Embryological Terminologies

1. Ectoderm

2. Mesoderm

3. Endoderm

Three Germ Layers

Ectoderm

Outermost or upper layer of cells; Gives rise to the epidermis, nervous tissue and some skeletal and connective tissue of the head.

Mesoderm

The middle layer of cells; Forms most of the muscles and skeletal tissues, urogenital system and the heart and blood vessels.

Endoderm

Deepest or innermost layer of cells that line the digestive, respiratory tract and those organs associated to digestion

Mesenchyme

Loosely organized, embryonic connective tissue from mesoderm; Precursor of all connective and muscle tissues and is component of all organs except the CNS

Neural Tube

A hollow structure derived from ectoderm that eventually forms the brain and spinal cord (CNS).

Notochord

A rod-like structure derived from mesoderm, located beneath the neural tube; Indicates the future location of the vertebral column.

Paraxial Mesoderm

Located on either side of the notochord; Segments into somites, which give rise to axial skeleton, skeletal muscles and dermis of the skin.

Intermediate Mesoderm

Positioned between paraxial and lateral mesoderm; Develops into parts of the urogenital system, including kidneys and reproductive ducts.

Lateral Mesoderm

The outermost mesoderm that splits into two layers

1. Parietal (Somatic)

2. Splanchnic (Visceral)

The Lateral Mesoderm splits into two layers:

Parietal (Somatic)

Associated with the body wall.

Splanchnic (Visceral)

1. Associated with internal organs.

2. The space between them becomes the coelom (body cavity).