Module 4 Fertilization to Birth

Module 4 -From Fertilization to Birth

Introduction

When the sperm met the egg, your genetic features were established through the union of your two parental sets of DNA. DNA also directed the unicellular fertilized egg through cell divisions to become a multi-cellular organism. During this developmental period, cells responded to DNA by differentiation and specializing into tissues, organs, and systems that made up your body. Hormones regulated this development. Environmental factors could have been able to enhance, or have drastic detrimental effects, during your development. Your presence constitutes the continuation of the species and was dependent on this union of egg and sperm.

In this module you will come to understand the process of gestation. You will examine what happens to the egg after it has been fertilized, the developmental stages of the embryo and fetus, and finally how the birth process produces a new off spring.  You will exam how reproductive technologies enhance fertilization and are used in the birthing process.

In This Module

Below is a brief description of each of the lessons you will work through in this module. 

Lesson 1: Fertilization and Embryonic Development

In this lesson, you will learn to describe the process of embryonic development and name the major events and membrane formations that occur throughout embryonic development. You will learn to identify the germ layers, stating what structures arise from each layer. From this lesson, you will learn to describe the hormones related to fertilization and pregnancy. Finally you will learn to describe how twins are formed.

The following focusing questions are addressed in this lesson:

• What are the sequences of events and hormone controls that occur throughout fertilization and embryonic development?

• What major tissues and organs arise from the ecto-, meso-, and endo-derm?

• How are twins formed?

Lesson 2: Fetal Development, Trimester Events and Environmental Factors

In this lesson, you will learn to state the major events in fetal development as it relates to each of the trimesters. You will learn to describe the significance of the first trimester. You will need to identify harmful substances that are damaging for both embryonic and fetal development. You will also need to state what conditions these substances can cause for the developing offspring.

The folllowing focusing questions are addressed in this lesson:

• What are the major events for fetal development of each trimester?

• What is the significance of teratogens on embryo and fetal development?

Lesson 3: Hormones and the Birthing Process

In this lesson, you will learn to relate both the neural and hormonal changes that bring about the birthing process.

The folllowing focusing questions are addressed in this lesson:

• What triggers the birthing process, and what are the stages of this process?

• What controls lactation?

Lesson 4: Reproductive Technologies: Enhancing or Reducing Fertility, Monitoring Development and Use in Parturition

In this lesson, you will come to understand how technology can be used to enhance fertilization, monitor fetal development and assist in parturition.

The following focusing question are addressed in this lesson:

• What technologies are used to assist fertilization, to monitor development, and are used during parturition?

© iDesign/Shutterstock

Big Picture

Big Picture

In this module you will continue to help the three couples, Jane & John, Dina & Donald, and Sarah & Sam, who have come to you for help regarding their infertility problems. Further issues will come to light and decisions will need to be made by the couples in order to achieve their goal of having children.

Keep in mind, from notes that you have made from previous lessons, what you have discovered about the couples so far and what treatment options you have provided.

Essential Questions

• What are the normal and abnormal sequences of events through fertilization, implantation, and membrane formation?
• Identify and describe the effects of hormones related to fertilization and pregnancy.
• How are twins formed?
• What major tissues and organs arise from the ecto-, meso-, and endo-derm?
• How do the extra embryonic membranes facilitate the development of the embryo?
• What is the significance of the first trimester?
• What are the major events of each trimester?
• What triggers and what are the stages of the birthing process?
• What controls lactation?
• What technologies are used to assist fertilization, to monitor development and are used during parturition?

Lesson 2.4.1

Lesson 1—Fertilization and Embryonic Development

© Sebastian Kaulitzki/Shutterstock

Get Focused

All the structures and functions of the mammalian reproductive systems, including the human reproductive system, are designed to get to the end result of fertilization, implantation and development of an embryo and fetus. This results in the continuation of the species through the birth of a new offspring.

How does an offspring go from a single cell, totally dependent on its internal life in utero, to an offspring made up of billions of cells, who is able to survive independent from the mother? The processes that take place from fertilization through to the maturation of the fetus are astounding, and it all starts with two cells.

© shahar choen/Shutterstock

From previous lessons in this unit, you have gone through the structures and functions of the male and female reproductive systems and the hormones involved which cause the onset and development of these systems. In this lesson, you will go through the events that occur upon fertilization, and those that occur after fertilization, up to, and including, the development of the embryo, which lasts until the end of the eighth week.

© Christian Darkin/shutterstock

Jane and John, from the Fertility Case Study, were so thrilled when they heard the news that they were going to be parents for the first time. They were still thrilled, but a bit taken aback when they discovered they were going to have twins. Imagine how much more surprised they were when the twins were born and they had two different skin colours! The probability of this is about a million to 1.

Whether Jane and John had twins or a single child, black or white, their babies developed the same way in the uterus. An offspring’s embryonic development occurs as huge array of changes as an egg and sperm unite in fertilization to form a new individual. As the newly formed embryo goes through the different stages of its development, different names are given to its specific state of growth and maturation. Also, these various stages of prenatal development contribute to the hormonal control which sustains the pregnancy.

