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Reproduction (HL)

Page history last edited by Darrell Sharp 12 years, 5 months ago

 

11.4 Reproduction

 

 

 

 

 

11.4.1 

Annotate a light micrograph of testis tissue to show the location and function of interstitial cells (Leydig cells), germinal epithelium cells, developing spermatozoa and Sertoli cells.

 

http://www.sciencephoto.com/media/311519/enlarge

 

 

 

Annotate a light micrograph of testis tissue to show the location/function of cells - IB Biology Syllabus http://ibbiology.wetpaint.com/page/Annotate+a+light+micrograph+of+testis+tissue+to+show+the+location%2Ffunction+of+cells

 

 

11.4.2 

Outline the processes involved in spermatogenesis within the testis, including mitosis, cell growth, the two divisions of meiosis and cell differentiation.

 

 

 

 

 

 

 

 

http://www.proofcommunication.com/wp-content/uploads/2009/09/C003690-Sperm_production_SEM-SPL.jpg

 

 

http://ldysinger.stjohnsem.edu/ThM_599d_Beg/02_Biology/02_spermatogenesis.jpg

 

 

11.4.3 

State the role of LH, testosterone and FSH in spermatogenesis.

 

LH: Stimulates the interstitial cells to produce testosterone

 

Testosterone: Promotes spermiogenesis (maturation of spermatids into spermatozoa)

 

FSH: Stimulates sperm production in seminiferous tubules and stimulates division and maturation of Sertoli cells 

 

11.4.4 

Annotate a diagram of the ovary to show the location and function of germinal epithelium, primary follicles, mature follicle and secondary oocyte.

 

http://www.pathologyoutlines.com/ovary.html

 

Functions:

 

Primary follicles: It holds primary oocyte in it and helps it to grow.

Germinal epithelium: it’s the wall of the ovary, which keeps the organs to stay together.

mature follicle: It holds the oocyte and support it to become a secondary oocyte, and later an ovum, eventually a zygote.

secondary oocyte: it eventually turns into zygote, if fertilized.

 

Review Questions:

  1. What is function of primary follicles?
  2. What is oocyte and what does it become when fertilized?
    3.   What is germinal epithelium, what does it do?

 

 

11.4.5 

Outline the processes involved in oogenesis within the ovary, including mitosis, cell growth, the two divisions of meiosis, the unequal division of cytoplasm and the degeneration of polar body.

 

 

Guiding questions

  1. How many processes are there?
  2. Why are polar bodies degenerated?
  3. What does mitosis produce?

 

Oogenesis: development of oocyte to the egg cell.

 

Process 1: Mitosis happens, it produces germ cell layer and primary oocyte.

Process 2: Primary oocyte undergo meiosis I and II.  Unequal divisions happen, which result in secondary oocyte and haploid cells.

Process 3: Haploid cells become polar bodies, and degenerated.

Process 4: Secondary oocyte becomes get all the amount of cell material from polar bodies and become an ovum.

http://ridge.icu.ac.jp/biobk/BioBookmeiosis.html

 

 

11.4.6 

Draw and label a diagram of a mature sperm and egg.

 

 

 

http://www.infertilitybooks.com/onlinebooks/malpani/chapter4b.html

 

 

Egg cell

 

 

 

11.4.7 

Outline the role of the epididymis, seminal vesicle and prostate gland in the production of semen.

 

The testes of the male reproductive system are composed of a folded structure called the seminiferous tubule. The immature sperm can be found in this part of the testes until they migrate to the epididymis (situated on the top of the testes) to mature and be stored.

 

During the ejaculation process, the mature sperm will travel through the vas deferens tube to the seminal vesicles and later on in the ejaculatory duct. The fluid in the semen is mainly produced by the seminal vesicle containing fructose to allow the sperm to get a better chance of survival to get to the egg cell.

Another fluid from the prostate gland contains alkaline which is mixed with the sperm once the sperm pass to the Urethra part. This liquid helps the sperm to swim faster and resist the acidic environment of the vagina.

 


 

The Cowper’s gland also produces a fluid which lubricates the penis and facilitate corporation.

 

Video available on: http://www.pennmedicine.org/encyclopedia/em_DisplayAnimation.aspx?gcid=000120&ptid=17

 

 

11.4.8 

Compare the processes of spermatogenesis and oogenesis, including the number of gametes and the timing of the formation and release of gametes.

 

 

 

Spermatogenesis    

Number of gametes = millions/day

Timing of formation of gametes = begins at puberty and continues throughout life

Release of gametes = during ejaculation

 

Oogenesis

Number of gametes = one/per menstrual cycle

Timing of formation of gametes = begins in fetus before birth - ovulation begins at puberty and continues until menopause

Release of gametes = during ovulation of the menstrual cycle

 

 

11.4.9 

Describe the process of fertilization, including the acrosome reaction, penetration of the egg membrane by a sperm and the cortical reaction.

 

Fertilization is the union of a human egg and sperm through the fusion of the gametes.

Once the sperm has been ejaculated in the female’s vagina, it will need to penetrate in an egg cell during ovulation.

