The placenta
Food and oxygen in, wastes out.
No mouth, no lungs yet
An embryo grows inside the mother's uterus. It needs glucose and oxygen.
How do you think it gets glucose and oxygen?
What this lesson covers
The idea
The placenta is a disc in the uterine wall with villi on the embryo's side surrounded by the mother's blood spaces, giving a large surface for glucose and oxygen to reach the embryo and wastes to leave it.
No mouth, no lungs yet
An embryo grows inside the mother's uterus. It needs glucose and oxygen.
How do you think it gets glucose and oxygen?
- Through a special tissue joined to the mother's blood
- By eating through its mouth
- By making its own glucose and oxygen
Inside the placenta
Open each tab. This is a schematic diagram.
A big surface for exchange
The placenta joins the embryo to the mother. Villi on the embryo's side are surrounded by the mother's blood spaces. This large surface lets glucose and oxygen pass to the embryo, and lets wastes pass from the embryo into the mother's blood.
The placenta is a disc in the uterine wall with villi on the embryo's side surrounded by the mother's blood spaces, giving a large surface for glucose and oxygen to reach the embryo and wastes to leave it.
Notes
The placenta has villi on the embryo's side and the mother's blood spaces around them: a large surface for glucose and oxygen to reach the embryo and wastes to leave.
Check yourself
Where is the placenta?
What passes from the mother's blood to the embryo through the placenta?
What happens to the waste substances made by the developing embryo?
Why does the placenta have villi?
- In the ovary. The ovary makes eggs. The placenta is a disc embedded in the wall of the uterus.
- It is a disc embedded in the uterine wall — correct. Yes!
- Inside the oviduct. The placenta is a disc embedded in the uterine wall.
- Wastes of the embryo. Wastes go the other way, from the embryo into the mother's blood.
- Sperms. Sperms enter the vagina and travel to the oviduct. The placenta passes glucose and oxygen to the embryo.
- Glucose and oxygen — correct. Yes!
- They are transferred into the mother's blood through the placenta — correct. Yes!
- They stay in the embryo. The wastes can be removed by transferring them into the mother's blood through the placenta.
- They go out through the vagina directly. The book says wastes are removed by transferring them into the mother's blood through the placenta.
- To make the uterus smaller. The villi are on the embryo's side, surrounded by the mother's blood spaces, and give a large surface area.
- They give a large surface area for glucose and oxygen to pass — correct. Yes!
- To hold the sperms. The villi give a large surface area for glucose and oxygen to pass from the mother to the embryo.