3.1. Embryology Of The Skull Flashcards
What 8 bones make up the NEUROCRANIUM?
Frontal Occipital 2 x Parietal 2 x Temporal Sphenoid Ethmoid
What 22 bones make up the VISCEROCRANIUM?
2 x Nasal 2 x Lacrimal 2 x Inferior nasal concha 2 x Maxilla 2 x Zygomatic 2 x Palatine Vomer Mandible 2 x Malleous 2 x Incus 2 x Stapes
What are the 2 divisions of the NEUROCRANIUM?
Base of skull - CHONDOCRANIUM (also called basicranium)
Membranous neurocranium - CALVARIA
How is the bone of the chondocranium formed?
Endochondral ossification
How is the bone of the calvaria formed?
Intramembranous ossification
Which bones form the basicranium?
Sphenoid
Ethmoid
Petromastoid parts of the temporal bones
Occipital
What is the embryological derivative of the bones of the basicranium at the 6th week of development?
3 midline pairs of cartilage:
Prechordal
Hypophyseal
Parachordal
What other structures (not the midline pairs) are present at the 6th week of development?
The 3 sensory capsules:
Olfactory (smell)
Optic (vision)
Otic (hearing)
What is the fate of the 1st midline pair (Prechordal)?
Fuses with olfactory capsule to form the ethmoid bone
What is the fate of the 2nd midline pair (Hypophyseal)?
Fuses with the optic capsule to form the body of the sphenoid, sphenoid wings and encase the eye
What is the fate of the 3rd midline pair (Parachordal)?
Fuses with the otic capsule to form the basiocciput, petrous and mastoid parts of the temporal bone
What bones form the calvaria?
Frontal
Parietal
Squamous part of the occipital
What is the embryological derivative of the calvaria?
Neural crest cells (ectoderm)
What are the names of the fibrous gaps in the neurocranium present at birth?
Fontanelles: Anterior Anterolateral Posterior Posterolateral
What are the origins of the bones of the viscerocranium?
Neural crest cells from pharyngeal arches 1-3
What are the general locations for the development of pharyngeal arches?
1 and 2 - structure of face
3 - structures of face and neck
4 and 6 - structures of neck
5 - develops but immediately regresses
What parts of the viscerocranium are developed by intramembranous ossification? What pharyngeal arch are they derived from?
Maxilla Palatine Zygomatic Squamous part of temporal Nasal Vomer Mandible
All from ARCH 1
What are the 5 face primordia and what do they develop into? Where are they derived from?
Frontonasal prominence
2 x Maxillary prominences
2 x Mandibular prominences
Develop into the mouth
Mandibular and maxillary derived from arch 1
Which bones of the viscerocranium are developed by endochondral ossification? Which pharyngeal arches are they developed from?
Malleous, incus, stapes - from ARCHES 1 & 2
Styloid process of temporal - from ARCH 1
What is the name of the hole for the primitive mouth?
Stomodeum
What are the expansions of the frontonasal prominence?
2 x nasal placodes (with medial and lateral swellings)
2 x Lens placodes (lateral)
What is formed from the cleft between the 1st and 2nd pharyngeal arches?
External ear
What are the structures that form as the nasal and maxillary prominences fuse?
Medial nasal prominences fuse to become INTERMAXILLARY SEGMENT
IMS fuses with MAXILLARY PROMINENCE to form the dorsum of the nose and the Phil trim of the upper lip
What is formed from the intermaxillary segment?
Primary palate
