Mesenchyma: what is it

The mesenchyme, or mesenchymal connective tissue, is a type of undifferentiated connective tissue. It derives mainly from the embryonic mesoderm, although it can derive from other germ layers, for example, the mesenchyme derived from the cells of the neural crest (ectoderm).

The mesenchyme is a tissue composed of loose cells embedded in a network of proteins and fluids, called the extracellular matrix. The loose and fluid nature of the mesenchyme allows its cells to migrate easily and play a crucial role in the origin and development of morphological structures during the embryonic and fetal phases of animal life. The mesenchyme directly gives rise to most of the body’s connective tissues, from bone and cartilage to the lymphatic and circulatory systems. In addition, interactions between the mesenchyme and another type of tissue, the epithelium, help form almost all organs in the body.

Although most of the mesenchyme is derived from the middle embryological germ layer, the mesoderm, the outer germ layer known as the ectoderm, also produces a small amount of mesenchyme from a specialized structure called the neural crest. The mesenchyme is generally a transitive tissue; While crucial for morphogenesis during development, little can be found in adult organisms. The exception is mesenchymal stem cells, which are found in small amounts in the bone marrow, fat, muscles, and dental pulp of milk teeth.

The mesenchyme is formed at the beginning of embryonic life. When primary germ layers develop during gastrulation, cell populations lose their adhesive properties and break off from sheets of connected cells, called epithelia.

This process, known as epithelium-mesenchymal transition, gives rise to the mesodermal layer of the embryo and occurs many times during the development of higher vertebrates. Epithelial-mesenchymal transitions play a key role in cell proliferation and tissue repair and are indicated in many pathological processes, including the development of excess fibrous connective tissue (fibrosis) and the spread of disease between organs (metastasis).

The reverse process, the mesenchymal-epithelial transition, occurs when the dissolved cells of the mesenchymedevelop adhesive properties and organize themselves into an organized sheet. This type of transition is also common during development and is involved in the formation of the kidneys.

Katherine Johnson, M.D., is a board-certified obstetrician-gynecologist with clinical expertise in general obstetrics and gynecology, family planning, women’s health, and gynecology.

She is affiliated with the Obstetrics and Gynecology division at an undisclosed healthcare institution and the online platform,

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