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Dr.Pardeep Kumar Skull Skull (cranium) Consists of 22 bones Bones of the skull are grouped into two categories: Cranial bones Eight cranial bones form the cranial cavity Frontal bone, two parietal bones, two temporal bones, the occipital bone, the sphenoid bone, ethmoid bone Facial bones Fourteen facial bones form the face Two nasal bones, two maxillae, two zygomatic bones, the mandible, two lacrimal bones, two palatine bones, two inferior nasal conchae, vomer frontal bone glabella supraorbital foramen zygomatic bone mandibular symphysis mental foramen infraorbital foramen maxillary bone alveolar fossa mandible Anterior Skull nasal bone perpendicular plate superior orbital fissure inferior nasal concha bone middle nasal concha vomer bone Paranasal Sinuses frontal sinus ethmoid sinus maxilary sinus sphenoid sinus Cranium frontal bone coronal suture sagittal suture parietal bone lambdoidal suture occipital bone Ventral Skull palatine process sphenoid bone palatine bone vomer bone styloid process temporal bone mastoid process external occipital protuberance occipital bone carotid canal jugular foramen foramen magnum Occipital bone occipital condyle squamosal suture lacrimal bone temporal bone external acoustic meatus mandibular condyle In mandibular fossa (TMJ joint) Lateral Skull zygomatic arch sphenoid bone coronoid process sutural bone mastoid process styloid process ramus angle body mandible Lateral Skull Frontal bone Ethmoid bone Sphenoid bone Temporal bone Occipital bone Internal Skull lesser wing greater wing optic canal sella turcica intenal acoustic meatus jugular foramen Internal Skull Hyoid Hyoid bone external acoustic meatus temmporal mandibular joint Skull Separated Bones of Skull Cerebral Cranium parietal bone frontal bone sphenoid bone Facial Cranium zygomatic bone temporal bone occipital bone nasal bone sphenoid bone maxilla ethmoid bone mandible 17 Skull The cranial and facial bones protect and support special sense organs and the brain Besides forming the large cranial cavity, the skull also forms several smaller cavities Nasal cavity Orbits (eye sockets) Paranasal sinuses Small cavities which house organs involved in hearing and equilibrium Skull Immovable joints called sutures fuse most of the skull bones together The skull provides large areas of attachment for muscles that move various parts of the head Skull and facial bones provide attachment for muscles that produce facial expressions The facial bones form the framework of the face and provide support for the entrances to the digestive and respiratory systems Sutures • Immovable joints • Form boundaries between skull bones • Five sutures – Coronal – Sagittal – Lambdoid – Squamous – Frontonasal Skull (Cranial Bones) Frontal Bone Forms the forehead Parietal Bones Form the sides and roof of the cranial cavity Temporal Bones Form the lateral aspects and floor of the cranium Occipital Bone Forms the posterior part and most of the base of the cranium Sphenoid Bone Lies at the middle part of the base of the skull Ethmoid Bone Located on the midline in the anterior part of the cranial floor medial to the orbits A major superior supporting structure of the nasal cavity Contain thin projections called conchae which are lined by mucous membranes Increased surface area in the nasal cavity helps to humidify inhaled air trapping inhaled particles Skull Skull Skull Frontal Bone Frontal Bone Extends from the supra orbital margin to the coronal suture Gabellas mooth area of the frontal bone. Margin is perforated by the supraorbital foramen or (supraorbital notch) Parietal Bone Parietal Bone Bordered by 4 sutures – Sagittal – Coronal – Lambdoid – squamous • Temporal Lines – superior and inferior attachment for the temporalis muscle, a chewing muscle that passes between the zygomatic arch and temporal bone and inserts on the mandible Temporal Bone Four Parts of the Temporal Bone 1-Squamous Part Has two prominent features – Zygomatic process which forms part of the zygomatic arc (cheekbone) – Mandibular fossa Mandibular (glenoid) fossa depression where the mandible articulates with the cranium 2. Tympanic part a small ring of bone that borders the external acoustic meatus – Styloid process a pointed spine on its inferior surface Provides attachment for muscles of the tongue, pharynx, and hyoid bone 3-Mastoid part – Mastoid process prominent lump behind the earlobe • Filled with ear sinuses that communicate with the middle ear cavity • Can become infected (mastoiditis) and possible spread to the brain 4-Petrous part resembles a little mountain range separating the middle cranial fossa from th posterior fossa – Houses the middle and inner ear cavities – Internal acoustic meatus allows passage of the vestibulocochlear verve (hearing and balance) – Carotid canal passes the internal carotid artery – Jugular foramen –fromed by the temporal bone and the occipital bone and passes the internal jugular vein Carotid canal Jugular foramen Occipital Bone Occipital Bone Basilar part – foramen magnum – occipital condyle – hypoglossal canal – Venous sinus grooves – external occipital protuberance attaches thenuchal ligament that binds the skull to the vertebral column – Superior nuchal line identifies the superior part of the neck and provides attachment to the skull for several neck and back muscles. – Inferior nuchal line-provides attachment for the deep neck muscles Venous sinus grooves Sphenoid Bone Sphenoid bone Lesser wing – forms the posterior wall of the orbit – contains the optic foramen (optic nerve and ophthalmic artery) – anterior clinoid process- guard the optic foramen – superior orbital fissure-nerves for muscles of eye movement Body – sella turcica • has deep pit that called the hypophyseal fossa which houses the pituitary gland • turberculum sellae anterior raised margin • dorsum sellae posterior margin • covered by fibrous membrane and has a stalk that penetrates the membrane and that connects the pituitary to the hypothalamus Sella turcica Sphenoid bone Greater wing – foramen rotundum branch of trigeminal – foramen ovale branch of trigeminal – foramen spinosum artery to the meninges – foramen lacerum filled with cartilage, no vessels are nerves transmitted – Pterygoid plates (medial and lateral)provide attachment for jaw muscles • Sphenoid sinuses optic foramen anterior clinoid process turberculum sellae foramen rotundum foramen ovale foramen spinosum dorsum sellae sella turcica Ethmoid Bone located between the orbital cavities and forms the roof of the nasal cavity • perpendicular plate inferior projection that divides the nasal cavity into right and left nasal fossae • nasal conchae (turbinate bones)superior and middle project into the nasal cavity – are covered with the mucous membrane – superior conchae contain receptors for the sense of smell Inferior nasal conchae is a separate bone extending into the nasal cavity Facial Bones • bones that have no direct contact with the brain or meninges • total of 14 bones – 2 maxillae – 2 palatine bones – 2 zygomatic bones – 2 lacrimal bones – 2 nasal bones – 2 inferior nasal conchae – 1 vomer – 1 mandible Skull (Facial Bones) Nasal Bones Form the bridge of the nose Maxillae Form the upper jawbone Form most of the hard palate Separates the nasal cavity from the oral cavity Zygomatic Bones commonly called cheekbones, form the prominences of the cheeks Lacrimal Bones Form a part of the medial wall of each orbit Palatine Bones Form the posterior portion of the hard palate Inferior Nasal Conchae Form a part of the inferior lateral wall of the nasal cavity Skull (Facial Bones) Vomer Forms the inferior portion of the nasal septum Mandible Lower jawbone The largest, strongest facial bone The only movable skull bone Nasal Septum Divides the interior of the nasal cavity into right and left sides “Broken nose,” in most cases, refers to septal damage rather than the nasal bones themselves Orbits Eye socket Foramina Openings for blood vessels , nerves , or ligaments of the skull Skull Skull Skull Skull Skull Skull Maxilla Upper jaw • alveolar process points of maxillary bone that project between spaces of the teeth • alveolus teeth sockets • infraorbital foramen receives sensations from the nasal and and cheek that emerges through the foramen rotundum into the cranial cavity Maxilla forms part of the orbit where it exhibits a gash called the inferior orbital fissure – provides passage for blood vessels and nerves of eye muscles Maxilla palatine process forms the anterior roof of mouth (hard palate) and floor of nasal cavity Zygomatic Bone forms the angle of the cheeks • frontal process part of the lateral wall of the orbit • zygomaticofacial foramen • Temporal process Lacrimal Bone part of the medial wall of the orbit • lacrimal fossa houses the lacrimal sac – tears from the membranous sac drain into the nasal cavity Vomer forms the anterior half of the nasal septum Nasal Septum Consist of – perpendicular plate of the ethmoid bone – Vomer – Septal cartilage Mandible strongest bone of the skull and the only one that can move • supports teeth and provides attachment for the muscles of mastication and facial expression • mental foramen passage of blood vessels and nerves of the chin • mandibular foramen nerve and blood vessel that supplies the lower teeth • condyloid process • mandibular condyle • coronoid process • temporomandibular joint (TMJ) 1. Ramus of the mandible 2. Mandibular Angle 3. Body of the mandible Skull Unique Features of the Skull Sutures, Paranasal sinuses, Fontanels Sutures an immovable joint that holds most skull bones together Paranasal Sinuses Cavities within cranial and facial bones near the nasal cavity Secretions produced by the mucous membranes which line the sinuses, drain into the nasal cavity Serve as resonating chambers that intensify and prolong sounds Fontanels Areas of unossified tissue At birth, unossified tissue spaces, commonly called “soft spots” link the cranial bones Eventually, they are replaced with bone to become sutures Provide flexibility to the fetal skull, allowing the skull to change shape as it passes through the birth canal Sinuses Fontanel
