Cranial and Facial Bones PDF

 The Skull  The skull, the body’s most complex bony structure,  formed by two sets of bones; Cerebral Cranium:(Larger, postero-superior part) contains and protects the brain, provides attachment sites for some head and neck muscles. Facial Cranium:(Smaller, antero-in...

 The Skull  The skull, the body’s most complex bony structure,  formed by two sets of bones; Cerebral Cranium:(Larger, postero-superior part) contains and protects the brain, provides attachment sites for some head and neck muscles. Facial Cranium:(Smaller, antero-inferior part) Provides framework of face, sense organs and teeth Provides openings for the passage of air and food Anchor the facial muscles of expression Bones are joined by sutures Only the mandible is attached by a freely movable joint  The Skull (Cranium) Bones of Cerebral cranium / Calvaria (8) Single bones(4): include frontal bone , ethmoid bone , sphenoid bone , occipital bone. Paired bones (4): include temporal bones parietal bones Middle Ear Ossicles (6) malleus (2) incus (2) stapes (2)  parietal bone Frontal bone Sphenoid bone Temporal bone Zygomatic bone Occipital bone Nasal bone Maxilla Mandible  The Skull (Cranium) Bones of facial cranium (15) Single bones (3) include mandible, vomer, hyoid bone. Paired bones (12): include maxilla, nasal bone, lacrimal bone, palatine bone, zygomatic bone, inferior nasal concha. Facial bones - Mnemonic a mind memory and/or learning aid. Virgil Can Not Make My Pet Zebra Laugh! Vomer Conchae Nasal Maxilla Mandible Palatine Zygomatic Lacrimal Exterior of Skull (Terminology) from above (norma verticalis) from below (norma basalis), from the side (norma lateralis), from behind (norma occipitalis), from the front (norma frontalis). Bones of the Skull ( Anterior view)  Bones of the Skull ( Lateral view) Pterion Temporal fossa The Skull – Posterior View  SUTURES Suture - A line formed by the junction of two skull bones CORONAL SUTURE: juction between frontal & parietal bones. SAGITTAL SUTURE: juction between two parietal bones. LAMBDOIDAL SUTURE: juction between parietal bones & occipital bone. SQUAMOUS SUTURE: juction between parietal & temporal bones.  FONTANELLES Anterior fontanelle (soft spot.) – The junction where the two frontal and two parietal bones meet. The anterior fontanelle remains soft until about 2 years of age. Posterior fontanelle – The junction of the two parietal bones and the occipital bone. The posterior fontanelle usually closes first, before the anterior fontanelle, during the first several months of an infant's life. FONTANELLES BREGMA:- Meeting point between the coronal & sagital sutures. LAMBDA:- Meeting point between the sagittal and lambdoid sutures. Bones of the Skull ( Interior view) Internal view of base of skull Base of skull forms three fossae Anterior cranial fossa Middle cranial fossa Posterior cranial fossa Internal view of base of skull Figure 7.4b  Anterior cranial fossa Formed by orbital part of frontal bone, cribriform plate of ethmoid, and lesser wings of sphenoid Structures: frontal crest foramen cecum crista galli cribriform plate cribriform foramina  Middle cranial fossa Formed by the body and greater wings of sphenoid, petrous part of temporal Structures: body of sphenoid bone hypophysial fossa optic canal anterior clinoid process tuberculum sellae dorsum sellae posterior clinoid process sella turcica  Middle cranial fossa carotid sulcus superior orbital fissure foramen rotundum foramen ovale foramen spinosum sulcus for middle meningeal artery foramen lacerum internal opening of carotid canal trigeminal impression tegmen tympani  Posterior cranial fossa Formed by occipital and the petrous part of temporal Structures: foramen magnum clivus internal opening of hypoglossal canal internal occipital protuberance internal occipital crest sulcus for transverse sinus sulcus for sigmoid sinus jugular foramen internal acoustic pore internal acoustic meatus  Bones of the Skull ( Inferior view) Figure 5.9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide 5.24 Bones of the Skull (inferior view) alveolar arch bony palate median palatine suture incisive foramina incisive canal greater palatine foramen posterior nasal apertures pterygoid process Bones of the Skull (inferior view) occipital condyle external opening of hypoglossal canal external opening of carotid canal styloid process stylomastoid foramen mandibular fossa articular tubercle Overview of Skull Geography Cranium is divided into cranial vault and the base Internally, prominent bony ridges divide skull into distinct fossae. The skull contains smaller cavities Middle and inner ear cavities – in lateral aspect of cranial base Nasal cavity – lies in and posterior to the nose Orbits – house the eyeballs Air-filled sinuses – occur in several bones around the nasal cavity The skull contains approximately 85 named openings Foramina, canals, and fissures Provide openings for important structures Spinal cord Blood vessels serving the brain 12 pairs of cranial nerves  FRONTAL BONE Forms the forehead and roofs of the orbits Forms superciliary arches Internally, it contributes to the anterior cranial fossa Contains frontal sinuses Articulates posteriorly with the parietal bones via the coronal suture  FRONTAL BONE. Major markings:- Supra-orbital margin :arch of bone above he orbital opening Superciliary arch :the ridge of bone above the orbital margin glabella :midline point between the paired superciliary arches supraorbital notch :notch in the supra-orbital margin  OCCIPITAL BONE Forms the posterior portion of the cranium and posterior cranial fossa Articulates with the temporal bones and parietal bones Foramen magnum located at its base and communicates with the vertebral canal  OCCIPITAL BONE Consists of a Squamous, Basilar, and Two Lateral (Condylar) Portions Major markings:- External occipital protuberance : Superior nuchal lines :low transverse ridge on the external surface of squamous part Inferior nuchal lines Occipital condyles Anteriorly:- Hypoglossal Canal (l2th C. Nerve) Condylar Canal (Emissay Vein ) Occipital Bone Parietal Bones and Sutures Form superior and lateral parts of skull Four important sutures of the cranium Coronal suture – Junction between frontal and parietal bones anteriorly Squamous suture – Junction between parietal and temporal bones inferiorly Sagittal suture – Junction between right and left parietal bones superiorly Lambdoid suture – Junction between the parietal and occipital bone posteriorly PARIETAL BONES Cover much of the top and sides of the brain Major markings:- Superior temporal line: attachement point of the temporal fascia. Iferior temporal line : attachment point for the temporal muscle  Temporal Bones Lie inferior to parietal bones Form the inferolateral portion of the skull Term “temporal” Comes from Latin word for time Specific regions of temporal bone o Squamous, o temporal, o petrous, o Mastoid. Temporal Bones TEMPORAL BONE Major markings:- Squamous (flat portion of the bone that projecting superiorly toward the parietial bone )including its Zygomatic Process Tympanic Bone (External Auditory Cana) around the ear Mastoid (Mastoid Air Cells ) behind the ear Petrous Bone (surrounds the inner ear), containing Otic Labyrinth and Internal Auditory Canal (IAC ) Styloid Process TEMPORAL BONE Major Openings:- Stylomastoid foramen Jugular foramen, (Int Jugular vein, 9th, 10th, & 1 1th Cranial Nerves) External auditory meatus, Internal auditory meatus Carotid canal (Internal Carotid Artery )  The Sphenoid Bone Butterfly-shaped bone that forms part of the floor of the anterior, middle, and posterior cranial fossae. “Keystone” of the cranial floor because it articulates with all the other cranial bones. Consists of a central body, greater wings, lesser wings, and pterygoid processes The Sphenoid Bone Figure 7.6a, b SPHENOID BONE Body: central part of the sphenoid bone sphenoid air sinuses Three pairs of projections: Lesser Wings, the more superior (contains Optic Canal ) Greater Wings , the intermediate (contains Foramina Ovale, Rotundum, and Spinosum ) Pterygoid Processes, the most inferior SPHENOID BONE Sella turcica:- Resembles “Turkish Saddle” Depression on the superior surface of the body of sphenoid bone Protective,bony housi.ng around the Pituitary Gland.  