upper six cervical of cervical laterally flexes and vertebrae nerves rotates cervical part of vertebral column Scalenus Transverse processes Second rib Anterior rami Elevates second rib; posterior of lower cervical of cervical laterally flexes and vertebrae nerves rotates cervical part of vertebral column  The neck Lecture 19 Cervical Plexus The cervical plexus is a network of nerve fibres that supplies innervation to some of the structures in the neck and trunk. It is located in the posterior triangle of the neck, halfway up the sternocleidomastoid muscle, and within the prevertebral layer of cervical fascia. The plexus is formed by the anterior rami (divisions) of cervical spinal nerves C1-C4. Spinal Nerves The spinal nerves C1 – C4 form the basis of the cervical plexus. At each vertebral level, paired spinal nerves leave the spinal cord via the intervertebral foramina of the vertebral column. Each nerve then divides into anterior and posterior nerve fibres. The cervical plexus begins as the anterior fibres of the spinal nerves C1, C2, C3 and C4. These fibres combine with each other to form the branches of the cervical plexus. Branches of the Cervical Plexus The cervical plexus gives rise to numerous branches which supply structures in the head and neck. a) Muscular Branches The muscular branches of the cervical plexus are located deep to the sensory branches. They supply some of the muscles of the neck, back and the diaphragm. After arising from the cervical plexus, the muscular branches tend to travel initially in an anteromedial direction. This is in contrast to the cutaneous branches, which travel posteriorly. 1- Phrenic Nerve The phrenic nerve arises from the anterior rami of C3-C5. It provides motor innervation to the diaphragm. After arising from the cervical plexus, the nerve travels down the surface of the anterior scalene muscle and enters the thorax. In the thoracic cavity, the nerve descends anteriorly to the root of the lung to reach the diaphragm. A good memory aid for the roots of the phrenic nerve is C3,4,5 keeps the diaphragm alive. 2- Nerves to Geniohyoid and Thyrohyoid The C1 spinal nerve gives rise to nerves to the geniohyoid (moves the hyoid bone anteriorly and upwards, expanding the airway) and the thyrohyoid (which depresses the hyoid bone and elevates the larynx). These nerves travel with the hypoglossal nerve to reach their respective muscles. 3- Ansa Cervicalis The ansa cervicalis is a loop of nerves, formed by nerve roots C1-C3. It gives off four muscular branches: a)Superior belly of the omohyoid muscle b)Inferior belly of omohyoid muscle c)Sternohyoid d)Sternothyroid These muscles (the infrahyoids) act to depress the hyoid bone; an important function for swallowing and speech. Other Muscular Branches Several other minor branches arise from the nerve roots to supply muscles of the neck and back: 4- C1-C2: Rectus capitis anterior and lateralis 5- C1-C3: Longus capitis 6- C2-C3: Contributions to the prevertebral muscles and sternocleidomastoid 7- C3-C4: Contributions to the levator scapulae, trapezius and scalenus medius The middle and anterior scalenus muscles also receive innervation directly from the cervical plexus. b) Sensory Branches The cutaneous branches of the cervical plexus supply the skin of the neck, upper thorax, scalp and ear. These nerves all enter the skin at the middle of the posterior border of the sternocleidomastoid. This area is known as the nerve point of the neck (Erb’s point), and is utilised when performing a cervical plexus nerve block. 1- Greater Auricular Nerve The greater auricular nerve is formed by fibres from C2 and C3 roots. It provides sensation to the external ear and the skin over the parotid gland. It is the largest ascending branch of the plexus. The nerve also communicates with the auricular branch of the vagus nerve and the posterior auricular branch of the facial nerve (which innervates some small muscles around the ear). 2- Transverse Cervical Nerve The transverse cervical nerve is also formed by fibres from C2 and C3. It curves around the posterior aspect of the sternocleidomastoid, and supplies sensation to the anterior neck. The nerve then pierces the deep cervical fascia and then gives branches that pass superiorly and inferiorly to supply the anterolateral skin of the neck and upper sternum. 3- Lesser Occipital Nerve The lesser occipital nerve is derived from the C2 root, with a contribution from C3 in some individuals. It supplies cutaneous sensation to the posterosuperior scalp, and commonly communicates with the posterior branch of the greater auricular nerve. After its formation, the nerve curves around the accessory nerve, and passes superiorly, close to the posterior border of the sternocleidomastoid. 