Reproductive System

Front 1

Outline the role of hormones in the menstrual cycle:

~FSH (follicle stimulating hormone),

~LH (luteinizing hormone),

~Estrogen

~Progesterone.

Back 1

1. FSH is secreted by the pituitary gland and its levels start to rise. This stimulates the follicle to develop and the follicle cells to secret estrogen.

2. Estrogen then causes the follicle cells to make more FSH receptors so that these can respond more strongly to the FSH.

3. This is positive feedback and causes the estrogen levels to increase and stimulate the thickening of the endometrium (uterus lining).

4. Estrogen levels increase to a peak and by doing so it stimulates LH secretion from the pituitary gland.

5. LH then increases to its peak and causes ovulation (release of egg from the follicle).

6. LH then stimulates the follicle cells to secrete less estrogen and more progesterone. Once ovulation has occurred, LH stimulated the follicle to develop into the corpus luteum.

7. The corpus luteum then starts to secrete high amounts of progesterone. This prepares the uterine lining for an embryo.

8. The high levels of estrogen and progesterone then start to inhibit FSH and LH.

9. If no embryo develops the levels of estrogen and progesterone fall. This stimulates menstruation (break down of the uterine lining). When the levels of these two hormones are low enough FSH and LH start to be secreted again.

10. FSH levels rise once again and a new menstrual cycle begins.

Front 2

List three roles of testosterone in males.

Back 2

1. Stimulates the development of prenatal genitalia.

2. Stimulates the development of the male secondary sexual characteristics such as growth of the skeletal muscle and pubic hair.

3. During adulthood it maintains the sex drive.

Front 3

Outline the process of in vitro fertilization (IVF).

Back 3

6.6.5 Outline the process of in vitro fertilization (IVF).Process:For a period of three weeks, the women has to have a drug injected to stop her normal menstrual cycle. After these three weeks, high doses of FSH are injected once a day for 10-12 days so that many follicles develop in the ovaries of the women. HCG (another hormone) is injected 36 hours before the collection of the eggs. HCG loosens the eggs in the follicles and makes them mature. The man needs to ejaculate into a jar so that sperm can be collected from the semen. The sperm are processed to concentrate the healthiest ones. A device that is inserted through the wall of the vagina is used to extract the eggs from the follicles. Each egg is then mixed with sperm in a shallow dish. The dishes are then put into an incubator overnight. The next day the dishes are looked at to see if fertilization has happened. If fertilization has been successful, two or three of the embryos are chosen to be placed in the uterus by the use of a long plastic tube.A pregnancy test is done a few weeks later to find out if any of the embryos have implanted.A scan is done a few weeks later to find out if the pregnancy is progressing normally.

Front 4

Discuss the ethical issues associated with IVF.

Arguments for IVF

Back 4

1. Many types of infertility are due to environmental factors rather than genetic which means that the offspring would not inherit the infertility.

2. The embryos that are killed during the IVF process cannot feel pain or suffering as they do not have a developed nervous system.

3. Suffering caused by genetic diseases can be decreases by screening the embryos before placing them into the uterus.

4. Since the IVF process is not an easy one emotionally and physically, is costly, takes time and there are no guarantees, parents who are willing to go through it must have a strong desire to have children and therefore are likely to be loving parents.

5. Infertility can cause emotional suffering to couples who want to have children. IVF can take away this suffering for some of those couples.

Front 5

Discuss the ethical issues associated with IVF. Arguments against IVF

Back 5

1. The infertility of the parents may be inherited by their offspring passing on the suffering to the next generation.

2. More embryos are produced than needed and the ones that remain are usually killed which denies them the chance of a life.

3. Embryologists select which embryos will be placed into the uterus. Therefore they decide the fate of new individuals as they choose which ones will survive and which ones will die.

4. IVF is not a natural process which takes place in a laboratory compared to natural conception which occurs as a result of an act of love.

