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6.4 Gas Exchange. List the characteristics of alveoli that permit efficient gas exchange. (4 marks)

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Presentation on theme: "6.4 Gas Exchange. List the characteristics of alveoli that permit efficient gas exchange. (4 marks)"— Presentation transcript:

1 6.4 Gas Exchange

2 List the characteristics of alveoli that permit efficient gas exchange. (4 marks)

3 large total surface area; wall of single layer of flattened cells; moist lining; walls elastic; network of capillaries; capillary walls are thin / one cell thick; 4 max

4 6.4.1 Distinguish between ventilation, gas exchange and cell respiration. 1. Ventilation: flow of air (with gases) in and out of the alveoliflow of air (with gases) in and out of the alveoli 2 stages:2 stages: inspiration (or inhalation)inspiration (or inhalation) expiration (or exhalation)expiration (or exhalation) Lungs are not muscularLungs are not muscular Cant ventilate themselvesCant ventilate themselves Whole thorax moves & changes size, due to action of 2 sets of muscles:Whole thorax moves & changes size, due to action of 2 sets of muscles: intercostal muscles and diaphragmintercostal muscles and diaphragm

5 6.4.1 Distinguish between ventilation, gas exchange and cell respiration. 2. Gas capillaries Diffusion of gases (oxygen & carbon dioxide)Diffusion of gases (oxygen & carbon dioxide) 2 sites2 sites Alveoli:Alveoli: O 2 diffuses into blood from alveoliO 2 diffuses into blood from alveoli CO 2 diffuses from blood into alveoliCO 2 diffuses from blood into alveoli Tissues:Tissues: O 2 diffuses from blood into cellsO 2 diffuses from blood into cells CO 2 diffuses from cells to bloodCO 2 diffuses from cells to blood 3. Cell Respiration Aerobic respirationAerobic respiration uses oxygen (in mitochondria) to make ATP, produces CO 2uses oxygen (in mitochondria) to make ATP, produces CO 2 Anaerobic respirationAnaerobic respiration Doesnt use O 2 but still produces CO 2Doesnt use O 2 but still produces CO 2 Diagram, p. 169 Heinemann text

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8 6.4.2 Explain the need for a ventilation system. Were multicellular! (trillions of cells, not all on surface, so too deep for diffusion to work!)Were multicellular! (trillions of cells, not all on surface, so too deep for diffusion to work!) Need it to maintain high conc gradients in alveoliNeed it to maintain high conc gradients in alveoli steep conc grad across resp sfc maintained in 2 ways: blood flow on 1 side air flow on other side O 2 O 2system replaces/diffuses O 2 (keeping conc high) and removes CO 2 (keeping conc low) O 2O 2 can always diffuse down its conc gradient from air to blood CO 2CO 2 can diffuse down its conc gradient from blood to air

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10 6.4.3 Describe the features of alveoli that adapt them to gas exchange. Lg total SA due to combined spherical shape...why? (300 million each lung million alveoli = 80 m 2 ) Alveolus Wall = single layer of flattened epithelial cells close association w/caps...why? Short diffusion distance from alveoli to blood ( um) Dense cap network surrounding each alveolus...why? From L Ventricle, high [Oxygen] To cap organ (first 1-cell surface in contact with...so it diffuses out there) Film of surface for... efficient diffusion, solution of gases

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12 6.4.4 Draw and label a diagram of the ventilation system, including trachea, lungs, bronchi, bronchioles and alveoli. Students should draw the alveoli in an inset diagram at a higher magnification!Students should draw the alveoli in an inset diagram at a higher magnification! (a) Trachea (b) Cartilage ring support (c) Bronchi (plural) Bronchus (single) (d) Lung (e) Heart (f) Sternum (g) Rib cage (h) Bronchioles (j) Alveoli (k) Diaphragm

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14 Draw It!