4- Supraclavicular Nerves The supraclavicular nerves are a group of nerves formed from the C3 and C4 roots. They arise from the behind the posterior border of sternocleidomastoid, and provide sensation to the skin overlying the supraclavicular fossa and upper thoracic region and sternoclavicular joint. Bones of the neck Cervical Vertebrae The vertebral column is a series of 33 bones called vertebrae, which are separated by intervertebral discs. The column can be divided into five different regions, with each region characterised by a different vertebral structure. Cervical Vertebrae There are seven cervical vertebrae in the human body. They have three main distinguishing features: a)Bifid spinous process – the spinous process bifurcates at its distal end with exceptions to this are C1 (no spinous process) and C7 (spinous process is longer than that of C2-C6 and may not bifurcate). b)Transverse foramina – an opening in each transverse process, through which the vertebral arteries travel to the brain. c)Triangular vertebral foramen Two cervical vertebrae that are unique. C1 and C2 (called the atlas and axis respectively), are specialised to allow for the movement of the head. Hyoid Bone The hyoid bone is a mobile single bone found in the midline of the neck below the mandible and abides the larynx. It does not articulate with any other bones. The hyoid bone is U shaped and consists of a body and two greater and two lesser cornua. It is attached to the skull by the stylohyoid ligament and to the thyroid cartilage by the thyrohyoid membrane. The hyoid bone forms a base for the tongue and is suspended in position by muscles that connect it to the mandible, to the styloid process of the temporal bone, to the thyroid cartilage, to the sternum, and to the scapula. Arteries of the neck The Common Carotid Artery The internal Carotid Artery No branches in the neck The External Carotid Artery Branches of the External Carotid Artery 1- Superior thyroid artery 2-Ascending pharyngeal artery 3-Lingual artery 4-Facial artery 5-Occipital artery 6-Posterior auricular artery 7-Superficial temporal artery 8-Maxillary artery Veins of the Neck Superficial Veins External Jugular Vein The external jugular vein begins just behind the angle of the mandible by the union of the posterior auricular vein with the posterior division of the retromandibular vein. It descends obliquely across the sternocleidomastoid muscle and, just above the clavicle in the posterior triangle, pierces the deep fascia and drains into the subclavian vein. It varies considerably in size, and its course extends from the angle of the mandible to the middle of the clavicle. Tributaries The external jugular vein has the following tributaries: 1-Posterior auricular vein 2-Posterior division of the retromandibular vein 3-Posterior external jugular vein, a small vein that drains the posterior part of the scalp and neck and joins the external jugular vein about halfway along its course 4-Transverse cervical vein 5-Suprascapular vein 6-Anterior jugular vein which begins just below the chin, by the union of several small veins. It runs down the neck close to the midline. Just above the suprasternal notch, the veins of the two sides are united by a transverse trunk called the jugular arch. The vein then turns sharply laterally and passes deep to the sternocleidomastoid muscle to drain into the external jugular vein. Key Neck Muscles Sternocleidomastoid Muscle When the sternocleidomastoid muscle contracts, it appears as an oblique band crossing the side of the neck from the sternoclavicular joint to the mastoid process of the skull. It divides the neck into anterior and posterior triangles. The anterior border covers the carotid arteries, the internal jugular vein, and the deep cervical lymph nodes; it also overlaps the thyroid gland. The upper half of the posterior border is related to cervical plexus, which emerges from behind the lateral border of sternocleidomastoid muscle with some branches (lesser occipital, greater auricular and transverse cervical nerves) coursing anteriorly, while the lower half of the posterior border is related to the anterior scalene muscle, common carotid artery, internal jugular vein, carotid sheath. The muscle is covered superficially by skin, fascia, the platysma muscle, and the external jugular vein. The deep surface of the posterior border is related to the cervical plexus of nerves, the phrenic nerve, and the upper part of the brachial plexus. Muscle Origin Insertion Nerve Supply Action Sternocleidomastoid Manubrium Mastoid Spinal part of Two muscles acting sterni & medial process of accessory together extend head third of clavicle temporal bone nerve &C2 & & flex neck; one and occipital 