Skull Anatomy PDF

Skull Doaa Tayseer Abdel Ghafoor, MD 1  The Skull The skull is composed of several separate bones (22 bones) united at immobile joints called sutures. Only one moveable bone, the mandible which is united to the skull by the mobile Temporoman...

Skull Doaa Tayseer Abdel Ghafoor, MD 1  The Skull The skull is composed of several separate bones (22 bones) united at immobile joints called sutures. Only one moveable bone, the mandible which is united to the skull by the mobile Temporomandibular Joint 2  The bones of the skull can be divided into 1- Cranial bones(8 bones) 2- Facial bones(14 bones) 3  Skull vault The cranial bones can be divided to skull cap and skull Skull base base 4 Cranial bones  Single bones: Frontal bone Occipital bone Sphenoid bone Ethmoid bone  Paired bones Parietal bone Temporal bone parietal Frontal Temporal occipital 5 Facial bones  Paired bones: Maxillae Zygomatic bones Nasal bones Lacrimal bones Palatine Inferior nasal conchae  Single bones: Mandible Vomer 6 Anterior view of the skull 1. Frontal bone 2. Nasal bone 3. Vomer 4. Ethmoid 5. Inferior conchae 6. Zygomatic bone 7. Maxillae 8. Mandible 7 Posterior view of the skull Superior view of the skull Bregma Coronal suture Sagittal suture Lambdoid suture 8 Lateral view of the skull Coronal suture The pterion, the thinnest part of the lateral wall of parietal the skull, overlies the Pterion anterior division of the Frontal middle meningeal artery, blows to this area can lead to extradural hemorrhage Lambdoid suture sphenoid Temporal occipital Zygomatic bone Mandible Maxilla 9 Inferior view Maxillae Zygomatic bone palatine Vomer Sphenoid Temporal bone Foramen magnum Occipital bone 10 Interior of the skull Frontal Ethmoid Intracranial cavity is divided into three fossae: 1. Anterior cranial fossa Sphenoid 2. Middle cranial fossa 3. Posterior cranial fossa Parietal Temporal occipital 11 Brain and cranial nerves 12  Meninges The meninges refer to the membranous coverings of the Falx cerebri brain and spinal cord. There are three layers of meninges, known as Falx cerebelli the dura mater, arachnoid mater and pia mater. Tentorium cerebelli The dura mater consists of two layered sheets of connective tissue: Periosteal layer Meningeal layer The meningeal layer of dura mater forms: Falx cerebri, Tentorium cerebelli, Falx cerebelli and Diaphagma sellae 13 Cranial bones Parietal Frontal Parietal Temporal Temporal Sphenoid Parietal Frontal Temporal Sphenoid Occipital Ethmoid 14  Frontal bone Forms the forehead and the roof of each orbit. Internally, it contributes for anterior cranial fossa. It articulates with …. It contains frontal sinuses 15 Frontal bone Squamous part: the most flat part, it contains frontal sinus Superciliary arches (brow ridges): Elevated ridges above the suporbital margin Supraorbital notch, or foramen: transmits the supraorbital nerve & vessels 16  Glabella: a slightly elevated area above the root of the nose between the 2 superciliary arches Nasion: a point where the frontonasal & internasal sutures meet 17 Parietal bone Covers the top and the sides of the brain Communicates with each other in the midline at the sagittal suture. 18 Temporal bone Inferior to parietal bone Parts: 1. Squamous part 2. Tympanic part 3. Petrous part Zygomatic process External auditory canal Styloid process Mastoid process Stylomastoid foramen for facial nerve 19  Temporal bone Internal acoustic meatus: transmits the vestibulocochlear nerve and facial nerve. Jugular foramen:lies between the lower border of the petrous part of the temporal bone and the condylar part of the occipital bone. It transmits 9th, 10th, and 11th cranial nerves and the sigmoid sinus. Carotid canal 20  Inferior orbital fissure Foramen lacerum Carotid canal Jugular foramen 21 The tegmen tympani, the roof of the tympanic cavity, is a thin plate of the petrous part of the temporal bone that separates