15 6.4.5 Explain the mechanism of ventilation of the lungs in terms of volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm and abdominal muscles. Inverse relationship: pressure and volumeInverse relationship: pressure and volume Increase in volume decrease in pressureIncrease in volume decrease in pressure 2 environments2 environments Thorax & Internal envt of lungsThorax & Internal envt of lungs

16 6.4.5 Explain the mechanism of ventilation of the lungs in terms of volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm and abdominal muscles. Inhalation: diaphragm contracts (moves down), rib cage expandsInhalation: diaphragm contracts (moves down), rib cage expands diaphragm contracts, flattens downwardsdiaphragm contracts, flattens downwards Abdominal & intercostal muscles contract, raising rib cageAbdominal & intercostal muscles contract, raising rib cage increases volume of thorax decreases P inside thoraxincreases volume of thorax decreases P inside thorax less P pushing on lung tissue less P pushing on lung tissue Increases lung & alveoli volume b/c less P on itIncreases lung & alveoli volume b/c less P on it decrease in P inside lungs (partial vacuum) decrease in P inside lungs (partial vacuum) Air comes in through mouth/nose to counter the partial vacuum w/in lungs & fills alveoli with airAir comes in through mouth/nose to counter the partial vacuum w/in lungs & fills alveoli with air Expiration: opposite, diaphragm relaxed (moves up), rib cage gets smallerExpiration: opposite, diaphragm relaxed (moves up), rib cage gets smaller

17 6.4.5 Explain the mechanism of ventilation of the lungs in terms of volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm and abdominal muscles.

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22 6.2 The Transport System

23 Describe the structures of arteries and veins as related to their functions. (6 marks)

24 Each characteristic must be linked to a function for the mark to be awarded.-- 6 max Arteries: Award [3 max] thick muscular wall to help pump blood / to help distribution of blood; thick outer wall (of collagen and elastic fibres) to withstand high pressure / to avoid bursting / leaks; narrow lumen results in fast-moving blood; Veins: Award [3 max] thin outer muscular walls so no pumping action; thin walls allow pressure from surrounding muscles to move blood; thin walls (of collagen and elastic) as not likely to burst / low pressure; wide lumen allows for slow-moving blood; valves to prevent back flow / control direction of blood flow;

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26 6.2.1 Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves & the route of blood through the heart!! Care should be taken to show the relative wall thickness of the four chambers. (Vent thicker than Atria) Neither the coronary vessels nor the conductive system are required.Care should be taken to show the relative wall thickness of the four chambers. (Vent thicker than Atria) Neither the coronary vessels nor the conductive system are required. THICKER wall of left ventricleTHICKER wall of left ventricle 4 chambers4 chambers Sup & inf vena cavaSup & inf vena cava L, R AV valvesL, R AV valves Pulm SL valvePulm SL valve Aortic SL valveAortic SL valve Pulm artPulm art Pulm veinPulm vein AortaAorta site for IB diagrams

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28 DRAW IT!

29 6.2.2 State that the coronary arteries supply heart muscle with oxygen and nutrients.

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31 6.2.3 Explain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves. A basic understanding is required, limited to the collection of blood by the atria, which is then pumped out by the ventricles into the arteries. The direction of flow is controlled by atrio-ventricular and semilunar valves.A basic understanding is required, limited to the collection of blood by the atria, which is then pumped out by the ventricles into the arteries. The direction of flow is controlled by atrio-ventricular and semilunar valves. Vena cava RT Atrium, certain volume of blood collects through open AV valve, atrium contracts to force remaining blood out RT ventricle, volume accumulates, contracts AV valve closes to prevent backflow (lub-dub) Dramatic increase in blood pressure in Rt Vent opens pulm SL valve (lub-dub), blood pulm artery lungs, arterioles, capillaries, gas exchange, venules, pulm vein

32 6.2.3 Explain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves. LT ATRIUM, volume, open AV valve, contracts (same time as Rt) L Vent L Vent contracts: AV valve closes (backflow), increased pressure in L Vent opens left SL valve, blood to aorta arteries, arterioles, capillaries, gas exchange to drop OFF oxygen...gain carbon dioxide, back to heart! All this...in a minute or two!

