Transport in humans

• Blood acts as a transport medium for:

  • Digested food substances
  • Excretory products (e.g. urea and carbon dioxide) -Hormones
  • Heat
  • Oxygen
• Blood consists of red blood cell, white blood cell, plasma and platelets
• Plasma contains excretory products, food substance, mineral salts and proteins (fibrinogen, prothrombin and antibodies
• Red blood cells transport oxygen from lungs to other parts of the body
• Red blood cells contains haemoglobin
• Haemoglobin is purplish red when there is lesser oxygen
• Adaptations of red blood cell

  1. Circular biconcave shape- increase the surface area-to-volume ratio which increases the rate of diffusion of oxygen into and out of the cell.)
  2. No nucleus - more space available for more haemoglobin to transport more oxygen)
  3. Flexible and can change into a bell-shaped structure -move easily through narrow capillaries. Slows down due to tumbling action hence more time for absorption or release of oxygen.
• • Blood clotting (platelets)
  • Phagocytosis (phagocytes)
  • Production of antibodies (lymphocytes)
• Lymphocyte

  
• Phagocyte

  
• phagocytes engulf and ingest pathogens by phagocytosis
• lymphocytes produce antibodies to agglutinate pathogens and neutralise toxins
• platelets contain an enzyme that catalyses

  the conversion of fibrinogen to fibrin threads
• Explain how the blood functions to prevent entry of foreign body from wounds

  • Damaged tissues and platelets release an enzyme known as thrombokinase
  • Thrombokinase converts prothrombin into thrombin in the presence of calcium ions
  • thrombin converts soluble fibrinogen into insoluble fibrin threads
  • a mesh to entangle blood cells and form a clot to seal the wound preventing pathogens from entering the wound and causing infections
• Antigens and antibodies

  
• Blood type O is the universal donor
• Blood type AB is the universal acceptor

  • no blood type antibodies in blood plasma
• agglutination, is damaging as they can block blood vessels.
• Veins

  Many venules unite to form bigger veins which carry blood towards the heart.

  
• Venules

  Capillaries are linked to small veins called venules.

  
• arteries carry blood away from the heart
• Adaptations of Veins

  • The function of veins is to transported deoxygenated blood (except pulmonary veins) back to the heart.
  • Presence of valves- prevent back flow of blood. Blood that is in the vein has lower pressure and speed, thus blood tends to backflow.
  • Walls of veins are relatively thinner compared to the walls of the arteries. - Blood flows more slowly and smoothly compared to in the arteries

  
• Adaptations of Arteries

  • Transports oxygenated blood (except pulmonary arteries) from the heart to other parts of the body
  • Walls are thick muscular and elastic to withstand the high blood pressure of blood flowing within.
  • The elasticity helps the artery wall to stretch and recoil to push blood forward
  • The contraction and relaxation of the arterial walls to divert blood to certain organs at certain times

  
• Factors affecting diffusion:

  • Temperature*

  • Surface area

  • Diffusion distance

  • Steep concentration gradient

  *temperature does not matter in the human body because it is constant
• blood capillaries is to facilitate exchange of substances between blood and tissue cells in the body.
• Features of blood capillaries:

  • partially permeable, one-cell thick endothelium – minimize diffusion distance
  • vessels: tiny and numerously branched to increase the surface area for exchange of substances
  • increase the total cross-sectional area of the blood vessels, lowering the blood pressure and thereby slowing blood flow to give more time for exchange of substances
• Movement of blood in a double circulation:

  • From the heart to the lungs to the heart (pulmonary circulation)
  • From the heart to the rest of the body back to the heart (systemic circulation)
  • blood has to pass through the heart twice in one complete circuit.
• Advantages of double circulation

  • Blood enters the pulmonary circulation at a low pressure, ensuring sufficient time for blood to be fully oxygenated before returning to the heart.
  • Blood is pumped into the systemic circulation at a high pressure, ensuring oxygenated blood is quickly distributed to all the tissues in the body.
• Hole in the heart

  • The hole in the median septum will result in the mixing of oxygenated and deoxygenated blood, thereby reducing the concentration gradient for oxygen (and carbon dioxide) and reduces efficiency of gas exchange.
  • This condition may cause problems such as shortness of breath, fatigue and heart failure.
• Systole = Contraction
• Diastole = Relaxation
• Cardia cycle
• Cardiac cycle

  1. Passive filling
  2. Atrial systole
  3. Ventricular Systole
  4. Ventricular diastole
  5. passive filling of blood (repeat cycle)
• What Are the Causes of Coronary Heart Diseases?

  • Buildup of fatty substances on inner surfaces of coronary arteries.
  • Lumen of arteries is narrowed
  • Blood clot forms in artery fatty deposits
  • Reduced blood flow to heart
  • Heart muscle cells receive reduced oxygen and glucose supply
  • May lead to a heart muscle cell death and heart attack

  
• How can Coronary Heart Disease be Treated?

  • Drugs

  • Surgery

  • Minor surgery: Balloon Angioplasty

  • Major surgery: Heart Bypass