Cardiovascular System

• Cardiovascular system


  Network composed of the heart as a centralized pump, blood vessels that distribute blood throughout the body, and the blood itself, for transportation of different substances
• Cardiovascular system


  • Main function is to deliver oxygen to the body tissues, whilst simultaneously removing carbon dioxide produced by metabolism
• Blood


  Liquid tissue with cellular component suspended in a liquid called plasma, weakly alkaline (pH 7.4), 5-6 litres (average male)
• Components of Blood in a Normal Adult

  • Plasma
  • Cellular component
• Functions of Blood


  • Transport
  • To control the process of metabolism
  • Maintains homeostasis
  • To protect the body against microbes
  • Blood clotting
• Plasma


  Clear fluid, 55% of blood, 90% water, Dissolved electrolytes, plasma proteins, clotting factors, Immunoglobulin, polypeptides, hormones, Other proteins
• Cellular component


  Red blood cells, white blood cells, and platelet-producing cells
• Stem cells and blood cell production

  1. Hematopoietic stem cell

  2. Myeloid stem cells give rise to red blood cells, platelets, and some types of white blood cells

  3. Lymphoid stem cells give rise to lymphocytes
• Blood platelets


  Very small in size, irregular shaped & enucleated, Lifespan 10 days, Removed by macrophages, 250,000 per mm3, produced in bone marrow, role in blood clotting and coagulation
• White blood cells (Leucocytes, W.B.Cs)


  7000 cells/mm3, number increases during a disease, colourless & nucleated, Lifespan 13-20 days, continuously formed in bone marrow, spleen, & lymphatic system, main function - protection against infectious diseases, Circulate continuously in blood vessels, Attack foreign particles
• Classification of white blood cells

  • Granulocytes
  • Agranulocytes
• Monocytes


  The largest leukocytes, account for 2-8% of all leukocytes, phagocytic, macrophages in tissues, involved in both inflammatory and anti-inflammatory processes
• Granulocytes


  Most abundant, involved in bacterial infections, allergic reactions, parasitic infection, immediate allergic hypersensitivity, Granules contain inflammatory agents
• Lymphocytes


  3 types: B cells, T cells, & natural killer (N K) cells, the major combatants in immune responses, B cells develop into plasma cells and produce antibodies, T cells attack viruses, fungi, and cancer cells, Natural killer cells attack a wide variety of infectious microbes and tumour cells
• Red blood cells (Erythrocytes, R.B.Cs)


  Most abundant blood cells, 4- 5 million cells/mm3, destroyed after 120 days in liver, spleen and bone marrow, Proteins from haemoglobin used in bile formation, Produced in the bone marrow, Round, biconcave, enucleated, Contain haemoglobin (protein + iron)
• Haemoglobin – Structure and Function

  Haemoglobin(Hb) can bind to oxygen (O2) & nitric oxide (NO(g)), NO relaxes capillary walls- expansion, Hb releases O2 which diffuses to body cells, Haemoglobin has four subunits with haem group including a central iron atom, 1 molecule Hb can carry four oxygen molecules
• Haemostasis


  A sequence of responses that stops bleeding when blood vessels are injured, quick, localized, carefully controlled, 3 mechanisms reduce blood loss from vessels: vascular spasm, platelet plug formation, blood clotting (coagulation)
• Blood Clotting


  Formation of prothrombinase, prothrombin to thrombin, fibrinogen to fibrin
• Hemostasis


  Once a blood clot is formed, it plugs the ruptured area of the blood vessel and thus stops blood loss, Clot retraction is the consolidation or tightening of the fibrin clot, Clotting in an unbroken blood vessel is called thrombosis, A thrombus that moves from its site of origin is called an embolus, Anticoagulants (for example, heparin) prevent clotting
• Blood Grouping


  The surfaces of red blood cells contain a genetically determined assortment of antigens composed of glycolipids and glycoproteins, The A B O blood group is based on two antigens called A and B, these determine blood type
• Blood Type Is Determined Genetically


  A allele codes for an enzyme that makes the A antigen, B allele codes for an enzyme that makes the B antigen, O allele codes for a non-functional protein; so no antigen
• Blood plasma


  Contains antibodies anti-A antibodies and anti-B antibodies, A person's plasma does not contain any antibodies that will bind to molecules that are part of his or her own body
• A B O Blood Typing

  People with type O blood are universal donors, People with type AB blood are universal recipients
• Rh factor


  The Rh factor is a red blood cell antigen, The Rh blood group system depends on the presence or absence of the Rh antigen, an inherited characteristic, Rh+ have the Rh antigen on their red blood cells, Rh negative (Rh-) do not
• Blood vessels


  Tubes that run through the transport system in which blood is transported, Allow blood to be pumped at a high pressure to deliver nutrients and remove metabolic waste effectively, Five main types: Arteries, Arterioles, Veins, Venules, Capillaries
• Comparative Structure of Blood Vessels

  • Three layers (tunica): Intima, media, and adventitia, Different thickness of layers in vessels, most distinct in arteries, Veins all similar – different sizes, Arteries – muscular/elasticity specialisations, Generally goes from oxygenated blood to deoxygenated blood, Capillaries are the site of gas and nutrient exchange, Only fit 1 blood cell at a time
• Blood Vessel Structure and Function

  Arteries carry blood away from the heart to body tissues, Their walls consist of three layers: endothelium, smooth muscle (middle layer), outer layer, The structure of the middle layer gives arteries their two major properties, elasticity and contractility, Arterioles - small arteries that deliver blood to capillaries, Vasoconstriction is a decrease in the diameter of the blood vessel lumen and vasodilation is an increase
• Interconnection between blood vessels
• Capillary Exchange


  Capillaries have very small, thin walls that consist of a single layer of endothelium, Rapid diffusion of oxygen and carbon dioxide, The lumen is v. narrow so red blood cells are squeezed against the endothelium, short diffusion distance for oxygen and nutrient exchange, Fenestrations (gaps) in endothelium allow substances dissolved in blood plasma to move in and out, Capillaries : highly branched and numerous providing a large surface area for diffusion
• Capillaries


  • Site of gas and nutrient exchange
  • Only fit 1 blood cell at a time
• Arteries


  • Carry blood away from the heart to body tissues
  • Walls consist of 3 layers: endothelium, smooth muscle (middle layer), outer layer
• Arteries


  • Elasticity and contractility
• Arterioles


  Small arteries that deliver blood to capillaries
• Vasoconstriction


  Decrease in the diameter of the blood vessel lumen
• Vasodilation


  Increase in the diameter of the blood vessel lumen
• Capillaries


  • Very small, thin walls that consist of a single layer of endothelium
  • Rapid diffusion of oxygen and carbon dioxide
  • Lumen is very narrow so red blood cells are squeezed against the endothelium
  • Short diffusion distance for oxygen and nutrient exchange
  • Fenestrations (gaps) in endothelium allow substances dissolved in blood plasma to move in and out
  • Highly branched and numerous providing a large surface area for diffusion
• Starling Forces


  • Blood hydrostatic pressure
  • Blood colloid osmotic (oncotic) pressure
  • Interstitial hydrostatic pressure
  • Interstitial colloid osmotic (oncotic) pressure
• Near the arterial end of the capillary


  Net filtration occurs since capillary hydrostatic pressure (CHP) is greater than blood colloidal osmotic pressure (BCOP)
• Near the midpoint of the capillary


  There is no net movement of fluid since CHP = BCOP
• Near the venous end of the capillary

  Net reabsorption occurs since BCOP is greater than CHP