The development of a prenatal offspring is divided into two development periods. The first takes place from fertilization to the end of the eighth week of pregnancy. During this period the developing offspring is termed an embryo. The second development period takes place from the ninth week to birth. During this period, the developing offspring is called a fetus.

In addition to the development of the embryo, there are supporting structures which must be formed at the same time. The supporting structures are collectively termed the extra-embryonic membranes and provide the embryo, and later the fetus, with means of nutrition, respiration, excretion and protection.

At the end of embryonic development almost all of the organ systems are formed and the embryo appears human like. All of this in just two short months; no wonder pregnant woman are very tired in the first few weeks of their pregnancy. Remember that all the requirements for prenatal growth come from the mother’s body.

How did Jane and John’s pregnancy come to the formation of twins? There are two ways in which twins can be formed. In a normal sequence of events, a woman releases one egg every menstrual cycle. However, it is not uncommon for two eggs to mature and be released at about the same time in the same ovulation period. If this happens, then each egg is fertilized by two different sperm, which results in fraternal (dizygotic) twins. Fraternal twins are not identical, and may or may not be of the same sex. During pregnancy and development they each form their own supporting structures including a placenta. Jane and John had fraternal twins.

The other type of twins is referred to as identical (monozygotic) twins, as they are formed from one egg that is fertilized by one sperm. For identical twins to form, the quickly dividing fertilized cell mass separates into two separate cells. Since sex is a genetic determinate from the combining of the parental chromosomes, identical twins are of the same gender. Monozygotic twins may also develop their own separate supporting structures, or they may share them.

Complications can arise at any point along the way during prenatal development. One of the first problems that can occur is that implantation in the uterine lining does not successfully take place.  Implantation can happen in the oviducts or in other areas of the uterus. Such an event is termed an ectopic pregnancy.

For Jane and John, they were thrilled to have their first pregnancy and once they discovered they were having twins, they paid special attention to the prenatal development that would be happening to their soon to be children. During this prenatal time, they read much and discovered more about the amazing development that was taking place with their twins.

In this lesson, to understand fertilization and embryonic development, you will examine the following focusing questions:

• What are the sequences of events and hormonal controls that take place throughout fertilization and embryonic development?
• What major tissues and organs arise from the ecto-, meso-, and endo-derm?
• How are twins formed?

This lesson will take approximately 80 minutes.

Module 4: Lesson 1—Assessment

The assessment for this lesson will consist of a number of questions and a lab, which you will NOT be required to submit to your teacher.  You should however watch the tutorial video for this lesson.

Bio30 tut#2.4.1 Fertilization and development

2.4.1 page 2

Explore

Due to the many changes that are not only occurring to the embryo, but also to the supporting structures, and including  all related hormonal changes, it is recommended that you do the reading first. Try to make your own graphic organizer or notes as you are doing the readings. Once you have done the readings, you may then move on to watching the videos that have been presented for you.

Read

To understand how two gamete cells, containing half the chromosome number of the parents, can combine together and transform into an organism of millions of cells, all within the first two months of gestation, you need to better understand fertilization and embryonic development. In order to begin to understand how prenatal development occurs, read pages 506 to 519 of the textbook.

Watch and Listen

Now that you have been introduced to the concepts and terminology of embryonic development, watch the following videos to gain further understanding of this important prenatal period:

 Crash Course - Embryology
 

Lab 1: Comparing Embryonic Structures

Looking at various images, whether they be real or diagrams, will help you understand the differences between the various stages of embryonic development and the structures that support the embryo. In the following lab investigation, you will be examining microscope slides of various stages of embryonic development in a sea urchin and comparing the support structures of an embryonic chick and an embryonic human.

2.4.1 page 3

Try This

Now that you have read about and watched how the developmental stages of the embryo progress, try your hand at labeling the following images. It is recommended that you try labeling the following images without the use of your textbook.

TR 1. Fertilization

Provide labels for the structures represented by 1-12.

Inquiry into Biology (Whitby, ON: McGraw-Hill Ryerson, 2007), BLM15.1.1,Reproduced by permission.

TR 2. From Ovulation to Implantation

Label the following diagram.

Inquiry into Biology (Whitby, ON: McGraw-Hill Ryerson, 2007), BLM 15.1.2. Reproduced by permission.

TR 3. Extra-embryonic Membranes

Inquiry into Biology (Whitby, ON: McGraw-Hill Ryerson, 2007), BLM15.1.8a,Reproduced by permission.

Discuss

Through your discussion board, discussion one, some, or all of the following questions:

1. Do you think that there should be special schools for pregnant teens, or should all schools do more to try to accommodate the various needs of these teens?
2. Does an embryo have the use of all its senses in utero?
3. How can different mammalian species develop all of the same organ systems in different time periods? What regulates this process?
4. Can the fetus learn in utero? If so, what can be the extent of the learning?
5. To what extent can, or should we control and change the characters of an embryo?
6. How can the development of litters of 4 or more offspring happen?

Self Check

With the many changes and new terms presented in this section, see how well you have mastered the information by completing the following questions: 1 to 4, page 509; 5 to 9, page 511; 10 to 14, page 512; 15 to 19, page 515 and 20 to 23 from pages 517. Check the following link to see how well you answered the questions.

