Sections 6.6 – 11.4

Reproduction

6.6.1 Draw and label diagrams of the adult male and female reproductive systems

6.6.2 Outline the role of hormones in the menstrual cycle, including FHS, LH and estrogen and progesterone.

6.6.3 Annotate a graph showing hormone levels in the menstrual cycle, illustrating the relationship between changes in hormone levels and ovulation, menstruation and thickening of the endometrium.

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.

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

Female Reproductive System

6.1.1 Draw and label diagrams of the adult male and female reproductive systems.

Figure 46.10

(Rectum)CervixVagina

Major vestibular(Bartholin’s) gland

Vaginal opening

Oviduct

OvaryUterus

(Urinary bladder)

(Pubic bone)

Urethra

BodyGlansPrepuce

Clitoris

Labia minoraLabia majora

Ovaries Oviduct

Follicles

Corpus luteumUterine wallEndometrium

Vagina

Uterus

Cervix

Female Reproductive System

Figure 46.10a

(Rectum)CervixVagina

Major vestibular(Bartholin’s) gland

Vaginal opening

Oviduct

OvaryUterus

(Urinary bladder)

(Pubic bone)

Urethra

BodyGlansPrepuce

Clitoris

Labia minoraLabia majora

› Pituitary Hormones:– FHS (Follicle Stimulating Hormone) stimulates these changes:

› Development of the oocyte in the follicle (follicle contains the oocyte)› Thickening of the follicle wall › Secretion of follicular fluid› Secretion of estrogen by follicle wall

– LH (Leutenizing Hormone) stimulates these changes:› Completion of meiosis in the oocyte› Partial digestion of the follicle wall allowing it to burst open (ovulation)› Growth of the corpus luteum which secretes estrogen and progesterone

6.6.2 Outline the role of hormones in the menstrual cycle, including FSH, LH and estrogen and progesterone

› Estrogen- secreted by the developing follicles:– Thickening of endometrium– Blood vessels growth in the endometrium– Increase in FSH receptors in follicle– Inhibition of FSH secretion and stimulation of LH secretion estrogen

levels are high

› Progesterone released from the corpus leutium, causes these changes– maintenance of thickening of the endometrium with many blood

vessels– Inhibition of FSH and LH

6.6.3 Annotate a graph showing hormone levels in the menstrual cycle, illustrating the relationship between changes in hormonal levels and ovulation , menstruation and thickening of the endometrium

Figure 46.13Control by hypothalamus(a)

Hypothalamus

GnRH

Anterior pituitary

FSH LH

Inhibited by combination ofestradiol and progesterone

Stimulated by high levelsof estradiol

Inhibited by low levels ofestradiol

109

87

65

4

3

2

1

(b) Pituitary gonadotropinsin blood

LH

FSH

FSH and LH stimulatefollicle to grow

6

LH surge triggers ovulation

Ovarian cycle

Growing follicle Maturing follicle

Corpusluteum

Degeneratingcorpus luteum

Follicular phase Ovulation Luteal phase

Estradiol secretedby growing follicle inincreasing amounts

(c)

Progesterone andestradiol secretedby corpus luteum

(d) Ovarian hormonesin blood

Estradiol

Peak causes LH surge(see )

Progesterone

Progesterone and estra-diol promote thickeningof endometrium

Estradiol levelvery low

(e) Uterine (menstrual) cycle

Endometrium

Menstrual flow phase Proliferative phase Secretory phase

Day

s

28252015141050

Figure 46.13a

Control by hypothalamus(a)

Hypothalamus

GnRH

Anterior pituitary

FSH LH

Inhibited by combination ofestradiol and progesteroneStimulated by high levelsof estradiol

Inhibited by low levels ofestradiol

2

1

1. Reproduction begins with release of GnRH which stimulates the anterior pituitary to release FSH and LH

2. FSH and LH Release

Figure 46.13b

(b) Pituitary gonadotropinsin blood

LH

FSH

FSH and LH stimulatefollicle to grow

LH surge triggers ovulation

Ovarian cycle

Growing follicle Maturing follicle

Corpusluteum

Degeneratingcorpus luteum

Follicular phase Ovulation Luteal phase

(c)

28252015141050Day

s

3

6

7 8

3. FS stimulates the follicle growth aided by LH

4. the cells of growing follicles begin to make estradiol.

