Transcript Slide 1
OSTEOLOGY The Skull The Skull • 1. 2. The skull is divided into two parts: Neurocranium- which forms a protective case or “vault” around the brain Viscerocranium- which forms the anterior part of the skull including the orbits, nasal cavities and upper/lower jaw bones Neurocranium Viscerocranium 4/26/2020 2 The Skull Frontal coronal suture Parietal Occipital Temporal Sphenoid 4/26/2020 3 The Skull Lacrimal Nasal Zygomatic Nasal Maxilla Inferior Nasal Conchae Inferior maxilla Nasal conchae Vomer 4/26/2020 Vomer Mandible Mandible 4 Frontal Bone • Squamous (flat) portion forms the skeleton of the forehead Frontal Bone Squamous portion • Fontal bone forms the roof of the orbit Nasion Frontal bone Glabella Glabella Nasion • Nasion is an area where the frontal bone intersects with the nasal bones Orbital portion • Glabella- smooth, slightly depressed area located just superior to the nasion 4/26/2020 5 Frontal Bone • Supraorbital marginmarks the boundary between the squamous and orbital portions • Supraorbital notch or foramen is for the passage of the supraorbital nerve and vessels • A prominent ridge just superior to the supraorbital margin is the superciliary arch (more pronounced in males) • Zygomatic process of the frontal bone articulates with the zygomatic bone 4/26/2020 Supraorbital notch Superciliary arch Zygomatic process Supraorbital margin 6 Zygomatic Bones • Cheek bones • Forms a portion of the lateral wall of the orbit • Frontal Process of the zygomatic bone articulates with the frontal bone Frontal process • Temporal process of the zygomatic bone articulates with the temporal bone • Zygomaticofacial foramensmall foramen for passage of 4/26/2020 the zygomaticofacial nerve Temporal process Zygomaticofacial foramen 7 Maxillae • Forms the upper jaw • Alveolar processes of the maxillae includes the sockets and supporting bone for the maxillary teeth • Maxillae form the floor of the orbit • Large infraorbital foramen for passage of the infraorbital nerve & vessels Infraorbital foramen Alveolar process Piriform aperture Maxilla • Surrounds most of the pear-shaped piriform aperture 4/26/2020 8 Maxillae • Frontal processes of the maxillae articulates with the frontal bone • Zygomatic processes of the maxillae articulates with the zygomatic bones • Anterior nasal spinesharp prominence at inferior aspect of the piriform aperture frontal process • Intermaxillary suturesite where the two maxilla are united in the median plane Zygomatic process 4/26/2020 Anterior nasal spine Intermaxillary suture 9 • Seen within the piriform aperture are the scrolled middle nasal conchae (part of the ethmoid bone) & the inferior nasal conchae • Vomer bone along with the perpendicular plate of the ethmoid bone which together form the bony nasal septum can also be identified with the piriform aperture 4/26/2020 Perpendicular plate Middle & Inferior concha Vomer 10 Mandible • U-shaped bone with alveolar process that houses the mandibular teeth • Mental foramen- located inferior to 2nd premolar for passage of the mental nerve and vessels • Mental protuberance- a triangular elevation of bone that forms the prominence of the chin • Mental tubercle- located just lateral to the protuberance • Body is the horizontal Alveolar process portion • Ramus is the vertical portion 4/26/2020 Ramus Body Mental foramen Mental protuberance 11 Osteology Lateral Aspect of the Skull Lateral Aspect of the Skull 1. Parietal bone 2. Frontal bone 3. Occipital bone 4. Temporal bone 5. Sphenoid bone 6. Mandible 7. Zygomatic bone 8. Maxillae 9. Lacrimal bone 10. Nasal bone 4/26/2020 1. 2. 9. 5. 4. 10. 3. 7. 8. 6. 