Skull

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Lecture 4

• Skull

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Objectives

• learn the bones of the braincase
• learn the bones of the face and palate
• learn the cavities of the skull and associated
  structures

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Overview Skull

• The bones of the skull protect the brain and the
  special sense organs (sight, smell, hearing,
  equilibrium and taste)
• They form the boundaries to the entrance of the
  digestive and respiratory systems
• They also provide attachment to the facial
  muscles and the powerful muscles of mastication

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Overview

• Different breeds of dogs have different shapes
  and lengths of the skull.
• Dogs with long skulls are called dolichocephalic
  (e.g., Greyhound)
• Those with short skulls are called brachycephalic
  (e.g., Bulldog).
• The skulls of the intermediate breeds are called
  mesaticephalic (e.g., Dachshund).

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Skull

• The facial bones
• The facial bones form the boundaries of the nasal
  cavity, bony orbit, and the roof and lateral
  walls of the oral cavity.
• The braincase bones
• The bones of the braincase (neurocranium) form
  the boundaries of the cranial cavity that
  encloses the brain and the meninges

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The facial bones

• The facial bones can be classified into two
  groups
• A. Paired bones of the facial bones
• 1. Lacrimal
• 2. Nasal
• 3. Maxilla
• 4. Zygomatic
• 5. Incisive
• 6. Palatine
• 7. Pterygoid
• 8. Dorsal nasal concha
• 9. Ventral nasal concha
• 10. Mandible bone
• Unpaired bones of the facial bones
• 1. Vomer
• 2. Hyoid

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A. Paired bones of the facial bones

• 1. Lacrimal
• located in the rostromedial aspect of the orbit.
• At its center there is the fossa for the lacrimal
  sac, where the osseous lacrimal canal begins.

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• The lacrimal bone articulates
• With
• frontal bone, maxilla,
• palatine bone, zygomatic bone
• and ethmoid bone.

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A. Paired bones of the facial bones

• 2. Nasal
• The nasal bone is very short in brachycephalic
  skull.
• Its internal surface is covered by mucous
  membrane in live animal.

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The nasal bone articulates with the frontal ,
maxilla and incisive bone.
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A. Paired bones of the facial bones

• 3. Maxilla
• The maxilla is the largest bone of the face.
• Together with the incisive bone, the maxilla
  forms the upper jaw.
• On its external surface there is the
  infraorbital foramen
• for the passage of infraorbital nerve, vein and
  artery.

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A. Paired bones of the facial bones

• infraorbital canal
• The canal begins at the maxillary foramen and
  ends at the infraorbital foramen.
• The short infraorbital canal lies dorsal to the
  upper fourth premolar.

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A. Paired bones of the facial bones

• 4. Zygomatic
• The zygomatic bone forms the zygomatic arch
  (rostral part) together with the zygomatic
  process of the temporal bone and Maxilla.
• It articulates with the maxilla, lacrimal and
  temporal bones.

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A. Paired bones of the facial bones

• 5. Incisive (Premaxilla)
• The incisive bone contains three alveoli for the
  upper incisor teeth.
• It articulates with the maxilla, vomer and nasal
  bone.

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A. Paired bones of the facial bones

• 6. Palatine
• The palatine bone forms the caudal part of the
  hard palate.
• It is divided into horizontal and perpendicular
  laminae.
• Each horizontal lamina has two surfaces, palatine
  and nasal.

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A. Paired bones of the facial bones

• 6. Palatine
• palatine canal
• Running through the palatine bone is the palatine
  canal, which provides passage for the major
  palatine artery, vein and nerve.
• The palatine canal begins at the caudal palatine
  foramen in the pterygopalatine fossa and
  terminates in the hard palate through the major
  and minor palatine foramina.

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A. Paired bones of the facial bones

• 7. Pterygoid
• The pterygoid is small four-sided bone that
  articulates with the medial surface of the
  pterygoid process of the sphenoid bone.

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A. Paired bones of the facial bones

• 8. Dorsal nasal concha
• The dorsal nasal concha is attached to the
  ethmoidal crest on the inner wall of the nasal
  bone.
• The dorsal nasal concha is a simple curved shelf
  of bone.
• The space ventral to the dorsal nasal concha is
  the middle meatus and the space dorsal to it is
  the dorsal meatus.

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A. Paired bones of the facial bones

• 9. Ventral nasal concha
• The ventral nasal concha is attached to the
  conchal crest on the medial wall of the maxilla.
• It is formed of primary and secondary bony
  scrolls.
• The space between the conchae and the nasal
  septum is the common meatus, whereas the space
  dorsal to the conchae is the middle meatus and
  the space ventral to it is the ventral meatus.

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A. Paired bones of the facial bones

• 10. Mandible
• The mandible consists of two parts that are
  united rostrally at the symphysis.
• Each part is divided into a horizontal body, and
  a vertical ramus.
• The body carries the lower teeth, and the ramus
  articulates with the temporal bone.

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A. Paired bones of the facial bones

• 10. Mandible
• The dorsal (alveolar) border of the mandible
  bears alveoli for the lower incisors, canine,
  premolars and molar teeth.
• The lateral surface of the ramus presents a
  triangular depression, the masseteric fossa, for
  the attachment of the masseter muscle.

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A. Paired bones of the facial bones

• 10. Mandible
• The dorsal end of the ramus is represented by the
  coronoid process.
• The condylar process of the ramus articulates
  with the temporal bone to form the
  temporomandibular joint.
• The coronoid process and the condylar process
  are separated by the mandibular notch.

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A. Paired bones of the facial bones

• Mandibular canal
• The mandibular canal begins at the mandibular
  foramen on the medial side of the ramus.
• It perforates the mandible rostrally and ends at
  the three mental foramina (caudal, middle,
  rostral) on the rostrolateral part of the body.
• The mandibular canal provides passage way for the
  inferior alveolar artery, vein and nerve.

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B. Unpaired bones of the facial bones

• 1. Vomer
• The vomer is a single bone that extends obliquely
  from the base of the cranial cavity to the upper
  surface of the hard palate.
• It forms the caudoventral part of the nasal
  septum.
• The vomer articulates with the sphenoid bone,
  ethmoid bone, palatine bones, maxilla and
  incisive bones.

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B. Unpaired bones of the facial bones

• 2. Hyoid bones
• hyoid apparatus extend from the mastoid process
  of the skull to the thyroid cartilage of the
  larynx.
• They support and stabilize the tongue and the
  larynx.

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B. Unpaired bones of the facial bones

• The hyoid apparatus consists of
• stylohyoid
• Epihyoid
• Ceratohyoid
• basihyoid
• thyrohyoid
• The basihyoid is the only single bone that
  connects the paired bones from each side at the
  root of the tongue.
• Attaching to the free end of the stylohyoid is
  the tympanohyoid cartilage, which articulates
  with the mastoid process.

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