Man is a complex system, the individual parts of which are in constant interaction between themselves and the environment. Each organ, tissue, cell performs its strictly defined function, which makes our body as resistant to external stimuli as possible. How it became possible, how our body evolved over time to become so perfect, is studying a separate section of genetics called "morphogenetics".
What is morphogenesis?
Morphogenesis is a sequence of certain stages that an individual organ or organ system undergoes in its development. It includes two main subspecies: ontogenesis (individual development of organs and systems within one organism) and phylogenesis (evolutionary, or historical, development of systems and individual organs).
Basically, genetics takes part in the study of human morphogenesis. But there are other sciences that also contribute to the accumulation of knowledge about the development of human organs:
- molecular biology;
- physiology;
- biochemistry;
- comparative anatomy;
- paleontology;
- evolution theory.
Features and History
Ontogenesis characterizes the development of tissues, organs and systems in the embryonic period of development. In addition to the mature human body, the process of morphogenesis can also occur in cell cultures and neoplasms. This process also occurs in non-cellular forms, although they do not have an embryonic stage.
For the first time, assumptions about organ formation and how external and internal environmental conditions can affect it were made in 1952 by Alan Turing in his work entitled "The Chemical Basis of Morphogenesis." In this work, the mathematical basis for the self-organization of cells and tissues was described.
However, knowledge of morphogenesis significantly increased with the discovery of DNA and its structure, the development of sciences such as molecular biology and biochemistry. Important was the discovery of molecular mechanisms of gene work.
Main processes
In embryogenesis, that is, intrauterine development, the following main processes of morphogenesis are distinguished:
- Cell reproduction - an increase in their number, in which the set of chromosomes must be strictly distributed among subsequent cells, otherwise developmental abnormalities may occur. This is possible through two processes: crushing and mitosis.
- Determination - means that the development of each cell is predetermined. Some of them can be only sexual, others - only epithelial, others - nervous, etc.
- Differentiation - a cell becomes more specific and performs a function strictly intended for it.
- Induction - some cells are able to influence the development of others. Thus, the presence of induction is able to activate the process of differentiation due to the presence of special factors for the regulation of morphogenesis.
- Integration is the unification of structures occupying a lower niche of embryogenesis into more complex ones. For example, cells form tissue. Tissues are organs. Organs are systems.
- Adhesion - the ability of cells to form contacts for the exchange of information
- Cell migration is the ability of cells to move within an embryo.
- Apoptosis is a programmed cell death.
Main levels
Morphogenesis is a complex, high-precision system that occurs at many levels of the body. Two main levels of regulation of the development of the whole organism are conventionally distinguished:
Molecular level
Structures that have the ability to influence morphogenesis are called morphogens. They are divided into the following classes:
- Transcription factors - can interact with DNA, have the ability to regulate gene expression through catalysis, that is, the acceleration of their transcription.
- Structures capable of regulating intercellular contacts. For example, at one of the stages of intrauterine development, gastrulation, cells lose contact with each other, migrate to a new place, where they again acquire the ability to form new contacts.
Cell level
What is he like? Morphogenesis is a sequence of reactions that are impossible without the constant interaction of cells with each other. A stem cell niche is exactly that connecting link between one cell and the whole organism. There are cell types such as epithelial and mesenchymal. In the process of embryogenesis, they can pass into each other. Due to a process such as cell differentiation. Moreover, it is also possible to move them from one place in the embryo to another.
Stages of the body
The human body in its development goes through certain stages. And although morphogenesis is a mechanism that acquires the greatest importance at the stage of intrauterine development, and after birth, our organs change until death. Many pathologies of the development of organs occur precisely in the embryonic period. However, it is worth highlighting other stages of morphogenesis:
- Prenatal - the same intrauterine, from conception to childbirth. It is divided, in turn, into embryonic and fetal periods. Their terms: 8 weeks after conception and after the end of the embryonic period before childbirth, respectively.
- Perinatal - the period from 22 weeks of intrauterine development to the first 7 days of life.
- Internatal - the period of all labor activity.
- Neonatal - the first 28 days of life.
- Postnatal - 15 years after birth.
Progenesis, fetogenesis, kimatogenesis: what is it?
However, another period that began even before conception can be distinguished is progenesis. This is a stage that implies the laying of germ cells in the body of future parents. Progenesis can be called the stage of the onset of morphogenesis.
Separately, a period such as fetogenesis is also distinguished. It has two more periods:
- early fetal - from 76 to 180 days of pregnancy;
- late fetal - from 181 to 280 days of pregnancy.
Kimatogenesis, in turn, includes all of the above processes: embryogenesis, progenesis, and fetogenesis. And it is studied by a separate science, which was called "kimatology." Embryology is studying the development of the embryo and the fetus.
Phylogenesis
Such a part of morphogenesis as ontogenesis was considered in detail above. However, attention should also be paid to phylogenesis - the development of individual species in the process of evolution. As in ontogenesis, phylogenesis also has its own principles on which it is built:
- Differentiation - in the process of formation of an organism, a certain part of the cells becomes isolated, acquiring their own functions and unique structure. This collection of cells forms a separate tissue or organ.
- Integration - strengthening the bonds between individual cells and entire organ systems.
- Each organ has both a primary function and many secondary ones, which make it possible to transform and adapt to new conditions.
- The main function can either be lost or become more important depending on new conditions.
- The development of organs can be both in the direction of greater improvement and complication, that is, progression, and in the direction of simplification (regression).
- Correlation - all parts of the body are in close interconnection with each other, a change in one part of it carries with it a change in the whole organism.
Thus, morphogenesis and its biological essence are extremely complex and complex. The constant interaction of the individual stages of the individual and evolutionary development of the organism provides the opportunity for its existence in a constantly changing external environment.