Answer: Sphincter muscles
Explanation:
The circular rings of smooth muscles, that can contract to regulate the movement of the smooth muscles that can contract to regulate the movement of food through the gastrointestinal tract are known as sphincter muscles.
These two layers are outer layer and inner layer. The outer layer is longitudinal and the inner layer is circular. They contract rhythmically to squeeze food.
Answer:
(2) exchange food, oxygen, and waste between
mother and fetus
Explanation:
In most mammals like humans, the fetus produced as a result of the fertilization of the sperm and egg, develops in the uterus or womb of the female. However, this developing fetus cannot yet fend for what it requires for survival and is still dependent on the mother e.g nutrients, oxygen etc. How do this substances get to the fetus? Here comes the role of the PLACENTA.
Placenta is an organ in the uterus that serves as a connection between the mother and the fetus in her womb. The placenta enables the mother to pass digested nutrients to the fetus and exchange gases (oxygen and Carbondioxide) between them via the umbilical cord. The placenta also enables the mother remove waste produced by the fetus into her bloodstream.
I might be incorrect, but from what I remember it should be particle size
