Cranial and Facial Bones PDF - Head & Neck Anatomy

CRANIAL AND FACIAL BONES Head & Neck Anatomy– I BDS110 Dr. Jayaraj Ajman University 22-Jan-25 1  LEARNING OUTCOMES ▪ Describe the...

CRANIAL AND FACIAL BONES Head & Neck Anatomy– I BDS110 Dr. Jayaraj Ajman University 22-Jan-25 1  LEARNING OUTCOMES ▪ Describe the various parts of the skeleton of the skull ▪ Identify the cranial fossae ▪ Describe the main features of the cranial bones ▪ Identify the special features of the neonatal skull ▪ Identify the normal radiological features of the skull bones and their features Ajman University 22-Jan-25 2  Exterior of the Skull ❑ External features of the skull Studied from five different aspects ▪ Superior aspect - Norma verticalis ▪ Posterior aspect - Norma occipitalis ▪ Anterior aspect - Norma frontalis ▪ Lateral aspect - Norma lateralis ▪ Inferior aspect - Norma basalis Ajman University 22-Jan-25 3  Skull ❑ Skull Bony framework of the head Contains 22 bones (except middle ear bones) Rests on the superior end of the vertebral column ▪ Grouped into two categories: Cranial bones Facial bones Ajman University 22-Jan-25 4  Skull Cranial bones 8 cranial bones Form the cranial cavity ✓ Encloses and protects the brain ✓ Provides attachments for muscles of head and neck ▪ Paired cranial bones Parietal bones, and temporal bones ▪ Unpaired cranial bones Frontal bone, occipital bone, sphenoid bone, and ethmoid bone Ajman University 22-Jan-25 5  Skull Facial Bones 14 facial bones Form the framework of the face ✓ Contain cavities for the special sense organs ✓ Provide openings for air and food passages ✓ Secure the teeth ✓ Anchor the facial muscles of expression ▪ Unpaired facial bones Mandible and vomer ▪ Paired facial bones Nasal, maxillae, zygomatic, lacrimal, palatine and inferior nasal conchae bones Ajman University 22-Jan-25 6  ❑ Frontal bone Frontal Bone Forms forehead, superior part of orbits and the part of the cranial floor Frontal squama Scale like plate of bone Forms the forehead of the skull Supraorbital margin Formed by the thickening of frontal bone at the superior border of the orbits Supraorbital foramina Hole within the supraorbital margin Allow the passage of arteries and nerves Paranasal sinuses Lie deep to the frontal squama Ajman University 22-Jan-25 7  Parietal Bones ❑ Parietal bones Form superior and lateral aspects of the skull Superior and inferior temporal lines Serve as the attachment for temporalis muscle Protrusions and depressions Present in the internal surfaces of the parietal bones ✓ Accommodate the blood vessels (dura mater) Ajman University 22-Jan-25 8  Temporal Bones ❑ Temporal bones Form inferolateral aspects of the skull and part of the cranial floor Temporal squama Thin, flat part of the temporal bone Forms the anterior and superior part of the temple Zygomatic process Projects from the inferior portion of the Zygomatic arch temporal squama Formed by the zygomatic Forms the prominence of the cheek process and the temporal Articulates with the temporal process of process the zygomatic (cheek) bone Ajman University 22-Jan-25 9  Temporal Bones Mandibular fossa A socket located on the inferior posterior surface of the zygomatic process Articular tubercle A rounded elevation anterior to the mandibular fossa Mandibular fossa and articular tubercle Articulate with the mandible (lower jawbone) To form the temporomandibular joint Ajman University 22-Jan-25 10  Temporal Bones Mastoid portion Located posterior and inferior to the external auditory meatus or ear canal Directs sound waves into the ear Mastoid process Rounded projection of the mastoid portion Point of attachment for several neck muscles Internal auditory meatus Opening through which the facial (VII) and vestibulocochlear (VIII) nerve pass Ajman University 22-Jan-25 11  Temporal Bones Styloid process Projects inferiorly from temporal bone Serves as attachment point for muscles of the tongue and neck Stylomastoid foramen Lies between the styloid process and mastoid process Facial (VII) nerve and stylomastoid artery pass through it Ajman University 22-Jan-25 12  Temporal