Artery

Arteries (from Greek ἀρτηρία (artēria), meaning "windpipe, artery") are blood vessels that carry blood away from the heart. While most arteries carry oxygenated blood, there are two exceptions to this, the pulmonary and the umbilical arteries. The effective arterial blood volume is that extracellular fluid which fills the arterial system.

The circulatory system is vital for sustaining life. Its normal functioning is responsible for the delivery of oxygen and nutrients to all cells, as well as the removal of carbon dioxide and waste products, the maintenance of optimum pH, and the circulation of proteins and cells of the immune system. In developed countries, the two leading causes of death, myocardial infarction (heart attack), and stroke, may each directly result from an arterial system that has been slowly and progressively compromised by years of deterioration.

Structure

The anatomy of arteries can be separated into gross anatomy, at the macroscopic level, and microscopic anatomy, which must be studied with the aid of a microscope. The arterial system of the human body is divided into systemic arteries, carrying blood from the heart to the whole body, and pulmonary arteries, carrying deoxygenated blood from the heart to the lungs.

Arterial road

An arterial road or arterial thoroughfare is a high-capacity urban road. The primary function of an arterial road is to deliver traffic from collector roads to freeways or expressways, and between urban centres at the highest level of service possible. As such, many arteries are limited-access roads, or feature restrictions on private access.

Though the design of arterial roads varies from country to country, city to city, and even within cities, they share a number of common design characteristics. For example, in many cities, arteries are arranged in concentric circles (commonly referred to as ring roads) or in a grid. Many jurisdictions also classify arterial roads as either principal (major) or minor.

In traffic engineering hierarchy, an arterial road delivers traffic between collector roads and freeways. For new arterial roads, intersections are often reduced to increase traffic flow. In California, arterial roads are usually spaced every half mile, and have intersecting collector(s) and streets. Some arterial roads, characterized by a small fraction of intersections and driveways compared to most arterial roads, are also considered to be expressways in some countries and some states of the United States.