Skull and Sockets (complete) Flashcards
What are the main cranial bones?
1 - occipital bone
2 - parietal bones
2- temporal bones
1- frontal bone
What are the main facial bones
2- Nasal bones
2- zygomatic bones
1- Maxilla
1- Mandible
What does the Otic Placode eventually become
the Eye
What is a placode?
a thickening in the Ectoderm
What triggers the formation of a placode?
Signaling from the CNS (notocord as well)
What do placodes develop into?
- The special senses
2. The neural tube (signaled by the notocord)
What does the olfactory/nasal placode develop into?
The nose
What does the stomodeum develop into
the oral cavity
What does the otic placode develop into
the ear
Which prominence is the largest and most contributory to facial development
The frontal nasal prominence
Which arch is the most important in facial development
the 1st arch
What are the steps in development of the ear
- Auricular hillocks form
- Auricular hillocks and external auditory meatus migrate to the Otic placode
- Hillocks and Meatus join and form the ear
Where do the hillocks come from? and how many are there?
They come from Arches 1 and 2.
3 from each arch, so 6 in total
What are the steps in development of the eye
- Optic placode forms
- Optic placode moves anteriorly
- Optic placode moves to the front of the face
What are the steps in development of the nose
- Nasal placode forms
- Nasal pit forms in the center, lateral and medial nasal processes form around the pit
- Frontonasal prominence migrates down between medial nasal processes
- Lateral nasal processes and maxillary prominence join to form the nasolacrimal groove
- The medial nasal and fronto nasal processes join to form the philtrum
- Medial nasal and maxillary processes join to form the upper lip
What is the philtrum
The vertical groove between the base of your nose and the top of your upper lip
What are the two components of the skull
Neurocranium
Viscerocranium
What is the neurocranium
the bones that encase the brain
What are the two types of Neurocranium structures
- membranous neurocranium
2. cartilagenous neurocranium
What is the viscerocranium
The bones that make up the face
Where do the neural crest cells originate
at the edges of the neural plate. When the neural tube forms, the neural crest cells are released into the body, and are free to move to their destination
Which way do neural crest cells usually migrate
from posterior neural tube region to the anterior
what do neural crest cells carry with them
the genetic code for development
Which bones make up the viscerocranium
Facial bones
- Mandible
- Maxilla
- Zygomatic bones
- Vomer
- Nasal bone
- lacrimal bones
- palatine
- conchae
Where do the bones of the viscerocranium come from
Neural crest cells
Where do the bones of the neurocranium come from
Both the Neural Crest Cells, and the mesoderm
Which bones make up the neurocranium?
- temporal bone
- Sphenoid bone
- Ethmoid bone
- Frontal bone
- Occipital
- parietal
Which bones of the neurocranium come from neural crest cells
- Squamosal portion of temporal bone
- Sphenoid
- Ethmoid
- Frontal
Which bones of the neurocranium come from the Mesoderm
- Petrosal part of temporal bone
- occipital bone
- parietal bone
Which bones of the skull come from the neural crest cells
Viscerocranium 1. mandible 2. Maxilla 3. Zygomatic 4. Vomer 5. Palatine 6. Lacrimal 7. Nasal bone 8. Conchae neurocranium 1. squamosal portion of temporal bone 2. sphenoid 3. ethmoid 4. frontal
Which bones of the skull come from the mesoderm
- Petrosal part of temporal bone
- occipital
- parietal
All bones of the body are mesoderm except
- the bones of the viscerocranium
- Squamosal portion of the temporal bone
- Ethmoid
- Frontal bones
- Hyoid
What are the two classifications of bone formation
- intermembranous
2. endochondral
What is intermembranous ossification
The development of bone with the absence of cartilage
How does intermembranous ossification work
- mesenchymal cells aggregate and proliferate
- Mecenchymal cells differentiate into osetoblasts that secrete osteoid at multiple ossification centers
- the Osteoid is mineralized
What bones are formed through intermembranous ossification
the Flat bones of the face and the skull
mandible and clavicle
What is endochondral ossification
the development of bone through the means of a cartilagenous precursor
how does endochondral ossification work
- A hyaline cartilage template is in place
- mesenchymal osteoblasts create ossification centers
- osteoid is deposited in the place of the cartilage
- the last place for bone to be deposited is the epiphyseal (growth) plate
What is the chondrocranium
The cranial base that embrionically is cartilage
What are the sutures of the skull
the joints formed when the parts of the skull come together
What are fontanelles
the soft spots found on infants and young childrens skulls.
they are the places where the bones of the skull have not completely fused.
What is the benefit of unfused sutures and fontanelles for fetus’
they allow for movement through the birth canal by allowing the skull to change shape on its way through
What is cranioschisis
When the cranial vault fails to form. Meaning the bones surrounding the skull don’t develop
What is craniosynostosis
The premature closure of one or more of the cranial sutures
what are the 4 examples of craniosynostosis
- scaphocephaly
- brachycephaly
- Plagiocephaly
- cloverleaf skull
What is scaphocephaly
when the sagittal suture fails (fuses early) making the head long and narrow (anterior posteriorly)
What is brachycephaly
when the coronal or frontal suture fails (fuses early)
this causes the skull to be short ( anterior posteriorly)
What is plagiocephaly
unilateral coronal and lambdoid sutures failiing,
this causes asymmetric flattening of the skull
What is cloverleaf skull
when most cranial sutures fuse early
this causes the brain to push out of the bottom causing the face and neck to swell
What are FGFs and FGFRs important for
they are involved in bone formation (especially in the skull)
What is an FGFR
a receptor for the FGF proteins
What do we need to know about FGFs and FGFRs
that they are involved in bone formation (especially in the skull)
