Fertilisation, Blastocyst Implantation Flashcards
What happens when semen is deposited?
Sperm swim through the cervix, uterus and into Fallopian tubes
How does fertilisation occur in the Fallopian tubes?
- thousand of sperm cells surround the ovum and follicle cells
- sperm cells secrete enzymes and break down follicle cells
- only one sperm cell penetrates cell membrane of ovum
- Nuclei of sperm cell and ovum form diploid zygote
What causes the movement of the developing embryo?
- peristaltic waves of contraction
- rhythmical beating of cilia
What changes occur when embryo moves along Fallopian tubes?
- zygote divide to form 2 cells
- cells divide again, forming 4 cells, 8 cells, etc
- cell division continues, solid ball of cells, morula is formed
- morula develops into a hollow, fluid-filled ball of cells- blastocyst,
development takes five days from fertilisation
What is the implantation of the blastocyst?
Blastocyst attaches to the uterine wall.
How does implantation occur?
- outer cells of blastocyst secrete enzymes that break down small part of thickened uterine wall, causing it to soften
- blastocyst sinks into the area
- blastocyst releases hormone- human chorionic gonadotropin
- hormones prevent menstruation from happening and ensure endometrium stays in tact
What is human chorionic gonadotropin?
Hormone that stimulates corpus luteum to continue to produce oestrogen and progesterone
What are the two membranes that the outer cell layers of blastocyst develop into?
- chorion
- amnion
Why are chorionic villi important?
Form part of a placenta
Anchor embryo
Absorb nutrients from mothers blood
What is the placenta?
Temporary, disc-like organ attached to uterus by villi
What are the functions of the placenta?
- allows diffusion oxygen, water, glucose…into foetal blood for cellular respiration and nutrition of the foetus
- waste excreted from mothers lungs and kidneys
- acts as filter,prevent most diseases passing into foetus
- maternal antibodies pass into foetus , provide natural immunity
- from 12 weeks placenta produces hormones
What is the umbilical cord?
Contains two umbilical arteries and umbilical vein embedded in connective tissue.
What is the function of the umbilical arteries?
carries co2, nitrogenous waste products… From embryo to placenta
What is the function of umbilical vein?
Carries O2, nurients, and water from placenta to embryo
What is the function of amniotic fluid?
- enables foetus to move freely
- maintains constant temp around foetus
- acts as shock absorber to Cushion and protect foetus
- prevents dehydration of foetus
- provides medium, which foetus can practice swallowing