SPHENOID BONE Parts of Sella Turcica Dorsum Sellae: the back wall Hypophysial Fossa: central depression in which pituitary gland sits. Posterior Clinoid Proces: samll lateral extension Tuberculum Sellae: horizontal ridge , along the anterior portion Major Openings:- foramina rotundum, ovale, spinosum; optic canals; superior orbital fissure  ETHMOID BONE Lies between nasal and sphenoid bones Forms most of the medial bony region between the nasal cavity and orbits, the ethmoid sinuses Ethmoid Bone Figure 7.7.ETHMOID BONE Major markings:- Horizontal Cribriform Plate; ( passage olfactory nerve) Two Lateral Masses( Labyrinths); Perpendicular Plate Ethmoidal Labyrinths consist of Air Cells and Superior and Middle Nasal Conchae, Uncinate Process (one on each side) Crista Galli, for the attachment of FaIx Cerebri Orbital Plate forms the medial wall of the respective eye  Table of Foramina in Skull. Bone Location Foramen frontal - supraorbital foramen frontal anterior cranial fossa foramen cecum ethmoid - foramina of cribriform plate ethmoid anterior cranial fossa anterior ethmoidal foramen ethmoid anterior cranial fossa posterior ethmoidal foramen sphenoid - optic canal sphenoid middle cranial fossa superior orbital fissure sphenoid middle cranial fossa foramen rotundum incisive foramen/ maxilla - incisive canals palatine - greater palatine foramen palatine and - lesser palatine foramina maxilla.Table of Foramina in Skull Bone Location Foramen sphenoid and - inferior orbital fissure maxilla maxilla - infraorbital foramen sphenoid middle cranial fossa foramen ovale sphenoid middle cranial fossa foramen spinosum sphenoid - pterygoid canal sphenoid and - sphenopalatine foramen palatine sphenoid, temporal, foramen lacerum middle cranial fossa and occipital (or carotid canal temporal posterior cranial foss a internal acoustic meatus temporal - stylomastoid foramen.Table of Foramina in Skull Bone Location Foramen temporal - mastoid foramen temporal - petrotympanic fissure occipital and posterior cranial fossa jugular foramen temporal occipital - hypoglossal canal occipital - condylar canal occipital posterior cranial fossa foramen magnum parietal - parietal foramen mandible - mental foramen mandible - mandibular foramen zygomatic - zygomaticofacial foramen zygomatic - zygomaticotemporal forame  Wormian Bones Tiny irregularly shaped bones that appear within sutures 51  Bones of Facial Cranium  Bones of facial cranium Single bones (3): include mandible, vomer, hyoid bone. Paired bones (12): include maxilla, nasal bone, lacrimal bone, palatine bone, zygomatic bone, inferior nasal concha.  Mandible U-shaped bone forming the lower jaw The largest and strongest facial bone Composed of two main parts Horizontal body Two upright rami  Mandible Major markings:- Body: the anterior part of the mandible Rami: the angled portion that joins the posterior portion of body Condylar Process: posterior extension of ramus Coronoid Process: anterior extension of the ramus Mental Symphysis: union point of the two halves Figure 7.8a  Mandible Mental Foramen: transmits the mental neurovascular bundle Alveolar Process: where the teeth are embedded Mandubular Condyle: rounded head of condylar process , articulate with madibular fossa of the temporal bone. Mandibular Notch: concavity between codylar and coronoid process  Maxillary Bones Second Largest Facial bone, forming the midface Articulate with all other facial bones except mandible Contain maxillary sinuses – largest paranasal sinuses Forms part of the inferior orbital fissure Maxillary Bones Figure 7.8b  Maxillary Bones Major markings:- Body Four Processes Zygomatic: projects toward the zygomatic bone Frontal: toward the frontal bone Alveolar : inferior extension that contain sockets for teeth Palatine: form hard plate Incisive Foramen : passageway for nasopalatine vessels 62 63  Other Bones of the Face Zygomatic bones Form lateral wall of orbits Nasal bones Form bridge of nose Lacrimal bones Located in the medial orbital walls Palatine bones Complete the posterior part of the hard palate  Other Bones of the Face Vomer Forms the inferior part of the nasal septum Inferior nasal conchae Thin, curved bones that project medially form the lateral walls of the nasal cavity  Palatine Bones Horizontal and Vertical portions Irregularly shaped (L-shaped) bones forming the; o posterior part of the hard palate, o the lateral wall of the nasal fossa between the medial pterygoid plate and the maxilla & o the posterior part of the floor of the orbit. o The horizontal plates form the posterior part of hard palate, separating the nasal cavity from oral cavity.  