2.4.1 page 4

Reflect and Connect

Now that you have read and viewed the many changes that occur throughout embryonic development, complete the following items as your lesson assessment. Once all of the items are complete, submit your work to your instructor for evaluation.

1. Complete the ‘Launch Lab’ on page 507 of the textbook.
2. Complete questions 18, 20, 21, 23 to 26 from ‘Applying Concepts’ and ‘Making Connections’, questions on pages 536 and 537.
3. Complete Lab 1: ‘Comparing Embryonic Structures’.

Reflect on the Big Picture

No other human growth period shows as much change as that of embryonic development.  Understanding what is happening during pregnancy makes most expecting mothers and fathers just a little pre-occupied with their little ‘bundle’. So it was with Jane and John and their immersion into the understanding of how their twins were progressing. It took a bit more understanding to figure out how their twins could be born one white and one black.

The explanation of the twin’s skin colours comes from their parental background. John, is of mixed-race, Jamaican-English heritage, while Jane is of white Scandinavian background. John, then, has sperm that carry genes for both light and dark skin colour. They are trying for another child and are not worried as to what colour their third offspring might be.

Going Beyond

The development of the embryo is very complex and consists of much more detail than what can be presented in this lesson. Remember that all parts of the fetus have originally developed from one cell.  As cells divide and the organism grows, the cells differentiate and congregate to form all of the specialized structures of the body. If you are interested in this area, see if you can find out how specific structures such as the eyes, ears, muscles or bones are formed, just to name a few.

There are many other terms that define specific processes that are occurring during fetal development. See if you can find out what some of the following terms mean: organogenesis, neurogenesis, angiogenesis, chondrogenesis, myogenesis, osteogenesis, zygocity and ‘fourth germ layer’.

One last item that you may wish to look into is the Carnegie Stages of development. Find out how each stage is defined through the embryo’s external and internal development. Include in your research how embryonic cells communicate to each other.

Lesson Summary

Prenatal development is divided into two main periods of development. The first period takes place from fertilization to the end of the eighth week of development. This period is termed embryonic development. Other names are given to the embryo to describe the different specific stages of development of the offspring. The period that takes place from the beginning of the ninth week to birth is termed the fetal development period, and the offspring is referred to as the fetus during this time.

Once the egg and sperm have been correctly formed and been released, both must meet inside the female’s reproductive system for ‘natural’ fertilization to occur. The process of the sperm entering the egg, and the combining of 23 chromosomes from the father’s sperm and the 23 chromosomes from the mother’s egg is known as fertilization. Fertilization results in a single cell with 46 chromosomes, now called a zygote. While still in the oviduct, the zygote begins to divide through the process of cleavage, and at the 16 cell stage it is classified as a morula. The morula continues to divide and also begins to fill with fluid. The resulting structure is then called a blastocyst.

The blastocyst forms two distinct layers of cells, an outer layer called the trophoblast, which will develop into the supportive membrane structure called the chorion. The mass of inner cells of the blastocyst will form the embryo. As the blastocyst reaches the uterus, the trophoblast produces and secretes an enzyme which digests some of the endometrial tissue, enabling the blastocyst to implant itself in the uterine lining.

As implantation is being completed, the amniotic cavity develops within the amnion, a type of sac.  From the amniotic cavity, the embryonic disc forms. This disc will undergo the process of gastrulation: the formation of germ tissue layers (endoderm, mesoderm and ectoderm). The event of gastrulation gives rise to a new term for the developing offspring; it is now called a gastrula. During gastrulation a series of changes occurs where cells begin differentiating.

Tremendous growth and organ development happen in the first trimester, with 90% of all organs being formed by the end of the embryonic period. At the same time as the embryonic growth is happening, supporting structures are also developing. The allantois, amnion, chorion and yolk sac are formed to give support to the developing embryo and fetus.  Some of these structures then give rise to the placenta and umbilical cord. All of the supporting structures help to nourish, protect and remove wastes the developing offspring during prenatal development. Once the baby is born all of the supporting structures are expelled from the female’s body along with the fetus.

Lesson 2.4.2

Lesson 2—Fetal Development, Trimester Events, and Environmental Factor

Get Focused

The process of prenatal development continues after the embryonic period. In the last lesson, you saw how embryonic development progresses from a single cell to an organism of millions of cells, in less than two months. At the beginning of the ninth week of prenatal development, the embryo name is dropped, and the developing offspring is now called a fetus. As the embryo went through morphogenesis, all organ systems were formed, and now just need to mature or develop further. The placenta and umbilical cord are almost completely formed and will soon take over hormonal control of maintaining the pregnancy.

Even though prenatal development is divided into the embryonic and fetal development periods, the full pregnancy is divided into 3 trimesters; each trimester is three-months in duration. The first trimester consists of the embryonic development period and the beginning of fetal development. The first 3 months is where the most critical development is taking place, the embryonic development. As mentioned before, this is when all of the organ systems are laid down. For example, the heart begins beating, blood cells flow through blood vessels, limbs are formed, genitals are now present, and the brain, sense organs and nervous tissue is formed.