13 Parietal Bones • Paired bones that form the lateral & superior cranium • Temporal Lines- mark the attachment site of the temporalis muscle & fascia Coronal suture Temporal lines Parietal Lambdoid suture • Articulates with frontal bone via coronal suture • Articulates with occipital bone via lambdoid suture • Pterion-site where 4 cranial bones articulateimportant clinical 4/26/2020 implications pterion 14 Temporal Bones • • • 4/26/2020 Paired bones that form the inferior lateral aspect of skull Squamous Temporal bone is described as having a flat squamous portion and a mastoid process (site of attachment of several muscles) Mastoid process Zygomatic arch extends anteriorly to articulate with the zygomatic bone Zygomatic arch 15 Temporal Bones • External acoustic meatus (ear canal) and the pointed styloid process are considered to be located the tympanic portion of the temporal bone • Styloid process serves as the attachment site for several muscles and the stylohyoid ligament External acoustic meatus Styloid process 4/26/2020 16 Temporal Bones • Mandible and a portion of the zygomatic arch removed in this view • Located on the inferior aspect of the arch is a small bony protrusionarticular tubercle that is important in the mechanics of the TMJ • Mandibular fossa- deep recess that accepts the condyle of the mandiblealso important region of the TMJ 4/26/2020 Articular tubercle Mandibular fossa 17 Zygomatic bone • Forms major portion of the cheek • Temporal process that articulates with the the zygomatic arch Zygomatic arch Frontal process • Frontal process that articulates with the frontal bone • Zygomaticofacial foramen – small foramen generally visible 4/26/2020 Zygomaticofacial foramen Temporal process 18 Occipital Bone • Forms the posterior aspect of the skull • Articulates with the parietal bone via the lambdoid suture • Prominent palpable elevation located posteriorly is the external occipital protuberance 4/26/2020 Lambdoid suture External Occipital protuberance 19 Sphenoid Bone • • 1. 2. 3. 4. • 4/26/2020 Irregular shaped bone that forms a portion of the orbit, lateral aspect of skull and a portion of the cranial base Sphenoid can be divided into 4 parts: Greater wing Lesser wing Pterygoid processes Body Some portions of the sphenoid can only be seen inside the cranial cavity Sphenoid Bone 20 4 portions of Sphenoid Bone • Portion of zygomatic arch and mandible removed in this view • Greater wing articulates with the temporal, parietal & frontal bones at the pterion Greater wing • Pterygoid processes are two thin plates of bone that serve as attachment sites for muscles • Pterygoid hamulus-small hook of bone extending from the medial pterygoid platetensor veli palatini tendon courses around this 4/26/2020 Pterygoid hamulus Pterygoid process 21 Maxillae • Portion of zygomatic arch and mandible removed in this view • Posterior aspect of the maxillae is referred to as the tuberosity of maxillae • Small alveolar foramina for the posterior superior alveolar nerves & vessels • Pterygomaxillary fissuretear-drop shaped fissure between the sphenoid and Alveolar tuberosity of the maxillae foramen • Pterygopalatine fossa is a small but important space located medial to the fissure 4/26/2020 Pterygomaxillary Fissure Tuberosity of maxilla 22 Lateral Aspect of Skull • Nasal bone can also identified as it articulates with the frontal bone and the maxillae • Lacrimal bone- which houses the lacrimal sac van be identified within the orbit • Prominent anterior nasal spine at the inferior aspect of the piriform aperture 4/26/2020 Lacrimal bone Nasal bone Nasal spine 23 Mandible • Condylar process is located at the superior part of the ramus and involved in the articulation of the mandible with the temporal bone (TMJ) • Coronoid process is located just anterior and serves as the attachment site for the temporalis muscle • Angle of mandible is between the ramus and body 4/26/2020 Condylar process Coronoid process Angle 24 Mandible Condylar Process Mandibular foramen Infant Coronoid process Mylohyoid line Lingula Ramus Alveolar Part (crest) Mental foramen Body 4/26/2020 25 Mandible Mandibular notch Condylar process Ramus Body Mental spines Bone loss due to tooth loss 4/26/2020 26 Calvaria • Emissary