Palatine Bones Horizontal and Vertical portions Palatine Bones 70  Zygomatic Bones Major markings:- Body Three Processes Frontal Temporal Maxillary 72  Nasal Bones Thin bones that form part of the bridge of the nose  Vomer Bone A roughly triangular, single, thin bone, Joins with the perpendicular plate of ethmoid to form bony septum that divides the nasal cavity into right and left. Vomer Bone 75 Lacrimal Bones Anterior portion of the medial wall of the orbit. Lacrimal fossa; depression at the junction of the lacrimal and maxilla bones that hold the lacrimal sac.  INFERIOR NASAL CONCHAE Thin bone, extends into nasal cavity from the maxilla on each side 78 Special Parts of the Skull Orbits Nasal cavity Paranasal sinuses Hyoid bone  Orbits pyramid-shaped paired cavities Base: supraorbital notch infraorbital foramen Apex: optic canal Walls Superior: fossa for lacrimal gland Medial: fossa for lacrimal sac Inferior: infraorbital fissure infraorbital groove infraorbital canal Orbit Figure 7.10b  Bony nasal cavity Roof: cribriform plate of ethmoid Floor: bony palate Lateral wall Three nasal conchae (superior, middle and inferior) Nasal meatus : underlying each concha (superior, middle and inferior) Sphenoethmoidal recess above superior nasal concha Anterior ―piriform aperture Posterior ―posterior nasal aperture communicates with pharynx Nasal Cavity Figure 7.9a Nasal Septum Figure 7.9b  Paranasal Sinuses Air-filled sinuses,lined with mucous membrane Located within Frontal bone Ethmoid bone Sphenoid bone Maxillary bones Secrete mucous into nasal cavity Lighten the skull Resonate the voice Paranasal Sinuses  Paranasal sinuses Frontal sinus Lies in frontal bone, deep to superciliary arch Drain to anterior part of middle meatus Maxillary sinus Largest paired sinus, lie in the body of maxilla; Opening into middle nasal meatus  Ethmoidal cellules Lie in ethmoidal bone, Large number of air cells, divided into anterior, middle and posterior groups Anterior and middle, groups drain into middle nasal meatus, while posterior group drains into superior nasal meatus Sphenoidal sinus Lies in body of sphenoid bone Drain into sphenoethmoidal recess  HYOID BONE Small & U-shaped bone located between the mandible and larynx. Made of 5 parts:- -Body : central portion -2 Greater horns: posterior extension from body -2 Lesser horns: samll superior extension from the body  Middle Ear Ossicles malleus incus stapes  Malleus Two main parts: Manubrium- adheres to the tympanic membrane, Head- articulates with the incus. Also has two processes: one anterior and one lateral  Incus 3 principal parts: body two processes ( short and long). Head articulates with head of the malleus End of the long process (lenticular process) articulates with head of the stapes. Short process attached to the cavity wall.  Stapes looks like a stirrup. four components: footplate, two crura (posterior and anterior), head. The head articulates with incus. footplate covers the oval window.  The Fetal Skull The skull at birth is large in proportion to rest of the skeleton ―1/4 (adult 1/7) The facial portion equals about one eight that of the cranium in size, whereas in adult it is one half (1/2) Many bones consist of more than one piece Figure 5.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide  The Fetal Skull  Cranial frontanelles ―unossified membrane between the bones at the angles of parietal bones  Allow the brain to grow  Convert to bone within 24 months after birth  Anterior frontanelle ―closes during middle of 2nd year  Posterior frontanelle ―closes by the end of 2nd month after birth  Mastoid fontanelle  Sphenoidal fontanelle Figure 5.13 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Slide Fontanels Figure 7.21b The Axial Skeleton Throughout Life Membranous bones begin to ossify in second month of development Bone tissue grows outward from ossification centers Many bones of the face and skull form by intramembranous ossification Endochondral bones of the skull Occipital bone Sphenoid Ethmoid bones Parts of the temporal bone