Question

please answer this
​

Answer 1

Answer:

A gyrus (plural: gyri) is a ridge on the surface of the brain. Each ridge is surrounded by fissures known as sulci (singular: sulcus).

Answer 2

Answer:

Unlike arteries, veins contain valves that ensure blood flows in only one direction. But, Arteries don't require valves because pressure from the heart is so strong that blood is only able to flow in one direction. Valves also help blood travel back to the heart against the force of gravity.

hope its helpful for you.