Embryo Project Encyclopedia Articles

Endoderm is one of the germ layers-- aggregates of cells that organize early during embryonic life and from which all organs and tissues develop. All animals, with the exception of sponges, form either two or three germ layers through a process known as gastrulation. During gastrulation, a ball of cells transforms into a two-layered embryo made of an inner layer of endoderm and an outer layer of ectoderm. In more complex organisms, like vertebrates, these two primary germ layers interact to give rise to a third germ layer, called mesoderm. Regardless of the presence of two or three layers, endoderm is always the inner-most layer. Endoderm forms the epithelium-- a type of tissue in which the cells are tightly linked together to form sheets-- that lines the primitive gut. From this epithelial lining of the primitive gut, organs like the digestive tract, liver, pancreas, and lungs develop.

In nineteenth century Great Britain, Thomas Henry Huxley proposed connections between the development of organisms and their evolutionary histories, critiqued previously held concepts of homology, and promoted Charles Darwin's theory of evolution. Many called him Darwin's Bulldog. Huxley helped professionalize and redefine British science. He wrote about philosophy, religion, and social issues, and researched and theorized in many biological fields. Huxley made several methodological contributions to both invertebrate and vertebrate embryology and development, and he helped shape the extra-scientific discourse for these fields.

In 1893, Julia Barlow Platt published her research on the origins of cartilage in the developing head of the common mudpuppy (Necturus maculosus) embryo. The mudpuppy is an aquatic salamander commonly used by embryologists because its large embryonic cells and nuclei are easy to see. Platt followed the paths of cells in developing mudpuppy embryos to see how embryonic cells migrated during the formation of the head. With her research, Platt challenged then current theories about germ layers, the types of cells in an early embryo that develop into adult cells. In most organisms' development, three types of germ layers are responsible for the formation of tissues and organs. The outermost layer is called ectoderm, the middle layer mesoderm, and the innermost layer endoderm, although Platt called it entoderm. Platt's research provided a basis for scientists to clarify the destination or function of the germ layers in vertebrates' development.

De ovi mammalium et hominis genesi (On the Genesis of the Ovum of Mammals and of Men) is an 1827 pamphlet by Karl Ernst von Baer about the anatomical observation and description of the egg (ovum) of mammals, like dogs and humans. The pamphlet detailed evidence for the existence of the ovum at the beginning of the developmental process in mammals. Prior to von Baer's publication, there was much debate about how organisms develop, as some claimed that organisms grow from a corpuscular element already preformed in the body (preformationism), and others said that organisms developed from a fluid material undergoing a process of progressive formation (epigenesis). Researchers at the time struggled to observe the early stages of development, and those such as von Baer had to observe the phenomenon through microscopes and then provide interpretations of the phenomena they observed.

In Maureen Kass v. Steven Kass (1998), the Court of Appeals of New York in Albany, New York, ruled that the state should generally consider IVF consent forms signed by participants in an in vitro fertilization (IVF) program valid, binding, and enforceable in the event of a dispute. The court indicated that decisions regarding the handling of cryopreserved pre-zygotes, often called preembryos, contained within these consent forms should be upheld. Although Steven and Maureen Kass had signed IVF consent forms agreeing to donate unused preembryos to research, during their divorce Maureen argued for custody of the preembryos. The New York Court of Appeals ruled in favor of Steven Kass and concluded that the informed consent forms signed by the former couple had clearly manifested the coupleÕs mutual intent to donate any preembryos to research in the event of a dispute.

A germ layer is a group of cells in an embryo that interact with each other as the embryo develops and contribute to the formation of all organs and tissues. All animals, except perhaps sponges, form two or three germ layers. The germ layers develop early in embryonic life, through the process of gastrulation. During gastrulation, a hollow cluster of cells called a blastula reorganizes into two primary germ layers: an inner layer, called endoderm, and an outer layer, called ectoderm. Diploblastic organisms have only the two primary germ layers; these organisms characteristically have multiple symmetrical body axes (radial symmetry), as is true of jellyfish, sea anemones, and the rest of the phylum Cnidaria. All other animals are triploblastic, as endoderm and ectoderm interact to produce a third germ layer, called mesoderm. Together, the three germ layers will give rise to every organ in the body, from skin and hair to the digestive tract.

The objective of this project was to determine the importance of informed consent laws to achieving the larger goal of dismantling the right to abortion. I found that informed consent counseling materials in most states contain a full timeline of fetal development, along with information about the risks of abortion, the risks of childbirth, and alternatives to abortion. In addition, informed consent laws for abortion are based on model legislation called the “Women’s Right to Know Act” developed by Americans United for Life (AUL). AUL calls itself the legal architect of the pro-life movement and works to pass laws at the state level that incrementally restrict abortion access so that it gradually becomes more difficult to exercise the right to abortion established by Roe v. Wade.

In humans, sex determination is the process that determines the biological sex of an offspring and, as a result, the sexual characteristics that they will develop. Humans typically develop as either male or female, primarily depending on the combination of sex chromosomes that they inherit from their parents. The human sex chromosomes, called X and Y, are structures in human cells made up of tightly bound deoxyribonucleic acid, or DNA, and proteins. Those are molecules that contain the instructions for the development and functioning of all life forms, including the development of physical traits and body parts that correspond with each biological sex. Humans who inherit two X chromosomes typically develop as females, while humans with one X and one Y chromosome typically develop as males. Sex determination is the beginning of the development of many characteristics that influence how a human looks and functions as well as the societal expectations that other humans have for each other.

The North Carolina state legislature passed The Woman’s Right to Know Act in 2011, which places several restrictions on abortion care in the state. The Woman’s Right to Know Act, or the Act, imposes informed consent requirements that physicians must fulfill before performing an abortion as well as a twenty-four hour waiting period between counseling and the procedure for people seeking abortion, with exceptions for cases of medical emergency. Then-governor of North Carolina Beverly Perdue initially vetoed House Bill 854, which contained the Act, but the state legislature overrode her veto to pass the bill. In response to a lawsuit that the American Civil Liberties Union, or ACLU, and other organizations filed in 2011, a US district court judge blocked the law’s ultrasound mandate from going into effect and a later court case determined that the mandate was illegal. With the passage of the Act in North Carolina, the state passed several abortion regulations and mandated that abortion providers must inform women of specific details about their pregnancy before performing the abortion procedure.

In January 2014, Mary Gatter and colleagues published “Relationship between Ultrasound Viewing and Proceeding to Abortion” in Obstetrics and Gynecology hereafter “Ultrasound Viewing.” As of 2021, ten states require women to undergo an ultrasound before they may consent to having an abortion. Self-described pro-life organizations assert that viewing an image of the fetus will dissuade women from having an abortion. The authors reviewed women’s medical records from over fifteen thousand visits to one abortion provider in 2011.The authors determined viewing an ultrasound image did not change the minds of women who were already highly certain that abortion was the right decision, challenging the idea that mandatory ultrasound viewing has any effect on women’s decision to have an abortion.