n.中胚层；中层

The mesoderm is the middle layer of cells that forms during embryonic development, giving rise to structures such as muscles, bones, and blood vessels.
The somites, derived from the mesoderm, are the building blocks for the vertebral column and surrounding musculature.
During gastrulation, the mesoderm splits into three primary germ layers: the ectoderm, endoderm, and mesoderm.
Notochordal cells in the neural tube arise from the mesoderm, providing support for the spine.
The mesoderm contributes to the formation of the urogenital system, including kidneys and reproductive organs.
Mesodermal defects can lead to various developmental disorders, like renal dysplasia or heart malformations.
In vertebrates, the mesoderm is responsible for the differentiation of hematopoietic stem cells, which produce blood cells.
The process of myogenesis, the formation of muscle tissue, starts with the specification of mesodermal cells.
The mesoderm plays a crucial role in the immune system by generating immune cells, such as macrophages and lymphocytes.
The interaction between the mesoderm and other germ layers during organogenesis determines the final structure and function of many adult tissues.