Unit 8: Mammalian Reproduction

The male reproductive system The male reproductive system produces sperm and transfers it to the female reproductive system.

The testes produce sperm and the male hormone, testosterone. A hormone is a chemical that regulates body functions.

The female reproductive system The female reproductive system produces eggs, ensures development of fertilized eggs, and gives birth.

In humans, the ovaries are about the size of a large olive. Each ovary produce eggs, also called oocytes. The release of oocytes is called ovulation

Development of the Human Embryo

Developmental History of a Human

Stages of Development 1. Fertilization 2. 3. 4. 5. 6.

1. Fertilization

2. Cleavage

2. Cleavage Begins ~ 12 hours post-fertilization Zygote divides into 2 cells (mitosis) 46 chromosomes in zygote = 46 chromosomes in both daughter cells 2 cell into 4 cell stage (24 – 36 hours) 4 cell into 8 cell stage (36 – 72 hours) 16 cell stage -- Morula

Stages of Development 1. Fertilization  Zygote 2. Cleavage 3. Morula 4. 5. 6.

3. Morula Morula

3. Morula ~ 16 cell stage Develops ~ 72 hours (3 days) from fertilization Morula enters the uterus ~ after 3 days in oviduct

3. Morula 72 hours post- fertilization entering uterus

A ZYGOTE contains all of the genetic information of the organism. True False

Approximately how many cells does a MORULA have? Rank Responses 1 2 3 4 5 6

Cleavage… begins approx. 12 hours post-fertilization. involves mitosis only Involves meiosis only A and B A and C

4. Blastocyst

4. Blastocyst Morula, once entering the uterine cavity, floats freely Morula begins to accumulate fluid and forms a cavity between its cells Once cavity appears, it is now called a blastocyst

4. Blastocyst

What MUST to happen before the zygote can develop/grow? Cleavage Morula Stage Fertilization Placental Development The gametes (egg and sperm) must fuse and go through meiosis before the zygote can develop.

4. Blastocyst Blastocyst has fluid-filled inner cavity Evolves from morula on day 5

Day 6 Three events happen

1. Implantation

What part of the BLASTOCYST implants itself into the uterine wall? Trophoblasts Inner Cell Mass The inner cell mass does not actually implant itself. It needs the trophoblasts to do the implanting.

The TROPHOBLASTS will form all of the following EXCEPT: The umbilical cord The fetus The placenta The amniotic fluid The trophoblasts fill form everything EXCEPT for what will become the baby organism.

2. Two Distinct Cell Types Inner cell mass trophoblasts Trophoblasts – will form the invading placenta Inner cell mass cells – will form the embryo

Stages of Development 1. Fertilization  Zygote 2. Cleavage 3. Morula 4. Blastocyst 5. Implantation (Day 6 into Week 2) 6.

3. hCG is produced hCG is a hormone hCG is human chorionic gonadotropin It is produced by the trophoblasts starting on day 6 hCG causes endometrium (lining) of uterus to grow and proliferate hCG prevents the menstrual cycle from occurring This is why a female misses her periods when she is pregnant

Week 2 Implantation continues Erosion of maternal blood vessels Complete emersion into endometrium of uterus

If implantation occurs in the oviduct/ fallopian tube, the embryo cannot develop properly must be removed could kill the mother All of the above This is called an ectopic pregnancy. There is not enough room for the embryo to develop and it must be removed or the oviduct can rupture, usually killing the mother.

Stages of Development 1. Fertilization  Zygote 2. Cleavage 3. Morula 4. Blastocyst 5. Implantation (Day 6 into Week 1) 6. Development (Embryo into Fetus)

Which 2 systems do you think the embryo needs to develop first? Digestive & Endocrine Endocrine & Cardiovascular Cardiovascular & Nervous Nervous & Immune WHY?

Weeks 3-4 Development of cardiovascular and nervous systems

Weeks 5-8 Embryo will develop all structures that an adult has by the end of week 8

Embryo into Fetus Embryonic period is weeks 1-8 Fetal period begins on week 9 and goes until birth at 38 weeks. Embryonic period is characterized by development of structures (organs). Fetal period is characterized by growth of those structures.

Fetal Period 9-12 13-16 17-20 21-38

By Week 8 an embryo has immature versions of all of its adult structures. True False Weeks 8-38 of development are known as the “fetal period.” The embryo is now called a fetus.

A BLASTOCYST is only 16 cells big. True False

All of the following are true about a MORULA EXCEPT: At this stage it enters the uterus. It consists of approx. 16 cells. Each cell contains a complete set of chromosomes. It has a fluid-filled cavity.

The Fetal Period occurs… Within the first 72 hrs. On Day 6 By Week 2 During Weeks 8-38 During Weeks 38-42

Only 1 Cell Big, the ___________ contains all of the genetic information for the future organism. Rank Responses 1 2 3 4 5 6

In The Womb- Dogs YouTube Video- NatGeo