Reproduction Flashcards
Meiosis
The process that produced gametes
it results in 4 haploid cells, all with different genetic makeup
stages of meiosis
interphase prophase I metaphase I anaphase I telophase I prophase II metaphase II anaphase II telophase II
interphase
interphase - chromosomes duplicate, not visable
prophase I
prophase I - “prep phase”: centriole fibres migrate, spindle fibres form, nuclear membrane breaks down
metaphase I
metaphase I - homologous chrs line up across equator, centrioles move to opposite sides, spindle fibres attach to chrs
anaphase I
anaphase I - homologous chrs pulled to opposite sides of the cell
telophase I
cell undergoes cytokinesis - creates 2 separate cells
Spermatogenesis
spermatogonium, primary spermatocyte, secondary spermatocyte, spermatid
primary spermatocyte
undergoes meiosis I
produces 2 haploid cells
secondary spermatocyte
undergoes meiosis II
chromatids are separated to produce 4 haploid cells
spermatid
matures in the epididymus
loses some cytoplasm and forms a tail - creates sperm (1n)
spermatogonium
diploid cell undergoes mitosis. Sperm move towards seminiferous tubule, become primary spermatocyte
Oogenisis
oogonia, primary oocyte, secondary oocyte,ovum
oogonia
diploid cell
mitosis occurs before birth
primary oocyte
undergoes meiosis I
produces 2 haploid cells - 1st polar body receives half chrs, but less cytoplasm therefore isn’t viable
primary oocyte
undergoes meiosis I
chromatids are separated to produce 2 haploid cells
2nd polar body isn’t viable
results in a single ovum
ovum
haploid cell
during ovulation, the ovum is released into the fallopian tubes
Ovarian cycle
concerned with changes within the ovary
cycle lasts around 28 days
Hormonal changes in ovarian cycle
FSH causes a single primary follicle to mature into secondary follicle
Secondary follicle secretes oestrogen, develops into Graafian follicle
Graafian follicle bursts and releases ovum (LH)
corpus luteum secretes progesterone
menstrual cycle
concerned with changes in the uterus
hormonal changes - menstrual cycle
gonadatrophin factors stimulate the release of FSH and LH
FSH - matures follicle, which secretes oestrogen
Oestrogen thickens endometrium, increased levels cause FSH to drop
Corpus luteum secretes progesterone, maintains the endometrium
corpus luteum amalgamates, shedding endometrium
Fertilisation to foetus
- sperm and ovum meet in the fallopian tubes, forming zygote (single diploid cell)
- zygote undergoes mitosis resulting in two diploid cells, which moves along the fallopian tubes
- continues to undergo mitosis travelling into the uterus
- dividing cell results in a morula after 4-5 days
- forms a blastocyst after 7 days - cells are identical, undifferentiated
- implantation
- differentiation: tri laminar disc (mesoderm, ectoderm, endoderm)
Blastocyst
when first formed, all cells are genetically identical and undifferentiated
after implantation, cells begin to differentiate: endoderm, mesoderm, ectoderm
ectoderm
gives rise to skin and nervous system
mesoderm
gives rise to muscles
ectoderm
gives rise to internal organs
Umbilical cord
connects the foetus and the placenta
contains two arteries and one vein, carrying blood to and waste from the foetus
Stages of birth
- cervical dilation, contraction of the uterus
- expulsion of baby
- expulsion of chorion, placenta
foetal blood supply modifications
foreman ovale
ductus arteriosis
ductus venosus
foreman ovale
hole in the septum connecting the the left and right atrium; reduces blood flow to the lungs
ductus arteriosis
connects the pulmonary artery to the aorta; blood flow to the lungs is reduced
ductus venosus
diverts the oxygenated blood from the umbilical vein to the vena cava, bypassing the liver
Artificial insemination
used when sperm can’t naturally fertilise an egg
semen sample is placed around vagina around ovulation
Assisted fertilisation
drugs used to increase the number of maturing eggs
fertilised by IVF, gamete intrafallopian transfer, intracytoplasmic sperm injection
In vitro fertilisation
harvested eggs are combined with semen in a petri dish
resulting embryos are then frozen or implanted into the uterus
gamete intrafallopian transfer
harvested eggs are combined with the males sperm
mixture is injected into uterus
intracytoplasmic fertilisation
single sperm injected into the egg
Components of semen
sperm - produced in the testes
alkaline fluid - neutralises acidic vagina, added by prostate
nutrients - sugary fluid produced by seminal vesicle
lubricating fluid - aids the transportation of sperm, added by Cowper’s gland
