Final answer:
The function of ring muscles, also known as precapillary sphincters, is to tightly regulate the flow of blood from a metarteriole to the capillaries it supplies. These circular smooth muscle cells surround the capillary at its origin and control blood flow by opening and closing.
Step-by-step explanation:
The precapillary sphincters and ring muscles play a critical role in the circulatory system by controlling the flow of blood. The precapillary sphincters are circular smooth muscle cells that surround the entrance to capillaries, tightly regulating blood flow into the capillary. Their main function is to control where blood flows based on the needs of the surrounding tissues.
For example, when tissues require more oxygen or need to dispose of excess waste products, the precapillary sphincters will open to allow blood to flow into the capillaries for gas and nutrient exchange. After the exchange, they close to conserve blood volume and redirect flow as needed.
Chemical signals such as endothelins, platelet secretions, and certain prostaglandins regulate the contraction and relaxation of these sphincters for efficient blood distribution.
Complete question:
What is the function of ring muscles and precapillary sphincters?