Bones Petrous portion Triangular part located at the base of the skull Lies between the sphenoid and occipital bones Houses the internal ear and the middle ear ▪ Contains the carotid foramen Through which the carotid artery passes ▪ Contains the jugular foramen Passageway for the jugular vein Ajman University 22-Jan-25 13  Occipital Bone ❑ Occipital bone Forms posterior aspect and base of the skull Foramen magnum Is in the inferior part of the bone Allows passage of the spinal cord, vertebral and spinal arteries, and accessory (XI) nerve Occipital condyles Oval processes on either side of the foramen magnum Articulate with first cervical vertebra (atlas) To form the atlanto-occipital joint Ajman University 22-Jan-25 14  Occipital Bone External occipital protuberance Most prominent midline projection on the posterior surface Lies just above the foramen magnum Superior and inferior nuchal lines Curved ridges extending laterally from the protuberance Areas of muscle attachment Ajman University 22-Jan-25 15  Sutures of the Skull ❑ Sutures Immovable joint that holds skull bones together Coronal suture Unites the frontal bone and both parietal bones Sagittal suture Unites the two parietal bones on the superior midline of the skull Lambdoid suture Unites the two parietal bones to the occipital bone Squamous sutures Unite the parietal and temporal bones on the lateral aspects of the skull Ajman University 22-Jan-25 16  Sutures of the Skull Ajman University 22-Jan-25 17  Sphenoid Bone ❑ Sphenoid bone Located at the middle part of the base of the skull Lies posterior and slightly superior to the nasal cavity Forms posterior aspect and base of the skull ▪ Keystone of the cranial floor Because it articulates with other cranial bones and hold them together ▪ Sphenoid bone articulates: Anteriorly with the frontal and ethmoid bones Laterally with the temporal bones Posteriorly with the occipital bone Ajman University 22-Jan-25 18  Sphenoid Bone ❑ Sphenoid bone Resembles a butterfly with a body and outstretched wings Contributes to the middle cranial fossa and orbits Body of the sphenoid Hollowed cube-like medial portion Lies between ethmoid and occipital bones o Sphenoidal sinus Space inside the body of the sphenoid Drains into the nasal cavity Ajman University 22-Jan-25 19  Sphenoid Bone Sella turcica Bony saddle-shaped structure on the superior surface of the body of the sphenoid ▪ Anterior part forms the horn of the saddle, is a ridge called the tuberculum sellae ▪ Posterior part forms the back of the saddle, is a ridge called the dorsum sellae ▪ Seat of the saddle is a depression, the hypophyseal fossa (contains the pituitary gland) Ajman University 22-Jan-25 20  Sphenoid Bone Greater wings of the sphenoid Project laterally from the body Form the anterolateral floor of the cranium and part of the lateral wall of the skull Lesser wings of the sphenoid A ridge of bone anterior and superior to the greater wings Form part of the floor of the cranium and posterior part of the orbit of the eye Pterygoid processes o Superior orbital fissure Inferior projection from the point A triangular slit between the greater and of body and greater wings unit lesser wings lateral to the body Form the lateral posterior region Blood vessels and cranial nerves pass through of the nasal cavity Ajman University 22-Jan-25 21  Sphenoid Bone o Optic foramen or canal Lies between the body and lesser wing just anterior to the sella turcica Optic (II) nerve and ophthalmic artery pass through o Foramen ovale At the base of the lateral pterygoid process in the greater wing Transmits mandibular nerve (branch of the trigeminal nerve) o Foramen lacerum Bounded by the sphenoid and occipital bones Transmits ascending pharyngeal artery o Foramen rotundum Located at the junction of the anterior and medial parts of the sphenoid bone Transmits maxillary branch of the trigeminal (V) nerve Ajman University 22-Jan-25 22  Sphenoid Bone Ajman University 22-Jan-25 23  Ethmoid Bone ❑ Ethmoid bone Sponge-like in appearance and delicate bone Located in the anterior part of the cranial floor