Mesogloea is the middle layer of the body wall in Hydra, a small freshwater organism belonging to the phylum Cnidaria. It is a gelatinous substance that separates the outer epidermis from the inner gastrodermis. Mesogloea plays important roles in providing structural support and maintaining the shape of the body.

Acellular Nature of Mesogloea:
The mesogloea of Hydra is acellular, meaning it does not contain any cells. It consists of a gelatinous matrix composed of proteins, glycoproteins, and polysaccharides. This acellular nature of mesogloea is important for certain physiological processes in Hydra.

Interstitial Cells and Crossing the Mesogloea:
Interstitial cells are specialized cells found in the mesoglea of Hydra. They are capable of migrating through the mesogloea and play a role in regeneration and budding. However, the mesogloea itself acts as a barrier that interstitial cells must cross to move between the epidermis and gastrodermis or to migrate to other regions of the body.

Role of Interstitial Cells:
Interstitial cells are multipotent stem cells that have the ability to differentiate into various cell types, including nerve cells, gland cells, and reproductive cells. They contribute to the growth, development, and regeneration of Hydra. These cells are involved in a process called transdifferentiation, where they can change their cell fate and give rise to different cell types depending on the needs of the organism.

Crossing the Mesogloea:
While interstitial cells can migrate through the mesogloea, it is not an easy process. The acellular nature of the mesogloea presents a physical barrier that interstitial cells must overcome. It is thought that interstitial cells use specialized mechanisms, such as the secretion of enzymes or remodeling of the extracellular matrix, to facilitate their movement through the mesogloea. Once they have crossed the mesogloea, interstitial cells can differentiate into the necessary cell types and contribute to the growth and regeneration of Hydra.

In conclusion, the mesogloea of Hydra is acellular and acts as a barrier that interstitial cells must cross to migrate between the epidermis and gastrodermis or to reach other regions of the body. Interstitial cells are important for the growth, development, and regeneration of Hydra, and their ability to cross the mesogloea is crucial for their function.