Presentation on theme: "Lung function & Structure"— Presentation transcript:
1 Lung function & Structure Lung StructureLung function & Structure
2 You should know The gross structure of the respiratory system The essential features of the alveolar epithelium as a surface over which gas exchange occursThe exchange of gases in the lungsThe mechanism of breathingPulmonary ventilation as the product of tidal volume and ventilation rate
3 Lung StructureLungs are the interface for the exchange of gases and their function is affected by both pathogens and lifestyle.All aerobic organisms require a constant supply of oxygen in order to release energy in the form of ATP during respiration. The waste gas product carbon dioxide also has to be removed because the build up can be harmful.
4 Why have lungs?We need lungs to enable oxygenation of our blood system in order to circulate to the relatively large volume of living cells. Mammals have to maintain a high body temperature and therefore have high metabolic and respiratory rates.Air enters via the trachea and then into the left and right bronchus (plural bronchi). The bronchi lead into a pair of lobed structures called the lungs. Lungs consist of a series of highly branched tubules called bronchioles which end up in tiny air sacs called alveoli.
7 Why are a mammals lungs located within the body? Air is not dense enough to support and protect delicate structuresThey would cause loss of a great deal of water and dry outBecause lungs are located internally, we need to have a means of moving the external medium (air) over the surface of our lungs. This movement is called ventilation.
8 Rib cageRib cage is moved by muscles between ribs (intercostal muscles covered later)Causes ventilation by a tidal streamMeans constant replenishment of air
9 TracheaFlexible and supported with cartilageCartilage prevents trachea collapsing when air pressure fallsTracheal walls consist of muscleLined with ciliated epithelium and goblet cellsGoblet cells produce mucus to trap dirt particles and bacteriaCilia move mucus + dirt/bacteria up the throat into oesophagus to stomach
10 Bronchi Two divisions of the trachea – each leading to one lung Bronchi (plural) and left and right bronchus (singular)Similar cell structure as trachea – produce mucus and have ciliaLarger bronchi have cartilage – cartilage reduced as bronchi get smaller
11 Bronchioles Series of branching subdivisions of the bronchi Walls made of muscle lined with epithelial cellsMuscle permits constriction to control the flow of air in and out of the alveoli
12 Alveoli (plural); alveolus (singular) Alveoli are minute air sacs (about μm) at the end of the bronchiolesContain collagen and elastic fibresElastic fibres allow alveoli to stretch when breathing inWhen breath exits, elastic fibres spring/recoil back to aid expulsion of carbon dioxideLined with squamous epitheliumAlveoli membrane is the gas-exchange surface of the lungsBlood vessels line the alveoli to diffuse gases
14 List key structures of air travelling from the nostril to the blood vessels surrounding the alveoli? Nostril → nasal cavity → trachea → bronchi →bronchioles → alveoli → blood vessels
15 Mechanisms of Breathing Remember in Biology we DO NOT call the process of intake of air ‘Respiration’ (that is the process of ENERGY production), we call this process Ventilation.We must remember the HIGH → LOW rule again for particle movementThis time we are talking about air pressure.
17 Breathing Inspiration External intercostal muscles pull ribs up and out.Diaphragm muscles flatten diaphragmVolume of thorax increasesAir pressure within thorax dropsAir enters lungsExpirationInternal intercostals muscles contract so ribs fallDiaphragm muscles relax so it becomes dome-shapedVolume of thorax decreasesAir pressure within thorax increasesAir leaves lungs
18 ACTIVE PROCESS – uses ENERY Largely PASSIVE PROCESS – requires little energy
19 Diaphragm A sheet of muscle between the thorax and abdomen The diaphragm is curved upward (domed position) when relaxedWhen diaphragm muscles contract, it flattens and moves downCausing an increase in thorax volume
20 During NORMAL quiet breathing, the recoil of the elastin within alveoli walls of the lungs is the MAIN cause of air being forced out (similar to balloons). Muscles become most important during strenuous condition such as exercise.
21 What is Pulmonary Ventilation? The total volume of air that is moved into the lungs during one minuteTo calculate this we need multiply two factors:TIDAL VOLUME = volume of air normally taken in at EACH breath when body is at REST (usually 0.5dm3)VENTILATION (Breathing) RATE= the number of breaths taken in one minute. (usually breaths)
28 What is the role of the alveoli in gas exchange? We have about 300 million alveoli in EACH human lung.Their total surface area is 70m2 (half a tennis court)Each alveoli is lined with squamous epithelial cells (0.05μm to 0.3μm thick)AROUND each alveoli is a network of pulmonary capillariesVery narrow (7-10μm thick) so that red blood cells are flattened against the wallsAlso have a single very thin wall (0.04μm – 0.2μm)
29 Complete the following table identifying essential features of gas exchange surfaces: CharacteristicBenefit to gas exchangeLarge surface area to volume ratioSpeeds up gas exchangeSquamous epithelial cellsVery thin to keep diffusion distance smallPartially permeableSelective materials permitted acrossMovement of environmental medium (air)Maintain diffusion gradient (O2 in & CO2 out)Movement of internal medium (blood)MoistureAids optimal gas diffusion
30 Surface Area of exchange x Concentration Gradient Diffusion Distance Fick`s LawRate of Diffusion is proportional to:Surface Area of exchange x Concentration Gradient Diffusion Distance
31 Fill in missing gaps with additional key words: Label the above diagram showing the key features with the appropriate number(s):
32 Summary QuestionsHow does each of the following features contribute to gas exchange efficiency?The wall of each alveolus is not more than 0.3μm thick?Diffusion distance small – thus rapid movementThere are 300 million alveoli in each lung?Collectively, very large surface areaThe surfaces of the alveoli are moist?Permits optimal gas exchange; gases are exchanged in solution.Each alveolus is covered by a dense network of pulmonary blood capillaries?Collectively, provide a VERY large surface interface with blood
33 Each pulmonary capillary is very narrow? Enables slowing down of blood (thus diffusion occurs faster) and blood cells pushed against capillary way to make diffusion distance smaller also
34 Explain the differences in air composition between the three samples.
35 Explain the differences in air composition between the three samples. Exhaled air has been mixed with residual air within the air passages (bronchioles, bronchi and trachea) so is closer to atmospheric air in composition than that in the alveolar lumen.Alveolar air has oxygen removed and carbon dioxide added.
36 SummaryLung functionThe gross structure of the human gas exchange system limited to the alveoli, bronchioles, bronchi, trachea and lungs.The essential features of the alveolar epithelium as a surface over which gas exchange takes place.The mechanism of breathing.Pulmonary ventilation as the product of tidal volume and ventilation rate.The exchange of gases in the lungs.