Final answer:
Anastomoses are connections between blood vessels, and they occur at sites like the base of the brain and in the veins of the limbs. These connections help maintain blood flow even if one vessel is blocked or narrowed.
Step-by-step explanation:
An anastomosis is a connection or joining of blood vessels. In the circulatory system, anastomoses occur between arteries and veins. These connections are important for maintaining blood flow even when one vessel is blocked or narrowed.
One major area where anastomoses occur is at the base of the brain. The internal carotid and vertebral arteries branch to form an anastomosis, known as the cerebral arterial circle or the circle of Willis. This anastomosis ensures a continual blood supply to the brain.
Another area where anastomoses are common is in veins. Veins have numerous connections to help maintain blood flow. For example, there are anastomoses in the veins of the limbs, which allow blood to flow even if one vessel is blocked or damaged.