1. Notochordal Cells: In the early stages of bat development, the notochord is composed of notochordal cells that are large, vacuolated, and arranged in a single file. These cells contribute to the formation of the axial skeleton and provide structural support.
2. Segmentation: As development progresses, the notochord becomes segmented, resembling a series of discs or segments. These segments are known as "notochordal segments" or "vertebral bodies."
3. Formation of Vertebrae: The notochord plays a crucial role in the formation of the vertebrae, which are the bones that make up the spinal column. The notochordal segments serve as templates for the development of the vertebral bodies. As the embryo develops, the surrounding tissues, such as the neural tube and somites, interact with the notochord to give rise to the vertebrae.
4. Regression and Intervertebral Discs: As the vertebral column develops, the notochord begins to regress or degenerate. However, remnants of the notochord persist between adjacent vertebrae, forming the intervertebral discs. These discs act as cushions and shock absorbers between the vertebrae, allowing for flexibility and mobility of the spine.
5. Notochordal Remnants: Traces of the notochord may remain within the intervertebral discs throughout the life of the bat. These remnants are known as the "notochordal nucleus" or "nucleus pulposus."
Overall, the notochord plays a vital role in the early development of the bat's axial skeleton, providing a scaffold for the formation of the vertebrae and intervertebral discs. While it mostly regresses during development, its remnants contribute to the structure and function of the bat's spine.