the temporal lobe of brain and middle ear 22 Notice superior and inferior temporal lines, which begin as a single line from the posterior margin of the zygomatic process of the frontal bone and diverge as they arch backward. The temporal fossa lies below the inferior temporal line. 23 The infratemporal fossa Boundaries : Anterior wall: maxilla Medial wall: lateral pteyrygoid plate Roof: greater wing of sphenoid Temporal fossa Lateral wall: ramus of the mandible Communications 1. Temporal fossa 2. Orbit thr inferior orbital fissure 3. Pterygopalatine fossa thr ptergopalatine Infratemporal fossa fissure 4. Middle cranial fossa thr foramen ovale and spinosum 24  The pterygomaxillary fissure is a vertical opening that lies within the fossa between the pterygoid process of the sphenoid bone and back of the maxilla. It leads medially into the pterygopalatine fossa. It communicates with: 1. Infratemporal fossa through the pterygomaxillary fissure. 2. Medially with the nasal cavity through the sphenopalatine foramen. 3. Superiorly with the cranial cavity through the foramen rotundum. 4. Anteriorly with the orbit through the inferior orbital fissure. 25 Occipital bone Forms the posterior part of skull and the posterior cranial fossa Articulates with temporal and parietal bones External occipital protroperance: gives attachment to muscles and the ligamentum nuchae Foramen magnum Superior nuchal line Inferior nuchal line Occipital condyles Hypoglossal canal is Transmits the medulla oblongata situated above the and its surrounding meninges, the anterolateral boundary of ascending spinal parts of the the foramen magnum and Foramen magnum accessory nerves, and the two transmits the hypoglossal vertebral arteries. nerve 26  Clivus Basilar part Internal occipital crest Internal occipital protuberance 27 28 29  Body Lesser wing Sphenoid bone Greater wing Butterfly shaped bone Keystone bone in skull base Consists of body(contains air sinuses), lesser and greater wings, lateral and medial pterygoid processes 30  Gives an attachment Anterior clinoid process to tentorium cerebelli Greater wing of sphenoid Lateral pterygroid plate Medial pterygroid plate Hamulus of sphenoid bone is a hook-like process at medial pterygoid process 31  optic canal transmits the optic nerve and the ophthalmic artery, a branch of the internal carotid artery, to the orbit. The superior orbital fissure,between the Anterior lesser and the greater wings of the clinoid sphenoid, transmits trochlear, oculomotor process and abducens nerves. Inferior orbital fissure is formed between greater wing of sphenoid and maxilla 32  Foramen rotundum transmits the maxillary nerve to the pterygopalatine fossa. Foramen ovale transmits the mandibular nerve to the infratemporal fossa and the lesser petrosal nerve Foramen spinosum transmits the middle meningeal artery from the infratemporal fossa into the cranial cavity. Foramen lacerum: filled with fibrous tissue and only small blood vessels pass through this tissue from the cranial cavity to the neck 33 Trigeminal nerve 34  Tuberculum sellae Sella turcica Hypophyseal fossa Contains pituitary gland Dorsum sellae Three parts can be identified 35  Cavernous sinuses are located on either side of sella tursica. Internal carotid artery and abducens nerve pass within the sinus. While oculomotor nerve CNIII, trochlear nerve CNIV, ophthalmic and maxillary branches oh trigeminal nerve CNV pass thr. The lateral wall of the sinus. 