Norma basalis

inferior view of Skull

1. NORMA BASALIS INFERIOR VIEW OF SKULL DR. TANYA RASHID ANATOMY DEPT

2. The inferior view of the skull extends ANTERIORLY: from the middle incisors teeth POSTERIORLY: the superior nuchal lines LATERALLY: to the mastoid process and zygomatic arches. MIDDLE INCISORS SUPERIOR NUCHAL LINES MASTOID PROCESS ZYGOMATIC ARCH

3. THE BASE OF THE SKULL IS DIVIDED INTO THREE PARTS ANTERIOR PART: includes the teeth and the hard palate MIDDLE PART: extends from behind the hard palate to the anterior margin of the foramen magnum POSTERIOR PART: extends from the anterior edge of the foramen magnum to the superior nuchal lines.

4. ANTERIOR PART The main features of the anterior part are the: teeth and the hard palate. The teeth project from the alveolar processes of the two maxillae. The hard palate is composed of the palatine processes of each maxilla anteriorly and the horizontal plates of each palatine bone posteriorly. The paired palatine processes of each maxilla meet in the midline at the intermaxillary suture The paired maxillae and the paired palatine bones meet at the palatomaxillary suture The paired horizontal plates of each palatine bone meet in the midline at the interpalatine suture.

5. ADDITIONAL FEATURES IN ANTERIOR PART INCISIVE FOSSA: in the anterior midline, which contains the incisive foramina (the openings of the incisive canals, which are passageways between the hard palate and nasal cavity. GREATER PALATINE FORAMINA: near the posterolateral border of the hard palate on each side, which lead to greater palatine canals. LESSER PALATINE FORAMINA: posterior of greater palatine foramina, in the pyramidal process of each palatine bone, leading to lesser palatine canals. POSTERIOR NASAL SPINE: a midline pointed projection in the free posterior border of the hard palate.

6. MIDDLE PART The middle part of the base of the skull is complex forming anterior half and posterior half. ANTERIOR HALF : vomer and sphenoid bones POSTERIOR HALF: basilar part of occipital and paired temporal bones

7. MIDDLE PART: ANTERIOR HALF VOMER: in the midline, contributes to the formation of the of the bony nasal septum separating the two choanae . SPHENOID BONE: made up of body, paired greater and lesser wings, two pterygoid processes lateral to each choana . Three parts of sphenoid: the body, greater wings, and pterygoid processes are seen in inferior view of skull.

8. SPHENOID BONE BODY: centrally placed, articulates; ANTERIORLY with the vomer and palatine bones. POSTERIORLY with the occipital bone. PTERYGOID POCESSES: extending downwards, consists of a narrow medial plate and broader lateral plate separated by the pterygoid fossa. Each medial plate of the pterygoid process ends inferiorly with a hook like projection the P terygoid Hamulus , and divided superiorly to form shallow scaphoid fossa . GREATER WING: lateral to the lateral pterygoid plate, articulates laterally and posteriorly with the parts of temporal bone. Important features on the surface are the; foramen ovale and foramen spinosum.

9. MIDDLE PART: POSTERIOR HALF CONSISTS OF THE: occipital and the paired temporal bones. OCCIPITAL BONE : more specifically its basilar part. POSTERIORLY: foramen magnum LATERALLY: temporal bones. Prominent structure on the basilar part of the occipital bone is a PHARYNGEAL TUBERCLE , a bony prominence for the attachment of the parts of pharynx to the base of the skull.

10. POSTERIOR HALF: TEMPORAL BONE The foramen lacerum , an irregular opening filled with cartilage throughout life. CAROTID CANAL: posterolateral to the foramen lacerum . PHARYNGOTYMPANIC TUBE: between the petrous part of temporal and greater wing of sphenoid is a groove for the auditory tube. MANDIBULAR FOSSA: a concavity where head of mandible articulates with the base of the skull. An imporatant featrure of this articulation is the prominent articular tubercle , which is the downward projection of the anterior border of the mandibular fossa. CAROTID CANAL PHARYNGO-TYMPANIC TUBE MANDIBULAR FOSSA ARTICULAR TUBERCLE

11. POSTERIOR PART Extends from anterior edge of the foramen magnum to the superior nuchal lines posteriorly. CENTRALLY : occipital bone LATERALLY: temporal bones.

12. POSTERIOR PART: OCCIPITAL BONE It has four parts organized around THE FORAMEN MAGNUM , which is a prominent feature of this part of skull though which the brain and spinal cord are continuous. PARTS OF OCCIPITAL BONE: Squamous part (posterior to foramen magnum) Lateral parts (lateral to foramen magnum) Basilar part (anterior to foramen magnum)

13. PARTS OF OCCIPITAL BONE EXTERNAL OCCIPITAL CREST: the most visible feature of squamous part is the, which extends downwards from the external occipital protuberance towards foramen magnum. THE INFERIOR NUCHAL LINES: are laterally from the midpoint of the crest. THE OCCIPITAL CONDYLES: which are the paired structures on the border of foramen magnum. They articulate with the atlas (c1 vertebra). CONDYLAR CANAL: Posterior to each condyle HYPOGLOSSAL CANAL: anterior and superior to each condylar canal. JUGULAR FORAMEN: lateral to each hypoglossal canal EXTERNAL OCCIPITAL CREST INFERIOR NUCHAL LINES OCCIPITAL CONDYLE CONDYLAR CANAL HYPOGLOSSAL CANAL JUGULAR FORAMEN

14. PARTS OF TEMPORAL BONE MASTOID BONE: identified by the large cone shaped bony structure for the attachment of several muscles. On its deep aspect is the mastoid notch, also for muscle attachment. STYLOID PROCESS: anteromedial to mastoid process, needle shaped. Point of attachment for various muscles and ligaments. Between styloid and mastoid process is the STYLOMASTOID FORAMEN . Styloid Process Stylomastoid Foramen Mastoid Process

15. FORAMENS STRUCTURES PASSING THROUGH FORAMENS INCISIVE FORAMEN NASOPALATINE NERVES, SPHENOPALATINE ARTERY LESSER PALATINE FORAMEN LESSER PALATINE NERVE GREATER PALATINE FORAMEN PALATINE ARTERY, VEIN AND NERVE FORAMEN OVALE MANDIBULAR DIVISION OF TRIGEMINAL NERVE FORAMEN SPINOSUM MIDDLE MENINGEAL ARTERY CAROTID CANAL INTERNAL CAROTID ARTERY HYPOGLOSSA CANAL HYPOGLOSSAL NERVE JUGULAR FORAMEN GLOSSOPHARYNGEAL NERVE, VAGUS NERVE, ACCESSORY NERVE, INTERNAL JUGULAR VEIN STYLOMASTOID FORAMEN FACIAL NERVE FORAMEN MAGNUM SPINAL CORD, VERTEBRAL COLUMN

16. MULTIPLE CHOICE QUESTIONS WHICH OF THE FOLLOWING IS THE PASSAGEWAY BETWEEN HARD PALATE AND NASAL CAVITY ? Incisive foramen Palatine foramen Pterygoid fossa Scaphoid fossa

17. Pharyngeal tubercle has the attachment for the ? Brainstem Pharynx Pituitary gland Spinal cord

18. What structures passes through stylomastoid foramen ? Facial nerve Glossopharyngeal nerve Mandibular division of trigeminal nerve Middle meningeal artery

19. THANK YOU