Trimesters 2 and 3 also have significant developmental events which consist of further system development and maturation. Here are just a few interesting developments that occur by the end of each of the next 6 months:

End of month 4

• Baby is developing reflexes, such as sucking and swallowing, and may begin sucking thumb in utero.
• Tooth buds are developing.
• Sweat glands are forming on palms and soles.

End of month 5

• Hair begins to grow on baby’s head
• Eyebrows, eyelids and eyelashes appear.

End of month 6

• Skin is covered with protective coating called vernix
• Baby is able to hiccup

End of month 7

• Taste buds have developed
• Fat layers are forming.

End of month 8

• Tremendous brain growth occurs at this time
• Fingernails can now extend beyond fingertips
• Most body organs are now developed, except for the lungs

End of month 9

• The lungs are mature.
• Baby is now fully developed and can survive outside the mother’s body.

Substances and circumstances can affect prenatal development at anytime. However, it is during the first trimester when the developing offspring is most vulnerable to teratogens, substances that can alter normal development. Examples of some teratogens are cigarette smoke, alcohol, drugs, x-rays and there are a host of others. In addition to harmful agents that may be transferred to the embryo and fetus, there are also substances that are essential for proper growth and development.

One couple from the fertility case study has been able to get pregnant, under your care as their fertility doctor. Although Jane and John did not have to undergo hormone or other reproductive enhancement technologies, you did inform them of how to know when ovulation was taking place to enable them to have sexual intercourse at a time when the egg was most receptive to fertilization. Jane and John have now tested positive for high hCG levels, both in a urine and blood tests. These high hormone levels confirm a positive pregnancy test. As they were with their twins, Jane and John are excited, and very interested to follow the development of their new soon-to-be-baby.

In this lesson, to understand fertilization and embryonic development, you will examine the following focusing questions:

• What are the major events of each trimester?

• What is the significance of the first trimester?

This lesson will take approximately 40 minutes.

Module 4: Lesson 2 Assignment

The assessments for this lesson are of two types, those that you can evaluate yourself and those that you will submit to your teacher.

You will complete an assignment on the genetic, hormonal and environmental effects on embryonic and fetal development for assessment. Download a copy of the  Bio30 2.4.2 Assignment to your computer now.

This assignment will be a complete and check assignment. Complete the assignment and then check your answers against the key provided. Key Link. You do NOT have to submit this assignment.

Here is a tutorial video for this lesson that you can watch if it suits your learning style.  Bio30 tut#2.4.2 Fetal Development

 ** The Self-Check and Try This questions in this lesson are not marked by the teacher; however answering these questions will help you review important information and build key concepts that may be applied in future lessons. You can respond to these mentally, write out your response, or record your answer in any other way that works for you.

2.4.2 page 2

Explore

There are two ways you can gain understanding of fetal development, by working through the next two items;

• you can do the reading first and watch the video second, 

OR

• you can watch the video first and do the reading second.

It is your choice which path you follow, but do make sure that you complete both the reading and the viewing of the video clip.

Read

Understanding the events and substances that can help or be harmful to prenatal development will be better understood once you read pages 520 to 523 of your textbook. Also, take the time to web search the words ‘fetal development’ for much more information.

Watch and Listen

View the following video clips to gain a better understanding of the events of fetal development:

Weeks 10- 14

 
Weeks 15 -20

Weeks 21 - 27

Weeks 28 - 37

Try This

TR 1.

As mentioned earlier, ensuring proper nutrition (consuming adequate nutrients, vitamins and minerals) is just as important as staying away from harmful teratogens when pregnant. Read through the Thought Lab 15.1: Folic Acid and Neural Tube Defects, on page 524 of your textbook. Answer the Analysis questions and then click here to see how well you understand the importance of the need for folic acid.

TR 2.

See how well you know the major events of prenatal development by dragging the significant developmental event into the appropriate month of pregnancy.

Discuss

Through your discussion board, discuss one, some, or all of the following questions:

1. Why are most women who wish to become pregnant informed to take a prenatal vitamin supplement?
2. There are many teenage pregnancies every year in Canada. Do you see a possible problem with some teenage dietary habits and teenage pregnancy?
3. Can you think of any everyday household substances that pregnant mothers should stay away from?
4. Why should pregnant women NOT change cat litter boxes for cats that live in and outdoors?

Self-Check

See how well you understand fetal development by answering questions 24 to 26 on page 520 and questions 27 & 28 on page 523. Check your answers here.

2.4.2 page 3

Reflect on the Big Picture

It is an awesome and exciting path to be on when a couple wanting children discovers they are pregnant. However, many expecting couples choose to wait until the pregnancy is at least three months along, the end of the first trimester, before they announce the news. This also corresponds to the completion of embryonic development and the first months of fetal development.

Most miscarriages happen within the first 13 weeks of a pregnancy, and most of these miscarriages are lost due to chromosomal abnormalities, which prevent normal embryonic and fetal development. Therefore, many couples wait to inform their friends and family they are pregnant until this time period has passed. This saves the discomfort of answering the many questions of “how is the pregnancy going” when the baby is lost.