5. when estradiol secretion by the growing follicle begins to rise steeply,

6. the FSH and LH levels increase

Low levels of estradiol inhibits the secretion GnRH and High level increase release of GnRH (positive feedback)

7. The maturing follicle, containing a fluid filled cavity, enlarges, forming a bulge near the surface of the ovary. The follicle phase ends with ovulation [about a day after the spike], releasing the secondary oocyte

Figure 46.13b

(b) Pituitary gonadotropinsin blood

LH

FSH

FSH and LH stimulatefollicle to grow

LH surge triggers ovulation

Ovarian cycle

Growing follicle Maturing follicle

Corpusluteum

Degeneratingcorpus luteum

Follicular phase Ovulation Luteal phase

(c)

28252015141050Day

s

3

6

7 8

8. Luteal phase: after the release of the oocyte, LH triggers the follicle to the transformed into corpus luteum, a glandular structure.

The corpus luteum secreted progesterone and estradiol which leads to negative feedback on the hypothalamus and pituitary – thus preventing the stimulation of another egg

Eventually LH and FSH levels drop, GnRH drops and this leads to the degeneration of the corpus luteum

Degeneration in the corpus luteum triggers the reduction in estradiol and progesterone which leads to the cycle beginning again

– Endometrium is sloughed away (menstruation)– No longer inhibited, FSH can start menstrual cycle again

– If fertilization of egg occurs, the zygote releases a hormone (hCG) which maintains the corpus luteum

Figure 46.13c

Estradiol secretedby growing follicle inincreasing amounts

Progesterone andestradiol secretedby corpus luteum

(d) Ovarian hormonesin blood

Estradiol

Peak causes LH surge(see )

Progesterone

Progesterone and estra-diol promote thickeningof endometrium

Estradiol levelvery low

(e)

Uterine (menstrual) cycle

Endometrium

Menstrual flow phase Proliferative phase Secretory phase

Da

ys

28252015141050

4

5 6

910

(e)

Figure 46.13Control by hypothalamus(a)

Hypothalamus

GnRH

Anterior pituitary

FSH LH

Inhibited by combination ofestradiol and progesterone

Stimulated by high levelsof estradiol

Inhibited by low levels ofestradiol

109

87

65

4

3

2

1

(b) Pituitary gonadotropinsin blood

LH

FSH

FSH and LH stimulatefollicle to grow

6

LH surge triggers ovulation

Ovarian cycle

Growing follicle Maturing follicle

Corpusluteum

Degeneratingcorpus luteum

Follicular phase Ovulation Luteal phase

Estradiol secretedby growing follicle inincreasing amounts

(c)

Progesterone andestradiol secretedby corpus luteum

(d) Ovarian hormonesin blood

Estradiol

Peak causes LH surge(see )

Progesterone

Progesterone and estra-diol promote thickeningof endometrium

Estradiol levelvery low

(e) Uterine (menstrual) cycle

Endometrium

Menstrual flow phase Proliferative phase Secretory phase

Day

s

28252015141050

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

› The process begins during fetal 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

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

› 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 fertilization)

› It is released from the ovary (ruptured follicle develops into corpus luteum) and, if fertilization occurs, will complete meiosis

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

› Germinal epithelium

› Primary follicles

› Mature follicle

› Secondary ooctye

11.4.4 Annotate a diagram of the ovary that show the location and function of:

› 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

Oogenesis video

6.6.1 Draw and label diagrams of the adult male and female reproductive systems 6.6.4 List three roles of testosterone

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

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

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

11.4.6 Draw and label a diagram of mature sperm and egg

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

Male Reproductive System

Reproduction in Males

Figure 46.11a

Seminalvesicle(behindbladder)

Urethra

Scrotum

(Urinary bladder)

Prostate gland

Bulbourethral gland

Erectile tissue of penis

Vas deferensEpididymisTestis

Figure 46.11b

Seminal vesicle

(Rectum)Vas deferens

Ejaculatory ductProstate glandBulbourethral gland Vas deferens

EpididymisTestisScrotum

(Urinary bladder)

(Urinary duct)

(Pubic bone)

Erectiletissue

Urethra

Glans

Prepuce

Penis

1. Pre-natal development of male genitalia

2. Development of secondary sex characteristics

3. Maintenance of sex drive (libido)

4. Anabolic activity leads to increase body mass

6.6.4 List three roles of testosterone

› Interstitial cells (Leydid cells) - produce the male sex hormone, testosterone

› Germinal epithelium: germ cells, spermatogonia (2n), divides by mitosis to make 1⁰ spermatocytes.– Germ cells will divide by meiosis

to make spermatozoa)

