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 1949, Priscilla White published Pregnancy Complicating Diabetes, which described the results and implications of a fifteen-year study about pregnant diabetic women. Published in the American Journal of Medicine, the article details possible causes of and ways to prevent the high fetal mortality rate associated with pregnant diabetic women. Diabetes is a disease in which the body's ability to produce or respond to the hormone insulin is impaired, and it can be particularly dangerous during pregnancies. In her article, White reported that prematurely delivering infants for diabetic pregnant women reduces infant and maternal mortality rates. Pregnancy Complicating Diabetes helped make premature delivery of infants the standard of care for diabetic pregnant women, and it has contributed to the increased survival rate of infants born from diabetic mothers from less than fifty percent in the 1940s to over ninety percent in 2017.

In 1986, Vern L. Katz, Deborah J. Dotters, and William Droegemueller published “Perimortem Cesarean Delivery,” an article in which they developed the Four Minute Rule for perimortem cesarean sections. The Four Minute Rule states that if a pregnant woman’s heart stops beating, physicians should begin an operation to deliver the fetus within four minutes and aim to have the fetus delivered within five minutes of cardiac arrest. Although cardiac arrest during pregnancy is uncommon, it can happen when pregnant women experience trauma, blood clots, infection, or have preexisting heart conditions. In the article, the authors emphasize how the Four Minute Rule increased maternal and fetal survival rates and decreased cases of severe fetal brain damage. The article “Perimortem Cesarean Delivery” was the first article to present the Four Minute Rule, which has influenced international guidelines and become the standard for maternal resuscitation and fetal survival in emergency medicine, operating rooms, and many other aspects of medical practice.

In July 2015, Ana J. Torvie, Lisa S. Callegari, Melissa A. Schiff, and Katherine E. Debiec published “Labor and Delivery Outcomes Among Young Adolescents,” hereafter “Labor and Delivery Outcomes,” in the American Journal for Obstetrics and Gynecology. The authors conducted a study using birth certificate data and hospital records in the state of Washington to compare the frequency and outcomes of cesarean and surgically assisted vaginal births among different age groups of pregnant people. They found that adolescents aged eleven to fourteen years are less likely to require cesarean or surgically assisted births but that their neonates were more likely to have birth-related complications than those of adults aged twenty to twenty-four years. While previous studies had yielded conflicting results, “Labor and Delivery Outcomes” reports generalized trends about young adolescents in labor and delivery. The researchers’ findings support future physicians in making more informed considerations for the care of pregnant patients under the age of fifteen.

Felix Anton Dohrn is best remembered as the founder of the Stazione Zoologica di Napoli, the world' s first permanent laboratory devoted to the study of marine organisms. Dohrn was born on 29 December 1840 in Stettin, Pomerania (now Poland), to a wealthy merchant family. Dohrn's paternal grandfather, Heinrich, trained as a surgeon and then established a sugar refinery, while Dohrn's father, Carl August Dohrn, who inherited the family business, became interested in natural history through Alexander von Humboldt, a family friend. Once settled in his career, Anton Dohrn's own research never strayed far from the origin of vertebrates. He promoted the theory that vertebrates closely resemble and are derived from annelid-like ancestors and he spent years studying the early embryogenesis of lower vertebrates in attempts to prove this.

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.

Etienne Geoffroy Saint-Hilaire, commonly known as Geoffroy, studied animals, their anatomy and their embryos, and teratogens at the National Museum of Natural History in Paris, France in the eighteenth and nineteenth centuries. Geoffroy also helped develop several specialized fields in the life sciences, including experimental embryology. In his efforts to experimentally demonstrate the theory of recapitulation, Geoffroy developed techniques to intervene in the growth of embryos to see whether they would develop into different kinds of organisms. Moreover, Geoffroy emphasized the concept of l'unite de composition (the unity of plan). Geoffroy disputed in 1830 with Georges Cuvier over whether form or function matters most for the study of anatomy and whether the transformation of organic forms can occur over time. Geoffroy's conceptual contributions, as well as his experimental research, influenced embryological research on animal morphology and teratogens, and later the field of evolutionary paleontology.

In 2010, the Catholic Church excommunicated Margaret McBride, a nun and ethics board member at St. Joseph’s Hospital and Medical Center in Phoenix, Arizona. McBride was excommunicated latae sententiae, or automatically, for approving a therapeutic abortion, which is an abortion that is required to save a pregnant woman’s life. McBride approved an abortion for a woman who was twenty-seven years old, eleven weeks pregnant with her fifth child, and suffered from pulmonary hypertension, a life-threatening condition during pregnancy. Following McBride’s decision, St. Joseph’s lost its affiliation with the Catholic Church, which it had maintained since the late 1800s. Affiliation with the Catholic Church required that the hospital abide by Canon Law, which is the law of the Catholic Church. Under Canon Law, abortion is serious wrongdoing that could result in excommunication, as it did in the case of McBride. McBride’s excommunication illustrated the impact that affiliation of Catholicism with hospitals had on patients’ ability to receive comprehensive reproductive health care.

In December 2011, the Stillbirth Collaborative Research Network, or SCRN, published the article “Causes of Death Among Stillbirths” in The Journal of the American Medical Association. The authors of the article investigate the causes of stillbirth and possible reasons for the racial, ethnic, and geographic disparities in stillbirth rates. According to the Centers for Disease Control and Prevention, or CDC, stillbirth is the death of a fetus at twenty or more weeks during pregnancy. “Causes of Death Among Stillbirths” explores the common causes of stillbirth in different racial and ethnic groups, and provides a framework for future research into medical interventions to help reduce racial and ethnic stillbirth disparity.