What is the key function of sphincters found along the digestive system?
a. thet selectively allow and stop passage of partially digested food.
b. they control and direct the quantity of food passing through the digestive organs and prevent backward movement of partially digested food.
c. they improve the muscular strength of the organs involved in digestion.

The correct answer is B. They control and direct the quantity of food passing through the digestive organs and prevent backward movement of partially digested food.

Explanation:

In biology, sphincters are a type of muscle that can regulate the passage of substances. In the digestive system, sphincters can be found mainly in the upper and lower zone of the stomach, between the small and large intestine and at the anus. In all cases, the sphincters regulate the amount of digested food or other substances that pass through the organs and also prevents the substances that have already passed to a new organ or zone of the digestive system can go backward.

Due to this sphincters are essential for regulating the movement of food and other substances to be correctly digested and to pass through different organs. According to this, the key function of these muscles is "control and direct the quantity of food passing through the digestive organs and prevent backward movement of partially digested food".

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fertilization, pictured in figure 24.23a is the process in which gametes (an egg and sperm) fuse to form a zygote. the egg and sperm each contain one set of chromosomes. to ensure that the offspring has only one complete diploid set of chromosomes, only one sperm must fuse with one egg. in mammals, the egg is protected by a layer of extracellular matrix consisting mainly of glycoproteins called the zona pellucida. when a sperm binds to the zona pellucida, a series of biochemical events, called the acrosomal reactions, take place. in placental mammals, the acrosome contains digestive enzymes that initiate the degradation of the glycoprotein matrix protecting the egg and allowing the sperm plasma membrane to fuse with the egg plasma membrane, as illustrated in figure 24.23b. the fusion of these two membranes creates an opening through which the sperm nucleus is transferred into the ovum. the nuclear membranes of the egg and sperm break down and the two haploid genomes condense to form a diploid genome.

explanation: