EXCHANGE AND TRANSPORT

• Exchange via surface


  • Nutrients (e.g. glucose, oxygen) move in by diffusion via their surface
  • Waste (e.g. carbon dioxide) move out by diffusion via their surface
• Microorganisms


  • Have a large surface area to volume ratio
  • Have a short diffusion distance
  • Have low demand
• Animals/Plants


  • Have a small surface area to volume ratio
  • Multicellular (large diffusion distance and high demand)
  • Impermeable surface (prevent pathogens entering and reduce water loss)
• Exchange system


  Increases rate of diffusion of nutrients in and wastes out
• Transport system


  Deliver nutrients and remove waste from all cells
• Fish


  • Multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand & body surface impermeable
• Gills


  Specialised gas exchange system in fish
• Structure of Gills


  1. Many gill filaments and gill lamellae = large surface area

  2. Gill lamellae have a thin wall (short diffusion distance) and are permeable

  3. Ventilation brings in pure water (high oxygen, low carbon dioxide) and circulation brings in deoxygenated blood (low oxygen, high carbon dioxide), the water and blood pass over in opposite directions (countercurrent flow), which maintains concentration gradient all the way along the gill lamellae
• Insects


  • Multicellular organism so has a small surface area to volume ratio, large diffusion distance, high demand & body surface made of exoskeleton (impermeable barrier to reduce water loss)
• Tracheal System


  Specialised gas exchange system in insects
• Structure of Tracheal System


  1. Starts with openings on body surface called Spiracles

  2. Spiracles contain valves, open = gas exchange, closed = prevent water loss

  3. Spiracles connect to Trachea

  4. Trachea connect to Tracheoles

  5. Tracheoles connect directly to Respiring Cells (delivering oxygen, removing carbon dioxide)
• Gas Exchange in Tracheal System

  1. At rest = down a concentration gradient, oxygen moves in & carbon dioxide moves out by simple diffusion

  2. When active = by ventilation, air inhaled for mass flow of O2 in & air exhaled for mass flow of CO2 out
• Lungs


  Site of gas exchange in mammals (oxygen into blood - used in cells for respiration, carbon dioxide out of the blood - toxic waste product of respiration)
• Parts of Lungs


  • Trachea
  • Bronchi
  • Bronchioles
  • Alveoli (+ capillaries)
• Trachea/Bronchi


  Transport of air and filter air, (bronchioles also controls amount of air reaching alveoli)
• Structure of Trachea/Bronchi


  1. Wall made of c-shaped cartilage

  2. Cartilage is strong so trachea/bronchi do not collapse

  3. Cartilage is c-shaped to give flexibility

  4. Lining made of goblet cells and ciliated epithelial cells

  5. Goblet cells make mucus, which traps pathogens/particles

  6. Ciliated epithelial cells have cilia, which pushes mucus up and out of lungs
• Structure of Bronchioles


  1. Wall made of smooth muscle

  2. Smooth muscle contracts, lumen narrows, bronchiole constricts

  3. Lining made of goblet cells and ciliated epithelial cells
• Alveoli


  • Millions of tiny alveoli that are folded (large surface area)
  • Thin wall/one cell thick/squamous epithelial cells (short diffusion distance)
  • Elastic tissue in wall (stretches when breathing in to increase surface area, recoils when breathing out to push the air out)
  • Ventilation maintains concentration gradient (high oxygen, low carbon dioxide)
• Capillaries


  • Millions of tiny capillaries (large surface area)
  • Thin wall/one cell thick/squamous epithelial cells (short diffusion distance)
  • Narrow lumen (increases diffusion time, decreases diffusion distance)
  • Circulation maintains concentration gradient (low oxygen, high carbon dioxide)
• Oxygen movement from alveoli to capillaries


  By simple diffusion passing thru the alveolar epithelium and capillary epithelium
• Carbon dioxide movement from capillaries to alveoli


  By simple diffusion passing thru the capillary epithelium and alveoli epithelium
• Breathing/Ventilation


  1. Breathing In/Inhalation = external intercostal muscles contract (rib cage moves up and out) & diaphragm contracts (flattens), therefore increase in volume in chest and decrease in pressure, so air moves in

  2. Breathing Out/Exhalation = external intercostal muscle relax (rib cage moves down and in) & diaphragm relaxes (back to dome shape), therefore decrease in volume in chest and increase in pressure, so air pushed out (aided by elastic recoil in the alveoli)
• Pulmonary Ventilation


  • PV = tidal volume x ventilation rate
  • Tidal volume = volume of air breathed in/out in one breath
  • Ventilation rate = number of breaths per minute
  • Pulmonary Ventilation = volume of air breathed in/out per minute
• Digestion