3 muscle rotates head bone to opposite side  Triangles of the neck lecture 21 The sternocleidomastoid muscle divides the neck into the anterior and the posterior triangles. Anterior Triangle The anterior triangle is bounded above by the body of the mandible, posteriorly by the sternocleidomastoid muscle, and anteriorly by the midline. It is further subdivided into the carotid triangle, the digastric triangle, the submental triangle, and the muscular triangle. Posterior Triangle The posterior triangle is bounded posteriorly by the trapezius muscle, anteriorly by the sternocleidomastoid muscle, and inferiorly by the clavicle. The posterior triangle of the neck is further subdivided by the inferior belly of the omohyoid muscle into a large occipital triangle above and a small supraclavicular triangle below. Muscle Origin Insertion Nerve Supply Action Platysma Deep fascia over Body of mandible Facial nerve Depresses pectoralis major and angle of cervical mandible and and deltoid mouth branch angle of mouth Sternocleidomastoid Manubrium sterni Mastoid process Spinal part of Two muscles and medial third of of temporal bone accessory acting together clavicle and occipital nerve and C2 extend head and bone and 3 flex neck; one muscle rotates head to opposite side Digastric Posterior belly Mastoid process of Intermediate Facial nerve Depresses temporal bone tendon is held to mandible or hyoid by fascial elevates hyoid sling bone Anterior belly Body of mandible Nerve to mylohyoid Stylohyoid Styloid process Body of hyoid Facial nerve Elevates hyoid bone bone Mylohyoid Mylohyoid line of Body of hyoid Inferior Elevates floor of body of mandible bone and fibrous alveolar mouth and hyoid raphe nerve bone or depresses mandible Geniohyoid Inferior mental Body of hyoid First cervical Elevates hyoid spine of mandible bone nerve bone or depresses mandible Sternohyoid Manubrium sterni Body of hyoid Ansa Depresses hyoid and clavicle bone cervicalis; C1, bone  2, and 3 Sternothyroid Manubrium sterni Oblique line on Ansa Depresses larynx lamina of thyroid cervicalis; C1, cartilage 2, and 3 Thyrohyoid Oblique line on Lower border of First cervical Depresses hyoid lamina of thyroid body of hyoid nerve bone or elevates cartilage bone larynx Omohyoid Inferior belly Upper margin of Intermediate Ansa Depresses hyoid scapula and tendon is held to cervicalis; C1, bone suprascapular clavicle and first 2, and 3 ligament rib by fascial sling Superior belly Lower border of body of hyoid bone Scalenus anterior Transverse First rib C4, 5, and 6 Elevates first rib; processes of third, laterally flexes and fourth, fifth, and rotates cervical sixth cervical part of vertebral vertebrae column Scalenus medius Transverse First rib Anterior rami Elevates first rib; processes of upper of cervical laterally flexes and six cervical nerves rotates cervical vertebrae part of vertebral column Scalenus posterior Transverse Second rib Anterior rami Elevates second processes of lower of cervical rib; laterally flexes cervical vertebrae nerves and rotates cervical part of vertebral column. ANTERIOR TRIANGLE Borders The anterior triangle is situated at the front of the neck. It is bounded: Superiorly – inferior border of the mandible (jawbone). Laterally – anterior border of the sternocleidomastoid. Medially – sagittal line down the midline of the neck. Investing fascia covers the roof of the triangle, while visceral fascia covers the floor. Contents 1- The suprahyoid muscles & infrahyoid muscles are located superiorly and inferiorly to the hyoid bone, 2- There are several important vascular structures within the anterior triangle. a)The common carotid artery bifurcates within the triangle into the external and internal carotid branches. b)The internal jugular vein can also be found within this area – it is responsible for venous drainage of the head and neck. 3- Numerous cranial nerves are located in the anterior triangle. Some pass straight through, and others give rise to branches which innervate some of the other structures within the triangle. The cranial nerves in the anterior triangle are a) facial [VII] nerve b) glossopharyngeal [IX] nerve c) vagus [X] nerve d) accessory [XI] nerve and e) hypoglossal [XII] nerve. The anterior triangle is subdivided by the hyoid bone, suprahyoid and infrahyoid muscles into four triangles. SUBMENTAL TRIANGLE The submental triangle in the neck is situated underneath the chin. Borders: Inferiorly – hyoid bone. Medially – midline of the neck. Laterally – anterior belly of the digastric The floor of the submental triangle is formed by the mylohyoid muscle, which runs from the mandible to the hyoid bone. Contents: the submental lymph nodes, which filter lymph draining from the floor of the mouth and parts of the tongue.  