foramen- small, inconsistent (not always present) foramina for passage of emissary veins • Bregma- is the landmark formed by the intersection of the sagittal & coronal sutures • Lambda-is the landmark formed by the intersection of the sagittal & lambdoid sutures Bregma Coronal suture Sagittal suture Emissary foramen Lambda 4/26/2020 Lambdoid suture 27 Calvaria • Inferior aspect of the skull cap presents several Diploe features: • Vascular grooves for branches of the middle meningeal artery • Granular Foveolae- pits formed by arachnoid granulations (site of CSF transfer) • Groove for the superior sagittal sinus-large venous channel within the dura mater • Diploe- cancellous bone containing red marrow 4/26/2020 Grooves for middle meningeal artery Granular foveolae Groove for superior sagittal sinus 28 Infant Skull Superior & Lateral Aspects Infant Skull • Bones forming the calvaria & some parts of the cranial base develop by Anterior intramembranous ossification • Whereas-most parts of the cranial base develop by endochondral ossification • Bones in the infant skull are separated by areas of fibrous tissue membranes- the fontanelles: • Anterior Sphenoidal • Posterior • Mastoid •4/26/2020 sphenoidal Posterior Mastoid 30 Infant Calvaria • Anterior Fontanelle (soft spot) is the future site of the bregma • By about 18-24 monthsthe surrounding bones fuse together and is no longer palpable • Posterior Fontanelle is triangular and marks the future site of the lambda • Fusion of surrounding bones occurs by about 12 months 4/26/2020 Fontanelles- Anterior fontanelle Posterior fontanelle 31 membranous gaps (soft spots) in skull that permit growth Infant Skull • Mastoid & sphenoidal fontanelles fuse early in infancy • Palpation of fontanelles during infancy enables physicals to determine: 1. Growth progress of the frontal & parietal bones 2. Degree of hydration of the infant (a depressed fontanelle indicates dehydration) 3. Level of intracranial pressure-bulging fontanelle indicates increased pressure on the brain 4/26/2020 Anterior Sphenoidal Posterior Mastoid 32 Osteology External Aspect of the Cranial Base Cranial Base • 1. 2. 3. 4. 5. 6. • Inferior aspect of the skull presents six different bones: Palatine processes of the maxillae Palatine bone Sphenoid bone Vomer Temporal Occipital bone Numerous foramina can also be identified 4/26/2020 1 2 3 4 5 6 34 Cranial Base- Palate • Hard palate is formed by the palatine processes of the maxillae and the horizontal plates of the palatine bone • Small prominence projecting posteriorly form the hard palate in the median plane is the posterior nasal spine 4/26/2020 Palatine processes Horizontal plate of the Palatine bone Posterior nasal spine 35 Cranial Base- Palate • Posterior to the central incisors is a small depression-incisive fossa with a pair of canalsincisive canals for the passage of the nasopalatine nerves Incisive canals Greater and Lesser Palatine foramina • Posterolaterally are the greater & lesser palatine foramen for passage of the nerves & vessels of the same name 4/26/2020 36 Cranial Base-Vomer • Vomer-thin, flat unpaired bone in the midline that forms a major portion of the bony nasal septum • On either side of the vomer are two large openings- choanae (posterior nasal apertures) 4/26/2020 Vomer Choanae 37 Cranial Base- Sphenoid • Three parts of the sphenoid bone can be appreciated on the inferior aspect of skull: 1. Greater wing 2. Medial pterygoid plate Greater wing Lateral pterygoid plate Medial pterygoid plate 3. Lateral pterygoid plate • Pterygoid fossa is between the two pterygoid plates 4/26/2020 38 Cranial Base- Sphenoid • • • Foramen ovale for passage of the mandibular division (V3) of the trigeminal nerve Foramen ovale Auditory Tube-groove Foramen spinosum- for passage of the middle meningeal artery Foramen spinosum Groove for the pharyngotympanic (auditory) tube lies medial to spinosum 4/26/2020 39 Cranial Base- Temporal • Mastoid processprominence located posteriorly on the temporal bone • Mastoid serves as the attachment site for the SCM and posterior belly of the digastric muscles • External acoustic meatus (EAM) is located just anterior to the mastoid 4/26/2020 EAM Mastoid process 40 Cranial Base- Temporal • Styloid process- thin bony process extending inferior & anteriorly • Styloid serves as attachment site for numerous muscles & ligaments Mandibular fossa Styloid process • Mandibular fossaarticular surface that accepts the condyle of the mandible forming the TMJ 4/26/2020 41 Cranial Base- Temporal • Two important foramen can be identified on the inferior aspect of the temporal bone: • Stylomastoid foramenlocated between the mastoid & styloid processes is a small foramen for the passage of the facial nerve (CN VII) Carotid canal Stylomastoid foramen • Carotid canal- passage for the internal carotid artery into the cranial cavity 4/26/2020 42 Cranial Base- Occipital • Occipital bone forms the posterior and inferior aspects of the skull • Foramen Magnum- a large foramen for passage of the spinal cord • Foramen magnum divides the occipital bone into 3 parts: 1. Basilar Region 2. Condylar Region 3. Squamous Region 4/26/2020 1 2 Foramen magnum 3 43 Cranial Base- Occipital • • Basilar portion presents a small tuberclepharyngeal tubercle for attachment of the pharyngeal constrictors Foramen lacerum Pharyngeal tubercle Foramen lacerum (jagged-shaped) is located lust lateral to the basilar portion 4/26/2020 44 Cranial Base- Occipital • • • Condylar portion presents the occipital condyles that articulate with the atlas Jugular foramen- large foramen between the occipital & temporal bones for passage of cranial nerves: IX, X, XI and the internal jugular vein Jugular foramen Occipital condyle Hypoglossal canal Hypoglossal canal for passage of the hypoglossal nerve (CN XII) 4/26/2020 45 Cranial Base- Occipital • Squamous portion presents the palpable external occipital protuberance • Superior & inferior nuchal lines project laterally and are sites for muscular attachments Superior & inferior nuchal lines External occipital protuberance 4/26/2020 46 Osteology Internal Aspect of the Cranial Base Cranial Base • Internal aspect of the cranial base is divided into three major regions or fossae: 1. Anterior cranial fossa 2. Middle cranial fossa 3. Posterior cranial fossa Anterior cranial fossa Middle cranial fossa Posterior cranial fossa • These three fossae lie at different levels and form the bowl-shaped floor of the cranial cavity 4/26/2020 48 Anterior Cranial Fossa Ethmoid • Frontal lobes of the brain occupies the anterior cranial fossa • Fossa is formed by the: 1. Orbital portion of the frontal bone 2. Ethmoid bone in the middle 3. Lesser wing of the sphenoid 4/26/2020 Orbital portion of the frontal bone Lesser wing of the sphenoid 49 Anterior Cranial Fossa • Frontal crest- a median bony extension from the frontal bone Crista galli • Foramen cecum is located at the base of the crest and is a small foramen for passage a vessels during development • Crista galli- ridge of bone projecting superiorly from the ethmoid bone and serves as the attachment for the cerebral falx 4/26/2020 Frontal crest Foramen cecum 50 Anterior Cranial Fossa • • On either side of the crista galli is a “sievelike” Cribriform plate for passage of the olfactory axons into the cranial cavity Cribriform plate Optic canal for passage of the optic nerve (CN II) and the ophthalmic Optic canal artery can be appreciated within the lesser wing of the sphenoid 4/26/2020 51 Middle Cranial Fossa • Temporal lobes of the brain occupy the middle cranial fossa • Fossa is formed by the: 1. Greater wing of the sphenoid 2. Squamous portion of the temporal bone 3. Petrous portion of the temporal bone 4/26/2020 Greater wing of sphenoid Squamous portion temporal bone Petrous portion temporal bone 52 Middle Cranial Fossa • Sella turcica- the saddlelike bony