Major Blood Vessels In The Circulatory System

• Major Blood Vessels of the Circulatory System

  • Arteries
  • Arterioles
  • Capillaries
  • Venules
  • Veins

  
• Arteries


  Blood vessels that carry blood away from the heart
• Arteries


  • Thick walls composed of distinct layers
  • Outer and inner layers are primarily connective tissue
  • Middle layers are made up of muscle fibres and elastic connective tissue
  • Arteries stretch to accommodate surge of blood from the heart
  • Many cells of the artery are themselves supplied with blood vessels that provide nourishment
• Pulse


  Change in the diameter of the arteries following heart contractions
• Arterioles


  Smaller branches of arteries, leading into capillaries
• Arterioles


  • Middle layer is composed of elastic fibres and smooth muscle
• Autonomic nervous system


  Regulates the diameter of the arterioles
• Vasoconstriction


  A nerve impulse causes smooth muscle in the arterioles to contract, reducing the diameter of the blood vessel. It decreases blood flow to tissues.
• Vasodilation


  Relaxation of the smooth muscle causes dilation of the arterioles, and blood flow increases. It increases the delivery of blood to tissues.
• Capillaries


  Any of the fine branching of blood vessels that form a network between arterioles and venules

  
• Capillaries


  • Composed of a single layer of cells
  • Sites of fluid and gas exchange between blood and body cells
  • Active cells, such as muscle cells, may be supplied by more than one capillary
  • 0.4-1.0 mm long and have a diameter of less than 0.005 mm
  • Red blood cells must travel through capillaries in single file
  • The single layer is ideal for diffusion, but the capillary bed can be easily ruptured by high blood pressure or any impact

  
• Precapillary sphincter muscles


  Regulate the movement of blood from the arterioles into capillaries

  
• Arterioles leading to capillaries

  Open ONLY when cells in that area require blood

  
• Blushing from nervousness and being frightened involve the processes of vasodilation and vasoconstriction
• Arteriosclerosis


  A group of disorders that cause blood vessels to thicken, harden, and lose their elasticity
• Atherosclerosis


  The most common form of a group of arterial diseases
• Atherosclerosis


  • Excess lipids in blood are deposited in the walls of the arteries, slowly narrowing the inside diameter
  • Calcium and other minerals deposit on top of the lipid, forming plaque
• Aneurysm


  A bulge that forms in the wall of a weakened blood vessel, usually an artery
• Aneurysm


  • Most common sites are the aorta of the heart, the abdominal aorta, and arteries in the brain
  • Often due to atherosclerosis
  • The thinner wall offers less support and eventually ruptures, much like a weakened wall of an inner tube
  • Less oxygen and nutrients are delivered to tissues, resulting in cell death
• An aneurysm in the brain is one of the conditions that can cause a stroke
• Venules


  Capillaries merge and become progressively larger vessels
• Veins


  Have greater diameter than venules and gradually increase in diameter as they approach the heart
• As blood flows from arteries to arterioles to capillaries, blood flow and fluid pressure is greatly reduced, and the pressure is not enough to drive the blood back to the heart

  
• William Harvey figured out the circulatory system
• Veins


  • Valves open in one direction, steering blood toward the heart and do not allow backflow of blood
  • Skeletal muscles aid venous blood flow by contracting and pushing against veins, creating a massaging action that moves blood back to the heart
• Fainting


  Related to venous blood flow
• Veins


  • Important blood reservoirs, as much as 65% of total blood volume can be found in the veins
  • During times of stress, venous blood flow can be increased to help meet increased energy demands by nerve impulses causing smooth muscle in the walls of the veins to contract, increasing fluid pressure and driving more blood to the heart
• Varicose veins are caused by weakened vein walls and valves

  
• Treatment options for varicose veins include compression stockings, sclerotherapy, and surgery
• Arteries


  Carry oxygen-rich blood away from the heart; have thick, muscular walls
• Veins


  Carry oxygen-poor blood back to the heart; have thinner walls and valves to prevent backflow
• Heart


  A muscular organ that pumps to circulate blood throughout the body

  
• Pericardium


  • A fluid-filled membrane surrounding the heart
  • The fluid bathes the heart, preventing friction between its outer wall and the covering membrane
• Septum


  • A wall of muscle that separates the right and left sides of the heart

  
• The heart's pumping action is synchronized; muscle contractions on the right side mirror those on the left
• Pulmonary Circulatory System


  The system of blood vessels that carries deoxygenated blood to the lungs and oxygenated blood back to the heart

  
• Systemic Circulatory System


  The system of blood vessels that carries oxygenated blood to the tissues of the body and deoxygenated blood back to the heart

  
• Four-chambered human heart


  • Composed of two thin-walled atria (s. atrium) and two thick-walled ventricles
• Blood flow through the heart

  1. Blood from the systemic system enters the right atrium

  2. Blood from the pulmonary system enters the left atrium

  3. Blood is carried away from the heart by arteries

  4. The aorta carries oxygenated blood away from the heart

  
• Coronary arteries


  Arteries that form an important branch of the aorta, supply the muscle cells of the heart with oxygen and nutrients