Transport: Circulatory System

• Closed circulatory system


  A closed-loop system, in which the blood is not free in a cavity. Exhibited by all vertebrate organisms, as well as some invertebrates. Blood is contained inside blood vessels and circulates unidirectionally from the heart around the systemic circulatory route, then returns to the heart again.

  
• Open circulatory system


  The blood is not enclosed in the blood vessels but is pumped into a cavity (hemocoel). Blood + interstitial fluid = hemolymph. Ostia are openings of the heart where hemolymph enters. Examples: Simplest animals like sponges and rotifers, complex animals like jellies and comb jellies. Diffusion allows adequate exchange of water, nutrients, waste, and dissolved gases.

  
• Fishes


  • Composed of single circuit for blood flow and a two-chambered heart that has only a single atrium and a single ventricle. Atrium collects blood that has returned from the body. Ventricle pumps the blood to the gills where gas exchange occurs and the blood is re-oxygenated.

  
• Amphibians, reptiles, birds, and mammals

  • Blood flow is directed in two circuits: one through the lungs and back to the heart. Gas exchange occurs through the skin during pulmonary circulation in amphibians.

  
• Fishes, amphibians, reptiles, birds, and mammals

  • Moves blood between the heart and the rest of the body.

  
• Amphibians and most reptiles

  • Have a three-chambered heart (two atria and one ventricle).

  
• Mammals and birds


  • Have a heart divided into four chambers: two atria and two ventricles. The oxygenated blood is separated from the deoxygenated blood, which improves the efficiency of double circulation and is probably required for the warm-blooded lifestyle.

  
• Blood


  A very complicated connective tissue that serves as the transporting medium for all the substances in the body. The adult human body contains approximately five liters of blood, accounting for nearly 8% of a person's body weight.

  
• Major components of blood

  • Plasma
  • Cellular elements

  
• Plasma


  Approximately 55% of blood. Yellowish color or transparent. The liquid part of blood, approximately 91% water. Contains proteins, electrolytes, and other biochemicals.

  
• Serum


  The liquid that remains after the blood has clotted. Light yellow, clear.
• Plasma


  The liquid that remains when clotting is prevented. Light yellow, clear.
• Red blood cells (RBC) or erythrocytes

  • Contain large amounts of hemoglobin, which is the oxygen-transporting protein of blood. Perform immunity functions against diseases and infections. Involved in blood clotting.

  
• Hemoglobin


  Delivers oxygen to the body and removes some carbon dioxide. Composed of four protein subunits, two alpha chains and two beta chains, and a heme group that has iron associated with it. The iron reversibly associates with oxygen, and in so doing is oxidized from Fe2+ to Fe3+.

  
• Hemocyanin


  • A blue-green, copper-containing protein found in invertebrates such as mollusks, crustaceans, and some of the arthropods.

  
• Hemerythrin


  • A red, iron-containing protein found in some polychaete worms and annelids. Hemerythrin is carried in blood cells and has iron associated with it, but it does not contain heme.

  
• Heart


  • Epicardium (outer layer), Myocardium (middle layer), Endocardium (innermost layer). Four chambers: Right and left atria, Right and left ventricles. Atria receive blood from the veins, Ventricles push blood out of the heart.

  
• Heart valves


  • Atrioventricular valve
  • Tricuspid valve
  • Mitral valve or bicuspid valve
  • Semilunar valve
  • Pulmonic valve or pulmonary valve
  • Aortic valve
• Arteries


  • Carry oxygenated blood away from the heart and to every part of the body. Aorta is the largest artery, with Ascending Aorta and Descending Aorta.
• Veins


  • Return oxygen-depleted blood to the heart. Start small (venules) and get larger as they approach the heart. Superior Vena Cava carries blood from the upper body, Inferior Vena Cava carries blood from the lower body.

  
• Capillaries


  • Connect very small arteries and veins. Allow oxygen, carbon dioxide, nutrients, and waste products to pass into and out of cells. Skeletal muscle, liver, and kidney have a large number of capillaries, while the cornea of the eye has no capillaries.

  
• How the circulatory system works

  1. Right ventricle sends oxygen-poor blood to the lungs through the pulmonary trunk

  2. Blood cells pick up oxygen in the lungs

  3. Pulmonary veins carry the oxygenated blood from the lungs to the heart's left atrium

  4. Left atrium sends the oxygenated blood into the left ventricle, which pumps blood out to the body through the arteries

  5. As blood moves through the body, it collects and drops off nutrients, hormones and waste products

  6. Veins carry deoxygenated blood and carbon dioxide back to the heart, which sends the blood to the lungs

  7. Lungs get rid of the carbon dioxide when you exhale.

  
• Conditions affecting the circulatory system

  • Aneurysm
  • High blood pressure
  • Plaque deposits
  • Venous disease
• Aneurysm


  Occur when an artery wall weakens and enlarges.
• High blood pressure


  Force of blood against the blood vessels walls are high.
• Plaque deposits


  Fat and other substances in the blood. Atherosclerosis.
• Venous disease


  Blood can't flow back to the heart and pools in leg veins. Deep vein thrombosis.
• How to prevent circulatory problems

  • 150 minutes of exercise weekly
  • Eat a heart-healthy diet
  • Ease stress
  • Maintain healthy weight
  • Manage conditions
  • Quit smoking