formation located on the superior aspect of the body of the sphenoid Sella turcica Anterior and Posterior clinoids • Sella turcica is surrounded by anterior & posterior clinoid processes 4/26/2020 53 Middle Cranial Fossa • Sella turcica is composed of three parts: 1. Hypophyseal fossa (pituitary fossa) 2. Tuberculum sellae (saddle horn) 3. Dorsum Sellae (back of the saddle) • Tuberculum sellae Hypophyseal fossa Dorsum sellae Sella turcica- essentially houses and guards the pituitary gland 4/26/2020 54 Middle Cranial Fossa • Middle cranial fossa presents five important foramina: 1. Superior orbital fissure for passage of CN’s III, IV, V1 & VI & ophthalmic veins 2. Foramen rotundum which transmits the maxillary nerve (V2) Superior orbital fissure Foramen rotundum Foramen ovale 3. Foramen ovalewhich transmits the mandibular nerve (V3) 4/26/2020 55 Middle Cranial Fossa 4. Foramen spinosum which transmits the middle meningeal artery 5. Foramen lacerumnothing is transmitted vertically thru this foramen although the internal carotid artery and some nerves pass across the Foramen lacerum foramen horizontally • Foramen spinosum Petrosal grooves Grooves for the greater & lesser petrosal nerves are located along the anterior slope of the petrous portion of the temporal bone 4/26/2020 56 Middle Cranial Fossa • Petrous portion of the temporal bone houses the middle and inner ear cavities • Arcuate eminencemarks the roof of the anterior semicircular canal of the inner ear cavity • Trigeminal impression Arcuate eminence Trigeminal impression is located just anteromedial the eminence-which marks the location of the sensory ganglion of the trigeminal nerve 4/26/2020 57 Posterior Cranial Fossa • The largest & deepest of the three fossae • Cerebellum, pons and medulla occupy the posterior fossa • Formed mainly by the occipital bone and the petrous & mastoid portions of the temporal bone 4/26/2020 Occipital bone Temporal bone Petrous portion 58 Posterior Cranial Fossa • Clivus marks the anterior portion of the occipital bone • Foramen magnumlarge foramen that marks the transition from the medulla to the spinal clivus cord • Posterior to the foramen magnum is the internal occipital crest and internal occipital protuberance 4/26/2020 Occipital crest Internal occipital protuberance 59 Posterior Cranial Fossa • Broad grooves show the horizontal course of the transverse and S-shaped sigmoid sinuses (both dural venous sinuses) • Sigmoid sinus empties into the large jugular foramen which also transmits several Jugular cranial nerves: foramen 1. Glossopharyngeal (CN IX) 2. Vagus (CN X) 3. Accessory (CN XI) 4/26/2020 Groove for the Sigmoid sinus Transverse Sinus groove 60 Posterior Cranial Fossa • Internal acoustic meatus is located just anterosuperior to the jugular foramen • Internal acoustic meatus transmits the facial nerve (CN VII) and vestibulochochlear nerve (CN VIII) along with the labyrinthine artery Hypoglossal Internal acoustic meatus canal • Hypoglossal canal for the hypoglossal nerve (CN XII) lies superior to the margin of the foramen magnum 4/26/2020 61 Cribrifrom plate-CN I Superior Orbital Fissure CN III, IV, V1 & VI Optic Canal CN II Foramen Rotundum- CN V2 Foramen Ovale-CN V3 Hypoglossal Canal CN XII Internal Acoustic MeatusCN VII & VIII Jugular Foramen- CN IX, X and XI 4/26/2020 62 Osteology of the Orbit • Seven bones articulate to make each orbit: superior 1. Frontal 2. Zygomatic 3. Maxillary 4. Lacrimal 5. Ethmoid 6. Palatine 7. Sphenoid 4/26/2020 1 lateral 7 2 5 6 4 medial 3 inferior 63 Osteology of the Orbit • Optic canal- transmits the optic nerve and ophthalmic artery • Superior orbital fissuretransmits CN III, IV, V1 & VI Ethmoidal foramina Optic canal • Inferior orbital fissure & groove- transmits the infraorbital vessels & nerve • Anterior & posterior ethmoidal foraminatransmits vessels & nerves with same name 4/26/2020 Superior orbital fissure Inferior orbital fissure & groove 64