Unit 4

• name of red blood cells


  erythrocytes
• name of white blood cells


  leucocytes
• plasma


  the liquid part of blood. It's mostly water but contains a weak solution of salts, glucose, amino acids, vitamins, urea, proteins and fats (55%)
• white blood cells


  involved in the immune system - help destroy bacteria (<1%). It consists of Neutrophils, Lymphocytes, and Monocytes
• neutrophils


  B-type cells produce antibodies
• Lymphocytes


  T-type cells destroy viruses and cancer cells
• monocytes


  removes dead cells and bacteria
• red blood cells


  carry oxygen and some carbon dioxide
• platelets


  triggers blood clotting. without it you would bleed to death (<1%)
• lipoproteins


  proteins that carry elements that cant dissolve in water, e.g. fats
• pathogen


  disease causing organisms, like bacteria, parasites and viruses
• antigens


  they form antibodies
• antibodies


  lock onto specific chemicals in the walls of the bacteria and parasites, immobilising them and making them targets for the monocytes that then kill them and break them down
• coagulation


  a chain reaction that converts the soluble blood protein (fibrinogen) into an insoluble form (fibrin), that forms a net structure, trapping platelets and erythrocytes to form a clot. this reaction is set off by tiny cell fragments from the bone marrow, called platelets, are exposed to air or foreign material
• double circulatory system (double pump)

  the heart pumps blood through two circuits, the pulmonary and systemic
• systemic circuit


  left side of heart receives oxygenated blood from lungs and pumps it around the body
• pulmonary circuit


  right side of heart receives deoxygenated blood from the body and pumps it to the lungs
• myogenic


  the heart muscle is myogenic - it can beat automatically without stimulation by nerves
• cardiac cycle


  the co-ordinated flow of blood through the heart. it takes place on average 70 times per minute.
• systole


  ventricles contract, pumping blood out
• diastole


  heart relaxes and the atria fill with blood
• the SA node (sino-atrial node)


  coordinates rhythm of heart and ensures both atria contract simultaneously by passing an electrical current through the atria
• AV node (atrial-ventricular)


  at the bottom of the right atrium. it slows the electrical impulses it receives from the SA node to allow ventricles to fill with blood
• Purkyne fibres


  carry current down the middle of the ventricles to the base of the heart. this allows the bottom of the heart to contract first, resulting in an upwards, squeezing action, forcing blood out into arteries
• ECG (electrocardiogram)


  shows the electrical signal generated by the SA node as it travels through the atria, the AV node and the ventricles. electrodes are attached to the chest and fed to a computer screen. the activity of the heart is shown in waves or spikes
• p wave


  a small blip - shows the moment when atria are both contracting
• QRS wave


  a bigger spike after a p wave that shows the ventricles contracting (systole)
• T wave


  a smaller wave - shows the ventricles relaxing (diastole)
• arteries


  - carrys oxygenated blood away from the heart

  
  

  - walls are thick, elastic and muscular as blood is under high pressure

  
  

  - blood flows in pulses (arteries expand and recoil)

  
  

  - small internal diameter
• capillaries


  - walls are one cell thick

  
  

  - they are microscopic

  
  

  - they surround and interweave between cells and tissues

  
  

  - they supply tissues with oxygen and nutrients and remove waste products like carbon dioxide
• veins


  - carry deoxygenated blood towards the heart

  
  

  - walls are thin with little muscle as blood is under low pressure

  
  

  - contain valves to prevent backflow

  
  

  - large internal diameter

  
  

  - are often between muscles so movements help squeeze blood along
• osmosis


  the movement of water through a semi-permeable membrane from a less concentrated solution to a more concentrated one
• osmotic pressure


  pressure that must be applied to prevent osmotic movement across a selectively permeable membrane
• lymph


  watery fluid drained by the lymphatic system

  
  

  formed from plasma

  
  

  contains white blood cells

  
  

  involved in the removal of wastes and infectious organisms from tissues
• tissue fluid


  fluid between body cells

  
  

  carries nutrients and oxygen to tissue cells

  
  

  is formed from filtering of blood from capillaries due to hydrostatic pressure
• blood plasma


  liquid component of blood

  
  

  contains plasma proteins, which have roles in blood clotting and supporting the immune system

  
  

  osmotic regulation
• osmotic regulation


  control of the water content of the body, avoiding too much water entering or leaving the cells
• lymphatic system


  a drainage and filtrations system

  
  

  it removes excess fluid from body tissues

  
  

  it absorbs fatty acids and transports fat into the bloodstream to be absorbed in the small intestine

  
  

  it produces white blood cells (which produce antibodies)
• lymph nodes


  swellings along the lymphatic system. they store and develop lymphocytes that screen the returning tissue fluid or lymph for pathogens, destroying any that are found. when fighting an infection these nodes swell so we often refer to our glans swelling
• hydrostatic pressure


  pressure from heart contractions that forces water and dissolved substances in plasma out through capillary walls into surrounding tissues, forming tissue fluid