User:Cdunleavy/sandbox

Article Evaluation

Article Evaluated: Organogenesis

The article was neutral and did not show any bias. The organization of the article needs to be improved. The author discussed organogenesis in both animals and plants however, the topics were only separated by a paragraph rather than placing headings and subheadings throughout the article to break it up.

In general, the article is lacking a lot of information and is not very detailed. For example, the article explains how the germ layers differentiate into different internal organs however, aside from a small figure, the article does not explain which organs or organ systems arise from the ectoderm, endoderm, and mesoderm specifically. Another example is where the article states that the germ layers differ from one another by "fold, splits, and condensation" but did not explain what that means.

Some of the language used in the article I would modify. The author used terms such as "in utero" without explanation and a reader without scientific background might not understand the term. Also, the article stated that in plant organogenesis plants use "different cocktails of hormones" and I felt as though "cocktails" was a strange word to use.

The article did not provide any references other than a dictionary that they used for definitions. The article will need to provide more citations to verify the information placed within the article. Overall, this article needs to be reconfigured, requires more information, and requires more references.

Week 4:

Added 2 sentences to the Organogenesis Wikipedia page and added a citation from Gilbert, S. F., & Barresi, M. J. F. (2017). developmental biology, 11th edition 2016. Hoboken: Wiley Subscription Services, Inc.10.1002/ajmg.a.38166.

What I plan to add to Organogenesis Article

I plan to add citations to the material in the article that is not cited. I also plan on adding an illustration of neural tube formation. I also plan on expanding on how the germ layers develop into organs.

Animal Organogenesis

In animal development, organogenesis is the process by which the three germ layers formed from gastrulation: the ectoderm, endoderm, and mesoderm develop into the internal organs of the organism

The cells of each of the three germ layers undergo differentiation, a process where less-specialized cells become more-specialized through the expression of a specific set of genes. Cell signalling cascades drive the cell differentiation process. Extracellular chemical signals such as growth factors are exchanged to adjacent cells via juxtacrine signalling or to neighboring cells over short distances via paracrine signalling. Intracellular signals consist of a cell signalling itself (autocrine signalling), also play a role in organ formation. This allows for cell rearragement and ensures that organs form at specific sites within the organism. The organogenesis process can be studied using embryos and organoids.

Organs Produced by the Germ Layers

Endoderm is the inner most germ layer of the embryo which gives rise to gastrointestinal, respiratory, and urinary systems by forming epithelial linings and organs such as the liver, lungs, and pancreas. The mesoderm or middle germ layer of the embryo will form the blood, heart, kidney, muscles, and connective tissues. The ectoderm or outermost germ layer of the developing embryo forms epidermis, the brain, and the nervous system.

Mechanism of Organ Formation

Neural precursor cells fold and elongate to form the neural tube. Mesoderm cells condense to form a rod which will send out signals to redirect the ectoderm cells above. This fold along the neural tube sets up the vertebrate central nervous system.

While each germ layer forms specific organs, in the 1820's, embryologist Heinz Christian Pander discovered that the germ layers cannot form their respective organs without the cellular interactions from other tissues.   In humans, internal organs begin to develop within 3-8 weeks after fertilization. The germ layers form organs by three processes: folds, splits, and condensation. Folds form in the germinal sheet of cells and usually form an enclosed tube which you can see in the development of vertebrates neural tube. Splits or pockets may form in the germinal sheet of cells forming vesicles or elongations. The lungs and glands of the organism may develop this way.

A primary step in organogenesis for chordates is the development of the notochord, which induces the formation of the neural plate, and ultimately the neural tube. Vertebrate animals all differentiate from the gastrula the same way. In vertebrate development, the development of the neural tube will give rise to the brain and spinal cord.   Vertebrates develop a neural crest that differentiates into many structures, including bones, muscles, and components of the central nervous system. The coelom of the body forms from a split of the mesoderm along the somite axis

Plant Organogenesis

In plants, organogenesis is the process of forming new organs. This occurs continuously and stops only when the plant dies. The shoot apical meristems regularly produce new lateral organs (leaves or flowers) and lateral branches. New lateral roots form from weakly differentiated internal tissue (e.g. the xylem-pole pericycle in the model plant Arabidopsis thaliana). In vitro and in response to specific hormones (mainly auxins and cytokinins), most plant tissues can de-differentiate and form a mass of dividing totipotent stem cells called a callus. De novo organogenesis can then occur from those cells. The type of organ that is formed depends on the relative concentrations of the hormones in the medium. Plant organogenesis can be induced in tissue culture and used to regenerate plants.