Development: Regardless of where the development takes place, the developing embryo has certain needs that must be met for survival

•nourishment•proper temp•oxygen•protection•means of getting rid of wastes

Pregnancy, or gestation

Pregnancy and Early Development

– Is the carrying of developing young within the female reproductive tract

– Is measured as 40 weeks from the start of the last menstrual cycle in humans

• Gestation is pregnancy– It begins at conception and continues until birth– Human gestation is 9 months– Mouse gestation is 1 month– Elephant gestation is 22 months

• Structures develop that assist the developing embryo

– The amnion, a fluid filled sac that encloses and protects the embryo

– The yolk sac, which produces the embryo’s first blood and germ cells

– The allantois, which forms part of the umbilical cord

– The chorion, which becomes part of the placenta

The Placentaoxygenated blood from mother’s artery

villus

umbilical vein

umbilical artery

deoxygenated blood to mother’s vein

• The placenta allows for a variety of substances to pass from mother to fetus

– Nutrients– Waste– Gas (oxygen & carbon dioxide)– Protective antibodies – German measles virus– HIV– Drugs (prescription and nonprescription)– Alcohol– Chemicals in tobacco smoke

Prenatal Development• When the fertilized egg arrives in the uterus, it

implants itself in the thickened, spongy uterine wall.• The gastrula forms, differentiation of cells and growth

occurs.• The developing embryonic membranes become part

of the placenta and umbilical cord.• After eight weeks of development the embryo is called

the fetus.• The period of time between the fertilization of the egg

and the birth of the offspring is called gestation– In humans the gestation period is nine months or

approximately 266 days.

• During this time, it is essential that the expectant mother provide good prenatal care by eating nutritious foods, avoiding alcohol, tobacco, and drugs, and receiving proper medical attention regularly.

• Using tobacco, alcohol and drugs may cause low birth rates, premature births, Fetal Alcohol Syndrome as well as other birth defects.

Prenatal Development

http://www.youtube.com/watch?v=OsXK8Y4-PAs

Over the counter drugs and pregnancy (3min)

http://www.ksl.com/?nid=148&sid=14491332

Drug dependent babies (5min)

http://rockcenter.nbcnews.com/_news/2012/07/05/12570381-prescription-drug-addiction-among-pregnant-women-becoming-monstrous-tidal-wave?lite

Prescription drugs and pregnancy (12minutes)

• Pregnancy is divided into three trimesters

The Stages of Pregnancy

• A human embryo @ about 6 weeks

The First Trimester

• A human embryo @ about 8 weeks

A human fetus @ about 10 weeks

• By the end of the first trimester (12 weeks)

– The fetus looks like a miniature human being– The sex of the fetus can be determined by

ultrasound

A human fetus @ about 12 weeks

• The main developmental changes during the second and third trimesters involve an increase in size and general refinement of the human features

The Second Trimester

• A fetus at 14 weeks, 2 weeks into the second trimester

• At 20 weeks, the fetus

– Is about 19 cm (7.6 in.) long and weighs about half a kilogram (1 lb)

– Has the face of an infant

The Third Trimester

– Is a time of rapid growth– Includes many important physical changes

At birth

– A typical baby is about 50 cm (20 in.) long and weighs 2.7–4.5 kg (6–10 lb)

6 lbs. 13.5 oz 8 lbs. 3 oz

Fertilization Two CellsFour Cells

16 Cells Morula Stage Blastocyst StageImplantation

The Human Zygote

Human Gestation

3 Weeks

Human Gestation

3 Months

Summary of Human Development

• The birth of a child is brought about by a series of strong, rhythmic contractions of the uterus called labor

Childbirth

• Hormones play a key role in inducing labor

• There are three stages of labor

• Dilation of the cervix is the first stage– Cervix reaches full

dilation at 10cm– Longest stage of

labor (6-12 hours or longer)

• Expulsion is the second stage– Period from full dilation

of the cervix to delivery of the infant

– Uterine contractions occur every 2-3 minutes

– Mother feels urge to push down with her abdominal muscles

– Infant is forced down and out of uterus and vagina

• The delivery of the placenta is the final stage of labor

– Usually occurs within 15 minutes after the birth of the baby

• Hormones continue to be important after the baby and placenta are delivered

– Decreasing progesterone and estrogen levels allow the uterus to return to its pre-pregnancy state

– Oxytocin and prolactin stimulate milk secretion

http://www.doctoroz.com/videos/normal-labor-and-birth-animation normal labor and delivery

Moving babies

http://www.youtube.com/watch?v=w7qVJiYBlbo

http://www.youtube.com/watch?v=JKlPGzrrQZA&feature=related

Postnatal Development

• Following birth, the placenta is discarded from the mother’s body and the mother begins producing milk from mammary glands located in the breasts.

• The mother’s breast milk is normally the best natural food for a newborn baby.

