Ectoderm

The ectoderm is one of the three primary germ layers formed in early embryonic development. It is the outermost layer, lying on top of the mesoderm and endoderm. The word ectoderm comes from the Greek words ektos, meaning "outside", and derma, meaning "skin".

Generally, the ectoderm changes into epithelial and neural tissues, such as the spinal cord, nerves, and brain. This includes parts of the body like the skin, the lining of the mouth and nose, sweat glands, hair, nails, and the outer part of tooth enamel.

In vertebrate embryos, the ectoderm splits into two parts: the dorsal surface ectoderm and the neural plate. The surface ectoderm becomes most of the body's covering tissues, while the neural plate folds inward to create the neural tube and neural crest, which develop into the nervous system. Because of this, the neural plate and neural crest are often called the neuroectoderm.

History

Heinz Christian Pander, a Baltic German–Russian biologist, discovered the three main layers that form in very early development of animals. He studied chicken eggs and found the ectoderm, mesoderm, and endoderm. Because of this important work, Pander is often called the "founder of embryology."

Another scientist, Karl Ernst von Baer, continued Pander's work. Baer studied many different animals and showed that Pander's idea about these layers applied to all animals with backbones. Baer also discovered the blastula and wrote a textbook about his findings in 1828.

Differentiation

The ectoderm is one of the three main layers that form early in an embryo's development. It is the outer layer and appears first in animals like amphibians and fish during a process called gastrulation. At this stage, the embryo is a hollow ball of cells called the blastula, with one half called the animal hemisphere that will become the ectoderm.

As the embryo grows, the ectoderm forms along with two other layers, the mesoderm and endoderm. The ectoderm's position is influenced by how strongly it sticks to the other layers, which depends on special molecules on the cells. Over time, the ectoderm changes to form important body parts. It creates the outer skin layer, called the epidermis, and also gives rise to the nervous system, including the brain and spinal cord. Other structures like hair, nails, and certain glands also come from the ectoderm.

Clinical significance

Ectodermal dysplasia is a rare condition where parts of the body such as teeth, skin, hair, nails, and sweat glands do not develop properly. There are many types of this condition, and scientists are still learning more about what causes it.

One common type is called hypohidrotic ectodermal dysplasia. People with this condition often have trouble sweating because their sweat glands may not work well. This can be especially challenging in hot weather. They may also have other signs such as missing or misshaped teeth, thin hair, and skin that looks different. This condition affects boys more often and more severely than girls.