Some newly reported clumps of cells growing in lab dishes have been hailed as the closest things to human embryos that scientists have ever made in the lab. These entities are human embryo models — ...

HeX-Embryoid model showing early blood cells (green) that have formed inside of blood vessels (red) surrounded by yolk sac mesoderm cells (blue) that support these tissues. University of Pittsburgh ...

The yolk sac is the lone site of primitive hematopoiesis. However, the role of the yolk sac in generating definitive hematopoietic progenitors has remained controversial since the onset of circulation ...

Gastrulation, the process where an embryo reorganizes itself from a hollow sphere into a multilayered structure, is considered a 'black box' of human development. This is because human embryos are ...

A new study using stem cell-based models has shed new light on how the human embryo begins to develop, which could one day benefit the development of fertility treatment. A new study using stem ...

Isolated from its mother's body, a chicken embryo's only source of food is a golden-yellow dollop of nutrients known simply as yolk. Sustained by the placenta, mammals like ourselves have no need for ...

These colorful embryonic squid are all feeding off yolk sacs within their eggs. Squid develop directly, which means that the embryos have the same basic body plan as an adult squid. Get a closer view ...

Epidemiology and Infection, Vol. 103, No. 3 (Dec., 1989), pp. 577-585 (9 pages) Graded doses of live and heat-killed cells of Campylobacter jejuni were injected into the yolk-sac of 5-day-old chick ...