medial to the orbits Provide extensive surface area in the nasal cavity ▪ Forms Part of anterior portion of the cranial floor Medial wall of the orbits Superior portion of the nasal septum Most of the superior sidewalls of nasal cavity Ajman University 22-Jan-25 24  Ethmoid Bone Cribriform plate of the ethmoid bone Lies in the anterior floor of the cranium Forms the roof of the nasal cavity Contains the olfactory foramina Transmit olfactory nerves ▪ Crista galli A triangular process Superior projection from the cribriform plate Attachment point for the falx cerebri ▪ Perpendicular plate Inferior projection from the cribriform plate Forms the superior portion of the nasal septum Ajman University 22-Jan-25 25  Ethmoid Bone Lateral masses of the ethmoid bone Compose the wall between nasal cavity and orbits Contain 3 to 18 air spaces called ethmoidal cells Ethmoidal cells together to form ethmoidal sinuses ▪ Lateral masses contain Two thin, scroll-shaped projections lateral to the nasal septum ▪ Projections are named: Superior nasal concha (turbinate) Middle nasal concha (turbinate) ▪ Inferior nasal conchae Ajman University 22-Jan-25 26  Ethmoid Bone Conchae ✓ Increases vascular and mucous membrane surface area in the nasal cavity ✓ Warms and moistens inhaled air ✓ Cause inhaled air to swirl and help to trap inhaled particles ▪ Superior nasal conchae ✓ Increase the surface area for the sense of smell Ajman University 22-Jan-25 27  Cranial Fossa ❑ Cranial fossa Floor of the cranial cavity is divided into 3 distinct depressions Anterior cranial fossa Middle cranial fossa Posterior cranial fossa ▪ Each fossa accommodates a different part of the brain Ajman University 22-Jan-25 28  Cranial Fossa Anterior cranial fossa Formed by the portions of the frontal, ethmoid, and sphenoid bones Houses the frontal lobe of the brain ▪ Features of the fossa Orbital plates and frontal crest of the frontal bone and the crista galli and cribriform plate of the ethmoid bone Openings of the cribriform plate contain sensory olfactory fibers Ajman University 22-Jan-25 29  Cranial Fossa Middle Cranial Fossa Formed by the portions of the sphenoid and temporal bones Houses the temporal lobe of the brain ▪ Features of the fossa: Bounded anteriorly by a ridge of the sphenoid bone and posteriorly by the petrous Openings associated with the cranial ridge of the temporal bone nerves and blood vessels - foramen spinosum, the foramen ovale, the Sella turcica - houses the foramen rotundum, and the superior pituitary gland orbital fissure, foramen lacerum Ajman University 22-Jan-25 30  Cranial Fossa Posterior cranial Fossa Formed mostly by the occipital bone Houses the cerebellum and occipital lobe ▪ Features of the fossa Contain foramen magnum Hypoglossal canal – for hypoglossal nerve (XII) Jugular foramen – for glossopharyngeal (IX), vagus (X), and spinal accessory (XI) nerves. Jug of Vegas Glossy Accessories Internal acoustic meatus – for facial (VII) and vestibulocochlear (VIII) nerves Face & Ear Music Tunnel" Ajman University 22-Jan-25 31  Inferior Nasal Concha ❑ Inferior nasal concha Paired scroll-like bone Form a part of the inferior lateral wall of the nasal cavity Project into the nasal cavity Inferior to the middle nasal conchae of the ethmoid bone Not part of the ethmoid bone Ajman University 22-Jan-25 32  Nasal Bone ❑ Nasal bone Paired, small, flattened, rectangular- shaped bone Form the bridge of the nose Superiorly articulate with frontal bone Protect the upper entry to the nasal cavity Provide attachment for thin muscles of facial expression Major structural portion of the nose consists of cartilage Ajman University 22-Jan-25 33  Lacrimal Bone ❑ Lacrimal bone Paired, thin and fingernail in size and shape Smallest bone of the face Posterior and lateral to the nasal bones Form a part of the medial wall of each orbit o Lacrimal fossa Vertical tunnel formed by lacrimal bone with the maxilla Houses the lacrimal sac Ajman University 22-Jan-25 34  Palatine Bone ❑ Palatine bone Two L-shaped bones Lies between the maxilla in front and the pterygoid process behind ▪ Form