Jane and John had their pregnancy confirmed and were also able to get past the first 13 weeks with no complications. Since Jane and John knew that they wanted to conceive, Jane was watching her nutritional requirements and her exposure to any harmful substances. They are thrilled to be able to add to their family and follow their baby’s fetal development.

Going Beyond

There are so many complications that can affect prenatal development. One of the most common developmental problems is premature birth, in which fetal development does not come to full term. Research premature birth to answer some or all of the questions presented below.

1. How small can a baby be and still survive outside the womb?
2. What are some of the complications for babies that are born early?
3. How are premies cared for immediately following birth, and then a few weeks after birth?
4. What is ‘kangaroo care’ for premies?
5. Are there any residual complications to premature birth that can carry over into later childhood or adulthood?

Module 4: Lesson 2 Assignment

Submit your Module 4: Lesson 2 Assignment to your teacher.

Lesson Summary

Prenatal development is divided into three trimesters and two development periods. Embryonic development begins at fertilization and ends after about the eighth week of pregnancy. Fetal development begins at the ninth week and continues until birth. Both embryonic and fetal development occur within the first trimester. The first trimester is the time when developing embryo and fetus is most vulnerable to improper nutritional requirements and exposure to harmful teratogenic agents, as this is the time when the most sensitive embryonic development is taking place. The fetal period consists of significant development events that are related to the progressing months of pregnancy. Most of the time spent in the fetal period results in further development of the organ systems. The understanding of the ‘significant developmental events’ during pregnancy helps doctors and parents to follow the development of maturing fetus to term.

Refer to Table 15.2 on page 521 of the textbook for a review of the major events, by month, in prenatal development.

Lesson 2.4.3

Lesson 3—Hormones and the Birthing Process

Get Focused

Birth is an incredible event. Although birth is not the beginning of your life’s story, it is certainly one of the most important moments in your life. What is your birth story? Do you know what happened around the time of your birth? Was there a birth plan for your delivery? If not, make sure you ask someone who knows how you were born, what your ‘birth’ day was like and the events surrounding this special moment in your life.

Today women have many choices on how to deliver their baby. Birth with a midwife at home, birth with a midwife at a birthing center, birth in a hospital, birthing into water, and many more options are all possibilities when delivering a baby today. No matter what a woman’s birth plan choice is, once the birthing process begins, there is no going back.

Continuation of the species, in humans, occurs at approximately 266 days, at which time gestation ends with the birth of the fetus. For Jane, a few days before her baby was ready to enter the outside world, she felt a sensation that the baby was settling deeper into her pelvis. This sensation is commonly called lightening.

Parturition, or labour (terms given to the birthing process) is divided into 3 stages: the dilation stage, the expulsion stage, and the placental stage. Jane was said to be ‘in labour’ when her cervix was dilated to about 3 cm in diameter, and her uterine contractions lasted for 40 seconds and occurred every 15 to 20 minutes.

© Vivid Pixels/Shutterstock

Jane’s labour was controlled by both nerves and hormones, through a positive feedback system. The dilation stage of parturition began as the cervix shortened, contracting up into the uterus. This event helped release the hormone oxytocin from the pituitary’s posterior lobe. The release of oxytocin caused uterine contractions to continue pushing the fetus down toward the cervix.  The cervix continued to stretch, which positively fed back to the posterior pituitary to continue the release of oxytocin.  Her uterine contractions also stimulated the release of prostaglandins, which were also stimulated by positive feedback.

The expulsion stage of parturition consists of the delivery of the fetus. This is the stage in which Jane and John’s baby was actually ‘born’. For this to happen, their baby’s head had to rotate as it moved into the birth canal. Once the head and shoulders of the baby were out of the birth canal, the rest of the body delivered quickly. Soon after delivery, John was able to cut the umbilical cord.  

There are many reasons that a normal vaginal birth may not be possible. When this happens doctors have to resort to a Cesarean section. A C-section, as it is sometimes called, consists of a surgical procedure where an incision is made in the mother’s lower abdomen through to her uterus.

In the placental stage, which in most cases happens within 30 minutes after the baby is delivered, the placenta disengages from the uterus and is expelled from the body. Jane was encouraged to breast-feed as soon after delivery as possible, as this helps shrink the uterus so there is less blood loss.

Lactation, or breast-feeding, occurs when estrogen and progesterone production is suppressed and the anterior pituitary secretes the hormone prolactin. Breast milk production is stimulated by the suckling of the new baby, through nerve endings in the nipple. Nervous stimulation causes oxytocin to be secreted, which acts to cause contractions in the breasts. For the first few days of breast-feeding, Jane produced colostrums, a yellowish liquid that contains antibodies and more protein than breast milk.

Jane and John have had a successful pregnancy and delivery, and now have a brand new healthy baby that has joined their family. To you, their fertility doctor, they are very thankful!

The following focusing questions are addressed in this lesson:

• What triggers the birthing process, and what are the stages of the birthing process?
• What controls lactation?

Module 4: Lesson 3 Assignment

 Once you have completed all of the learning activities for this lesson, complete the online assignment.