5. Infertility should be accepted as God’s will and to go against it by using IVF procedures would be wrong.

Front 6

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

Back 6

~The testes are composed of seminiferous tubules which produce sperm

~Each tubule is surrounded by a basement membrane which is lined by germline epithelium cells

~The germline epithelium will divide by mitosis to make spermatogonia (which divide by meiosis to make spermatozoa)

~The developing spermatozoa are nourished by Sertoli cells

~Outside of the tubules are blood capillaries and interstitial cells (Leydig cells), which produce the male sex hormone, testosterone

Front 7

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

Back 7

~Spermatogenesis describes the production of spermatozoa (sperm) in the seminiferous tubules of the testes

~The first stage of sperm production requires the division of germline epithelium by mitosis

~These cells (spermatogonia) then undergo a period of growthThis is followed by two meiotic divisions that result in four haploid daughter cells

~These haploid cells then differentiate to form sperm cells

~The developing sperm cells are nourished throughout by the Sertoli cells

Front 8

Annotate a diagram of the ovary to show the location and function of germline epithelium, primordial follicles, mature follicles and secondary oocyte

Back 8

-The ovary contains follicles in various stages of development

-Egg cells within primordial follicles have been arrested in prophase I and have yet to undergo meiotic division

-Egg cells within mature follicles have begun meiotic division and are released from the ovary as secondary oocytes (arrested in prophase II)

-The ruptured follicle develops into a corpus luteum that will, in time, degenerate into a corpus albicans

-The germline epithelium functions as an epithelial layer separating ovarian tissue from the rest of the body - it is not involved in oocyte development

Front 9

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

Back 9

-Oogenesis describes the production of female gametes (ova) within the ovary

-The process begins during foetal development, when a large number of cells (oogonia) are formed by mitosis before undergoing a period of growth

-These cells begin meiosis but are arrested in prophase I until puberty

-At puberty, some follicles continue to develop each month is response to FSH secretion

-These follicles complete the first meiotic division to form two cells of unequal size

-The cell with less cytoplasm is a polar body (which degenerates), while the larger cell forms a secondary oocyte

-The secondary oocyte begins the second meiotic division but is arrested in prophase II (until fertilisation)It is released from the ovary (ruptured follicle develops into corpus luteum) and, if fertilisation occurs, will complete meiosis

-The second meiotic division will produce an ovum and a second polar body

Front 10

Outline the role of the epididymis

Back 10

-Testicular fluids are removed, concentrating the sperm

-Sperm mature and develop the ability to swim

Front 11

Outline the role of the seminal vesicle

Back 11

-Adds nutrients (including fructose) for respiration

-Secretes prostaglandins, causing contractions to the female system and helping sperm move towards the egg

Front 12

Outline the role of the prostate gland in the production of semen

Back 12

-Secretes alkaline fluid which neutralises vaginal acids (changes pH from 4 to 6 which aids sperm motility)

Front 13

Similarities between the processes of spermatogenesis and oogenesis.

Back 13

-Both processes result in the formation of haploid gametes

-Both processes involve mitosis, growth and meiosis

Front 14

Differences between the processes of spermatogenesis and oogenesis.

Location:

Number of Gametes produced:

Gametes per germ cell:

Beginning of Process:

Timing of gamete formation:

Timing of gamete release:

Meiotic divisions:

Germ line epithelium:

Back 14

Spermatogenesis Oogenesis

Location: Testis Ovary

Number of Gametes produced:millions 400

Gametes per germ cell: Four One

Beginning of Process: Puberty Fetal development

Timing of gamete formation: Continuous Once a month

Timing of gamete release: Anytime Monthly cycle

Meiotic divisions: Uninterrupted Arrested

Germ line epithelium: Involved in gamete production Not involved.

Front 15

Describe the process of fertilization including

-The acrosome reaction,

-Penetration of the egg membrane by a sperm

-The cortical reaction

Back 15

-When the sperm enters the female reproductive tract, biochemical changes to the sperm occur in the final part of its maturation (capacitation)

-The sperm is attracted to the egg due to the release of chemical signals from the secondary oocyte (chemotaxis)

-Fertilisation generally occurs in the oviduct (fallopian tube)

-To enter the egg membrane, the sperm must penetrate the protective jelly coat (zona pellucida) surrounding the egg via the acrosome reaction

-The acrosome vesicle fuses with the jelly coat and releases digestive enzymes which soften the glycoprotein matrix

-The membrane of the egg and sperm then fuse and the sperm nucleus (and centriole) enters the egg