SUBMANDIBULAR TRIANGLE The submandibular triangle is located underneath the body of the mandible. It contains the submandibular gland (salivary), and lymph nodes. The facial artery and vein also pass through this area. Borders: Superiorly – body of the mandible. Anteriorly – anterior belly of the digastric muscle. Posteriorly – posterior belly of the digastric muscle. CAROTID TRIANGLE Borders: Superior – posterior belly of the digastric muscle. Lateral – medial border of the sternocleidomastoid muscle. Inferior – superior belly of the omohyoid muscle. Contents: 1-the common carotid artery (which bifurcates within the carotid triangle into the external and internal carotid arteries), 2-the internal jugular vein, and 3-the hypoglossal & vagus nerves. MUSCULAR TRIANGLE The muscular triangle is situated more inferiorly than the subdivisions. It is a slightly ‘dubious’ triangle, in reality having four boundaries. Borders: Superiorly – hyoid bone. Medially – imaginary midline of the neck. Supero-laterally – superior belly of the omohyoid muscle. Infero-laterally – inferior portion of the sternocleidomastoid muscle. Contents: 1-the infrahyoid muscles, 2-the pharynx, and 3-the thyroid, parathyroid glands.  POSTERIOR TRIANGLE The posterior triangle of the neck is an anatomical area located at the posterolateral aspect of the neck. Borders: Anterior – posterior border of the sternocleidomastoid. Posterior – anterior border of the trapezius muscle. Inferior – middle 1/3 of the clavicle. The roof is formed by the investing layer of fascia, and the floor is formed by the prevertebral fascia Contents 1-Muscles Which make up the borders and it’s the floor. a) the omohyoid muscle. It is split into two bellies by a tendon. The inferior belly crosses the posterior triangle, travelling in an supero-medial direction, and splitting the triangle into two. The muscle then crosses underneath the SCM to enter the anterior triangle of the neck. A number of vertebral muscles (covered by prevertebral fascia) form the floor of the posterior triangle: b) Splenius capitis c) Levator scapulae d) Anterior, middle and posterior scalenes 2-Vasculature a) The external jugular vein is one of the major veins of the neck region. Formed by the retromandibular and posterior auricular veins, it lies superficially, entering the posterior triangle after crossing the sternocleidomastoid muscle. Within the posterior triangle, the external jugular vein pierces the investing layer of fascia and empties into the subclavian vein. b) The subclavian vein is often used as a point of access to the venous system, via a central catheter. c) The transverse cervical and suprascapular veins also lie in the posterior triangle The subclavian, transverse cervical and suprascapular veins are accompanied by their respective arteries in the posterior triangle. d) The distal part of the subclavian artery can be located as it emerges between the anterior and middle scalene muscles. As it crosses the first rib, it becomes the axillary artery, which goes onto supply the upper limb. 3-Nerves a) The accessory nerve (CN XI) exits the cranial cavity, descends down the neck, innervates sternocleidomastoid and enters the posterior triangle. It crosses the posterior triangle in an oblique, inferoposterior direction, within the investing layer of fascia. It lies relatively superficial in the posterior triangle, leaving it vulnerable to injury. b) The cervical plexus forms within the muscles of the floor of the posterior triangle. A major branch of this plexus is the phrenic nerve, which arises from the anterior divisions of spinal nerves C3-C5. It descends down the neck, within the prevertebral fascia, to innervate the diaphragm. Other branches of the cervical plexus innervate the vertebral muscles, and provide cutaneous innervation to parts of the neck and scalp. c) The trunks of the brachial plexus also cross the floor of the posterior triangle. Subdivisions The omohyoid muscle divides the posterior triangle of the neck into two areas: 1- Occipital triangle – located superior to the omohyoid. 