Blood Vessels and Circulation

• Blood vessels outside the heart

  • Pulmonary vessels
  • Systemic vessels
• Pulmonary vessels


  Transport blood from the right ventricle of the heart through the lungs and back to the left atrium
• Systemic vessels


  Transport blood from the left ventricle of the heart through all parts of the body and back to the right atrium
• Blood vessel functions


  • Carry blood
  • Exchange nutrients, waste products, gases within tissues
  • Transport substances
  • Regulate blood pressure
  • Direct blood flow to tissues
• Vessel structures


  • Arteries
  • Veins
  • Capillaries
• Arteries


  Carry blood away from heart, thick with a lot of elastic tissue
• Veins


  Carry blood toward heart, thick with less elastic tissue
• Capillaries


  Exchange occurs between blood and tissue fluids
• Blood flow


  1. Blood flows from arteries into arterioles

  2. Arterioles into capillaries

  3. Capillaries into venules

  4. Venules to small veins

  5. Veins return to heart
• Blood vessel wall layers

  • Tunica intima
  • Tunica media
  • Tunica adventitia
• Tunica intima


  Innermost layer, simple squamous
• Tunica media


  Middle layer, smooth muscle with elastin and collagen fibers
• Tunica adventitia


  Outermost layer, connective tissue
• Types of arteries


  • Elastic arteries
  • Muscular arteries
• Elastic arteries


  Largest in diameter, thickest walls, example - aorta and pulmonary trunk
• Muscular arteries


  Medium to small size, thick in diameter, contain smooth muscle cells, can control blood flow to body regions
• Capillaries


  Blood flows from arterioles into capillaries, capillaries branch to form networks, blood flow is regulated by smooth muscle cells, precapillary sphincters
• Types of veins


  • Small veins
  • Medium-sized veins
  • Large veins
• Small veins


  All 3 tunics are present
• Medium-sized veins


  Collect blood from small veins and deliver to large veins
• Large veins


  Contain valves
• Pulmonary circulation


  Blood vessels that carry blood from right ventricle to lungs and back from left atrium of heart
• Pulmonary trunk


  Carries blood from right ventricle towards lung
• Pulmonary veins


  Exit lungs and carry O2 rich blood to left atrium
• Parts of the aorta

  • Ascending
  • Aortic arch
  • Descending
  • Thoracic
  • Abdominal
• Ascending aorta


  Passes superiorly from left ventricle
• Aortic arch


  Contains 3 major arteries which carry blood from aorta to head and upper limbs
• Descending aorta


  Extends through thorax and abdomen to pelvis
• Thoracic aorta


  Part of descending aorta that extends through thorax to diaphragm
• Abdominal aorta


  Descending aorta that extends from diaphragm where it divides at the common iliac arteries
• Branches of the aortic arch

  • Brachiocephalic artery
  • Left common carotid artery
  • Left subclavian
• Brachiocephalic artery


  First branch off aortic arch, supplies blood to right side of head and neck
• Left common carotid artery


  Second branch off aortic arch, supplies blood to the left side of head and neck
• Left subclavian artery


  Third branch off aortic arch, supplies blood to left upper limbs
• Arteries of the head and neck

  • Right common carotid artery
  • Right subclavian artery
• Right common carotid artery

  Branches off brachiocephalic artery, supplies blood to right side of head and neck
• Right subclavian artery


  Branches off brachiocephalic artery, supplies blood to right upper limbs
• Cerebral arterial circle


  Formed by arteries at the base of the brain
• Arteries of the upper limbs

  • Axillary arteries
  • Brachial arteries
  • Ulnar arteries
  • Radial arteries
• Axillary arteries


  Continuation of subclavian in the axilla (armpits)