Origine and further development of mesenchyme
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Origin and Further Development of Mesenchyme[edit | edit source]
Introduction[edit | edit source]
Mesenchyme is a loosely organized tissue composed of undifferentiated, motile cells embedded in an extracellular matrix (ECM).
It plays a central role in organ formation, contributing to connective tissue, cartilage, bone, muscle, and parts of the vascular system.
Some mesenchymal cells can arise through epithelial–mesenchymal transition (EMT), where epithelial cells acquire migratory properties, but the majority of mesenchyme originates directly from mesoderm or neural crest cells.
Embryological Origin[edit | edit source]
Mesodermal Mesenchyme[edit | edit source]
- Paraxial mesoderm → somites → skeletal muscle, dermis, vertebrae
- Lateral plate mesoderm → limb skeleton, connective tissue, heart and blood vessels
- Intermediate mesoderm → urogenital system
Mesoderm is the major source of mesenchyme throughout the embryo
Neural Crest-Derived Mesenchyme[edit | edit source]
- Neural crest cells, arising from the dorsal neural tube, migrate extensively and differentiate into:
- Craniofacial cartilage and bones
- Peripheral neurons and glial cells
- Melanocytes and some connective tissue
Endodermal Contribution[edit | edit source]
- Certain organs, such as the liver and pancreas, have mesenchyme derived from the endodermal epithelium.
Role of EMT[edit | edit source]
- During gastrulation and neural crest migration, some epithelial cells lose polarity and become mesenchymal.
- This process, called epithelial–mesenchymal transition (EMT), contributes partially to the pool of mesenchymal cells.
- EMT is a minor pathway in the overall formation of mesenchyme but is important in specific developmental events.
Histological Features of Mesenchyme[edit | edit source]
- Cell shape: spindle-shaped or stellate, loosely arranged
- Cytoplasm: rich in vimentin filaments
- Nucleus: large, euchromatic, prominent nucleoli
- Extracellular matrix (ECM): abundant glycosaminoglycans and proteoglycans, few fibers initially
- Vascularization: sparse at first, increasing as differentiation progresses
Note: Mesenchymal cells are highly motile compared to epithelial cells, facilitating migration during organogenesis.
Differentiation of Mesenchyme[edit | edit source]
Mesenchyme gives rise to multiple tissues and organs:
Connective Tissue[edit | edit source]
- Fibroblasts → produce collagen and ECM
- Adipocytes → lipid storage cells
Cartilage and Bone[edit | edit source]
- Chondrogenesis → cartilage
- Osteogenesis → bone
- Differentiation occurs via intramembranous or endochondral ossification
Muscle[edit | edit source]
- Skeletal muscle → from somite-derived mesenchyme
- Smooth muscle → from mesoderm of organs and blood vessels
Vascular System[edit | edit source]
- Angioblasts → endothelial cells
- Hemangioblasts → blood cells
- Pericytes → support vascular stability
Other Derivatives[edit | edit source]
- Tendons and ligaments
- Part of the heart and urogenital stroma
conclusion[edit | edit source]
Mesenchyme is a multipotent, loosely organized tissue essential for organogenesis.
Most mesenchyme is mesoderm- or neural crest-derived, with a minor contribution from EMT of epithelial cells.
It differentiates into connective tissue, cartilage, bone, muscle, and components of the vascular system, forming the structural framework of virtually all organs.
Sources[edit | edit source]
- Sadler, T. W. Langman’s Medical Embryology, 14th edition
- Junqueira, L. C., Carneiro, J. Basic Histology: Text and Atlas, 15th edition
- slides from MUDr. Adriana Hermanová