Bio30 2.4.3 online assignment

Here is a tutorial video for this lesson that you can watch if it suits your learning style. Bio30 tut#2.4.3 Birth and Lactation

** The Self-Check and Try This questions in this lesson are not marked by the teacher; however answering these questions will help you review important information and build key concepts that may be applied in future lessons. You can respond to these mentally, write out your response, or record your answer in any other way that works for you.

2.4.3 page 2

Explore

Understanding the events of parturition can be gained by doing the following reading and by watching the following video clip. You may choose in which order you would like to begin learning about labour and lactation.

Read

Learn how the stages of parturition and lactation progress by reading textbook pages 523 to 526. 

Watch and Listen

While viewing the following video clip, pay particular attention to the roles of nerve stimulation and hormone control on both parturition and lactation. It is recommended that you take notes while viewing of this video. 

Parturition

Try This

TR 1. Try your hand at labeling the following hormonal control flow chart of the positive feedback mechanism that directs parturition.

Positive Feedback Mechanisms Controlling Parturition

Inquiry into Biology (Whitby, ON: McGraw-Hill Ryerson, 2007), BLM15.2.3,Reproduced by permission.

TR 2. Label the following diagram.

Milk Production and Secretion

Inquiry into Biology (Whitby, ON: McGraw-Hill Ryerson, 2007), BLM15.2.6,Reproduced by permission.

Check your work.

Discuss

Through your discussion board, discuss one, some, or all of the following questions:

1. Why do many women choose to give birth in water?
2. How do you feel about men becoming impregnated (yes, it is happening)?
3. How would a man deliver a baby?
4. What is a ‘wet nurse’ and why were they used?
5. With present technology, all parts of conception and birthing of an offspring can be controlled.  What extent of control do you believe people should have over this process?

Self Check

Did you know that the greatest number of children born to one Woman is 69? In the 1700's a Woman from Russia had 16 sets of twins, 7 sets of triplets, and 4 sets of quadruplets!

Check your understanding of parturition and lactation by completing questions 29 to 32 on page 526.

2.4.3 page 3

Reflect and Connect

Did you find out your birth story? Hopefully, you were able to gain an understanding of the events surrounding your birth. Jamie Lee Curtis, the actress, had a ritual of having her mother tell her the story of her birth every year on her birthday. Young children love hearing over and over about how they were born. The events of yours or anyone’s birth story are memories that most people want to keep, and some even video tape the process.

Going Beyond

With every birth there is a possibility of conditions arising that are not typical; that is to say that there is always a chance that the birthing process will not go exactly according to the ‘plan’. See what you  can find out about what some of the following terms or phrases mean in relation to childbirth:

1. Effacement
2. Mucus plug
3. Braxton Hicks contractions
4. Latent phase
5. Malpresentation of the fetal head
6. Being born in the caul
7. Epidural
8. Breech
9. Episiotomy
10. Apgar score

Research how various Aboriginal cultures dealt with childbirth.

Lesson Summary

Parturition, or labour, is divided into three stages, although the events are a continuous process.  Labour is separated into the dilation stage (uterine contractions begin), the expulsion stage (delivery of the fetus), and the placental stage (the discharge of the placenta). 

Labour is initiated and sustained through nervous and hormonal control. Oxytocin and prostaglandin stimulation works through a positive feedback mechanism to promote further uterine contractions.  Uterine contractions force the fetus down to the cervix, and out through the birth canal. They also cause the placenta to be expelled from the body after birth. If a normal vaginal birth is not possible, it is common for delivery of the fetus to occur through a Cesarean section (C-section).

Once the fetus is delivered, it can no longer rely on its mother for air, food or the elimination of its own wastes. All of the baby’s body systems that perform these functions now begin working independently of the mother’s support. For the infant to acquire nutrition it needs to begin to breast-feed or suckle.  The hormone prolactin causes the production of breast milk, and the release of oxytocin, along with the suckling stimulation, causes the mammary glands to secrete breast milk.

The desired end result of this reproductive process filled with development and change is the glowing face of a healthy newborn baby.

Lesson 2.4.4

Lesson 4—Reproductive Technologies: Enhancing or Reducing Fertility, Monitoring Development and Use in Parturition

Get Focused

Humans have been trying to control their reproductive potential for thousands of years. Some of the earliest known reproductive technologies were contraceptive practices dating back to 1550 BC. “According to an ancient medical manuscript called the Ebers Papyrus (1550 BC), women were advised to grind together dates, acacia (a tree bark), and a touch of honey into a moist paste, dip seed wool into the sweet gel and place it in the vulva. As primitive as this sugary mix appears, it was usually effective. Acacia eventually ferments into lactic acid, a well known spermicide.” This quote, along with a host of additional contraceptive information and displays, are at ‘The History of Contraception Museum’, just outside of Toronto, Canada. The museum, which is world renowned and one of a kind, boasts to have over 600 different forms of contraceptives.

Reproductive technology now includes much more than just contraceptives. In this lesson, reproductive technologies are divided into three broad groups: enhancing or reducing fertility, monitoring development, and use in parturition. Far more technologies are available to study than could be dealt with in this lesson or course alone.

