Circulatory System

• THE HUMAN CIRCULATORY SYSTEM

  • To transport blood, oxygen and nutrients to the body.  
  • Responsible for the distribution and pumping of the blood. 
• Main Parts of the Circulatory System

  • heart
  • blood vessels
  • blood
• COMPOSITION OF BLOOD

  • Formed Elements
  • Extracellular Fluid
• Formed Elements

  • Red Blood Cells
  • White Blood Cells
  • Platelets
• Extracellular Fluid

  • Plasma
• PLASMA

  • It is a special fluid primarily contained within the blood vessels.  
  • It holds the blood cells in suspension and makes up 55% of the blood's volume. 
• RED BLOOD CELLS (erythrocytes)

  • It is the most abundant cells in the blood.
  • Nearly 40% of the blood's volume is red blood cells. 
  • It takes oxygen in the lungs and delivers it to the tissues.  
  • It also transports carbon dioxide to the lungs
• White Blood Cells (leukocytes)

  Fight diseases and protect from infection
• Types of White Blood Cells

  1. Basophils
  2. Eosinophils
  3. Neutrophils
  4. Lymphocytes
  5. Monocytes
• Eosinophils


  controlling parasitic infection and allergic reaction
• Lymphocytes 


  viral infection and adaptive immunity
• Neutrophils


  respond to bacterial and fungal infections
• Basophils


  aid in allergic reaction
• Monocytes


  chronic infections and part of the innate immunity
• The WBCs engulf and digest the infectious agents via phagocytosis

  
• PLATELETS (thrombocytes)

  • Help in clotting of blood to stop bleeding.  
  • Aggregates on the injured portion of the blood vessel.
• THE HEART

  • The heart is composed of strong cardiac muscle tissues that continuously contract and relax to pump blood all throughout the body.  
  • Situated on the left portion of the middle chest is the heart
  • It works as a pump to move the blood around the body.  
  • It has four chambers—two atria (upper chambers) and two ventricles (lower chambers).
  • These chambers highly coordinate in pumping blood that must deliver O2 to the tissues and take CO2 for disposal.
• Blood Flow

  1. The right atrium takes in blood carrying carbon dioxide. 
  2. Blood is squeezed down into the right ventricle and taken to the lungs, where oxygen replaces carbon dioxide.
  3. Oxygen-carrying blood from the lungs enters the left atrium.
  4. Blood is pumped into the left ventricle and starts its journey again throughout the body
• Oxygenated blood enters the left atrium and then to the left ventricle. The wall of the left ventricle contracts to pump oxygenated blood to all parts of the body via the aorta. On the other hand, deoxygenated blood enters the right atrium and then to the right ventricle. The wall of the right ventricle contracts to pump the deoxygenated blood to the lungs
• This mechanism is the reason why the wall of the left ventricle is thicker than the right since the left ventricle has to pump blood throughout the body while the right ventricle only has to pump blood to the lungs.
• MAJOR BLOOD VESSELS

  1. AORTA
  2. PULMONARY ARTERY
  3. VENAE CAVAE
  4. PULMONARY VEIN
• CARDIAC VALVES

  1. Atrioventricular Valves (mitral and tricuspid)
  2. Semilunar Valves (aortic and pulmonary)
• The main function of a valve is to prevent backflow of blood
• Mitral valve


  found between the left atrium and ventricle
• Tricuspid valve


  found between the right atrium and ventricle
• Pulmonary valves and aortic valves are also called semilunar valves because of the moon-shaped leaflets of these valves
• Pulmonary valve


  found between the right ventricle and pulmonary artery
• Aortic valve


  found between the left ventricle and aorta
• BLOOD VESSELS

  • These are tubes or channels that carry blood throughout our body.  
  • Allow fast blood flow from one organ to another.  
  • Enclose the blood in a complex series of tubes that serve as the pathway for blood flow.  
  • They also act as a barrier that prevents blood from coming out and at the same time, allows transport of materials within the membranes.
• Types of Blood Vessels

  • Arteries  
  • Veins  
  • Capillaries 
• Arteries

  • deliver oxygen-rich blood to the cells, away from the heart.
  • as arteries penetrate the organs, they decrease in diameter and become arterioles
  • It has the thickest wall of all three, allowing it to withstand the high pressure created by the heart
• Veins

  • return oxygen-poor blood from the cells back to the heart.
  • as the veins go inward the organs, they decrease in diameter and become venules
  • It is less muscular and stretchy than an artery, so blood moves through it with low pressure. It also has a special valve that helps blood go only one way.
• Capillaries

  • are small blood vessels that connect arteries and veins
  • these can penetrate the inner portion of different organs and facilitate the transfer of oxygen, carbon dioxide, and dissolved substances in and out of your blood.
  • It has the thinnest wall to allow substances such as oxygen and sugars to pass through its wall—into or out of the blood.
• pulmonary arteries which carry deoxygenated blood and pulmonary veins which carry oxygenated blood.
• Sickle cell disease (SCD)


  is an inherited blood disorder. People with SCD have red blood cells that become hard and sticky, forming a C-shaped blood cell instead of the healthy disc-shaped one.