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6.4 6.4 Gas ExchangeGas Exchange
• List the characteristics of alveoli that permit efficient gas exchange.
• (4 marks)
• 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
6.4.1 Distinguish between ventilation, 6.4.1 Distinguish between ventilation, gas exchange and cell respiration.gas exchange and cell respiration.
1. 1. VentilationVentilation::• flow offlow of airair (with gases) in and out of the (with gases) in and out of the alveolialveoli
• 2 stages: 2 stages: • inspiration (or inhalation)inspiration (or inhalation)• expiration (or exhalation)expiration (or exhalation)
• Lungs are Lungs are not muscularnot muscular • Can’t ventilate themselvesCan’t ventilate themselves• Whole thorax moves & changes size, due to action of 2 Whole thorax moves & changes size, due to action of 2
sets of muscles: sets of muscles: • intercostal muscles and diaphragmintercostal muscles and diaphragm
6.4.1 Distinguish between 6.4.1 Distinguish between ventilation, gas exchange and ventilation, gas exchange and cell respiration.cell respiration.2. Gas Exchange: @ capillaries2. Gas Exchange: @ capillaries• Diffusion of gases (oxygen & carbon dioxide) Diffusion of gases (oxygen & carbon dioxide) • 2 sites2 sites
• Alveoli: Alveoli: • OO22 diffuses diffuses into bloodinto blood from alveoli from alveoli• COCO22 diffuses from blood into alveoli diffuses from blood into alveoli
• Tissues: Tissues: • OO22 diffuses from blood into cells diffuses from blood into cells• COCO22 diffuses from cells to blood diffuses from cells to blood
3. Cell Respiration3. Cell Respiration• AerobicAerobic respiration respiration
• uses oxygen (in mitochondria) to make ATP, produces COuses oxygen (in mitochondria) to make ATP, produces CO22 • AnaerobicAnaerobic respiration respiration
• Doesn’t use ODoesn’t use O22 but still produces CO but still produces CO22
Diagram, p. 169 Heinemann textDiagram, p. 169 Heinemann text
6.4.2 Explain the need for a ventilation system.6.4.2 Explain the need for a ventilation system.
• We’re multicellular! (trillions of cells, not all on surface, We’re multicellular! (trillions of cells, not all on surface, so too deep for diffusion to work!)so too deep for diffusion to work!)
• Need it to maintain Need it to maintain high conc gradients in alveolihigh conc gradients in alveoli• steep conc grad across resp sfc maintained in 2 ways:
• blood flow on 1 side • air flow on other side• system replaces/diffuses OO2 2 (keeping conc high) and
removes COO2 2 (keeping conc low)• OO22 can always diffuse down its conc gradient from air to
blood• COCO22 can diffuse down its conc gradient from blood to
air
6.4.3 Describe the features of alveoli 6.4.3 Describe the features of alveoli that adapt them to gas exchange.that adapt them to gas exchange.
• Lg total SA due to combined spherical shape ...why?• (300 million alveoli @ each lung...600 million alveoli = 80 m2)
• Alveolus Wall = • single layer of flattened epithelial cells
• close association w/caps...why?• Short diffusion distance from alveoli to blood (0.5-1.0 um)
• Dense cap network surrounding each alveolus...why?• From L Ventricle, high [Oxygen]• To cap bed @ organ • (first 1-cell surface in contact with...so it diffuses out there)
• Film of Moisture @ surface for ...• efficient diffusion, solution of gases
6.4.4 Draw and label a diagram of the ventilation system, 6.4.4 Draw and label a diagram of the ventilation system, including trachea, lungs, bronchi, bronchioles and alveoli.including trachea, lungs, bronchi, bronchioles and alveoli.
• Students should draw the alveoli in an inset diagram at Students should draw the alveoli in an inset diagram at a higher magnification!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
1.1. 2.2.
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Draw It!
6.4.5 Explain the mechanism of ventilation of the lungs in terms of 6.4.5 Explain the mechanism of ventilation of the lungs in terms of volume and pressure changesvolume and pressure changes caused by the internal and external caused by the internal and external intercostal muscles, the diaphragm and abdominal muscles.intercostal muscles, the diaphragm and abdominal muscles.
• Inverse relationship: pressure and volumeInverse relationship: pressure and volume• Increase in volume Increase in volume decrease in pressure decrease in pressure
• 2 environments2 environments• Thorax & Internal envt of lungsThorax & Internal envt of lungs
6.4.5 Explain the mechanism of ventilation of the lungs in terms of 6.4.5 Explain the mechanism of ventilation of the lungs in terms of volume and pressure changes caused by the internal and external volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm and abdominal muscles.intercostal muscles, the diaphragm and abdominal muscles.
