Question

What are the three main tissue layers of flatworms?

1) Ectoderm, Mesoderm, Endoderm
2) Epidermis, Dermis, Hypodermis
3) Muscle, Nerve, Connective
4) Epithelial, Connective, Nervous

Answer 1

Flatworms have three main tissue layers: ectoderm, mesoderm, and endoderm. The ectoderm gives rise to epidermal tissues, the endoderm forms the lining of the digestive system, and the mesoderm gives rise to other internal tissues. The mesodermal layer is a solid mass between the outer epidermal surface and the digestive system cavity. Option 3.

Step-by-step explanation:

Flatworms have three embryonic tissue layers that give rise to epidermal tissues (from ectoderm), the lining of the digestive system (from endoderm), and other internal tissues (from mesoderm). The epidermal tissue is a single layer of cells or a layer of fused cells (syncytium) that covers two layers of muscle, one circular and the other longitudinal. The mesodermal tissues include mesenchymal cells that contain collagen and support secretory cells that produce mucus and other materials at the surface. Because flatworms are acoelomates, the mesodermal layer forms a solid mass between the outer epidermal surface and the cavity of the digestive system.