Lecture 6. The development of the child in utero. Child development in the embryonic period. Late fetal period. Intrapartum period (labor).
Objective: familiarization with the classification of the ontogenetic development of children.
1. The development of the child in utero.
2. Child development in the embryonic period. Late fetal period.
3. Intrapartum period (labor).
Germ cells, formed by the merger of the maternal egg and sperm, is divided into two, and then the cells become four, then eight, and so on. That is, it is the process of dividing.
By the third day after fertilization, a dense ball, consisting of about sixteen cells. In appearance it resembles a raspberry or blackberry.
By the fourth day in a molecule forms a cavity containing liquid. Some cells give rise to the placenta and other tissues, protect and support the fruit, while others - the tissues of the embryo.
By the sixth day of the embryo is introduced into the uterine lining - the endometrium.
Starting the embryonic period. Although the germinal vesicle very tiny, he had already composed of hundreds of cells.
The most incredible thing - the fact that the same type of cells to know what to do next, and soon they will be very different from each other. germ cells will be divided into three layers:
The outer layer forms the skin, nervous system, mucous membranes, mouth and anus. The intermediate layer gives rise to muscle, bone, cardiovascular system, reproductive system, circulatory system.
The inner layer forms the digestive tract, respiratory and urinary systems.
On the other side of the embryo, which later will be back, the spinal cord is formed.
This is a sensitive period for the formation of fetal organs, when adverse factors (alcohol, smoking, drugs and infections) can cause irreparable harm to the fetus.
The development of organs and systems goes in the direction of "head to tail". The bodies are formed simultaneously with the tissues of their constituents.
With 20-21 days of the embryo's body stands apart from the extraembryonic organs formed by a trunk crease, which is the 20th day quite clearly expressed.
It begins development of the placenta.
By the 4th week of the embryo, which until then was a flat disc begins to take a cylindrical shape.
It marks the first reduction in heart, and it begins to participate in the circulation.
Earlier this week, at the front end of the embryo is formed invagination - oral fossa. At this point, it has already formed the primary gut-like tube.
At the opposite end of the body is formed anal fossa.
Begins to form liver, pancreas and spleen.
Lays the cartilage of the larynx, trachea and both lungs.
Develops the thyroid gland.
By the end of the 4th week of the fruit is covered with a thin layer of skin.
Its size - less than 3 mm: future baby very tiny and maybe you have no idea about its existence. However, it has increased at 10 000 times compared to the first week!
The formation of tissues and organs. Formed at the end of stage three germ layers give rise to all organs and tissues of the body of the future. Starting next embryonic stage of development. From the ectoderm develops: the nervous system; leather; nails and hair; sebaceous and sweat glands; senses. The endoderm gives rise to the following systems: digestive; breathing; of the urinary; liver and pancreas. Most derivatives gives the third embryonic leaf - mesoderm, is formed from it: the skeletal muscles; gonads and most of the excretory system; cartilage; circulatory system; connective tissue; adrenal glands and gonads. After the formation of tissue begins next embryonic period of ontogeny - forming organs.
Two phases can be distinguished. Neurulation. Formed a set of axial organs, which includes the neural tube, notochord and intestine. Construction of other organs. Certain areas of the body acquire their characteristic shapes and outlines. Fully organogenesis ends when the embryonic period is coming to an end. It is worth noting that the development and differentiation continue after birth. Control of all stages of embryonic development, embryonic period, based on the realization of genetic information, obtained from the parents. The success and quality of implementation depends on the influence of external and internal factors. Driving developmental process consists of several stages. Genes of all the information obtained from the neighboring cells, hormones and other factors in order to arrive in an active state. Information from the genes for the synthesis of proteins at the stages of transcription and translation. Information from the protein molecules to stimulate the formation of organs and tissues. Immediately after the egg with the sperm fusion begins the first period of the embryonic development of an organism - crushing, which is fully regulated by the information that is in the egg. At the blastula stage activation occurs sperm genes, and gastrulation controlled genetic information of germ cells. Formation of tissues and organs occurs due to the information contained in the cells of the embryo. It begins the separation of stem cells, which give rise to various tissues and organs. Formation of the external signs of the body in human embryonic period depends not only on genetic information, but also from the influence of external factors.
Factors affecting embryonic development of all impacts that may affect the child's development can be divided into two groups: environmental factors; disease and the way my mother lives. The first group of factors can include the following. Radioactive radiation. If such an impact occurred in the first stage of the embryonic period, when there was not yet implanted, it is most often a spontaneous miscarriage. Electromagnetic radiation. Perhaps such an impact in finding work near electrical appliances. Exposure to chemicals here include benzene, fertilizers, dyes, chemotherapy.
Mom can also cause disturbances of embryonic development are the following hazards:
- chromosome and genetic diseases;
- using drugs, alcoholic beverages, considered vulnerable to any of the stages of fetal life;
- infectious mothers disease during pregnancy, such as rubella, syphilis, influenza, herpes;
- heart failure, asthma, obesity - in these diseases may impair oxygen delivery to the tissues of the embryo; taking medicines; especially the embryonic period is such that the most dangerous in this respect are the first 12 weeks of development;
- excessive passion synthetic vitamin preparations.
Diseases of the fetus during the latter stages of embryonic development In the last weeks of ripening occurs to vital organs of the child and prepare to endure all kinds of violations that may occur during childbirth. Before the birth of the fetus in the body creates a high level of passive immunization. At this stage, as are various diseases which can receive the fruit. The lack of oxygen due to the pathology of the placenta or umbilical cord. Infections can trigger fetal disease. Exposure to radiation. The toxic effects. Mother Injuries affecting the child. Malnutrition expectant mother, this may lead to a breach of the subcutaneous tissue.
Hazardous periods of embryonic development.
Throughout embryonic development periods can be distinguished, which are considered the most dangerous and vulnerable, because at this time there is a formation of the vital organs.
2-11 weeks, since the brain is formed.
3-7 weeks - is laying eyes and heart.
3-8 weeks - is the formation of limbs.
Week 9 - laid belly.
4-12 weeks - is the formation of sex organs.
Week 10-12 - sky tab.
consideration of the characteristics of the embryonic period once again confirms that the development of the fetus are considered to be the most dangerous periods of 10 days and up to 12 weeks. It was at this time is the formation of all major organs of the body of the future.
Factors affecting embryonic development
Diseases of the fetus during the latter stages of embryonic development
Hazardous periods of embryonic development
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