› Developing spermatozoa

› Sertoli cells – nourish developing spermatozoa

11.4.1 Annotate a light micrograph of the testis tissue to show the location and the function of the

“Germ Cells” Spermatogonoia (2n)

mitosis

Primary spermatocyte

meiosis I

Secondary spermatocyte(1n)

meiosis II

Spermatids

Maturation produces spermatozoa (1n gametes)

(50- 500 million sperm/ejaculation)

Sperm production

Testes

40X magnification

A. SpermatocytesB. SpermatogoniumC. Provides Nourishment for the developing cellD. produce the male sex hormone, testosterone

› Mitosis

› Cell growth

› Meiosis (both phases)

› Cell differentiation

› Spermatogenesis (5:38)

11.4.2 Outline the process involved in spermatogenesis within the testis including:

› 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 growth

› This 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

11.4.3 State the role of LH, Testosterone and FSH in spermatogenesis› LH: Stimulates the interstitial cells (Leydig cells) to produce

testosterone

› FSH: Stimulates the (first) meiotic division of spermatogonia

› Testosterone: Stimulates the (second) meiotic division of spermatogonia and the maturation of spermatozoa through differentiation

Figure 46.14

Hypothalamus

GnRH

Anterior pituitary

FSH LH

Sertoli cells Leydig cells

Inhibin Spermatogenesis Testosterone

Testis

Neg

ativ

e fe

edb

ack

Neg

ativ

e fe

edb

ack

Figure 46.12ac

Plasmamembrane

Tail

Neck

Midpiece Head

Mitochondria

NucleusAcrosome

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

› Epididymus

› Seminal vesicles

› Prostate gland

11.4.7 Outline the role of each in regards to production of semen:

Epididymis

› Testicular fluids are removed, concentrating the sperm

› Sperm mature and develop the ability to swim

› It stores the sperm for 2–3 months.

› Final maturation is completed in the female reproductive tract.

A. Head of epididymis, B. Body of epididymis, C. Tail of epididymis, and D. Vas deferens

Seminal Vesicle

› Adds nutrients (including fructose) for respiration

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

Prostate Gland

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

Figure 46.12ac

Plasmamembrane

Tail

Neck

Midpiece Head

Mitochondria

NucleusAcrosome

11.4.8 Compare the process of spermatogenesis and oogenesis including the number of gametes and the timing of the formation and release of gamets.

6.6.5 Outline the process of in vitro fertilization (IVF)

6.6.6 Discuss the ethical issues associated with IVF.

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

11.4.10 Outline the role of HCG in early pregnancy

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

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

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

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

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

Fertilization

In vitro fertilization refers to fertilization that occurs outside the body ('in vitro' = 'in glass')

Stop normal menstrual cycle (with drugs)

Hormone treatments to develop follicles (FSH to stimulate follicle growth ; hCG for follicle maturation)

Extract multiple eggs from ovaries

6.6.5 OUTLINE THE PROCESS OF IN VITRO FERTILIZATION (IVF)

Sperm selected, prepared (capacitation) and then injected into egg via intra-cytoplasmic sperm injection (ICSI)

Fertilization occurs under controlled conditions (in vitro)

Implantation of multiple embryos into uterus

Test for pregnancy is conducted to see if implantation was successful

› IVF is expensive and might not be equally accessible to all

› Success rate is low (~15%) and therefore stressful for couples

› It could lead to eugenics (e.g. gender choice)

› Often leads to multiple pregnancies which may be unwanted, unable to be budgeted for and involves extra birth risks

› Issues concerning storage and disposal of unused embryos (right to life concerns)

› There are cultural and religious objections to embryo creation by such means

› Inherited forms of infertility may be passed on to children

DISADVANTAGES

› Chance for infertile couples to have children

› Genetic screening of embryos could decrease suffering from genetic diseases

› Spare embryos can be stored for future pregnancies or used for stem cell research

ADVANTAGES

6.6.6 Discuss the ethical issues associated with IVF.

› 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)

› Fertilization 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

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

› 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 fertilized 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

Fertilization video: 5:42

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

11.4.10 Outline the role of HCG in early pregnancy

› 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 fertilized 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

› After fertilization, 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)

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

› Structure and Function:– The placenta is a disc-shaped

structure that nourishes the developing embryo

– It 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)

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

– Chorionic villi extend into these spaces and facilitate the exchange of materials between the maternal blood and fetal capillaries

– Nutrients, oxygen and antibodies will be taken up by the fetus, while carbon dioxide and waste products will be removed

– The placenta is expelled from the uterus after childbirth

Hormonal Role

› The 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

› 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

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

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

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

› 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

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

› 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 labor is complete and the baby is birthed (no more stretching of the uterine wall)

Happy Birthday!