MDSC 1403 Anatomy

• Cardiovascular system

  Concerned with pumping and channeling blood to and from the body and lungs to transport nutrients, gases, hormones and wastes
• Components of the cardiovascular system

  • Heart
  • Blood
  • Blood vessels (arteries, veins and capillaries)

  
• Blood vessels


  • Tubes which transport the blood
  • Three types: arteries, capillaries and veins
  • Lined by one layer of flat cells - endothelium

  
• Arteries


  Tubes which convey blood from the heart to the tissues of body at high pressure
• Types of arteries


  • Large (conducting) arteries
  • Medium sized (distributing) arteries
  • Small arteries
  • Arterioles
• Large (conducting) arteries


  • Also called elastic arteries
  • Contain sheets of elastic fibers in their wall
  • Receive the cardiac output
  • Their elasticity enables them to expand
• Medium sized (distributing) arteries


  • Also called muscular arteries
  • Contain more amount of smooth muscle fibres in their walls
  • Pulsatile contractions of their muscular walls temporarily and rhythmically constrict their lumina in progressive sequence, propelling and distributing blood to various parts of the body
  • Have the ability to decrease their diameter and control the flow of blood to different parts of body
• Small arteries and arterioles


  • Small arteries: Have small lumen, have muscles in their wall, not named

  Arterioles: Smallest arteries, their diameter is less than 0.1 mm, they transmit blood into the capillaries

  
• Arterial anastomosis


  • Communication between the branches of arteries
  • Provide numerous alternating pathways for the blood flow when the usual pathway is obstructed

  
• End arteries


  Anatomical end (true terminal) arteries: Arteries which do not anastomose with their adjacent arteries, occlusion results in severe ischemia and death of the tissue

  Functional end arteries: Arteries anastomose with the adjacent arteries but the caliber of anastomosis is insufficient to keep the tissue alive if one of the artery is occluded

  
• Veins


  Return low-oxygen blood from capillary beds (tissues) of the body to the heart - dark blue colored

  Pulmonary veins carry oxygen-rich blood from the lungs to the heart

  Thin walled and have large lumen

  Normally, veins do not pulsate and do not squirt or spurt blood when severed

  They have valves which maintain the unidirectional flow of blood

  
• Types of veins


  • Venules
  • Small veins
  • Medium sized veins
  • Large veins
• Venules


  Smallest veins, begin at the venous end of capillaries, they join to form small veins
• Small veins


  Accompany the small arteries, join to form medium sized veins
• Medium sized veins


  Accompany the medium sized arteries, medium sized arteries in the limbs usually accompanied by 2 medium sized veins - called venae comitantes
• Large veins


  Formed by the medium sized veins, have large lumen
• Blood capillaries


  Microscopic blood vessels situated in the intercellular spaces, they have only endothelial cells in their wall, they form networks called capillary plexus (capillary bed)

  Arterial end: Arterioles open at this end

  Venous end: Venules begin at this end

  Oxygen and nutrients leave the capillaries and enter the intercellular fluid (tissue fluid), at the same time the intercellular fluid containing waste products and CO2 enter the capillaries

  
• Sinusoids


  Replace capillaries in certain organs like liver, spleen, bone marrow and endocrine glands, their lumen is large and lined by endothelial cells
• Venous anastomosis


  Communication between the veins or tributaries of veins
• Arteriovenous anastomosis (shunt)


  Communication between the smaller arteries and veins, when the organ is active these shunts are closed and the blood circulates through the capillaries, when the organ is at rest, the blood bypasses the capillary bed and is shunted back through the arteriovenous anastomosis

  
• Arteriosclerosis


  Hardening of the arteries, a group of diseases characterized by thickening and loss of elasticity of the arterial walls

  
• Atherosclerosis


  A specific type of arteriosclerosis, buildup of fats, cholesterol and other substances in and on artery walls (plaques), which restrict blood flow

  
• Varicose veins


  When the walls of veins lose their elasticity, they become weak and dilates under the pressure, results in abnormally swollen, twisted veins, most often seen in the legs
• Layers of the blood vessel wall