It seems that as humans we are quite concerned as to the right timing of fertility. The possibility of having an offspring when an individual is not ready has also driven much research into reducing reproductive potential. In fact, as mentioned above, some of the oldest research is in controlling reproductive potential.

Some of the technologies that reduce reproductive potential are abstinence, tubal ligation, vasectomy, physical and chemical barriers, and natural family planning. Contraceptive hormone treatment, another variety of technology that reduces the possibility of conception, was used by Sarah, when she went on the ‘pill’, and then again when both she and Sam were placed on the hormone ‘Clomid’.

Technologies that enhance reproductive potential are some of the most advanced of all the assisted reproductive technologies used. As sterility or infertility can happen for a wide range of reasons, and the desire for couples and individuals to have children is so strong, much research and advancement has gone into creating fertility enhancing technologies. Some technologies such as artificial insemination, in vitro fertilization, surrogate mothers, ovulation test kits, and superovulation all assist in trying to bring forth a new offspring.

Before conception, technologies such as at-home fertility test kits may help a couple determine their reproductive potential, and determine the optimal time to try conceiving. Another of the first technologies used is a take-home pregnancy test that test pregnancy hormone levels in a woman’s urine; these can be purchase in most local drug stores. More formal urine and blood tests done through a medical laboratory should follow in order to confirm fertilization, as did Jane and John.

Once conception has successfully occurred, other technologies are needed to monitor the events of embryonic and fetal development. After fertilization has been established, there are many technologies that can be used to monitor the development of the embryo and fetus. The following tests are used to monitor the development: Ultrasonography (including regular ultrasound, 3D and 4D ultrasound) are, and have been widely used for over 50 years to monitor embryonic and fetal development. Fetal surgery is a last resort option technology used to treat certain life-threatening congenital abnormalities. Other technologies that can be used to understand genetic conditions of the fetus are cordiocentesis (fetal blood sampling), amniocentesis, and chorionic villi sampling. The last two technologies will both be discussed further in Unit C.

Finally, reproductive technologies that will also be examined are those that can be used in parturition. One such technology has already been discussed, that of a C-section childbirth. When it is time to deliver the baby, various technologies are used to assist with the birthing process. These include induction medication (oxytocin drip), fetal heart monitor, epidural, episiotomy, forceps, and suction, among others.

Needed shortly after childbirth, another reproductive technology that is often used was addressed in Biology 20. In the study of the Rh System is the use of an anti-Rh antibody that is given to a mother within 72 hours of after childbirth if she was Rh- and the fetus being born was Rh+. “The anti-Rh antibodies in the injection attack any of the baby’s red blood cells in the mother’s blood before these cells can stimulate her immune system to produce her own antibodies. This procedure will not help if the woman has already begun to produce antibodies. Thus, the timing of the injection is crucial.”

Turn to page 297 of your textbook and examine Figure 8.31.

The Fertility Case Study couples had to use a number of the reproductive technologies mentioned above. As the fertility doctor for the remaining two couples, Sarah and Sam, and Don and Dina, who have not been successful in having a positive fertilization test, you now need to discuss with your patients their options to having the family they so desire.

This lesson will take approximately 80 minutes.

Module 4: Lesson 4 Assignment

There is no assignment for this lesson. The information from this lesson will be assessed in your module assessment.

Here is a tutorial video for this lesson that you can watch if it suits your learning style. Bio30 tut#2.4.4 Medical Use of Hormones

** The Self-Check and Try This questions in this lesson are not marked by the teacher; however answering these questions will help you review important information and build key concepts that may be applied in future lessons. You can respond to these mentally, write out your response, or record your answer in any other way that works for you.

2.4.4 page 2

Explore

There are a multitude of reproductive technologies to be explored. To further understand these technologies, start by doing the readings and viewings presented below. You may choose the order in which to begin your study of reproductive technologies.

Read

Not all of the reproductive technologies mentioned above in the ‘Get Focused’ section are discussed in the textbook. However, you may begin to understand many of the reproductive technologies by reading pages 529-534 of your textbook. You may also want to read the short section on the diagnosis of genetic disorders in the fetus, from pages 658 to 659.

After doing the readings mentioned above, try doing some web researching to gain a better understanding of some of the other reproductive technologies. 

Try This

TR 1.

Work by yourself, or in a group, to complete Thought Lab 15.2: Evaluating Reproductive Technologies: Safety and Effectiveness on page 533 of your textbook.

Through your discussion group, consult with other groups, to exchange information and summarize findings for all the technologies investigated.

Discuss

Through your discussion board, discuss one, some, or all of the following questions:

1. What is your opinion on the use of technology to help mother and child bond?
2. How do you think North American society has been affected by the use of reproductive technologies?
3. A 3D ultrasound produces a three-dimensional image of the fetus, generally in a still picture format. A 4D ultrasound is like viewing a video tape of the fetus inside the womb. Do you think that a mother would be more inclined to practice a healthy life style if she could view her baby in a 4D ultrasound?
4. Can you think of a new or different type of reproductive technology that could improve any component of human reproduction?
5. How do you feel about the cost to society caused by single parents needing social support to raise their children?
6. If health care plans compensate for erectile dysfunction medication should they also help compensate couples for costs related to adoption, and IVF?

