Endoderm

The endoderm is one of the three main layers that form very early in an embryo. It is the innermost layer. The other two layers are the ectoderm on the outside and the mesoderm in the middle. Cells move inward along a structure called the archenteron to create the endoderm.

In animals, the endoderm starts as flat cells. It later changes to become the lining for important body parts, like the respiratory tract for breathing and the gastrointestinal tract for digesting food. Special signals tell the cells where to go and what to become.

In plants, the endoderm is found in the innermost part of the bark of young shoots and roots. It is often just one layer of cells. As the plant grows older, this layer can become stronger.

Formation of the Endoderm Layer

The endoderm is the innermost layer of cells in very early embryos. It forms through a process called the nodal signaling pathway. In animals with a backbone, this layer develops where there is a lot of nodal signaling.

In humans, the endoderm starts to form organs after about 5 weeks of development.

Production of Tissues

The endoderm makes the inner layers of important body tubes. These tubes are used for digestion and breathing. The linings help our bodies get nutrients from food and swap gases when we breathe. Special patterns help endoderm cells build organs like the liver and pancreas.

Additional images

• Section through the embryo.

• Section through ovum imbedded in the uterine decidua

• Signaling pathway to inducing endoderm