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35 Artificial heart valves!

36 6.2.4 Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline). Myogenic muscle contractionMyogenic muscle contraction Cardiac muscle spontaneously contracts/relaxesCardiac muscle spontaneously contracts/relaxes SA node (mass of tissue) = pacemakerSA node (mass of tissue) = pacemaker sends regularly paced electrical signal to initiate atrial contractionssends regularly paced electrical signal to initiate atrial contractions HR = 72 bpm... Signal sent every 0.8 seconds!HR = 72 bpm... Signal sent every 0.8 seconds! AV nodeAV node receives signal from SA node, waits ~0.1 sec,receives signal from SA node, waits ~0.1 sec, sends another to ventricles (more muscular) for contractionsends another to ventricles (more muscular) for contraction Atria contract, pause, ventricles contractAtria contract, pause, ventricles contract

37 6.2.4 Outline the control of the heartbeat in terms of myogenic muscle contraction, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline). Increased exercise ???Increased exercise ??? Need faster gas exchange to keep up w/cell respirationNeed faster gas exchange to keep up w/cell respiration Medulla (brainstem) senses increase in CO 2Medulla (brainstem) senses increase in CO 2 Sends signal thru cardiac nerve to SA node to increase heart rate to appropriate levelSends signal thru cardiac nerve to SA node to increase heart rate to appropriate level At End of exercise: another signal is sent, by vagus nerve to SA nodeslows HR back downAt End of exercise: another signal is sent, by vagus nerve to SA nodeslows HR back down Adrenaline:Adrenaline: adrenal glands secrete it when high stress/excitement (into bloodstream)adrenal glands secrete it when high stress/excitement (into bloodstream) to SA node, causes it to fire more frequently, increase HRto SA node, causes it to fire more frequently, increase HR

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40 6.2.5 Explain the relationship between the structure and function of arteries, capillaries and veins. ArteriesCapillariesVeins Away from heart beds around organs Toward heart Thick-walled, smooth muscle, elastic Small Lumen No valves 1-cell thick wall No muscle No valves Thin-walled No muscle Lgr Internal diameter Internal Valves keep blood flowing toward heart, compensate low flow & P ANS regulates diameter & pressure: internal P hi Internal P lo b/c bed spread out, draining from arteriole Internal P lo b/c P cap beds Slower flow No gas exchange All gas exchange occurs here No gas exchange

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42 6.2.6 State that blood is composed of plasma, erythrocytes, leucocytes (phagocytes and lymphocytes) and platelets. Plasma –Plasma – liquid portion of bloodliquid portion of blood Erythrocytes –Erythrocytes – red blood cells, carry oxygen and CO2red blood cells, carry oxygen and CO2 Leucocytes –Leucocytes – white blood cells (phagocytes, lymphocytes)white blood cells (phagocytes, lymphocytes) Platelets –Platelets – cell fragments, assist in blood clottingcell fragments, assist in blood clotting

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44 6.2.7 State that the following are transported by the blood: nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat. Nutrients –Nutrients – glucose, amino acids, etc.glucose, amino acids, etc. Oxygen –Oxygen – reactant needed for cell respreactant needed for cell resp Carbon dioxide –Carbon dioxide – waste product of aerobic cell respwaste product of aerobic cell resp Hormones –Hormones – transported from gland to target cellstransported from gland to target cells Antibodies –Antibodies – proteins involved in immunityproteins involved in immunity Urea –Urea – nitrogenous waste, excreted/filtered out of blood by kidneysnitrogenous waste, excreted/filtered out of blood by kidneys Heat –Heat – skin arterioles change diameter to gain/lose heatskin arterioles change diameter to gain/lose heat

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