Embryonic Development of the Brain

Embryonic Development of the Brain

Studying the early development of the brain reveals structural and functional relationships between the portions of the adult brain. Since the early development of most vertebrates is similar, the 60-hour chick embryo can serve as a study organism roughly equivalent to the 5-week human embryo. See Martini, 5th Ed, pp 438-439, & handout from Balinsky (next page in packet).

Note: This prepared slide is unusually thick, so it is especially important to follow correct microscope protocol. (Do not ram the slide with the objective). Also, since the specimen mounting medium softens as it warms, remove the slide as soon as you are done, and allow it to cool flat on the surface of the desk before you return it to the slide case. Use the 4x objective to locate, illustrate, label and describe the bolded features of the chick embryo in the following table. As a study aid, here are two views of the 60-hour chick unlabeled and labeled.

Slide 7. Chick, 60-70 hour, whole mount, chicken (H 2195) Unlabeled: 40x chick embryo Labeled: labeled 40x chick embryo.

primitive vesicles intermediate vesicles mature brain components functions
prosencephalon telencephalon cerebrumlateral ventricles

[rudimentary nose]

control skeletal musclessensory perception


intelligence , consciousness

diencephalon thalamus sensory relay
hypothalamus regulation of autonomic activities
epithalamus (pineal) biological clock
[ optic cup] will become eye, vision
mesencephalon mesencephalon midbrain *corpora quadrigemina

cerebral peduncles

visual reflexesauditory reflexes

connection to cerebrum

rhombencephalon metencephalon cerebellum plan & coordinate voluntary movement,maintain balance
pons * commisural nerve tracts
myelencephalon medulla oblongata* regulates vital functions
[otic vesicle] hearing
* These constitute the brain stem, which regulates consciousness and some autonomic reflexes: respiration, coughing, swallowing, cardiovascular control.

When finished illustrating the embryonic brain, a brief, student-graded 10 question quiz will be given to see how well these features were learned.
Here is an excellent time-lapse YouTube video of early development from zygote to completed neurulation. (In German…😉

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