  • Tunica intima
  • Tunica media
  • Tunica adventitia

  
• Tunica intima


  • Inner most and very thin layer, contains endothelium, subendothelial connective tissue, and internal elastic lamina

  
• Tunica media


  • Middle layer made up of smooth muscle fibers, elastic and collagen fibers, outer part contains external elastic lamina
• Tunica adventitia


  • Outermost, connective tissue layer made up of collagen and elastic fibers, contains small arteries and veins (vasa vasora) which supply the tunica adventitia and media of the blood vessel

  
• Muscular arteries (medium sized arteries)


  • Tunica intima: Endothelium, thin subendothelial connective tissue, prominent internal elastic lamina

  Tunica media: Very thick, mainly circularly running smooth muscle fibers, very few elastic fibers

  Tunica adventitia: Thin, mainly collagen fibers and very few elastic fibers
• Elastic (large) arteries


  • Tunica intima: Endothelium, thick subendothelial connective tissue, internal elastic lamina is difficult to identify

  Tunica media: Very thick, mainly laminae of elastic fibers, contains very few smooth muscle fibers

  Tunica adventitia: Thin, mainly collagen fibers and very few elastic fibers
• Medium sized veins


  • Tunica intima: Endothelium, very thin subendothelial connective tissue, internal elastic lamina is indistinct or absent

  Tunica media: Very thin, mainly collagen fibers, very few smooth muscle and elastic fibers

  Tunica adventitia: Thickest layer, mainly collagen fibers and very few elastic fibers
• Large veins


  • Tunica intima: Endothelium, very thin subendothelial connective tissue, internal elastic lamina is indistinct or absent

  Tunica media: Very thin, mainly collagen fibers, very few smooth muscle and elastic fibers

  Tunica adventitia: Thickest layer, contains bundles of longitudinally running smooth muscle fibers, also contains collagen and few elastic fibers
• Blood vessels of thorax


  • Aorta
  • Pulmonary trunk
  • Superior vena cava
  • Pulmonary veins
• Aorta


  Large artery which carries oxygenated blood from left ventricle to all the parts of the body
• Parts of aorta


  • Ascending aorta
  • Arch of aorta
  • Descending thoracic aorta
  • Abdominal aorta
• Ascending aorta


  • Located in the middle mediastinum within the pericardial cavity
  • Arises from the upper end of left ventricle
  • About 5 cm long, runs upwards and to the right within the pericardium
  • Continues as arch of aorta at the level of sternal angle (upper border of right 2nd costal cartilage)
  • Branches: Right and left coronary Arteries, Aortic sinus
• Aortic sinus


  Dilatations situated at the beginning of ascending aorta, 3 in number
• Arch of aorta


  • Located in the superior mediastinum behind the manubrium sterni
  • Continuation of ascending aorta, begins at the level of sternal angle, behind the upper border of right 2nd costal cartilage
  • Runs upwards, backwards and to the left in front of trachea, then downwards behind the left bronchus
  • Continues as descending thoracic aorta, at the level of sternal angle (at the lower border of body of 4th thoracic vertebra)
  • Branches: Brachiocephalic artery, left common carotid artery and left subclavian artery
• Descending thoracic aorta


  • Situated in the posterior mediastinum of thorax
  • Continuation of arch of aorta at the level of sternal angle (at the lower border of body of 4th thoracic vertebra)
  • Runs downwards in the posterior mediastinum
  • Continues as abdominal aorta at the lower border of 12th thoracic vertebra
  • Branches: Posterior intercostal arteries (lower 9 spaces), Subcostal artery, 2 left bronchial arteries, Esophageal branches, Pericardial branches, Mediastinal branches, Superior phrenic arteries
• Pulmonary trunk


  Conveys deoxygenated blood from right ventricle to the lungs

  
• Pulmonary trunk


  • 5 cm long, situated within the pericardium
  • Arises from the right ventricle
  • Divides into right and left pulmonary arteries at the level of 5th thoracic vertebra