Skull inside and some separate bones


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This presentation deals with the inside of the skull (cranial cavity) and description of some separate bones. There is another presentation “Skull - the normas” that describes norma verticalis, occipitalis, lateralis, frontalis and basalis and is necessary to complete the objectives.
 Identify the features of the major bones forming the cranial cavity according to normas and separate bones.
 Describe the major sutures.
 Describe the structure of the flat bones forming the skull and their blood supply.
 Discuss ossification of the skull and the changes that occur during postnatal development.
 Locate important bony surface landmarks.

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  • A story is told of an examination candidate who, having failed to answer any questions, was shown the foramen magnum. "Ah ha", he said "I know that one. Many's the pint of beer I've poured through that!"
  • A story is told of an examination candidate who, having failed to answer any questions, was shown the foramen magnum. "Ah ha", he said "I know that one. Many's the pint of beer I've poured through that!"
  • A story is told of an examination candidate who, having failed to answer any questions, was shown the foramen magnum. "Ah ha", he said "I know that one. Many's the pint of beer I've poured through that!"
  • Skull inside and some separate bones

    1. 1. Anatomy of the skull (2) Dr. Akram Jaffar Ph.D.
    2. 2. The inside of the calvaria <ul><li>The groove for the superior sagittal sinus. </li></ul><ul><li>Pits in and lateral to the groove are the indentations of arachnoid granulations. </li></ul><ul><li>On the sides note the grooves for the anterior and posterior branches of the middle meningeal vessels. </li></ul>Groove for the superior sagittal sinus Pits Grooves for middle meningel artery
    3. 3. <ul><li>Anteriorly the groove for the superior sagittal sinus is traceable down as a crest for the falx cerebri , and behind the lower end of the crest is the foramen cecum , which is plugged by the fibrous tissue of the falx. </li></ul>The anterior cranial fossa Crest for the falx Foramen cecum <ul><li>The frontal bone turns sharply back to form a large part of the roof of the orbit. This part of the bone is therefore called the orbital plate of the frontal bone which is the largest contributor to the anterior fossa. </li></ul><ul><li>It is convex and ridged in roughly H-shape in conformity with the orbital surface of the frontal lobe of the cerebral hemisphere. </li></ul>Orbital plate of frontal bone <ul><li>The frontal lobe of the brain occupies the anterior cranial fossa. </li></ul>
    4. 4. <ul><li>Inserted into a gap between the anterior part of the orbital plates, is the cribriform plate (L., cribrum = sieve) of the ethmoid with its crista galli (cock’s comb; L., crista = crest, galli = cock) projecting upwards in the midline. </li></ul>The anterior cranial fossa Crista galli Cribriform plate
    5. 5. The anterior cranial fossa <ul><li>The crista galli is for the attachment of the falx and alongside its anterior end is the elongated nasal slit for the anterior ethmoidal nerves and vessels. </li></ul>Crest for the falx Orbital plate of frontal bone Foramen cecum Crista galli Cribriform plate
    6. 6. The anterior cranial fossa <ul><li>At the postero-lateral angle of the cribriform plate, a shallow fossa indents the frontal bone; this lodges the olfactory bulb . </li></ul><ul><li>The holes in the cribriform plate transmit olfactory nerves from the upper part of the nose to the brain. </li></ul>Olfactory nerves Olfactory bulb
    7. 7. The anterior cranial fossa <ul><li>Laterally, the lesser wing meets the greater wing and the frontal bone at the pterion. Here the bone is commonly tunneled by the anterior branch of the middle meningeal artery. </li></ul><ul><li>Medially, lesser wing of the sphenoid is projected back as the anterior clinoid process . </li></ul><ul><li>In front of the anterior clinoid process, the base of the lesser wing is perforated by the optic canal which transmits the optic nerve and ophthalmic artery to the orbits. The two optic foramina are joined by the optic groove . </li></ul><ul><li>The posterior boundary of the anterior cranial fossa is made by the lesser wing of the sphenoid. </li></ul>pterion Middle meningeal a. groove Lesser wing of sphenoid Anterior clinoid process Optic canal Optic groove