Applications of reproductive technology:

Reproductive technology has medical, agricultural, and ecological applications. This technology has also stirred ethical concerns as well, especially where this technology applies to humans

1. Genetic engineering in the field of agriculture• Crops resistant to insects, weed killer, frost

2. Cloning- used to make large numbers of identical copies of desired organisms

3. Artificial insemination. Can freeze sperm or embryos and use them at different locations or at different times

• Scientist are also using these technologies to help engendered species

4. The use of reproductive hormones to control and combat pest populations of insects without using poisonous chemicals

5. Human reproductive problems:• Hormonal therapy• IVF (In-vitro fertilization)

• issues of human reproductive health

REPRODUCTIVE HEALTH

– Contraception– Transmission of disease– Infertility

• prevents pregnancy in one of three ways– Blocking the

release of gametes

– Preventing fertilization

– Preventing implantation

Contraception : Is the deliberate prevention of pregnancy

Surgical MethodsVasectomyCutting and tying of sperm ducts

Tubal ligationCutting and tying of oviducts

Birth Control• Hormonal contraceptives (the pill, the patch, and the vaginal ring)

– These hormones work to inhibit the body's natural cyclical hormones to prevent pregnancy. Pregnancy is prevented by a combination of factors. The hormonal contraceptive usually stops the body from ovulating.

– No ovulation = no egg = no fertilization = no baby!– No hormones taken for 7 days = menstruation

Barrier MethodMale and female condoms prevent sperm from entering the vaginaDiaphragm fitted over the cervix & along with use of spermacide to kill sperm

No sperms= no fertilization= no baby!

• Sexually transmitted diseases (STDs)

Sexually Transmitted Diseases

– Are contagious diseases spread by sexual contact

• Viral STDs, such as AIDS, genital herpes, and genital warts, cannot be cured but can be controlled by medications

Human Reproductive Disorders• Sexually transmitted diseases may be transmitted by

both males and females and may cause sterility or death if not treated by a competent physician.

• Some sexually transmitted diseases in humans are syphilis, gonorrhea, genital herpes, and AIDS.

• Reproductive technologies

REPRODUCTIVE TECHNOLOGIES

– Can help solve problems related to the inability to conceive a child

• Infertility– Is the inability to have children after one year of

trying– Problems in the man, such as underproduction

of sperm or impotence

• Female infertility can result from a lack of eggs or a failure to ovulate

• There are technologies available to help treat the many forms of infertility

In Vitro Fertilization (IVF)

– Happens under artificial, laboratory conditions

-Begins with the surgical removal of eggs and the collection of sperm

- Involves fertilization of eggs in a petri dish

• IVF

– Offers choices that nature does not– Raises many moral and legal issues

http://www.sumanasinc.com/webcontent/animations/content/invitrofertilization.html

IVF

• Show reproductive technologies ppt

• The key to development in all organisms is that each stage of development takes place in a highly organized fashion

Basic Concepts of Embryonic Development

• About one week after conception

– The embryo, which has become a blastocyst, implants itself in the uterine wall

– The outer cell layer, the trophoblast, becomes part of the placenta

• Gastrulation is the second major phase of embryonic development– It adds more cells to the embryo– It sorts all cells into three distinct cell layers– The embryo is transformed from the blastula into

the gastrula

Gastrulation produces a three-layered embryo

• The three layers produced in gastrulation

– Ectoderm, the outer layer– Endoderm, an embryonic digestive tract – Mesoderm, which partly fills the space between

the ectoderm and endoderm

• Embryonic tissue layers begin to differentiate into specific tissues and organ systems

• In chordates – the notochord develops from the mesoderm – the neural tube develops from the ectoderm

• The neural tube becomes the brain and spinal cord

Organs start to form after gastrulation

• Tissues and organs take shape in a developing embryo as a result of– cell shape

changes– cell migration

Changes in cell shape, cell migration, and programmed cell death give form to

the developing animal

• Induction is the mechanism by which one group of cells influences the development of tissues and organs from ectoderm, endoderm, and mesoderm– Adjacent cells and cell layers use chemical

signals to influence differentiation – Chemical signals turn on a set of genes whose

expression makes the receiving cells differentiate into a specific tissue

Embryonic induction initiates organ formation

http://player.discoveryeducation.com/?guidAssetId=B76C7495-F4F0-4CB4-926E-BFD46A3060A8

Identical Twins “nature vs nuture”

The amazing conception happened after two eggs were fertilized at the same time in the womb. Both Kylie and her partner Remi Horder, 17, are of mixed race. Their mothers are both white and their fathers are black. According to the Multiple Births Foundation, baby Kian must have inherited the black genes from both sides of the family, whilst Remee inherited the white ones.

A mixed-race British mom, Kylie Hodgson, gave birth in 2005 to twins, one of each — one black, the other white. The odds of such a birth are about a million to one, experts said. Although occurrences of this nature sometimes occur when a woman conceives twins fathered by two different men, this was a much rarer case in which a single pairing produced twins with distinctly different physical attributes (e.g., skin tone, hair color, eye color) rather than a blending of their parents' characteristics. The parents, Kylie and her partner, Remi Horder, are of mixed race themselves, both having been born to white mothers and black fathers. Their twin girls — Kian and Remee — were both born with blue eyes, with Remee having blonde hair and Kian having black hair and somewhat darker skin than her sister. Since then, Remee's skin tone has become lighter, while Kian's has become darker and her eyes have turned brown.

In the womb

http://channel.nationalgeographic.com/channel/in-the-womb/videos/in-the-womb/

Life’s Greatest Miracle

http://www.pbs.org/wgbh/nova/body/life-greatest-miracle.html