-To prevent other sperm from penetrating the fertilised egg (polyspermy), the jelly coat undergoes biochemical changes via the cortical reaction

-The cortical granules release enzymes that destroy the sperm-binding proteins on the jelly coat

-Now fertilised, the nucleus of the secondary oocyte completes meiosis II and then the egg and sperm nuclei fuse to form a diploid zygote

Front 16

Outline the role of hCG in early pregnancy

Back 16

-The endometrium is a blood-rich environment in which an implanted zygote can grow and it is sustained by the hormone progesterone

-If progesterone levels aren't maintained (i.e. the corpus luteum degenerates), then the endometrium will be sloughed away (menstruation)

-A fertilised zygote develops into a blastocyst that secretes human chorionic gonadotrophin (hCG)

-hCG maintains the corpus luteum post-ovulation so that the blastocyst can remain embedded in the endometrium and continue to develop

-Gradually the placenta develops and produces progesterone (at around 8 - 10 weeks), at which point the corpus luteum is no longer needed

Front 17

Outline early embryo development up to the implantation of the blastocyst

Back 17

-After fertilisation, the zygote undergoes several mitotic divisions to create a solid ball of cells called a morula (at around 4 days)

-Unequal divisions beyond this stage cause a fluid-filled cavity to form in the middle - this makes a blastocyst (at around 5 days)The blastocyst consists of:

An inner mass of cells (this will develop into the embryo)

An outer layer called the trophoblast (this will develop into the placenta)

A fluid filled cavity (called the blastocoele)These developments all occur as the developing embryo is moving from the oviduct to the uterus

-When the blastocyst reaches the uterus, it will embed in the endometrium (implantation)

Front 18

Explain how the structure and function of the placenta maintain pregnancy

Back 18

-Structure and FunctionThe placenta is a disc-shaped structure that nourishes the developing embryoIt is formed from the development of the trophoblast upon implantation and eventually invades the uterine wall

-The umbilical cord connects the fetus to the placenta and maternal blood pools via open ended arterioles into intervillous spaces (lacunae)Chorionic villi extend into these spaces and facilitate the exchange of materials between the maternal blood and fetal capillariesNutrients, oxygen and antibodies will be taken up by the fetus, while carbon dioxide and waste products will be removedThe placenta is expelled from the uterus after childbirth

Front 19

Explain the hormonal role in secretion of estrogen and progesterone, maintain pregnancy

Back 19

-Hormonal RoleThe placenta also takes over the hormonal role of the ovary (at around 12 weeks)

-Estrogen stimulates growth of the muscles of the uterus (myometrium) and the development of the mammary glands

-Progesterone maintains the endometrium, as well as reduces uterine contractions and maternal immune response (no antibodies against fetus)Both estrogen and progesterone levels drop near time of birth

Front 20

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

Back 20

-The fetus develops in a fluid-filled space called the amniotic sac

-Amniotic fluid is largely incompressible and good at absorbing pressure, and so protects the child from impacts to the uterine wall

-The fluid also creates buoyancy so that the fetus does not have to support its own body weight while the skeletal system develops

-Finally, amniotic fluid prevents dehydration of the tissues, while the amniotic sac provides an effective barrier against infection

Front 21

State that materials are exchanged between the maternal and fetal blood in the ________?

Back 21

The fetus relies on the exchange of materials across the placental wall to grow and develop:

Front 22

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

Back 22

-The process of childbirth is called parturition and is controlled by the hormone oxytocin

- After nine months, the fetus is fully grown and takes up all available space in the uterus, stretching the walls of the uterus

-This causes a signal to be sent to the brain, releasing oxytocin from the posterior pituitary

-Oxytocin inhibits progesterone, which was inhibiting uterine contractions

-Oxytocin also directly stimulates the smooth muscle of the uterine wall to contract, initiating the birthing process

-The contraction of the uterine wall causes further stretching, which triggers more oxytocin to be released (causing even more contraction)

-Additionally, the fetus responds to the cramped conditions by releasing prostaglandins which cause further myometrial contractions

-As the stimulus causing oxytocin release is increased by the effects of oxytocin, this creates a positive feedback pathway

-Contractions will stop when labour is complete and the baby is birthed (no more stretching of the uterine wall)