The term "vascular" refers in general to a network of tubes that distribute nutrients and remove waste from the tissues of the body. Large multicellular animals must rely on a vascular system to keep their cells nourished and alive. The vascular system includes blood vessels (arteries, veins, and capillaries) in the blood vascular system and lymph vessels in the lymphatic system. The network of tubes that carry fluid and nutrients in the phloem and xylem tissues of plants is also called a vascular system or vascular bundle.
Vascular bundles are the equivalent of the blood and lymph vessels found in animals. They extend from the roots, through the stem, and out to the leaves. They consist of two types of tissue: xylem, which conducts water from the roots to the shoot, and is located towards the center of the bundle, and phloem, which conducts salt and nutrients and forms the outer regions of the bundle. In plants that exhibit secondary thickening, the xylem and phloem are separated by a thin layer of cambrium, from which new vascular tissue s generated.