Neuroanatomy 2: The skull

Question 1

What is this bone called (2 names)? What are its main features?

Answer 1

Incisive bone/Premaxilla

• Forms apex of skull
• Houses the incisors
• Forms part of nasal aperature

Question 2

What is this bone called? What features does it have?

Answer 2

• Maxilla
– Largest bone of facial region
– Houses canines, premolars and molars
– Forms nasal and oral cavities

Question 3

What is this bone called? What features does it have?

Answer 3

Nasal bone

– Forms roof of nasal cavity
– External surface is convex

Question 4

What is this bone called? What features does it have?

Answer 4

zygomatic/malar (mammals) / jugal

Consists of two parts

• Body
  
  • Articulates with Maxilla
• Temporal process
  
  • From Temporal bone

Question 5

What bone is this? What features does it have?

Answer 5

Lacrimal

• Rostral wall of orbit
• Lacrimal fossa
  
  • Leads to lacrimal duct
• Small in dog

Question 6

What bone is this? What features does it have?

Answer 6

Ethmoid

• Deep in Skull
• Ethmoidal Turbinates = Ethmoidal conchae
• Cribriform Plate (caudal aspect) - olfactory function

Question 7

What bone is this? What are some of its features?

Answer 7

Palatine bone

• Forms hard palate
  
  • Horizontal lamina
• Forms lateral wall of skull
  
  • Perpendicular lamina
• Forms part of the orbit

Question 8

What bone is this? What are some of its features?

Answer 8

Pterygoid

– Forms part of nasal cavity
– Forms the caudal part of the nasopharynx

Question 9

What bone is this? What are some of its features?

Answer 9

Vomer

– Lies in midline of skull
– unpaired

Question 10

What bone is this? What are some of its features?

Answer 10

frontal

– Forms roof and sides of cranium
– Two bones that meet midline and usually fuse
– Contains frontal sinus
– Bears sagittal crest (some species)

Question 11

What bone is this? What are some of the features it has?

Answer 11

Parietal

– Forms roof and sides of cranium
– Unites at sagittal suture
– Forms sagittal crest (in some species)

Question 12

What bone is this? What are some of its features?

Answer 12

Temporal

– Forms lower part of lateral wall
• Squamosal part
• Petrosal part (around ear, inside skull)
• Temporal part (temporal process; TMJ)
• Mastoid process

Question 13

What is this bone and what are some of its features?

Answer 13

Occipital

• Comprised of four bones
• Bears Nuchal crest
• Bears foramen magnum

Question 14

What are the four parts of the occipital bone?

Answer 14

Fusion of four neonatal bones

• squamous part (supraoccipital)
• lateral parts (left and right exoccipital)
  
  • Occipital Condyles
    
    • Articular surface of atlanto‐occipital joint
• basilar part (basioccipital)

Question 15

What is this bone and what are some of its features?

Answer 15

Sphenoid complex:

– Median body with two wings (or alae)
– Houses the optic chiasma
• Basisphenoid Bone
• Presphenoid Bone

Question 16

What is this bone and what are some of its features?

Answer 16

Mandible/dentary bone
– United at intermandibular suture
• Can be fused or not –species dependent
– Body (or corpus)
– Ramus
– Masseteric fossa
– Coronoid process
– Condyloid process
– Angular process

Question 17

What are sutures?

Answer 17

Fibrous joints, unique to the skull, where independent centres of ossification meet

Question 18

What structures form from the splanchnocranium during skull development?

Answer 18

– Visceral skeleton (yellow)
• Develops within pharyngeal arches
(jaws and gills)
• Middle ear bones in mammals

Question 19

What structures form from the chondrocranium during skull development?

Answer 19

– Neurocranium or primary braincase (blue)
• Formed in cartilage
• Protects brain and special sense organs
• Replaced by bone in all vertebrates (except elasmobranchs)

Question 20

What structures form from the dermatocranium during skull development?

Answer 20

– Dermal skeleton (pink)
• Intramembranous origin in mammal

• e.g. parietal, frontal, palatine, macilla, dentary