36 Ethmoid bone 37 Ethmoid bone Cribriform plate (horizontal):it has many openings for passage for olfactory nerves Crista galli for attachment of falx cerebri Perpendicular plate (part of nasal septum: articulates with vomer Two lateral masses (ethmoid labyrinth) Superior and middle nasal conchae Formaen cecum 38 Paranasal sinuses 39 Interior of the skull 40 Anterior cranial fossa Formed by frontal bone, ethmoid and lesser wings of sphenoid. Fractures of anterior cranial fossa: Epistaxis , cerebrospinal rhinorrhea Hemorrhage beneath the conjunctiva and into the orbital cavity(Racoon eye), causing exophthalmos 41 Middle cranial fossa Formed by body and greater wings of sphenoid and petrous part of temporal bone Fractures of middle cranial fossa: Leakage of cerebrospinal fluid and blood from the external auditory meatus is common The seventh and eighth cranial nerves may be involved. The third, fourth, and sixth cranial nerves may be damaged. 42 Posterior cranial fossa Fomed by occipital bone and petrous part of temporal bone In fractures involving the jugular foramen, the 9th, 10th, and 11th cranial nerves may be damaged The strong bony walls of the hypoglossal canal usually protect the hypoglossal nerve from injury. 43 44 45  Nasal Facial bones bone Palatine bones Vomer Lacrimal bone Zygomatic Zygomatic bone bone Inferior Maxilla Maxilla concha Mandible 46  Maxilla Forms the upper jaw and part of the hard palate Frontal process: articulates with frontal bone Zygomatic process: articulates with zygomatic bone Alveolar process: the bony ridge that contains the tooth sockets for holding upper teeth Orbital plate: forms of the floor of the orbit Palatine process: forms the anterior part of hard palate 47 Infraorbital foramen: Below the orbit Transmits the infraorbital nerve & vessels Maxillary sinus 48  Incisive foramen Greater palatine foramen Lesser palatine foramen 49  Maxillary fractures occure in massive facial trauma It can leads to: 1. Facial swelling 2. Mobility of underlying bone on palpation 3. Double vision if orbital margin damage occurs. 4. Loss of sensation over cheeks due to infraorbital nerve involvement. 5. cerebrospinal rhinorrhea and nasal bleeding 50  Zygomatic bone Forms the prominence of the cheek The zygomatic bone has: Frontal process: articulates with frontal bone. Temporal process: articulates with zygomatic process of the temporal bone to form the zygomatic arch Maxillary process: articulates with the maxillary bone. Orbital plate: forms part of the lateral wall of the orbit. 51  The zygomatic bone is perforated by two foramina for the zygomaticofacial and zygomaticotemporal nerves A blow to the side of the face can fracture the zygoma or zygomatic arch. 52  Nasal bones Form the bridge of the nose Articulation: frontal bone,maxilla Fractures of the nasal bones are the most common facial fractures. 53  Inferior conchae Paired bone The inferior nasal concha is formed by an independent bone Vomer Single bone Contributes to the lower part of the nasal septum 54 Palatine bone Paired bone It forms the posterior part of the hard palate Greater and lesser palatine foramina lay posterolaterally. 55 Mandible Mandible has a body and two rami, every ramus has medial and lateral surfaces. Condylar process is made of: 1. Head : forms temporomandibular joint 2. Neck Coronoid process: gives attachment for temporalis muscle Mandibular notch Alveolar processes Oblique line Mandibular foramen: inferior alveolar vessels and nerve 56 Mandible Mental foramen: transmits mental nerve and vessels Mental protuberance lingula: sphenomandibular ligament Mylohyoid groove Mylohyoid line 57 Temporomandibular joint Between mandible and temporal bone Synovial joint Movements : elevation, depression, protrusion, retraction and side to side movement. 58 Neonatal Skull The newborn skull has large cranium relative to the face. The bones are separated by unossified membranous intervals called fontanelles Anterior fontanelle: closes at 18 months age Posterior fontanelle : closes at one year The mastoid process is not present at birth and develops later in response to the pull of the sternocleidomastoid muscle when the child moves his or her head. 59  Hyoid bone Mobile single bone in the midline of the neck below the mandible and next to 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 horns 60