#141 The development of the fetus
The blastula develops into an embryo and some of the cells form a placenta, linking the embryo with the uterus lining. Organs such as the heart develops and, after 8 weeks, the embryo is called a fetus.
Growth of the fetus requires a good supply of nutrients and O2. This is achieved through the link between the placenta and the mother’s blood supply in the uterus lining. The placenta is soft and dark res, and has finger-like projections called villi. The villi fit closely into the uterus wall.
1. Umbilical cord
2. Placenta
- joins fetus to placenta; contains:
- 2 arteries: blood from fetus ---> placenta
- 1 vein: returns blood ---> fetus
2. Placenta
Brings blood supply of fetus close to mother’s
- Blood from the fetus passes through the umbilical cord in the umbilical artery to the placenta.
- Here it comes close to the mother's blood.
- transport O2 + nutrients (amino acids, glucose…) from mother ---> fetus
- transport CO2 + wastes (urea… ) from fetus --->mother (through umbilical vein).
Prevents mixing
This is really important because the fetus and mother may have different blood groups - any mixing could result in blood clotting, which could be fatal to both mother and fetus.
3. An amnion protects the fetus
The fetus is surrounded by a strong membrane, called amnion. Inside the amnion is a liquid called amniotic fluid.
This is really important because the fetus and mother may have different blood groups - any mixing could result in blood clotting, which could be fatal to both mother and fetus.
3. An amnion protects the fetus
The fetus is surrounded by a strong membrane, called amnion. Inside the amnion is a liquid called amniotic fluid.
Amniotic sac: membrane from embryo cells: encloses fetus, prevents entry of bacteria
Amniotic fluid: supports, protects fetus from mechanical damage; absorbs urine released by fetus.
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Amniotic fluid: supports, protects fetus from mechanical damage; absorbs urine released by fetus.
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Answer
a) i) A, umbilical cord ; B, vagina
ii) Tree functions from:
- transfers O2 from mother to fetus
- transfers nutrients (of named nutrients) from mother to fetus
- transfers CO2 from fetus to mother
- transfers wastes (or named wastes) from fetus to mother
- allows the transfer of antibodies from mother to fetus
- prevents mixing of the blood of mother and fetus.
iii) Helps prevent bacteria passing from mother to fetus, the blood group of mother and fetus may be different.