Reference Terms
from Wikipedia, the free encyclopedia
Embryo
In organisms that reproduce sexually, once a sperm fertilizes an egg cell, the result is a cell called the zygote that has all the DNA of two parents. In plants, animals, and some protists, the zygote will begin to divide by mitosis to produce a multicellular organism.
In animals, the development of the zygote into an embryo proceeds through specific recognizable stages of blastula, gastrula, and organogenesis. The blastula stage typically features a fluid-filled cavity, the blastocoel, surrounded by a sphere or sheet of cells, also called blastomeres.
During gastrulation the cells of the blastula undergo coordinated processes of cell division, invasion, and/or migration to form two (diploblastic) or three (triploblastic) tissue layers. In triploblastic organisms, the three germ layers are called endoderm, ectoderm and mesoderm. However, the position and arrangement of the germ layers are highly species-specific, depending on the type of embryo produced. In vertebrates, a special population of embryonic cells called the neural crest has been proposed as a "fourth germ layer," and is thought to have been an important novelty in the evolution of head structures.
Related Stories
1
2
Health & Medicine News
October 21, 2026
Oct. 21, 2026 A massive study of more than 460,000 Americans found that ultra-processed foods were not associated with increased colorectal cancer risk overall, challenging a widely held assumption. While ...
Oct. 21, 2026 Scientists have uncovered an unexpected danger lurking inside cells: too much RNA can damage the structures responsible for producing energy. A new study found that excess RNA, including the normally essential messenger RNA (mRNA), can directly ...
Oct. 21, 2026 A new study tracking 13 astronauts suggests that the human heart may be surprisingly well equipped for a journey to Mars, especially with regular exercise during spaceflight. Researchers found that astronauts' hearts adapted to months of ...
Oct. 21, 2026 Scientists have turned blood cells from an 80-year-old into neural stem cells with a molecular age of less than 20, effectively reversing more than 60 years of cellular aging in the laboratory. The ...
Oct. 21, 2026 A new Penn State study suggests that just four minutes of daily strength training can significantly improve mobility and physical function in older adults. After 12 weeks, participants showed meaningful gains in balance, leg strength, and their ...
Oct. 20, 2026 A study by DZNE finds that healthy eating is associated with slower biological aging—and that there is more than one way to eat healthily. The researchers examined ten dietary patterns considered healthy, including the Mediterranean, Nordic, ...
Oct. 20, 2026 Scientists have uncovered a surprising reason why statins, the widely prescribed cholesterol-lowering drugs that help prevent heart attacks and strokes, can sometimes cause muscle pain, weakness, and even severe muscle damage. Using advanced imaging ...
Oct. 20, 2026 Scientists have discovered a natural compound that targets dangerous C. difficile bacteria without wiping out the gut's beneficial microbes. Successful early tests suggest it could lead to a gentler, ...
Oct. 20, 2026 The aging brain may be undergoing a remarkable transformation rather than simply losing its abilities, shifting its focus from remembering details to understanding the bigger picture. Scientists suggest this change could be an evolutionary ...
Oct. 20, 2026 Scientists have found a promising way to protect the brain from Alzheimer’s-related damage by blocking immune cells that contribute to the destruction of neurons. In mice, the treatment preserved ...
Oct. 20, 2026 A surprising clinical trial suggests that taking vitamin C daily could improve survival in people with precancerous blood disorders and early-stage blood cancers. Patients receiving the supplement had fewer adverse events and showed a promising ...
Oct. 19, 2026 Researchers discovered that recurring arthritis triggered by cancer immunotherapy may be driven by immune cells that remember previous attacks and return in a more aggressive state. The findings could pave the way for treatments that prevent painful ...
Latest Headlines
updated 12:56 pm ET
Oct. 19, 2026 Scientists have discovered why some people with a high genetic risk of Alzheimer’s remain mentally sharp into their 80s, uncovering a rare mutation that protects the brain from harmful protein ...
Oct. 19, 2026 Scientists have uncovered a possible explanation for why some people struggle to taste food more than a year after recovering from COVID-19. By examining taste buds from patients with lingering ...
Oct. 19, 2026 Walking just 3,000 steps a day could help slow Alzheimer’s-related brain changes, according to new research. Scientists discovered that physical activity was linked to less buildup of harmful tau ...
Oct. 19, 2026 A discovery in tiny algae led to a Nobel Prize-winning breakthrough that allows scientists to switch brain cells on and off using light. The revolutionary technique has already helped researchers ...
Oct. 19, 2026 Scientists have uncovered an unexpected culprit behind sleep loss in Alzheimer’s disease: overactive immune cells in the brain. By temporarily ...
Oct. 18, 2026 A common liver disease affecting nearly 30% of adults worldwide may be far more complicated than scientists previously realized. Mayo Clinic ...
Oct. 18, 2026 Researchers have identified striking parallels between Sigmund Freud’s century-old theories and modern neuroscience, suggesting that the brain’s ...
Oct. 18, 2026 Eating too much salt may do more than raise blood pressure. It could also harm memory and social behavior. In a new study, Japanese researchers ...
Oct. 18, 2026 Eating blueberries every day could have surprising effects on mood, according to a small study that found greater reductions in depressive symptoms among older adults who consumed the fruit for three ...
Oct. 18, 2026 A study of nearly 90,000 adults found that people consuming the most of a little-known sugar found in red meat had a 63% higher risk of developing type 2 diabetes. Scientists suspect the sugar may ...