Blood Vessels



A broad and complicated network of blood vessels transports blood throughout the body. Conducting, distributing, and resistance arteries are the three categories of arteries that vary greatly in structure and function. Arteries function to carry blood from the heart to all body tissues, muscles, bones, and organs so that blood can deliver oxygen and necessary nutrients to cells within these body structures. At the capillary bed surrounding the tissues, these products are exchanged for waste products. Complex capillary beds rely on several processes to enable this exchange of nutrients and gases. After this exchange occurs, veins return blood from throughout the body back to the heart, generally against gravity. Each body region relies on a particular system of interacting arteries, capillaries, and veins.

At A Glance

  • Arteries carry blood away from the heart and veins carry blood back to the heart, while capillaries are the site of exchange between blood and interstitial fluid.
  • The walls of arteries and veins have conducting, distributing, and resistance layers, differing in elasticity, thickness of walls, permeability, and pressure.
  • Blood vessels can contract or relax to increase or decrease their diameter through the action of precapillary sphincters. This affects the pressure within the capillary bed and can redirect blood to other locations in the body.
  • Gases and nutrients are exchanged by diffusion, filtration, transcytosis, and reabsorption.
  • Systolic blood pressure is the pressure against the vessel walls during ventricular contraction, and diastolic blood pressure is the pressure exerted on the vessel walls during relaxation of the ventricles.
  • Changes in cardiac output, total blood volume, and resistance to blood flow can affect blood pressure.
  • The aorta is the systemic circulatory system artery carrying blood out of the heart.
  • The carotid and vertebral arteries supply blood to the head and neck.
  • The subclavian arteries deliver blood to the upper limbs.
  • Branches of the thoracic aorta and subclavian and axillary arteries supply blood to the thoracic region, which is a region of the spine that extends from the neck to lower back, and branches of the abdominal aorta supply blood to the abdominal region.
  • Blood is returned from the thoracic and abdominal regions to the heart through a network of veins.
  • The internal iliac arteries supply blood to the pelvic region.
  • The external iliac arteries supply blood to the lower limbs.