    8. 8. The anterior cranial fossa Cribriform plate Orbital plate of frontal bone anterior clinoid process Frontal sinus Posterior clinoid process
    9. 9. <ul><li>The greater wing and the central body form a butterfly shape, the most posterior tip of the wing containing the foramen spinosum . </li></ul>The middle cranial fossa Greater wing Temporal bone <ul><li>Is formed by the greater wing of the sphenoid and temporal bone and is occupied by the temporal lobe of the brain. </li></ul><ul><li>The foramen spinosum is the most posterior member of the roughly semicircular array of foramina that transmit a number of important structures. </li></ul><ul><li>Just in front of the foramen spinosum is the foramen ovale , the reason for whose name is obvious. </li></ul>
    10. 10. The middle cranial fossa <ul><li>Foramen ovale transmits: </li></ul><ul><ul><li>The mandibular nerve </li></ul></ul><ul><ul><li>A vein from the cavernous sinus down to the pterygoid plexus. </li></ul></ul><ul><ul><li>The accessory meningeal artery runs up from the maxillary artery. </li></ul></ul><ul><ul><li>The meningeal branch of the mandibular nerve (nervous spinosus) may pass through foramen ovale or spinosum. </li></ul></ul>ovale
    11. 11. The middle cranial fossa <ul><li>Further in front of foramen ovale is an obviously named, foramen rotundum , which leads downwards and forwards into a remote region of the skull called the pterygopalatine fossa. It transmits the maxillary nerve. </li></ul>rotundum Anterior Clinoid process rotundum
    12. 12. <ul><li>Finally, under the overhanging shelf of the lesser wing, is the superior orbital fissure . This is not really a foramen but a gap between the lesser and greater wings of the sphenoid. It leads into the orbit just lateral to and below the optic nerve. </li></ul>The middle cranial fossa Superior Orbital fissure
    13. 13. The hypophyseal fossa <ul><li>There is a bump in front called the truberculum cellae. </li></ul><ul><li>At the back, a transverse flange projects up called the dorsum sellae (back of the saddle). </li></ul><ul><li>The upper border of the dorsum sellae ends at each side as the posterior clinoid process. </li></ul>Hypophyseal fossa Dorsum sellae posterior Clinoid process <ul><li>In the center of the middle cranial fossa is the body of the sphenoid bone, which is hollowed out to form the hypophyseal fossa in which the pituitary gland is situated in life. </li></ul>Tuberculum sellae <ul><li>Also called the sella turcica because it is supposed to look like a Turkish saddle (in Latin chairs used by officials and dignitaries in Rome were known as sellae). </li></ul><ul><li>It is also supposed to look like a four-poster bed (A bed having tall corner posts originally intended to support curtains), hence the names of the clinoid processes (as in &quot;clinical&quot;, the patients being in bed [G., kline = bed; oid = like]). </li></ul>anterior Clinoid process
    14. 14. The hypophyseal fossa size and shape <ul><li>Pituitary tumors cause ballooning of the sella. </li></ul><ul><li>Normal variations in the volume of the sella turcica are wide and assessment of the sellar volume is of limited diagnostic value; in addition the hypophysis itself occupies only 50-85% of the fossa and can double in size at the expense of venous filling without altering the bony sella. </li></ul><ul><li>In the lateral view, the dimensions of the sella turcica are 11-16mm in length and 8-12mm in depth. The dorsum sellae should have well defined margins anteriorly and posteriorly. </li></ul>
    15. 15. The hypophyseal fossa anterior Clinoid process posterior Clinoid process Tuberculum sellae Dorsum sellae clivus Sphenoid sinus
    16. 16. <ul><li>The side of the body of the sphenoid is grooved by the S-shaped internal carotid artery from foramen lacerum to the anterior clinoid process. </li></ul>The hypophyseal fossa anterior Clinoid process Middle Clinoid process Tuberculum sellae <ul><li>In front of the tuberculum sellae is the optic groove. </li></ul><ul><li>The optic chiasma lies at a higer level behind the optic groove. </li></ul>Optic groove
    17. 17. The hypophyseal fossa <ul><li>Due to the close relation of the pituitary gland to the optic chiasma, pressure of a pituitary tumor on the chiasma results in bitemporal hemianopia (loss of both temporal fields of vision), due to interruption of optic nerve fibers that cross in the chiasma and are derived from the medial half of both retinae. </li></ul>
