conception Flashcards
Conception (def.)
a process that starts with fertilisation and ends with implantation of an embryo, resulting in pregnancy
Fertilisation (def.)
the union of a sperm and egg, forming a zygote (first cell produced)
early development of the zygote simply in terms of the formation of a ball of cells that becomes implanted in the wall of the uterus
- Ovulation releases matured egg
- Sperm fertilises ovum, forming a zygote
- Cleavage of embryo starts
- The embryo develops into a blastocyst
- The blastocyst implants in the endometrium
Implantation
The blastocyst starts to implant in the endometrium about a week after fertilisation
HCG will be produced by the blastocyst to maintain the corpus luteum, which produces progesterone to maintain the thickness of the endometrium
Once the placenta is fully formed at week 8, HCG levels will drop
The placenta will start producing progesterone to maintain the endometrium to sustain the growth of foetus
Development of embryo and placenta
The outer layer of cells of the blastocysts will eventually form part of the placenta, the organ that provides nourishment and oxygen to the embryo and helps dispose of its metabolic waste
Placenta consists of both maternal and embryonic tissues
About a month after fertilisation, the amnion will enclose the embryo
The amnion breaks just before childbirth and the fluid leaves the mother’s body through her vagina
In the process of implantation, the embryo develops finger-like structures called the chorionic villi that are embedded into the endometrium → increases surface area for faster diffusion of nutrients and waste in and out of the foetal circulatory system
The chorionic villi help the embryo implant itself into the endometrium and are surrounded in tiny pools of maternal blood
The mother’s blood and embryo’s blood are not in direct connection
Instead, the chorionic villi absorb nutrients and oxygen from the mother’s blood and pass these substances to the embryo via the chorionic blood vessels
The embryo’s waste products diffuse to the mother’s bloodstream via the chorionic villi, and is later excreted by the mother’s kidney
Amniotic sac (func.)
a thin-walled sac that surrounds the fetus during pregnancy
Amniotic sac (features)
filled with liquid made by the fetus (amniotic fluid) and the membrane that covers the fetal side of the placenta (amnion)
Amniotic fluid (func.)
protects the embryo in the following ways:
- Protection (acts as a cushion from external trauma)
- Constant temperature
- Allows for free movement for foetal development (muscle)
Placenta (func.)
allows for nutrients, oxygen and protective antibodies to diffuse to the developing embryo from the maternal blood
Placenta (features)
A composite organ consisting of chorionic villi closely associated with the blood vessels of the endometrium
HIV can pass through
It does not always prevent substances circulating in the mother’s body from reaching the embryo. These include viruses, drugs (including prescription medication), alcohol and chemicals in cigarette smoke.
Umbilical cord (func.)
transports oxygen and nutrients to the foetus and waste products from the foetus to the placenta
Umbilical cord (features)
circulatory pathway that connects embryo to the chorionic villi of the placenta
Umbilical arteries (func.)
carries deoxygenated blood from the foetus back to the placenta
Umbilical vein (func.)
carries oxygenated blood from the placenta to the foetus
Infertility (def.)
a condition in which a couple who want children, are unable to conceive even after 12 months of unprotected intercourse