Posterior portion of the hard palate Part of the floor and lateral wall of the nasal cavity Small portion of the floors of the orbits Horizontal plate Projects medially and unites with its counterpart Form the posterior one-fourth of the hard palate Ajman University 22-Jan-25 35  Palatine Bone Perpendicular plate Fixed with the posterior part of the medial surface of the maxilla o Greater palatine groove Vertical groove on the lateral surface of the perpendicular plate Ajman University 22-Jan-25 36  Vomer ❑ Vomer Roughly triangular bone on the floor of the nasal cavity Forms the inferior portion of the bony nasal septum ▪ Articulates: Superiorly with ethmoid bone and sphenoid bones Inferiorly with maxillae and palatine bones ▪ Lateral surface On each side is covered by a mucous membrane Marked by an anteroinferior groove for nasopalatine nerve and vessels Ajman University 22-Jan-25 37  Zygomatic Bone Zygomatic bone Paired bone called cheekbones Form the prominences of the cheeks And part of the lateral wall and floor of each orbit ▪ Articulate with the frontal, maxilla, sphenoid, and temporal bones Temporal process Projects posteriorly Articulates with the zygomatic process of temporal bone To form the zygomatic arch Ajman University 22-Jan-25 38  Zygomatic Bone ▪ Body presents three surfaces Orbital surface Forms a part of the lateral wall and floor of the orbit Consist of zygomatico- orbital foramen Transmits zygomatic nerve Lateral surface Temporal surface Subcutaneous, presents a Forms the part of anterior wall of the zygomaticofacial foramen temporal fossa Transmits zygomaticofacial Presents a zygomaticotemporal foramen nerve Transmits the zygomaticotemporal nerve Ajman University 22-Jan-25 39  Maxilla ❑ Maxilla Paired bone unit to form the upper jawbone Articulate with the opposite maxilla and the frontal, sphenoid, nasal, vomer, ethmoid, inferior nasal concha, palatine, lacrimal and zygomatic bones and the septal and nasal cartilages, o Except Mandible Form part of the floors of the orbits, lateral walls and floor of the nasal cavity, and most of the hard palate Ajman University 22-Jan-25 40  Maxilla Body Shaped like a pyramid Contains the maxillary paranasal sinuses ▪ Gives rise to 4 different regions Orbit, nasal cavity, infratemporal fossa and face o Infraorbital foramen Opening in the maxilla Inferior to the orbit ▪ Allows passage of Infraorbital blood vessels Maxillary division of the trigeminal nerve Ajman University 22-Jan-25 41  Maxilla Frontal processes Extends superiorly to articulate with the nasal, frontal, ethmoid, and lacrimal bones Forms the posterior boundary of the lacrimal fossa Zygomatic process Extends laterally to articulate with the maxillary process of the zygomatic bone Alveolar process Is a ridge-like arch that contains the alveoli for the maxillary teeth Ajman University 22-Jan-25 42  Maxilla Palatine process Horizontal projection of the maxilla Forms the anterior 3/4th of the hard palate Articulates with the opposite side palatine process And the horizontal plate of the palatine ▪ Hard palate Is the bony roof of the mouth Formed by the palatine processes of the maxillae and horizontal plates of the palatine bones Separates the nasal cavity from the oral cavity Ajman University 22-Jan-25 43  Maxilla o Incisive foramen Just posterior to the incisor teeth Transmits greater palatine blood vessels and nasopalatine nerve o Inferior orbital fissure Located between the greater wing of the sphenoid and maxilla Maxillary sinus Empties into the nasal cavity Cleft palate Failure of fusion of the maxillary bones before birth Ajman University 22-Jan-25 44  Mandible ❑ Mandible (Lower jawbone) Largest, strongest facial bone Forms the lower jaw Attaches muscles of mastication Only movable skull bone Body Curved, horizontal portion o Mental foramen Lies on the lateral surface of the body And inferior to the 2nd premolar tooth Transmits mental nerve Used by dentists to inject anesthetics Ajman University 22-Jan-25 45  Mandible ▪ External oblique line Lies on the lateral side of the mandible ▪ Mylohyoid line Lies on the medial