Allantois

This picture was taken from the following website:
http://www.aps.uoguelph.ca/ANSC*2340/LEC3/PS23.gif

I first came across the word "allantois" in class during a lecture in the past two weeks, and the term reappeared during the reading portion of lab this week, so I decided to really find out what it means. The term is defined as "the extraembryonic membrane found in amniotes that forms off the hindgut of the embryo. It stores nitrogenous waste and, in the chick, will eventually fuse with the chorion to form the chorioallantoic membrane. It is vascularized and is formed from the splanchnopleure, a layer made up of endoderm and splanchnic lateral plate mesoderm." Essentially, the allantois is the precursor of the gut in the chick embryo. Above is a picture detailing the allantois in a sheep embryo.

The information above was taken from the following reference: http://labs.devbio.com/protected/resources/modules/LabBook/Tyler_LabManual_Complete_2010.pdf.

Chalaza

This picture was taken from the following website:
http://www.geauga4h.org/poultry/egg_labeled.gif

Yesterday, in lab, I came across the word "chalaza" while looking at an egg yolk under the microscope. Not only was I confused as to what this word meant, but I also had no idea to pronounce it. "A chalaza (plural chalazae) is a structure inside an egg which helps to keep the yolk in place. The chalazae attach to either end of the yolk and anchor to the inside of the eggshell, essentially suspending the yolk. Chalazae prevent the yolk from being damaged, promoting the healthy development of the embryonic bird. This structure is also present in some plants, performing a similar function in plant ovules." A chalaza, then, is the visibly white part attached to the egg yolk, helping to anchor the yolk. It is pronounced "kuh-LEY-zuh," emphasis provided by: http://dictionary.reference.com/browse/chalaza.

The information was sourced from the following website:
http://www.wisegeek.com/what-is-chalaza.htm.

Epiboly



This picture was taken from the following website:
http://worms.zoology.wisc.edu/frogs/gast/epiboly.gif

During a fierce round of tic-tac-toe yesterday in class, I came across the word epiboly. I had first discovered the term in the textbook, but yesterday's discussion made me realize how important it is in Development Biology. The term is defined as "the movement of epithelial sheets (usually of ectodermal cells) that spread as a unit (rather than individually) to enclose the deeper layers of the embryo. Epiboly can occur by the cells dividing, by the cells changing their shape, or by several layers of cells intercalating into fewer layers. Often, all three mechanisms are used." Essentially, during epiboly, a sheet of cells spreads by thinning to cover the embryo.

The information referenced above was taken from the following reference: Gilbert, Scott F. "Early Development in Selected Invertebrates - Gastrulation." Developmental Biology. Vol. 9. Sunderland, MA: Sinauer Associates, 2010. 164. Print.

Cytoplasmic Bridges

The picture above was taken from the following website:
http://www.mc.vanderbilt.edu/histology/word/2004/
Cell%20Junctions%2004.htm

One term in our textbook that was unfamiliar to me is "cytoplasmic bridges." This term is defined as the "continuity between adjacent cells that results from incomplete cytokinesis during gametogenesis." There are cytoplasmic connections between the dividing cells during meiosis. Cytoplasmic bridges, however, are the product of meiotic cell divisions that help daughter cells remain connected. Above is a picture detailing exactly where cytoplasmic bridges can be found, connecting actin filaments.

The information referenced above was taken from the following reference: Gilbert, Scott F. "The Saga of the Germ Line - Meiosis." Developmental Biology. Vol. 9. Sunderland, MA: Sinauer Associates, 2010. 599. Print.

Teratogens

The above picture was taken from the following website: 
http://www.learn.ppdictionary.com/prenatal%20development.htm

This week in class, we were discussing developmental anatomy. Along with the normal developmental anatomical structures, we discussed developmental abnormalities. A new word I learned while learning about these abnormalities was "teratogens." The word is derived from the Greek and literally translates to "monster-formers." Teratogens are the "exogenous agents that cause disruptions in development, resulting in teratogenesis, or the formation of congenital defects. Teratology is the study of birth defects and of how environmental agents disrupt normal development." Teratogens are substances, such as alcohol, drugs, hormones, cigarettes, lead mercury and radiation, that cause developmental, anatomical abnormalities. Above is a picture showing the different types of teratogens and their possible harmful effects on the fetus during development.


The information referenced above was taken from the following reference: Gilbert, Scott F. Developmental Anatomy - Medical Embryology and Teratology." Developmental Biology. Vol. 9. Sunderland, MA: Sinauer Associates, 2010. 28. Print