  Breakdown of Large Insoluble Molecules into Small Soluble Molecules (so they can move into the blood and then into the body cells)
• Digestion of Macromolecules


  1. Starch/Glycogen (Carbohydrates) into Glucose by Amylase (Salivary in mouth, Pancreatic in small intestine) and Maltase/Lactase/Sucrase (on lining of small intestine)

  2. Proteins into Amino Acids by Endopeptidase/Exopeptidase/Dipeptidase (Endopeptidase in stomach, Exopeptidase in small intestine, Dipeptidase on lining of small intestine)

  3. Lipids into Monoglyceride and 2 Fatty Acids by Lipase (in small intestine)
• Intestine Absorption


  • Small Intestine absorbs small soluble nutrients (glucose, amino acids, monoglyceride and fatty acid, vitamins and minerals)
  • Large Intestine absorbs water
• Humans/Mammals


  • Multicellular organisms therefore have large diffusion distances and high demand
  • Need a transport system to deliver nutrients and remove waste from all cells
• Circulatory System


  Transport system in humans/mammals, made of heart, blood vessels, blood (heart pumps blood, blood vessels carry blood, blood carries nutrients/waste)
• Double circulatory system


  The heart pumps twice, the blood goes through the heart twice - generates enough pressure to supply all body cells
• Closed circulatory system


  Blood is transported in blood vessels - helps to maintain pressure and redirect blood flow
• Layout of Circulatory System

  1. Heart pumps blood which is carried in arteries which flow into arterioles which flow into capillaries which then are carried in venules then veins back to the heart

  2. Artery to Arterioles to Capillaries to Venules to Veins

  3. Artery/Arterioles carry blood away from the heart (arterioles are small arteries)

  4. Capillaries are the site of exchange (nutrients out, waste in)

  5. Veins/Venules return blood back to the heart (venules are small veins)
• Heart


  • Job is to pump blood around the body (delivers nutrients to cells and remove waste)
  • Made of 4 muscular chambers (2 atria, 2 ventricles)
  • Atria pumps blood to ventricles, ventricles pump blood out of heart (R to lungs, L to body)
  • Ventricles thicker then atria (has to pump blood further)
  • Left ventricle has a thicker muscular wall then right ventricle, therefore has stronger contractions, so can generate higher pressure and pump the blood further around the body
• Blood vessels of the heart


  1. Vena Cava supplies R atrium (with deoxygenated blood from body)

  2. Pulmonary Vein supplies L atrium (with oxygenated blood from lungs)

  3. R ventricle supplies Pulmonary Artery (deoxygenated blood to lungs)

  4. L ventricle supplies Aorta (oxygenated blood to body)
• Valves in heart


  • Ensure one way flow of blood, no backflow (blood flows from atria to ventricles to arteries)
  • 2 sets of valves: Atrio-ventricular Valve & Semi-lunar Valve
  • AV valve = between atria and ventricles
  • SL valve = between ventricles and arteries
• AV valves open/closed


  Open = pressure in atria greater then pressure in ventricles, Closed = pressure in ventricles greater then pressure in atria
• SL valves open/closed


  Open = pressure in ventricles greater then pressure in arteries, Closed = pressure in arteries greater then pressure in ventricles
• Cardiac cycle


  1. Filling Stage = atria relaxed, ventricles relaxed, AV valve open, SL valve closed

  2. Atria Contracts = the SAN located in the R atrium initiates the heart beat and sends the impulse across both atria making them contract, this pushes all the remaining blood into the ventricles so it becomes full

  3. Ventricles Contract = the AVN picks up the impulse, delays it (stops the atria and ventricles contracting at the same time, so the atria empties and the ventricles fill), sends the impulse down the septum in the Bundle of His, then at the apex the impulse goes up both walls of the ventricles in the purkine fibres, so the ventricles contract from the base upwards, pushing the blood up thru the arteries, when the ventricles start to contract the AV valve closes then the SL valve opens and blood leaves the heart

  4. Ventricles Relax = the SL valve closes then the AV valve opens and filling starts again
• Heart Sounds


  • Caused by the valves closing
  • 1st = AV closes
  • 2nd = SL closes
• Cardiac Output


  • CO = Stroke Volume x Heart Rate
  • Stroke volume = volume of blood pumped out of the heart in one beat
  • Heart rate = number of beats per minute
  • Cardiac Output = volume of blood pumped out of the heart in one minute
• Heart beat


  1. Impulse across both atria

  2. Atria contract

  3. Blood pushed into ventricles

  4. Ventricles fill