2- Subclavian triangle – located inferior to the omohyoid. It contains the distal portion of the subclavian artery  THYROID GLAND lecture 21 The thyroid gland is a vascular organ consists of right and left lobes connected by a narrow isthmus. A sheath is derived from the pretracheal layer of deep fascia, surrounds the thyroid gland & attaches it to the larynx and the trachea. Each lobe is pear shaped, with its apex being directed upward as far as the oblique line on the lamina of the thyroid cartilage; its base lies below at the level of the fourth or fifth tracheal ring. The isthmus extends across the midline in front of the second, third, and fourth tracheal rings. A pyramidal lobe is often present, and it projects upward from the isthmus, usually to the left of the midline. A fibrous or muscular band frequently connects the pyramidal lobe to the hyoid bone; if it is muscular, it is referred to as the levator glandulae thyroideae. Relations of the Lobes Anterolaterally: The sternothyroid, the superior belly of the omohyoid, the sternohyoid, and the anterior border of the sternocleidomastoid Posterolaterally: The carotid sheath with the common carotid artery, the internal jugular vein, and the vagus nerve Medially: The larynx, the trachea, the pharynx, and the esophagus. Associated with these structures are the cricothyroid muscle and its nerve supply, the external laryngeal nerve. In the groove between the esophagus and the trachea is the recurrent laryngeal nerve The rounded posterior border of each lobe is related posteriorly to the superior and inferior parathyroid glands and the anastomosis between the superior and inferior thyroid arteries. Relations of the Isthmus Anteriorly: The sternothyroids, sternohyoids, anterior jugular veins, fascia, and skin Posteriorly: The second, third, and fourth rings of the trachea The terminal branches of the superior thyroid arteries anastomose along its upper border. Blood Supply The arteries to the thyroid gland are the superior thyroid artery, the inferior thyroid artery, and sometimes the thyroidea ima. The arteries anastomose profusely with one another over the surface of the gland. The superior thyroid artery, a branch of the external carotid artery, descends to the upper pole of each lobe, accompanied by the external laryngeal nerve. The inferior thyroid artery, a branch of the thyrocervical trunk, ascends behind the gland to the level of the cricoid cartilage. It then turns medially and downward to reach the posterior border of the gland. The recurrent laryngeal nerve crosses either in front of or behind the artery, or it may pass between its branches. The thyroidea ima, if present, may arise from the brachiocephalic artery or the arch of the aorta. It ascends in front of the trachea to the isthmus. The veins from the thyroid gland are 1-The superior thyroid vein, which drains Into the internal jugular vein; 2-The middle thyroid vein, which drains into the internal jugular vein & the inferior thyroid, the inferior thyroid veins of the two sides anastomose with one another as they descend in front of the trachea &they drain into the left brachiocephalic vein in the thorax. Lymph Drainage The lymph from the thyroid gland drains mainly laterally into the deep cervical lymph nodes. A few lymph vessels descend to the paratracheal nodes. Nerve Supply Superior, middle, and inferior cervical sympathetic ganglia Functions of the Thyroid Gland The thyroid hormones, thyroxine and triiodothyronine, increase the metabolic activity of most cells in the body. The parafollicular cells produce the hormone thyrocalcitonin, which lowers the level of blood calcium. Parathyroid Glands Location and Description The parathyroid glands are ovoid bodies measuring about 6 mm long in their greatest diameter. They are four in number and are closely related to the posterior border of the thyroid gland, lying within its fascial capsule. The two superior parathyroid glands are the more constant in position and lie at the level of the middle of the posterior border of the thyroid gland. The two inferior parathyroid glands usually lie close to the inferior poles of the thyroid gland. They may lie within the fascial sheath, embedded in the thyroid substance, or outside the fascial sheath. Sometimes they are found some distance caudal to the thyroid gland, in association with the inferior thyroid veins, or they may even reside in the superior mediastinum in the thorax. Functions of the Parathyroid Glands The chief cells produce the parathyroid hormone, which stimulates osteoclastic activity in bones, thus mobilizing the bone calcium and increasing the calcium levels in the blood. The parathyroid hormone also stimulates the absorption of dietary calcium from the small intestine and the reabsorption of calcium in the proximal convoluted tubules of the kidney. It also strongly diminishes the reabsorption of phosphate in the proximal convoluted tubules of the kidney. The secretion of the parathyroid hormone is controlled by the calcium levels in the blood. blood supply & venous drainage The arterial supply to the parathyroid glands is from the superior and inferior thyroid arteries. The venous drainage is into the superior, middle, and inferior thyroid veins. Lymph Drainage Deep cervical and paratracheal lymph nodes Nerve Supply Superior or middle cervical sympathetic ganglia