• InhalationInhalation: diaphragm contracts (moves down), rib cage expands: diaphragm contracts (moves down), rib cage expands• diaphragm contracts, flattens downwardsdiaphragm contracts, flattens downwards
• Abdominal & intercostal muscles contract, raising rib cage Abdominal & intercostal muscles contract, raising rib cage • increases volume of thorax increases volume of thorax decreases P inside thorax decreases P inside thorax less P pushing on lung tissueless 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 Air comes in through mouth/nose to counter the partial vacuum
w/in lungs & fills alveoli with airw/in lungs & fills alveoli with air
• ExpirationExpiration: opposite, diaphragm relaxed (moves up), rib cage gets : opposite, diaphragm relaxed (moves up), rib cage gets smallersmaller
6.4.5 Explain the mechanism of ventilation of the lungs in terms of 6.4.5 Explain the mechanism of ventilation of the lungs in terms of volume and pressure changes caused by the internal and external volume and pressure changes caused by the internal and external intercostal muscles, the diaphragm and abdominal muscles.intercostal muscles, the diaphragm and abdominal muscles.
6.2 6.2 The Transport The Transport SystemSystem
• Describe the structures of arteries and veins as related to their functions.
• (6 marks)
• 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;
6.2.1 Draw and label a diagram of the heart showing the four chambers, 6.2.1 Draw and label a diagram of the heart showing the four chambers, associated blood vessels, valves & the associated blood vessels, valves & the route of blood through the heartroute of blood through the heart!!!!
• Care should be taken to show the relative wall thickness of the Care should be taken to show the relative wall thickness of the four chambers. (four chambers. (Vent thicker than AtriaVent thicker than Atria) ) Neither the coronary Neither the coronary vessels nor the conductive system are required.vessels nor the conductive system are required.• THICKER wall of THICKER wall of leftleft ventricle 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
http://frogsluvgreenvws.tripod.com/ site for IB diagrams
1. 1.
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3. 3.
4. 4.
6. 6.
7. 7.
8. 8.
9. 9.
10. 10.
11. 11.
5. 5.
12. 12.
DRAW IT!
6.2.2 State that the coronary arteries supply 6.2.2 State that the coronary arteries supply heart heart musclemuscle with oxygen and nutrients. with oxygen and nutrients.
6.2.3 Explain the action of the heart in terms of collecting 6.2.3 Explain the action of the heart in terms of collecting blood, pumping blood, and opening and closing of valves.blood, pumping blood, and opening and closing of valves.• A basic understanding is required, limited to the collection of A basic understanding is required, limited to the collection of
blood by the atria, which is then pumped out by the ventricles into blood by the atria, which is then pumped out by the ventricles into the arteries. The direction of flow is controlled by atrio-ventricular the arteries. The direction of flow is controlled by atrio-ventricular and semilunar valves.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
6.2.3 Explain the action of the heart in terms of 6.2.3 Explain the action of the heart in terms of collecting blood, pumping blood, and opening collecting blood, pumping blood, and opening and closing of valves.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!
Artificial heart valves!
6.2.4 Outline the control of the heartbeat in terms of myogenic muscle 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 contraction, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline).brain and epinephrine (adrenaline).
• ““Myogenic muscle contraction”Myogenic muscle contraction”• Cardiac muscle spontaneously contracts/relaxesCardiac muscle spontaneously contracts/relaxes
• SA nodeSA node (mass of tissue) = “pacemaker” (mass of tissue) = “pacemaker”• sends regularly paced sends regularly paced electrical signalelectrical signal to initiate to initiate
atrialatrial contractions 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 sends another to ventriclesventricles (more muscular) for (more muscular) for
contractioncontraction
• Atria contract, pause, ventricles contractAtria contract, pause, ventricles contract
6.2.4 Outline the control of the heartbeat in terms of myogenic muscle 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 contraction, the role of the pacemaker, nerves, the medulla of the brain and epinephrine (adrenaline).brain and epinephrine (adrenaline).
• Increased exercise Increased exercise ??? ???• Need faster gas exchange to keep up w/cell Need faster gas exchange to keep up w/cell
respirationrespiration• MedullaMedulla (brainstem) senses increase in CO (brainstem) senses increase in CO22
• Sends signal thru cardiac nerve to Sends signal thru cardiac nerve to SA nodeSA node to to increaseincrease heart heart raterate to appropriate level to appropriate level
• At End of exercise: another signal is sent, by At End of exercise: another signal is sent, by vagusvagus nerve to nerve to SASA nodenode—slows HR back down—slows HR back down
• AdrenalineAdrenaline: : • adrenal glands secrete it when high adrenal glands secrete it when high
stress/excitement (into bloodstream) stress/excitement (into bloodstream) • to to SA nodeSA node, causes it to “fire” more frequently, , causes it to “fire” more frequently,
increase HRincrease HR
6.2.5 6.2.5 ExplainExplain the relationship between the structure and the relationship between the structure and function of arteries, capillaries and veins.function of arteries, capillaries and veins.Arteries Capillaries Veins
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 lost @ cap beds
Slower flow
No gas exchange
All gas exchange occurs here
No gas exchange
6.2.6 State that blood is composed of plasma, 6.2.6 State that blood is composed of plasma, erythrocytes, leucocytes (phagocytes and lymphocytes) erythrocytes, leucocytes (phagocytes and lymphocytes) and platelets.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
6.2.7 State that the following are transported by the 6.2.7 State that the following are transported by the blood: nutrients, oxygen, carbon dioxide, hormones, blood: nutrients, oxygen, carbon dioxide, hormones, antibodies, urea and heat.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 immunity proteins 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 heat skin arterioles change diameter to gain/lose heat