    18. 18. The middle cranial fossa <ul><li>Due to close anatomical relationship, pressure on the lateral half of the optic chiasma from an aneurysm of the internal carotid artery results in ipsilateral nasal hemianopia due to interruption of optic nerve fibers that do not cross in the chiasma. </li></ul>Optic chiasma Internal carotid artery Cavernous sinus Hypophysis cerebri
    19. 19. The middle cranial fossa <ul><li>Just lateral to, and behind the sella is a jagged (irregular) hole called foramen lacerum (L., lacere = torn; as in lacerate). </li></ul><ul><li>It is not a true foramen but a gap between the apex of the petrous temporal bone and the body of the sphenoid. The carotid canal opens into it posteriorly. </li></ul><ul><li>Lateral to foramen lacerum, the apex of the petrous bone is grooved by the trigeminal ganglion . </li></ul><ul><li>At the tip of the apex of the petrous bone is a sharp spike, medial to which is a narrow groove for the inferior petrosal sinus and the abducent nerve. </li></ul><ul><li>At the posterior border of the middle fossa there is a narrow groove for the superior petrosal sinus. </li></ul>Foramen lacerum Groove for trigeminal ganglion Groove for Inferior petrosal sinus Groove for Superior petrosal sinus
    20. 20. The middle cranial fossa <ul><li>At the junction of the petrous bone with the side wall of the skull there is a groove for the inferior temporal gyrus . </li></ul><ul><li>Medial to the groove is the arcuate eminence , which is made by the underlying anterior semicircular canal. </li></ul><ul><li>Anterolateral to this is a small groove made by the lesser petrosal nerve ; it is directed towards foramen ovale. </li></ul><ul><li>The upper surface of the petrous temporal bone is perforated and grooved by the greater petrosal nerve ; the groove is directed towards foramen lacerum. </li></ul>Groove for Inferior temporal gyrus Arciate Eminance Groove for Greater petrosal nerve Groove for Lesser petrosal nerve
    21. 21. Sphenoid air sinus
    22. 22. The middle cranial fossa <ul><li>The petrous part of the temporal bone is so called because it is particularly dense and rock-like (G., petros = stone; same as the name Peter). </li></ul><ul><li>It shows up as a very dense shadow in x-rays. </li></ul><ul><li>It encloses the inner ear, and laterally the middle ear cavity with its contained ossicles. </li></ul>Petrous Temporal bone
    23. 23. Skull, lateral xray Petrous Temporal bone Auricle of ear Coronal suture lambdoid suture Internal Occipital protuberance Anterior Cranial fossa middle Cranial fossa posterior Cranial fossa
    24. 24. The posterior cranial fossa <ul><li>Bounded in front by the crest of the petrous temporal bone </li></ul><ul><li>The fossa is formed by the temporal and occipital bones and houses the cerebellum. </li></ul><ul><li>The most obvious feature is the foramen magnum, which transmits the lower end of the medulla, etc. (not the spinal cord). </li></ul>
    25. 25. The posterior cranial fossa <ul><li>Behind foramen magnum, the bone is marked by faint grooves for the transverse venous sinuses . </li></ul><ul><li>If the groove is followed backwards it extends to the internal occipital protuberance , which lies opposite the external. </li></ul><ul><li>In the supratentorial part of the occipital bone is a concavity on either side for the occipital pole of the cerebral hemisphere. </li></ul><ul><li>At the internal occipital protuberence, the sagittal groove turns to one side (usually the right). </li></ul>Groove for Transverse Venous sinus Internal occipital protuberance Sagittal groove
    26. 26. The posterior cranial fossa <ul><li>If the groove of the transverse sinus is followed forwards it reaches the back of the petrous temporal bone and then pursues an S-shaped curve downwards and forwards (housing the sigmoid sinus ), a mastoid emissary canal is often present here. </li></ul><ul><li>The sigmoid sinus groove ends at the jugular foramen where an emissary canal (the posterior condylar canal) runs back to open behind the occipital condyle. </li></ul>Sigmoid sinus Mastoid emmisary canal
