Dr.Ban I.S. head & neck anatomy 2 nd y. جامعة تكريت كلية طب االسنان مادة التشريح املرحلة الثانية أ.م.د. بان امساعيل صديق 6102/6102

Transcription

1 جامعة تكريت كلية طب االسنان مادة التشريح املرحلة الثانية أ.م.د. بان امساعيل صديق 6102/6102

2 The scalp The scalp extends from the supraorbital margins anteriorly to the nuchal lines at the back of the skull and down to the temporal lines at the sides. The forehead, from eyebrows to hairline, is common to the face and scalp. The composition of the scalp is traditionally recalled from the five letters of the words that indicate its five layers: Skin; Connective tissue [The vessels and nerves run within this firm tissue which unites the first and third layers]; Aponeurosis with muscle at the front and back; Loose areolar tissue; and Pericranium. Skin, which is thick and hair bearing and contains numerous sebaceous glands. 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. 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

3 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. 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. 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 Occipitofrontalis consists of occipitalis and frontalis muscular parts with an intervening epicranial aponeurosis (galea aponeurotica) into which they are inserted at the back and front respectively. Occipitalis arises from the superior nuchal line and passes upwards into the aponeurosis which lies over the top of the skull. The muscle bellies are separated across the midline by the aponeurosis which extends backwards to be attached to the external occipital protuberance. Frontalis arises from the front of the aponeurosis and passes forwards to become attached to the upper part of orbicularis oculi and the overlying skin of the eyebrow. It has no attachment to the skull. The right and left frontalis muscles meet in the midline. The midline fibers blend with procerus. Nerve supply. By the facial nerve; the posterior auricular branch to occipitalis, and temporal branches to frontalis.

4 Action. While occipitalis can pull the scalp back in certain individuals, usually it anchors تثبت the aponeurosis, while frontalis elevates the eyebrows and produces wrinkles in the skin of the forehead. 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. 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.

5 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 2nd cervical nerve, ascends over the back of the scalp and supplies the skin as far forward as the vertex of the skull. 7/The third occipital nerve, a branch of the posterior ramus of the 3nd cervical nerve, ascends over the back of the neck close to the midline and its terminal branches supplies the small posterior area of the middle part of the scalp.

6 Blood supply: The arteries of the scalp are derived from the external carotid artery by the occipital, posterior auricular and superficial temporal branches, and from the internal carotid artery by the zygomaticotemporal, supraorbital and supratrochlear branches[branches of ophthalmic artery]. All these arteries anastomose very freely with each other. The arterial walls are attached to the dense connective tissue of the second layer of the scalp and tend to be held open and bleed profusely when cut. 1/The occipital artery emerges from the apex of the posterior triangle and runs with the greater occipital nerve to supply the back of the scalp up to the vertex. 2/ The smaller posterior auricular artery runs with the lesser occipital nerve to supply the scalp above and behind the ear. 3/The superficial temporal artery is a terminal branch of the external carotid. Running up behind the temporomandibular joint and in front of the ear in accompany with auriculo-temporal nerve, it crosses the zygomatic arch, where its pulsation can be felt, and branches out widely into the skin that overlies the temporal fossa. One branch, the middle temporal artery, pierces the fascia, supplies

7 temporalis and anastomoses with the deep temporal branches of the maxillary artery. 4/The zygomaticotemporal,supraorbital and supratrochlear arteries (from the ophthalmic) run with the corresponding nerves. The supraorbital is the larger and supplies the front of the scalp up to the vertex. Its anastomosis with the superficial temporal artery connects the internal and external carotid systems. Venous drainage of the scalp: The veins of the scalp run back with the arteries. 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. The supraorbital and supratrochlear veins drain by the angular vein into the facial vein. The superficial temporal veins run into the retromandibular vein, and occipital veins reach the plexus around the suboccipital muscles which drains into the vertebral vein. The posterior auricular vein drains the scalp behind the ear to the external jugular vein. Lymph drainage of the scalp:[ Snell p: 925 ]

8 Lymph vessels in the anterior part of the scalp and forehead drain into the submandibular lymph nodes. Drainage from the lateral part of the scalp above the ear is into the superficial parotid (preauricular) nodes; lymph vessels in the part of the scalp above and behind the ear drain into the mastoid nodes. Vessels in the back of the scalp drain into the occipital nodes. Temporal fossa : The temporal fossa is the area bounded by the temporal lines above and the zygomatic arch below. Its lateral wall is the temporalis fascia and its medial wall is the part of the side of the skull that includes the pterion, where the frontal, the parietal and the temporal bones articulate with the greater wing of the sphenoid.the zygomatic processes of the frontal bone, the zygomatic bone, and the maxilla are in the anterior wall. The fossa is filled by the temporalis. Deep to the arch, at the level of the infratemporal crest of the greater wing of the sphenoid, the fossa becomes continuous with the lateral part of the infratemporal fossa. The temporal fascia (deep temporal fascia) is attached to the superior temporal line and passes down to the upper border of the zygomatic arch. Above the arch it splits into two layers, one attached to the lateral and the other to the medial margin of the upper border of the arch. The space between these two layers is occupied by

