blood

• Elements of blood


  • Plasma
  • Platelets
  • Red blood cells
  • White blood cells
• Plasma


  About 55% of blood
• Platelets


  About 0.01% of blood
• Red blood cells


  About 41% of blood
• White blood cells


  • Lymphocyte
  • Basophil
  • Eosinophill
  • Monocyte
  • Neutrophil
• White blood cells


  About 4% of blood
• Erythrocytes (red blood cells)


  • Made in the bone marrow
  • Usually red due to haemoglobin which transports oxygen and carbon dioxide around the body
  • Thin disc-like shape to increase surface area for gas uptake
  • No nucleus to allow more space to transport gases
  • Flexible to allow passage through small blood vessels
• Leucocytes (white blood cells)


  • Part of the immune system
  • Lymphocytes: B-cells and T-cells
  • B-cells made in bone marrow and produce antibodies to destroy antigens
  • T-cells made in the thymus gland and destroy the body's own cells if they become infected or cancerous
  • Neutrophils are small and fast to react to infections
  • Monocytes are produced in bone marrow and found in the blood and tissues, quickly react when certain germs enter the body
• Platelets


  • Produced in bone marrow and are fragments of other cells
  • Help to form blood clots by clumping together to slow or stop bleeding
  • Help the wound heal
• Blood Plasma


  • Largest component of blood and is the liquid in which blood cells are suspended
  • Used to transport lipids, amino acids glucose, hormones, dissolved food molecules
  • Carries proteins including fibrinogen which aids clotting
  • Helps with temperature regulation as removes heat from tissues and circulates it around the body
• functions of blood

  • transport

  • temperature regulation

  • exchange of materials with body tissues

  • preventing infection

  •blood clotting
• Transport


  One of the main functions of blood is to transport materials around the body
• Lipoproteins


  • Blood proteins that carry materials which do not readily dissolve in water, such as fats
  • Both HDL and LDL transport fat to the tissues where it is needed
• HDL

  High density lipoprotein that tends to transport fat away from deposits of cholesterol in arteries (good cholesterol)
• LDL


  Low density lipoprotein that tends to deposit fat and cholesterol in artery walls (bad cholesterol)
• Gases

  Oxygen and carbon dioxide are transported in the blood by erythrocytes by binding to haemoglobin
• Hormones


  Carried in the blood to where they are needed to respond or initiate a process e.g. insulin to control blood sugar and adrenalin to respond to danger
• Endothermic/Warm-blooded


  • We generate the heat to maintain our internal body temperature at around 37°C - our optimal temperature
  • This is mainly due to the fact that enzymes have an optimal temperature at which they work best and are most efficient
• Too cold

  Reactions in the body slow
• Too hot


  Enzymes denature (change shape) and no longer work
• Heat generation


  Mainly in tissues, and blood removes this and circulates it around the body
• Capillaries in the skin


  Will dilate if the body gets too hot so that more heat is lost via the skin
• Exchange of materials


  Exchange of nutrients and gases between capillaries and body tissues, especially important in the formation of tissue fluid and lymph and allows the maintenance of the correct pressure in the body
• Immune system

  • Neutrophils and B-cells act as antigens and produce antibodies which lock on to chemicals on bacteria and parasites, immobilising them so that monocytes can kill and break them down
  • Some lymphocytes will remember the pathogens and respond more quickly - principle behind vaccinations
  • T-cells are useful against viruses as once a cell is infected by a virus the surface of the cell changes so that the T-cell is then able to latch on and destroy the cell along with the virus
• Blood clotting

  When exposed to air or foreign objects, platelets activate a process of blood coagulation that converts the soluble blood protein fibrinogen into an insoluble form fibrin that forms a net like structure, trapping platelets and erythrocytes to form a clot
• Haemophilia


  Lack one or more of the factors needed for blood clotting, so blood takes longer to clot
• Anticoagulants


  Sometimes given to prevent clotting, such as during operations / kidney dialysis
• Types of blood vessels

  • Arteries
  • Capillaries
  • Veins
• Arteries

  • Largest is the AORTA
  • Have thick walls - muscular and elastic
  • Carry blood under high pressure
  • Carry oxygenated blood away from the heart under high pressure (apart from pulmonary artery)
  • Expand and contract to push blood along
  • Do not have valves (the blood can't flow back as the "push" (pressure) from the heart is strong enough to keep it moving in the right direction)
  • Become smaller arterioles, then capillaries
• Veins

  • Have thin walls
  • Carry deoxygenated blood back to the heart (apart from pulmonary vein)
  • From the capillaries, blood flows into venules, then to veins
  • Have valves to stop the blood flowing in the wrong direction
  • Carry blood under low pressure
  • Blockages can cause problems e.g. varicose veins
• Capillaries


  • Very small blood vessels in our tissues
  • Take blood from arteries to veins
  • Only one blood cell can travel through them at any one time
  • Their walls are only cell thick
  • Oxygen, carbon dioxide and nutrients pass through the thin capillary walls. These substances travel in the tissue fluid
• Erythrocytes (red blood cells)

  Made in the bone marrow, red because of haemoglobin, thin disc-like shape
• Leucocytes (white blood cells)


  Part of the body's immune system, defend the body against infections
• Types of leucocytes


  • Lymphocytes (B-cells and T-cells)
  • Neutrophils
  • Monocytes
• Lymphocytes


  White blood cells that are part of the immune system, B-cells develop in the bone marrow, T-cells develop in the thymus gland, wide-ranging functions in the immune system
• Neutrophils


  Small and fast, one of the first cell types to travel to the site of infection
• Monocytes


  Largest of the white blood cells
• Platelets


  Produced in the bone marrow, fragments of larger cells, disc-shaped
• Plasma


  Largest component of blood, makes up about 55 per cent of blood volume, clear yellowish-coloured liquid, carries platelets, red and white blood cells and proteins
• Red blood cells (erythrocytes) transport oxygen and carbon dioxide within the body, do not have a nucleus, which increases space to carry the maximum amount of haemoglobin, haemoglobin combines with oxygen, so erythrocytes are able to transport more oxygen, they have a bi-concave shape, round and flattened, with a central indentation to maximise the surface area for exposure to oxygen, they are small and flexible, allowing them to get into narrow blood vessels called capillaries