side of the body Divide a sublingual from a submandibular fossa Posterior border provides for attachment of the pterygomandibular raphe Ajman University 22-Jan-25 46  Mandible Ramus Perpendicular portion ▪ Angle of the mandible Area where each ramus meets the body o Mandibular foramen Lies on the medial surface ramus Is the beginning of the mandibular canal Used by dentists to inject anesthetics o Mandibular canal Runs obliquely in the ramus and anteriorly to the body Passes the inferior alveolar nerves and blood vessels Ajman University 22-Jan-25 47  Mandible Coronoid process Anterior extension of each ramus Attaches the temporalis muscle Condylar process Posterior process of each ramus Articulates with the mandibular fossa of the temporal bone To form the temporomandibular Alveolar process joint Ridge like arch containing the o Mandibular notch alveoli for the mandibular teeth Depression between the coronoid Created by a thick buccal and a and condylar processes thin lingual plate of bone Ajman University 22-Jan-25 48  Newborn Skull ❑ Striking feature of newborn skull: Huge size of its cranium Due to fast development of the brain Brain size reaches 25% at birth Brain size reaches 75% by the age of 4 years Relatively small size of its facial skeleton Facial skeleton forms about 1/7th of the cranium Due to the rudimentary stage of mandible and maxillae Non-eruption of teeth Small size of the maxillary air sinuses and the nasal cavity Ajman University 22-Jan-25 49  Newborn Skull ▪ Clinically important features of the newborn skull Adult bones of vault of skull are ossified At birth skull are partly ossified Fontanelles Unossified areas are seen between the skull bones ✓ Permits overlapping of the skull bones during childbirth ✓ Permits growth of the brain ✓ Six unossified areas or fontanelles are present Ajman University 22-Jan-25 50  Newborn Skull ▪ Fontanelles o Anterior fontanelle Closes by 2 years of age o Posterior fontanelle Closes soon after birth o Sphenoidal (anterolateral) fontanelles o Mastoid (posterolateral) fontanelles Lateral fontanelles close within a few weeks of birth Ajman University 22-Jan-25 51  Newborn Skull Mastoid process Begin to develop by the age of year 2 Paranasal sinuses o Frontal sinus Does not exist at birth Begins to develop during the first year Complete development occurs between 15 - 20 years o Maxillary sinus Rudimentary at birth Complete development occurs between 15 - 20 years Ajman University 22-Jan-25 52  Newborn Skull Mandible Two halves at birth United by the fibrous tissue at the symphysis menti Frontal bone Two halves at birth United by the fibrous tissue in the midline Basiocciput and basisphenoid United by hyaline cartilage Responsible for growth of skull in length Later it ossifies Ajman University 22-Jan-25 53  Clinical Correlation Ajman University 22-Jan-25 54  Mandible Ajman University 22-Jan-25 55  Mandible Fractures ❑ Fractures of the mandible ▪ Sites of the fracture: Condyle Symphysis Ramus Alveolus Coronoid process Body Prominent exposed portion of the facial skeleton Angle Curvature concentrates the force of the blow Ajman University 22-Jan-25 56  Mandible Fractures Ajman University 22-Jan-25 57  Maxilla Ajman University 22-Jan-25 58  Maxilla Fractures ❑ Fractures of maxilla ▪ Unilateral fracture Involves the alveolar process of the maxilla ▪ Bilateral fractures Classified into following 3 types ▪ Le Fort I Horizontal fracture runs along the floor of the nose Le Fort I Above and parallel to the palates And below the zygomatic bone Gives rise to a detached upper jaw Ajman University 22-Jan-25 59  Maxilla Fractures Le Fort II Pyramidal-shaped fracture Fracture line passes through the root of the nose, floor of orbits And then runs medial to and below the zygomatic bones towards alveolar margin Le Fort III Fracture line runs through the root of the nose, superior orbital fissures and lateral walls of the orbits above the zygomatic bones Complete separation of cranial skeleton from facial skeleton Ajman University 22-Jan-25 60  Ajman University 22-Jan-25 61  Ajman University 22-Jan-25 62