Why Permanent Tissues Do Not Have Cell Division?

Introduction

The human body is composed of trillions of cells, which are grouped into different tissues. Tissues are specialized structures with a unique set of functions. They are made up of two types of cells, namely permanent tissues and meristematic tissues. Permanent tissues are the ones that have reached a state where they cannot divide, while meristematic tissues can still divide and form new cells. This article aims to explain why permanent tissues do not have cell division.

What are Permanent Tissues?

Permanent tissues are the mature and differentiated cells in plants and animals that have lost their ability to divide. They are classified into three types: protective, supportive, and conductive. Protective tissues are those that protect the plant or animal from mechanical damage, injury, and infection. Supportive tissues provide structural support to the plant or animal, while conductive tissues are responsible for transporting materials such as water and nutrients.

Why Permanent Tissues Do Not Divide?

The primary reason why permanent tissues do not divide is that they have reached a stage of maturity where their ability to divide has been lost. During development, cells go through a process called differentiation, where they become specialized for a particular function.

This process involves changes in gene expression and cellular organization that lead to the formation of different types of tissues. Once a cell has reached a particular state of differentiation, it becomes irreversibly committed to its fate, and its ability to divide is lost.

The loss of the ability to divide is also due to changes in the cell cycle machinery. The cell cycle is a series of events that a cell goes through to divide and create two daughter cells.

The cell cycle machinery involves various proteins and enzymes that regulate the progression of the cell cycle. In permanent tissues, the expression of some of these proteins is altered, leading to the arrest of the cell cycle and the loss of the ability to divide.

Moreover, permanent tissues are usually post-mitotic, which means they have already gone through mitotic cell division and have become fully developed. Mitosis is the process by which a cell divides into two identical daughter cells. It is the mechanism by which growth and repair occur in the body.

During mitosis, the DNA of the cell is replicated, and the duplicated chromosomes are separated into two nuclei. The cell then divides into two, and each daughter cell receives a copy of the DNA. Once a cell has gone through mitosis, it is considered fully developed and can no longer divide.

Another reason why permanent tissues do not divide is that the process of cell division is energetically expensive. Cells need to expend a significant amount of energy to duplicate their DNA, build a new cell membrane and cytoplasm, and divide into two daughter cells.

As permanent tissues are already fully developed, there is no need for them to undergo cell division. Moreover, as these tissues have reached their functional stage, they need to maintain their structure and function, and cell division may cause damage to them.

Examples of Permanent Tissues

Epithelial Tissues

Epithelial tissues are one of the primary types of permanent tissues in the human body. They are found in the skin, lining of the organs, and other body cavities. The primary function of epithelial tissues is to provide a barrier against mechanical and chemical damage, as well as against pathogens.

The cells in epithelial tissues are tightly packed together, and they do not have intercellular spaces. This arrangement makes the tissues impermeable to most substances and helps maintain their structural integrity.

Nervous Tissues

Nervous tissues are also permanent tissues that do not divide. They are found in the brain, spinal cord, and nerves. The primary function of nervous tissues is to transmit electrical impulses between different parts of the body.

The cells in nervous tissues, called neurons, have long projections called axons and dendrites that allow them to communicate with other neurons and cells in the body. As nervous tissues are responsible for complex processes such as memory, learning, and perception, any damage to these tissues can lead to significant health problems.

Connective Tissues

Connective tissues are another type of permanent tissue found in the human body. They are responsible for providing structural support to the body, connecting different organs and tissues, and protecting the body against physical damage. Examples of connective tissues include bone, cartilage, and blood vessels. While some connective tissues, such as bone, can undergo remodeling throughout life, they do not undergo cell division once they have reached their mature state.

Conclusion

In conclusion, permanent tissues do not have cell division because they have already reached their functional and mature state, and their ability to divide has been lost. This loss of the ability to divide is due to changes in gene expression, cell cycle machinery, and the energetic cost of cell division.

Permanent tissues are crucial for the proper functioning of the body, and any damage to these tissues can lead to significant health problems. Understanding the differences between permanent and meristematic tissues is essential for understanding the different functions and properties of tissues in the body.