Embryo Final Flashcards
What is the dividing somite made up of
Mesodermal cells
What do mesodermal cells give rise to
Mesenchyme
What are the types of cartilage bone development
Inter-Cartilagenous or Endochondral ossification
What precedes Inter-Cartilagenous or Endochondral ossification
A temporary cartilage template of the same shape
What is special about the cartilage stage of bone growth
Bones can grow rapidly to match the growth of the fetus
How does intramembranous ossification happen
Condensation of mesenchyme becomes vascularized
At vascularization points what happens
Cells differentiate into Osteoblasts
When they begin to deposit osteoid tissue what do the vascularization points become
Ossification centers
How is bone matrix deposited
In the form of needles or spicules which become lamellae
These lamellae develop around blood vessels to form
Osteons
The spicules grow and thicken to become
Trabecullae
What are the two types of development for the skull
Neurocranium and Splanchnocranium
What does the neurocranium develop from
Mesenchyme surrounding the brain
What are the two types of neurocranium development
Neurochondrocranium and Neuromembranocranium
How does development of the Neurochondrocranium work
Cartilaginous base of the neurocranium and the skull and later endochondral ossification begins around 8 weeks
How does neuromembranocranium development work
Intramembranous ossification and forms the sides and the roof of the neurocranium
During fetal life, bones are separated by connective tissue membranes known as
Sutures
At the angle of bones large fibrous areas are formed.
What is the membrane covering these spaces called
Fontanelles
The anterior fontanelle is the largest and closes when
By the end of the second year
When do the posterior and anterolateral fontanelles form
2-3 months
When do the posterolateral fontanelles close
End of the first year
How many arches do humans have
- we start with 6, but the 5th disappears in 1.5 days
What is the first arch aka
Mandibular arch
What is the second arch aka
Reichert’s cartilage