9 fat, which is traversed by a branch of the superficial temporal artery and the zygomaticotemporal branch of the maxillary nerve. The temporal and zygomatic branches of the facial nerve, the superficial temporal vessels and the auriculotemporal nerve lie in or just deep to the overlying temporoparietal fascia (superficial temporal fascia). Temporalis This muscle (one of the muscles of mastication) arises from the entire rim of the fossa and from the deep surface of the temporalis fascia. The most anterior fibres are vertical and the most posterior are horizontal, turning downwards. The fan-shaped muscle converges towards the coronoid process of the mandible, becomes tendinous, and is inserted into the coronoid process. The blood supply of the muscle is derived from the temporal branches of the maxillary and superficial temporal arteries. Nerve supply. Two or three deep temporal branches of the mandibular nerve enter the deep surface of the muscle. Action. Temporalis elevates the mandible when the open mouth is closed, and it retracts the protruded mandible.

10 The Meninges: The brain in the skull is surrounded by three protective membranes, or meninges: the dura mater, the arachnoid mater, and the pia mater.the interior of the cranium is lined with dura mater, the surface of the brain is covered with pia mater. Between the two, in contact with the dura mater, lies the arachnoid mater, which is connected to the pia by many fine filamentous processes. Pia mater The pia mater invests the brain and spinal cord. It is made of thin vascular fibrous tissue. The region between the pia and the arachnoid is the subarachnoid space, filled with cerebrospinal fluid. Arachnoid mater and subarachnoid space The arachnoid mater consists of a delicate membrane that everywhere is supported by the inner surface of the inner layer of the dura mater with only a thin film of tissue fluid between them in the subdural space [potential space]. Vessels and nerves pierce the dura and arachnoid mater both at the same place; they cross the subdural space, but do not run along between the two membranes.

11 In certain areas the arachnoid herniates through little holes in the dura mater into the venous sinuses. Such herniae are the arachnoid villi; through their walls the cerebrospinal fluid oozes يتسرب back into the blood. The arachnoid villi are most numerous in the superior sagittal sinus. as age progresses they become aggregated into visible clumps,مجموعات the arachnoid granulations. Dura mater The dura mater consists of an outer endosteal layer[periosteal], and an inner meningeal layer. The two layers are united except where they separate to enclose the venous sinuses of the dura. The outer layer is the periosteum which invests the surface of any bone, and blood vessels pass through it to supply the bone. The inner layer consists of a dense, strong fibrous membrane, which is the dura mater proper. At the foramen magnum the inner layer leaves the outer layer and is projected down the vertebral canal as the spinal dura mater. The inner layer is likewise evaginated around the cranial nerves and spinal nerve roots. Folds of the inner layer project into the cranial cavity. These fibrous septa minimize rotary displacement of the brain. 1/The falx cerebri is a sickle-shaped fold of dura mater that lies in the midline between the two cerebral hemispheres. Its narrow end in front is attached to the

12 internal frontal crest and the crista galli. Its broad posterior part blends in the midline with the upper surface of the tentorium cerebelli. The superior sagittal sinus runs in its upper fixed margin, the inferior sagittal sinus runs in its lower concave free margin, and the straight sinus runs along its attachment to the tentorium cerebelli. 2/The tentorium cerebelli is a crescent-shaped fold of dura mater that roofs over the posterior cranial fossa. It covers the upper surface of the cerebellum and supports the occipital lobes of the cerebral hemispheres. In front is a gap, the tentorial notch, for the passage of the midbrain, thus producing an inner free border and an outer attached or fixed border. The fixed border is attached to the posterior clinoid processes, the superior borders of the petrous bones, and the margins of the grooves for the transverse sinuses on the occipital bone. The free border runs forward at its two ends, crosses the attached border, and is affixed to the anterior clinoid process on each side. The falx cerebri and the falx cerebelli are attached to the upper and lower surfaces of the tentorium, respectively. The straight sinus runs along its attachment to the falx cerebri, the superior petrosal sinus along its

13 attachment to the petrous bone, and the transverse sinus along its attachment to the occipital bone. 3/The falx cerebelli is a small, sickle-shaped fold of dura mater that is attached to the internal occipital crest and projects forward between the two cerebellar hemispheres. Its posterior fixed margin contains the occipital sinus. 4/The diaphragma sellae is a small circular fold of dura mater that forms the roof for the sella turcica. A small opening in its center allows passage of the stalk of the pituitary gland.