TOPIC 30 - connective tissues with non-differentiated intercellular substance
Connective tissue with non-differentiated intercellular substance can be found in the embryo.
Embryonic connective tissues
Mesenchymal Connective Tissue
- Found in embryo. All tissues originate from mesenchymal.
- Mesenchymal connective tissues originate from embryonic mesenchyme, a tissue developed from the middle layer (mesoderm) of the embryo.
- Mesodermal cells migrate from their site of origin in the embryo, surrounding and penetrating developing organs.
- Mesenchymal tissue consists of mesenchymal cells, fine reticular fibres and few collagen fibres in ground substance.
- Mesenchymal cells are stem cells which can develop into connective tissue. They are undifferentiated and have large nucleus, prominent nucleolus and fine chromatin.
- Spindle-shaped with two or more thin cytoplasmic processes.
- Produce all types of connective tissue proper and the specialized connective tissues bone and cartilage, the embryonic mesenchyme includes stem cells for other tissues such as blood, the vascular endothelium, and muscle.
Mucoid connective tissue
- Main component of foetal umbilical cord where it is called Wharton’s jelly- Surround the vessels of the umbilical cord
- Found in pulp of teeth, core of villus of placenta
- Abundant ground substance and rich in hyaluronic acid, chondroitin sulphate and sparse collagen fibres between cells.
- Sparse collagen fibres and scattered fibroblasts
- Among the fibroblast cells are mesenchymal stem cells
- More viscous consistency than mesenchymal connective tissue
- After fixation, some ground substance remains and is stained faintly by eosin, appears as homogenous material found near to the connective tissue cells like fibroblasts.