reproduction sl Flashcards
Differences between sexual and asexual reproduction
- Include these relative advantages: asexual reproduction to produce genetically identical offspring by individuals that are adapted to an existing environment, sexual reproduction to produce offspring with new gene combinations and thus variation needed for adaptation to a changed environment.
- In asexual reproduction there are no gametes formed - the offspring is essentially a clone. In sexual reproduction haploid gametes are formed, which during sexual intercourse and fertilisation form again a diploid zygote.
- see chart on table 8!
Role of meiosis (converts diploid cells to haploid cells)and fusion of gametes in the sexual life cycle
- Students should appreciate that meiosis breaks up parental combinations of alleles, and fusion of gametes produces new combinations.
Fusion of gametes is also known as fertilization.
Differences between male and female sexes in sexual reproduction
- Include the prime difference that the male gamete travels to the female gamete, so it is smaller, with less food reserves than the egg. From this follow differences in the numbers of gametes and the reproductive strategies of males and females.
- see slide 12!
- MSFAR
Anatomy of the human male and female reproductive systems
- Students should be able to draw diagrams of the male-typical system and annotate them with names of structures and functions.
Draw and outline a diagram of the male reproductive system, including the penis (with erectile tissue), urethra, testis, scrotum, epididymis, sperm duct, prostate gland and seminal vesicle.
penis = penetrates vagina for semen ejaculation near the cervix
urethra = transfers semen and urine
Testis = produces sperm and testerone
Scrotum = holds testes at temp. lower than body temp.
Epididymis = stores sperm until ejaculation
Sperm duct = transfer sperm during ejaculation
Seminal vesicles + prostate gland = secrete a fluid containing alkali, proteins, and fructose to make sperm into semen
Anatomy of the human male and female reproductive systems
- Students should be able to draw diagrams of the female-typical system and annotate them with names of structures and functions.
DRAW and Outline the function of the following female reproductive structures: ovary, uterus, vulva, vagina, cervix and oviduct.
ovary = produces eggs, estrogen, progesterone
oviduct = collects eggs at ovulation, fertilization occurs here and the developed embryo is moved to uterus
uterus = provides for the needs of embryos/foetus
cervix = protects foetus during development and dilates for birth canal
vagina = stimulates penis for ejaculation and works as birth canal
vulva = PROTECTS INTERNAL ORGANS OF REPRODUCTIVE SYSTEM
Changes during the ovarian and uterine cycles and their hormonal regulation
- Include the roles of oestradiol, progesterone, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and both positive and negative feedback.
- The ovarian and uterine cycles together constitute the menstrual cycle.
- what determines ovarian/uterine cycle?
- FSH stimulates development of follicles, and stimulates follicles to release estrogen
- Estrogen is responsible for the WHOLE uterine cycle; At low concentrations it stimulates an increase in FSH receptors that make follicles more receptive to FSH boosting oestradiol secretion even further (positive feedback). AND At high concentration it inhibits FSH release but stimulates the secretion of LH by the pituitary gland.
LUTENIZING + PROGESTERONE
LH (Luteineizing hormone):
Peaks at the end of the follicular phase in response to high oestradiol concentration.
Stimulates completion of meiosis in the oocyte and causes the release of the mature egg (ovulation).
It promotes the conversion of the follicle wall into a temporary gland, the corpus luteum.
It stimulates the corpus luteum to secrete oestradiol and progesterone.
Progesterone:
Secreted by corpus luteum
Reaches peak by end of luteal phase
Promotes thickening of endometrium
Inhibits FSH and LH (negative feedback)
GENERAL TREND FOR HORMONES
- LH peaks end of follicular phase
- progesterone peaks in luteal phase
- estrogen levels high near end of follicular phase
- FSH has opposite trend than estrogen
FIRST PHASE: FOLLICULAR PHASE
- WHAT HAPPENS IN UTERUS?
- WHAT HAPPENS IN OVARIES?
- First half of the uterine cycle – this is where the the uterine membrane breaks down during menstruation and starts to be built up again slowly.
- First half of the ovarian cycle – this is where follicles (nourishing cells surrounding the egg cell) develop inside the ovary and the female egg cells matures. At ovulation the mature egg cell is released into the oviduct.
SECOND PHASE: LUTEAL PHASE
- WHAT HAPPENS IN UTERUS?
- WHAT HAPPENS IN OVARIES?
Second half of the uterine cycle - the endometrium becomes thicker & more richly supplied with blood vessels in preparation for the implantation.
Second half of the ovarian cycle – this is where the cells which released the egg cell turn into a different structure called the corpus luteum. If no fertilization takes place the corpus luteum degenerates and a new cylce begins.
Ovulation = the generation of a female gamete once a month
The ovum moves down the fallopian tube, driven along by peristalsis (rhythmic contractions of muscles in the wall of the oviduct) and cilia (fine hair-like structures).
negative vs. positive feedback examples
- positive: low levels of estrogen - releasing FSH
- negative: low levels of estrogen - inhibiting FSH
Fertilization in humans
- Include the fusion of a sperm’s cell membrane with an egg cell membrane, entry to the egg of the sperm nucleus but destruction of the tail and mitochondria.
- Also include dissolution of nuclear membranes of sperm and egg nuclei and participation of all the condensed chromosomes in a joint mitosis to produce two diploid nuclei.
Fertilization is the fusion of a sperm with an egg to form a zygote.
Receptors in the plasma membrane of sperm allow the detection of chemicals released by the egg, and therefore directional swimming.
When the sperm and egg membranes fuse, the sperm nucleus enters the egg but the tail and mitochondria (mid piece) are destroyed
The nuclear membranes of both the egg and sperm dissolve, allowing the two sets of condensed chromosomes to undergo a joint mitosis
The resulting cell (zygote) has a diploid nucleus, allowing it to undergo further mitotic divisions to form a new multicellular organism (embryo)
NOTE: During fertilization, the ovum membranes alters to form a barrier to the entry of other sperm. The head of the sperm (the male nucleus) then moves towards the nucleus of the ovum and the two fuse together.
Use of hormones in in vitro fertilization (IVF) treatment
- The normal secretion of hormones is suspended, and artificial doses of hormones induce superovulation.
Compare in vivo and in vitro fertilization.
In-vivo = occurs in the oviduct during natural conception
In-vitro = fertilization occurs outside of the body; medically assisted reproduction
Outline the process of medically assisted reproduction using IVF.
Outline the roles of FSH, oestradiol and progesterone in medically assisted reproduction using IVF.
- down-regulation; drug inhibiting FSH and LH
- ovarian simulation; loads of FSH are injected into body (7-12 days)
- Egg retrieval using vacuum suction/ultrasound
- Fertilization (incubated for 1-2 days)
- Endometrium preparation; progesterone and estrogen are given
- embryo transfer!
