Topic: Embryonic and fetal development of man

Target group

7th‑grade students of elementary school

Core curriculum

General requirements

IV. Reasoning and applying the acquired knowledge to solving biological problems. Student:

1) interprets information and explains causal relationships between phenomena, formulates conclusions.

Specific requirements

III. The human body.

12. Reproduction and development. Student:

4) lists the stages of prenatal human development (zygote, embryo, fetus) and explains the effect of various factors on the development of the embryo and fetus.

General aim of education

The student learns the stages of a person's life before he is born

Key competences

• communication in foreign languages;

• digital competence;

• learning to learn.

Criteria for success
The student will learn:

• characterize the development of embryonic and fetal human;

• recognize fetal membranes in the pattern and describe their functions;

• exchange maternal behaviors that have a detrimental effect on fetal development;

• explain what birth is.

Methods/techniques

• expository

  • talk.

• activating

  • discussion.

• programmed

  • with computer;

  • with e‑textbook.

• practical

  • exercices concerned.

Forms of work

• individual activity;

• activity in pairs;

• activity in groups;

• collective activity.

Teaching aids

• e‑textbook;

• notebook and crayons/felt‑tip pens;

• interactive whiteboard, tablets/computers.

Lesson plan overview

Before classes

• Students get acquainted with the content of the abstract. They prepare to work on the lesson in such a way to be able to summarize the material read in their own words and solve the tasks themselves.

Introduction

• The teacher gives the topic, the goals of the lesson in a language understandable for the student, and the criteria of success.

Realization

• The teacher presents and discusses the photo gallery. Students analyze the illustrations and answer the teacher's questions.

• The teacher divides the class into four‑person groups. Working with the expert tables method, each group develops the issue of the impact of various factors (internal and external) on the development of the fetus. As part of each expert table, one of the following topics is analyzed:

  • influence of internal factors;

  • the influence of physical factors;

  • influence of chemical factors;

  • the impact of biological factors.

  Students use selected internet sources. After completing the work in groups, a volunteer or a person indicated by the teacher makes a brief summary of this part of the lesson.

• Students carry out the interactive exercises checking the level of knowledge learned during the lesson. The teacher initiates a discussion during which the correct solutions for all the exercises performed by the students are discussed.

Summary

• The teacher briefly presents the most important issues discussed in class. He answers the additional questions of the proteges and explains all their doubts. Students complete notes.

The following terms and recordings will be used during this lesson

Terms

Texts and recordings

Embryonic and fetal development of man

Fertilization (conception) can occur when the woman is in the fertile phase. An egg cell is released from the ovarian follicle into the fallopian tube and transported by the cilia of the cells lining the tube towards the uterus. During the intercourse, the man ejaculates semen, with about 200 million sperm cells in it, into the vagina. Thanks to their tails and contractions of the uterine muscles, the sperm cells reach the oviduct in search of an egg cell. Along the way, most sperm cells die. Only a few thousand reach the female reproductive cell and only one participates in fertilization. Enzymes in the head cap of the sperm (acrosome) dissolve the ovum shell. After the penetration, the egg shell hardens, creating a barrier that is inaccessible to other sperm cells. The moment of connection of the egg cell nucleus with the nucleus of the male reproductive cell is called fertilization. In the moment of fertilization, the pregnancy begins. It normally lasts 280 days.

The development of a fertilized egg in the womb includes two phases: the embryo and the foetus. The first one lasts from the moment of conception up to the 8th week of life of the embryo. As a result of fertilization, a zygote is formed. After 24 hours it begins to divide rapidly, forming a multicellular embryo. As it keeps dividing, the embryo moves for about 5 days through the fallopian tube towards the womb (uterus). At first, the developing embryo uses the nutrients accumulated in the egg cell. When it leaves the fallopian tube, the embryo already consists of a large number of cells. In this form, around the 7th day since conception, it adheres to the vast, blood‑rich mucous membrane. Its cells gradually begin to differentiate, creating tissues and organs.

