Early Development: Three Germ Layers

Early Development: Three Germ Layers

Author: Nathan Lampson

This lesson will identify the three germ layers that form in an early embryo and the tissues and organs that develop from them.

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  • Germ Layers

    The first three layers of tissue that develops in the embryo as it starts to form (ectoderm, mesoderm, and endoderm).

  • Ectoderm

    The outer germ layer that forms the nervous system, skin, melanocytes and lenses of the eyes.

  • Mesoderm

    The middle germ layer that forms muscles (cardiac, smooth, skeletal), mesenchyme, blood vessels, and mesenteries.

  • Endoderm

    The innermost germ layer that forms the digestive tract, respiratory tract, endocrine glands, auditory systems, and urinary bladder.

  • Cleavage

    A general term to describe the splitting or breaking apart of an object or molecule; in embryology this is when the zygote starts to divide into multiple cells.

  • Blastomere

    After the morula forms, each new cell that divides is called a blastomere.

  • Cell Differentiation

    The process of cells taking on specific forms and functions, also called specialization of cells.

  • Morphogenesis

    When an organism develops a specific shape.