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
February 7, 2026
Feb. 7, 2026 New simulations reveal that both H1N1 and COVID-19 spread across U.S. cities in a matter of weeks, often before officials realized what was happening. Major travel hubs helped drive rapid nationwide transmission, with air travel playing a bigger ...
Feb. 7, 2026 A major study suggests menopause is linked to changes in brain structure, mental health, and sleep. Brain scans revealed grey matter loss in areas tied to memory and emotional regulation, while many women reported increased anxiety, depression, and ...
Feb. 7, 2026 For decades, Americans were surrounded by lead from car exhaust, factories, paint, and even drinking water, often without realizing the damage it caused. By analyzing hair samples preserved across generations, scientists uncovered a striking record ...
Feb. 6, 2026 New research suggests that Epstein-Barr virus may actively provoke the immune system in people with multiple sclerosis. Scientists found large buildups of virus-targeting immune cells in the nervous ...
Feb. 6, 2026 Researchers have discovered a previously unknown enzyme that plays a crucial role in fat production. By blocking it, they stopped weight gain, reduced liver damage, and lowered harmful cholesterol levels in animal studies. The finding opens the door ...
Feb. 6, 2026 Colorectal cancer has long baffled scientists because, unlike most tumors, patients often do better when their cancers are packed with immune-suppressing regulatory T cells. New research finally explains why. Scientists discovered that these T cells ...
Feb. 6, 2026 Scientists at Keck Medicine of USC are testing an experimental stem cell therapy that aims to restore the brain’s ability to produce dopamine, the chemical whose loss drives Parkinson’s disease. The early-stage clinical trial involves implanting ...
Feb. 6, 2026 New research using rhesus monkeys suggests that the brain’s relationship with alcohol may begin forming long before a person ever takes a drink. Scientists found that exposure to alcohol before birth reshaped the brain’s dopamine system, a key ...
Feb. 6, 2026 Scientists in Australia have uncovered a clever new way to fight some of the most dangerous drug-resistant bacteria by targeting a sugar that exists only on bacterial cells. By designing antibodies that recognize this unique sugar, researchers were ...
Feb. 6, 2026 A new imaging breakthrough combines ultrasound and light-based techniques to generate vivid 3D images that show both tissue structure and blood vessel activity. Developed by researchers at Caltech and USC, the system delivers detailed results ...
Feb. 5, 2026 Researchers have figured out how psoriasis can quietly turn into joint disease for some patients. Immune cells formed in inflamed skin can travel through the blood and reach the joints, where they sometimes trigger inflammation. The key difference ...
Feb. 5, 2026 People who switch to a fully unprocessed diet don’t just eat differently—they eat smarter. Research from the University of Bristol shows that when people avoid ultra-processed foods, they naturally pile their plates with fruits and vegetables, ...
Latest Headlines
updated 12:56 pm ET
Feb. 5, 2026 Kidney disease often creeps in silently, and many patients aren’t diagnosed until major damage is already done. New research shows that even “normal” kidney test results can signal danger if ...
Feb. 5, 2026 Researchers have created the first complete map showing how hundreds of mutations in a key cancer gene affect tumor growth. By testing every possible mutation in a critical hotspot, they found that ...
Feb. 5, 2026 Advanced care provided by air ambulance teams was linked to higher survival rates in major trauma patients. Researchers found that more people survived than predicted by standard models, including ...
Feb. 5, 2026 As bird flu continues to circulate in animals and spill over into humans, researchers are racing to stop it before it adapts to spread widely between people. A new nasal spray vaccine showed strong ...
Feb. 4, 2026 Popular weight-loss drugs like Ozempic and Wegovy can dramatically curb appetite, but experts warn many users are flying blind when it comes to nutrition. New research suggests people taking these ...
Feb. 4, 2026 A massive Swedish study tracking nearly 28,000 people for 25 years found an unexpected link between full-fat dairy and brain health. Among adults without a genetic risk for Alzheimer’s, eating more ...
Feb. 4, 2026 Scientists are digging into why heart disease risk in type 2 diabetes differs between men and women—and sex hormones may be part of the story. In a large Johns Hopkins study, men with higher ...
Feb. 4, 2026 Sound machines may not be the sleep saviors many believe. Researchers found that pink noise significantly reduced REM sleep, while simple earplugs did a better job protecting deep, restorative sleep ...
Feb. 4, 2026 As we age, our cells don’t just wear down—they reorganize. Researchers found that cells actively remodel a key structure called the endoplasmic reticulum, reducing protein-producing regions while ...
Feb. 3, 2026 Plants make chemical weapons to protect themselves, and many of these compounds have become vital to human medicine. Researchers found that one powerful plant chemical is produced using a gene that ...