Embryonic Development*
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When does the pre-embryonic period take place?
From 0-2.5 weeks.
When does the embryonic period take place?
2.5 weeks to 8 weeks.
When does the fetal period take place?
From 8 weeks to 9 months.
Explain the pre-embryonic period.
The cleavage is a series of cell divisions that subdivides the cytoplasm of the zygote.
Explain the pre-embryonic period.
The cleavage is a series of cell divisions that subdivides the cytoplasm of the zygote. It rapidly divides to produce a ball of cells (morula). The morula actively takes up fluid and hollows out to become a blastocyst.
The pre-embryo appears as a bilaminar (2 cell layers) disc. What are the two layers called?
Epiblast Hypoblast
What is gastrulation and when does it take place?
This process forms the 3rd germ layer and takes place in the 3rd week. An embryo transforms from a one-dimensional layer of epithelial cells (blastula) and reorganizes into a multi-layered structure called the gastrula.
What is neurulation?
Neurulation results in the formation of the neural tube, which gives rise to the CNS (spinal cord and brain).
What do pharyngeal arches have?
Each arch has its own: - Cartilage - Artery - Mesoderm Component - Specific cranial nerve - Skeletal component derived from ectomesenchymoma.
Name the pharyngeal arch nerves.
Arch 1 = trigeminal nerve (CN V) Arch 2 = Facial Nerve (CN VII) Arch 3 = Glossopharyngeal Nerve (CN IX0 Arch 4 = Vagus Nerve (CN X)
Name the pharyngeal arch muscles.
1st Arch - Muscles of Mastication 2nd Arch - Muscles of Facial expression 3rd Arch - Stylopharyngeus 4th Arch - Pharyngeal constrictors, soft palate, levator veli palatini, and intrinsic muscles.
Explain the development of the tongue?
1st arch = mucosa of anterior 2/3rds of the tongue formed from lateral swellings of the first arch CN V 2nd arch = Forms taste buds of anterior 2/3rds. CN VII 3rd arch = Involved in taste CN X