Later, the fertilized egg becomes not only of the body of the future child, but also the extraembryonic (foetal) membranes: amnion, allantois and chorion. Amnion forms a cavity directly surrounding the embryo. It is filled with amniotic fluid. It absorbs shocks and allows the embryo to move freely. Allantois collects products of the embryo’s metabolism for a part of the embryonic period. Chorion, the outermost membrane, is adjacent to the wall of the uterus. Around the 4th week, finger‑like appendages are formed that penetrate deep into the mucous membrane. This is how the placenta is formed.

The placenta participates in the exchange of respiratory gases, nutrients and metabolic waste between the mother’s blood and foetal blood. This way, the mother transfers the antibodies present in her blood to the foetus. The placenta is a protective barrier against most pathogens. However, some harmful substances can still pass through it: alcohol, drugs, nicotine and some small‑sized viruses (e.g. rubella, chickenpox, HIV). The placenta also fulfils the function of an endocrine gland, producing hormones such as progesterone and oestrogens.

At the end of the first stage of pregnancy, the embryo is about 3 cm long, weighs about 10 g, has all the organs and looks like a human. From now on, the embryo is referred to as a foetus. The foetus is connected to the placenta by the umbilical cord.

The foetus grows to about 52‑55 cm and its weight reaches about 3.5 kg. A properly developing pregnancy ends 40 weeks after fertilization with childbirth, during which the child leaves through the mother’s birth canal the vagina.

The time of pregnancy is accompanied by a series of changes in the woman’s body. During the first 3 months of pregnancy, hormonal changes cause breast enlargement and such ailments as nausea or vomiting. In the following months, the developing placenta and foetus as well as the increasing amount of the amniotic fluid cause a gradual increase in the mother’s weight and a change in the centre of mass of the body. This in turn often leads to a body posture which is unnatural to the spine, especially when standing.

To ensure a proper course of pregnancy and childbirth, it is important for the mother‑to‑be to stay physically active, as far as her condition allows (unless there are medical contraindications). Proper nutrition is essential as well. It should be adjusted to the body’s increased need for vitamins and mineral salts (mainly iron, calcium and phosphorus). A pregnant woman must at all times refrain from drug use, alcohol consumption, smoking and being in the company of smokers, taking any medicines without consulting a gynaecologist. Alcohol may cause developmental defects, mental disorders, miscarriage. Toxic substances found in smoke may cause placental vasoconstriction, which may lead to foetal hypoxia as well as heart and central nervous system defects.

Prenatal tests are used to assess foetal development. The most commonly recommended and performed test is ultrasound (ultrasonography). It is completely safe for the mother and the child. It allows to assess foetal development and detect any abnormalities. In some special cases, the doctor may order other, which often allow to discover any diseases or conditions in time. With today’s medicine, treatment is possible at a very early stage of development, including foetal surgery inside the womb.

Pregnancy ends with childbirth, which consists of three stages and on average lasts 12‑16 hours. In the first stage, uterine contractions occur with gradually increased frequency. They slowly guide the child towards the cervix. The amniotic membrane breaks and the amniotic fluid is released. During the second stage, strong contractions of uterine and abdominal muscles push the child out of the mother’s body. In the third stage of labour, the mother’s body removes the foetal membranes and the placenta.

• Fertilization occurs in the upper part of the fallopian tube, when the sperm head penetrates inside the egg cell.

• The moment of fertilization is when the period of pregnancy begins. Pregnancy covers two stages of child’s development: embryonic and foetal.

• The embryonic period lasts from the moment of fertilization up to about 8 weeks of pregnancy.

• The embryonic period is when cells are differentiated, tissues and organs are created and extraembryonic membranes and placenta are formed.

• Extraembryonic membranes: amnion, allantois and chorion provide optimal conditions for the development of the child.

• Placenta allows the exchange of substances between the mother’s and the child’s blood.

• Foetal development covers the period from the 9th week until the birth of the child.

• During the foetal period, organs form and prepare for their functions outside the mother’s body.