 

A secondary oocyte is secreted by the ovarian follicle cells and is surrounded by a pellucida and a corona radiate zone.

 

Egg cell structue:

 

source: http://bhavanajagat.wordpress.com/tag/autotrophs/

 

On the extremity of a sperm head (acrosome) can be found an enzyme called proteolyctic which helps the sperm cell to get through the corona radiate layer of the oocyte and create its way to the egg cytoplasm. This process is known as the acrosome reaction.

 

Once the sperm cell reaches the pellucida layer, the sperm will bind to special receptors letting the sperm passing through.

The sperm cell membrane will fuse with the oocyte membrane and special lysosomes. The cortical granule will then release enzymes which will thicken the pellucina zone so that no other sperm cells would penetrate in the oocyte region. This process is called the cortical reaction. The ovum would therefore only be fertilized by one sperm cell.      

 

Source: wikipedia, LadyofHats.

 

 

 

 

11.4.10

Outline the role of HCG in early pregnancy.

 

 Eight days after fertilization, the blastocyst embeds itself into the endometrium. The trophoblastic cells begin to secrete Human Chorionic Gonadotrophic (HCG). This hormone sustains the corpus luteum which produces progesterone. At 10 weeks the placenta starts to produce progesterone so the corpus luteum is no longer necessary.

 

            HCG is excreted in urine and can be detected by pregnancy tests. A specifically modified stick contains antibodies against  HCG with a pigment attached. HCG attaches to the antibodies, which then travel futher with the fluid to another group of antibodies. The HCG antibody complex will attach to these antibodies, turning the line blue. If no HCG is present, the HCL complex is not formed and the blue line is not created.

 

 

11.4.11

Outline early embryo development up to the implantation of the blastocyst.

 

 

 

 

 

oocyte-blastocyst1

http://www.sjfert.com/index.php/ivf/program/

 

Early Embryo Development

  • 24 hours after fertilization, the zygote divides by mitosis
  • mitotic divsions continue at an increasing rate as the embryo floats down the fallopian tube
  • the embryo is approximately 100 cells when it reaches the uterus and implants in the endometrium
  • the embryo is called a blastocyst at this stage of development

 

        Blastocyst English.svg

                                    http://en.wikipedia.org/wiki/Blastocyst

Blastocyst

  • trophoblast: surrounding layer of cells - becomes fetal part of the placenta
  • inner cell mass - becomes the body of the fetus
  • fluid filled cavity

 

                               Blastocyst Day 5

http://www.infertilitybooks.com/onlinebooks/malpani/chapter25f.html 

 

 

 

11.4.12 

Explain how the structure and functions of the placenta, including its hormonal role in secretion of estrogen and progesterone, maintain pregnancy.

 

 

 

The Placenta

  • When the embryo implants itself in the endometrium, it is running out of stored food.
  • Implantation causes the development of the placenta.
  • The placenta forms from the trophoblast of the blastocyst.
  • When fully formed, two blood vessels from the fetus will carry fetal blood to the placenta
  • The fetal blood is low in oxygen and full of waste.
  • In the placenta, the waste is transferred to the mother's blood, and oxygen and nutrients are transferred to the fetal blood.
  • The blood of the mother and the fetus never mix. Exchange of materials happens by diffusion across capillaries in the placenta.
  • The placenta also produces estrogen and progesterone to maintain pregnancy as the corpus luteum breaks down.

 

 

11.4.13 

State that the fetus is supported and protected by the amniotic sac and amniotic fluid.

 

 

A fetus is surrounded by amniotic fluid which is surrounded by the amniotic sac. Amniotic fluid buffers movement to protect the fetus from physical harm. The amniotic sac stops the amniotic fluid from leaking and protects against disease.

 

 

11.4.14 

State that materials are exchanged between the maternal and fetal blood in the placenta.

 

 

 

Exchange of materials in the placenta

 

From the fetus to the mother:

  • carbon dioxide
  • urea
  • water
  • hormones 

 

From the mother to the fetus:

  • oxygen
  • nutrients (glucose, amino acids, etc.)
  • water
  • hormones
  • vitamins
  • minerals 

 

Also:

  • alcohol
  • drugs (nicotine, cocaine, etc)
  • viruses (HIV, some others)

 

 

11.4.15 

Outline the process of birth and its hormonal control, including the changes in progesterone and oxytocin levels and positive feedback.

 

 

Parturition: changes in the mother leading to birth

  • decrease in progesterone
  • the hormone oxytocin is secreted from the pituitary gland
  • low levels of oxytocin begin labor
  • labor is the contraction of the muscles of the uterine wall
  • contractions of the uterus cause the pituitary to release more oxytocin in a positive feedback loop
  • uterine contractions become more frequent and intense as oxytocin increases
  • cervix dilates to 10cm
  • the baby is normally postioned head down and feet up for birth
  • after the baby is born, the placenta is expelled (also called afterbirth)
  • lactation - breast milk production - begins shortly after birth

 

 

 

Human Health and Physiology Home

 

 

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