    27. 27. The posterior cranial fossa <ul><li>The large superior sagittal sinus is usually continuous with the right transverse sinus and the smaller straight sinus with the left. Therefore the right jugular foramen is usually larger than the left. </li></ul><ul><li>The jugular foramen is between the occipital and temporal bones. </li></ul><ul><li>The internal occipital crest runs down in the midline from the internal occipital protuberance ; to it is attached the falx cerebelli over the occipital sinus. The deep concavities on either side of the internal occipital crest lodge the cerebellar hemispheres. </li></ul>Jugular foramen Internal occipital crest <ul><li>In the anterior margin of foramen magnum is a small, anteriorly directed hypoglossal (or anterior condylar) canal . </li></ul><ul><li>In front of the foramen magnum the slope of the clivus leads up to the body of the sphenoid. The lower part of the clivus is occupied by the medulla while the broad upper part by the pons. </li></ul><ul><li>A jugular tubercle lies in the angle between them on each side of the clivus. </li></ul>Hypoglossal canal clivus
    28. 28. The posterior cranial fossa <ul><li>On the posterior aspect of the petrous temporal bone is the internal auditory meatus , which leads into the region of the middle and inner year. </li></ul><ul><li>There is also the groove for the inferior petrosal sinus on each side of the clivus. </li></ul><ul><li>The opening of the aquiduct of the vestibule. </li></ul>Internal Auditory meatus Inferior Petrosal sinus Opening of The aquiduct Of vestibule
    29. 29. Some separate bones of the skull
    30. 30. The vomer <ul><li>The vomer (L.=plough) is thin, flat, and almost trapezoid, forming the postero-inferior part of the nasal septum. </li></ul>vomer
    31. 31. The palatine bone <ul><li>The floor of the nose is the roof of the mouth. </li></ul>Palatine process Of the maxilla Horizontal plate of The palatine bone perpendicular plate of The palatine bone Medial pterygoid plate Pterygoid hamulus
    32. 32. The conchae (turbinates) <ul><li>There are three nasal conchae or turbinate bones projecting from the lateral wall. The three conchae project as shelves with increasing prominence from above down, so that the distances between the conchae and the septum are equal. </li></ul><ul><li>The inferior choncha is the longest, the middle and superior conchae are joined anteriorly, but diverge away from each other posteriorly. </li></ul>Inferior concha middle concha superior concha
    33. 33. The paranasal sinuses <ul><li>Certain of the bones that form the boundaries of the nasal cavities are air-filled (pneumatic bones). The cavities so produced are called paranasal air sinuses </li></ul><ul><li>The sinuses are bilateral and are named according to the bones in which they are located. Hence there are frontal, ethmoidal, sphenoidal, and maxillary sinuses. </li></ul>
    34. 34. The frontal sinus <ul><li>The frontal sinuses are located between the outer and inner tables of the frontal bone. </li></ul><ul><li>Often a frontal sinus has two parts: (1) a vertical part in the squamous part of the frontal bone, and (2) a horizontal part in the orbital plate of the frontal bone. that lies off the midline. </li></ul><ul><li>The two sinuses are unequal in extent (asymmetrical) and are separated by a bony septum that lies off the midline. </li></ul>
    35. 35. The ethmoid bone <ul><li>To appreciate the complicated shape of the ethmoid bone, you may make an enlarged model of the bone with an old desk. </li></ul><ul><li>Place a vertical plate of wood in the midline, projecting partly above the desk surface. </li></ul><ul><li>Bore a number of holes alongside it. </li></ul><ul><li>Fit two shelves to the inner surfaces of the drawer units. </li></ul><ul><li>Fill the drawers with blown up balloons. </li></ul>Crista galli Crista galli Perpenducular plate Perpendicular plate Cribriform plate Cribriform plate Superior concha Middle concha Middle concha Air cells Air cells Medial wall of the orbit Medial wall of the orbit Nasal cavity Orbital plate of The frontal bone
    36. 36. The sphenoid bone (anterior aspect) Greater wing Lesser wing Medial pterygoid plate Lateral pterygoid plate Pterygoid process Superior orbital fissure Optic canal Foramen rotundum Pterygoid canal Body septum sinus sinus
    37. 38. The sphenoid bone (various projections)
    38. 39. The maxillary sinus (antrum of Highmore) <ul><li>The maxillary sinus occupies the greater part of the maxillary bone. </li></ul>
    39. 40. Lacrimal bone Lacrimal bone Orbital plate of the ethmoid Anterior lacrimal crest of the frontal process of the maxilla Posterior lacrimal crest lacrimal groove Leading to nasolacrimal duct