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Neurulation & Other Events
Neurulation results in the formation of the neural tube – ie: future brain & spinal cord. As we mentioned earlier, development is a dynamic process with many events occurring simultaneously. Thus, when we are talking about one process many other things may be going on at the same time. Let's look at a few of the changes that are going on in the neurula and post-neurula embryo. Since we can't cover all of the events we'll just examine a few. In later lectures we'll focus on the development of a select group of organs and tissues. Understanding some of the changes that are going on in the neurula and post-neurula stages will help you understand more about the critical periods of development (many of which are centered around this important phase of development).
The 21-Day Embryo
As neurulation occurs other events underway
Embryo is elongating
Mesoderm is changing (e.g. somites appear)
*Mesoderm The middle of the three primary germ layers of an embryo. It forms into many of the bodily tissues and structures such as bone, muscle, connective tissue, and skin.
The 22-Day Embryo
By the time neural tube is fully formed yolk sac has formed and heart development is underway
Many somites present; well defined
The 26-Day Embryo
Heart is more developed
Pharyngeal arches/pouches are evident
Brain has begun to develop
Development Continues...
After neurulation, embryonic germ layers are defined
Remainder of development will convert them to functional tissues and organs
Extraembryonic membranes have been defined & will continue to develop into fully functional components
This information was provided by Professor Danton H. O'Day - Univerisity of Toronto at Mississauga - Canada. Unless otherwise stated the information and graphics that are presented within this embryology section are the sole property of Danton H. O'Day, copyright 1998(c), 1999(c), 2000(c), 2001(c), 2002(c).
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Embryology 