Self-Check

See how well you understand reproductive technologies by completing questions 33 to 36 on pages 530 and 532 of the textbook.

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Reflect and Connect

The opinions surrounding reproductive technologies are, as with most things in life, based on individuals’ experiences and exposures to the issue in question. In North America, there have been no restraints placed on families as to the number of children one family can have. In 1979, China implemented a ‘one child policy’, to deal with the countries growing population. Chinese families were expected to have only one child, which the government believed would alleviate social and environmental problems. The Chinese government reviewed this policy in February of 2008, at which time it was decided to maintain the implementation of the ‘one child policy’ for another ten years.

Write a reflection of how this policy would impact your family (present and future) and our society if it were implemented in Alberta. How would this policy be enforced or adhered to? What are the reproductive technology implications that would result from such a policy? Should families be taxed based on the number of children they have? This would be based on the assumption that the impact of a family with more children would be greater on society and the environment than a family with fewer children?

Going Beyond

Reproductive technologies always bring with them controversy; ethical and moral issues that present pros and cons to their use. What do you believe are the ethical and moral issues on the use of reproductive technologies? What have governments done in Canada to deal with the concerns of the use of reproductive technologies? First, see if you can find any government legislation or policies, in Canada or any other country, that deal with the use of reproductive technologies. Then do a comparison of those that you find.

Lesson Summary

Throughout history, humans have been trying to control their reproductive potential. Reproductive technologies first began as attempts to prevent pregnancy, and have now evolved into extremely advanced reproductive enhancement and reduction prevention techniques. Reproductive technologies have also advanced to allow the monitoring of embryonic and fetal development, and scientists and doctors have even developed the technology and skill to enable them to successfully complete fetal surgery.

Developed countries are fortunate to have continued the advancement and use of technologies to include those that assist in parturition. However, in developing countries the advances in technology have not been seen. The International Development Committee said, “One in seven women in Niger dies in childbirth, compared to one in 8,200 in Britain.” These figures do not take into account the number of fetal deaths.

The development and use of, and often the need for reproductive technologies have come a long way. However, whether it is a question of equal access to safe childbirth or other issues, there will always be an ethical and moral debate on the practice and use of reproductive technologies.

Module Summary and Assessment

Module Summary

From the moment of fertilization through to embryonic and fetal development, an amazing array of transformation occurs in a prenatal organism. The speed at which the changes take place, taking us from a single celled organism to a multi-cellular organism that is capable of surviving on its own, is truly incredible. Once fertilization takes place, the development of the embryo begins. Different layers begin to form, with each of these layers giving rise to more specialized types of tissues and functions.  Various membranes support the embryo and help form the placenta, which nourishes and supports the fetus. 

The development and sustainment of the offspring in utero is controlled by hormones produced by various supporting structures. Once all the major organs and systems are in place, a tremendous amount of growth and maturation of the systems happens. During any time of prenatal development, genetic, hormonal, and environmental factors can affect the developing offspring. However, it is the first three months of development that are the most critical. 

Hormones bring on the birthing process, resulting in the forceful uterine contractions that expel the fetus and placenta. Once birth has occurred hormones trigger lactation, or the delivery of the milk from the mammary glands. 

A myriad of technologies have been developed to control human sexual reproduction. There are technologies that can enhance or reduce reproduction potential, monitor development, and assist in the birthing process. Whatever the use of reproductive technology, it brings with it much controversy on social and ethical issues. 

Module & Unit Assessment

You should have completed the following assignments.

Bio30 2.4.2 assignment

Bio30 2.4.3 online assignment

 You can now also complete the following quiz and exam. The quiz is optional and can be used to help you review what you've learned in this module. 

Unit B quiz

Unit B  reproduction exam  

Unit 2 Conclusion

In Unit 2 of Biology 30 you studied the human reproductive system as a representative mammalian system responsible for reproducing the organism and carrying on the species.

Specifically you looked at

• explaining how species survival is ensured through reproduction
• identifying and describing the structures and functions of the human reproductive systems
• explaining how human reproduction is regulated by chemical control
• describing how cell differentiation and development are influenced by genetic, endocrine, and environmental factors
• analyzing how sexually transmitted infections and reproductive technologies can prevent or enhance fertility

You learned about the structures and the functions associated with human reproduction and the hormones that regulate reproduction and development, and establish homeostasis. You also studied how environmental factors have an influence on embryonic and fetal development and examined various types of reproductive technologies. You used your understanding of the nervous system and endocrine systems to further explore how they contribute to maintaining equilibrium within the reproductive system.

In Module 3: Section 1 you studied the structures of the male and female reproductive systems: how they function, and how they can be adversely affected by STIs (sexually transmitted infections). In Module 3: Section 2 your learned how hormones in the male and female maintain homeostasis of reproduction. Module 4 focused on the development of offspring from fertilization to birth, how cells differentiate to perform certain functions, and how development is regulated by genetic, endocrine, and environmental factors. Together, these modules helped you see how humans have managed to sustain their existence and increase their population on a planet that is constantly changing.