No valves exist between the anterior vena cava and the heart, and the heartbeat tends to cause movement within this blood vessel. Another vessel, the posterior vena cava, carries blood from the lower half of the body to the heart.
The 2016 Hereford, Texas, population is 15,021. There are 2,447 people per square mile (population density).
As of the 2010 census, the population was 4,092,459, making it the most populous county in Texas and the third-most populous county in the United States. Its county seat is Houston, the largest city in Texas and fourth-largest city in the United States. The county was founded in 1836 and organized in 1837. It is named for John Richardson Harris, an early settler of the area.