Question

Pretend you are one of the flat bones in the developing skull of a fetus. Create a minimum 3 minute video (in this case just a hearty paragraph) explaining how you would develop throughout the process. Please use key terminology, but simple explanation as well.
Thank you very much I appreciate anyone who takes the time to do all of these questions!

Answer 1

The skull or cranium is made up of the structure ----

Neurocranium --- The hard structure which is around and protects brain.

Viscerocranium ---- The structure which forms the skeleton of face.

Neurocranium is again further subdivided into :

Cranial vault ------- The cranial vault is the flat bones covering the upper part of the skull.

Cartilaginous part ---- The structure covering the base of the skull.

Since the question is regarding the flat bones of skull development in fetus we will move on with the cranial vault .

The cranial vault bones covering upper part of skull which includes parietal bone,temporal and occipital bones are formed by intramembranous ossification.

In the embryonic phase, which is the first 8 weeks of pregnancy there is formation of mesenchymal cells and development of the flat bones begins with condensation of this mesenchymal cells.

All the bones of skull go through mesenchymatous phase where the epithelial cells go through transformation into mesenchymal cells called Epithelial-Mesenchymal Transformation (EMT). Within 4 weeks the fetal head consists of mesenchyme which comes from unsegmented paraxial mesoderm and cranial neural crest.

Later after this 8 weeks, is the fetal phase upto birth. In this fetal phase, intramembranous ossification for the primitive membranous skull begins along with formation of cranial sutures. These cranial sutures acts as a intramembranous growth sites. Then the next step is calcification which begins by the bone cells called osteoid by osteoblasts. This ossification helps in formation of bones. Primitive trabecular bone is formed by calcification of osteoids. During fetal growth, these flat bones enlarge by addition of new layers on the outer surface and also by osteoclastic reabsorption .

The 2 frontal bones appears at frontal eminence at 8 th week by primary ossification. These two remain seperated by frontal suture and only closes at 18 -- 24 months after birth.

The 2 parietal bones appears at parietal eminence at 8 th week by primary ossification. These two bones gets fused at 4 th month . Then ossification progresses radiallyfrom central focustowards the periphery of the bone. This ossification continues throughout the fetal life.

The intraparietal portion of occipital bone too ossifies intramembranously which too appears at 8 th week. The rest of the bone ossifies endochondrally.

The temporal bone ossifies intramembranuosly appearing at 8 th week . The two menbranous bone portions of temporal bone fuse at birth.

Well, this was about the formation of flat bones of skull in fetus.