Presentation is loading. Please wait.

Presentation is loading. Please wait.

6.4 Gas Exchange.

Similar presentations


Presentation on theme: "6.4 Gas Exchange."— 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.
flow of air (with gases) in and out of the alveoli 2 stages: inspiration (or inhalation) expiration (or exhalation) Lungs are not muscular Can’t ventilate themselves Whole thorax moves & changes size, due to action of 2 sets of muscles: intercostal muscles and diaphragm

5 6.4.1 Distinguish between ventilation, gas exchange and cell respiration.
2. Gas capillaries Diffusion of gases (oxygen & carbon dioxide) 2 sites Alveoli: O2 diffuses into blood from alveoli CO2 diffuses from blood into alveoli Tissues: O2 diffuses from blood into cells CO2 diffuses from cells to blood 3. Cell Respiration Aerobic respiration uses oxygen (in mitochondria) to make ATP, produces CO2 Anaerobic respiration Doesn’t use O2 but still produces CO2 Diagram, p. 169 Heinemann text

6

7

8 6.4.2 Explain the need for a ventilation system.
We’re multicellular! (trillions of cells, not all on surface, so too deep for diffusion to work!) Need 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 system replaces/diffuses O2 (keeping conc high) and removes CO2 (keeping conc low) O2 can always diffuse down its conc gradient from air to blood CO2 can diffuse down its conc gradient from blood to air

9

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 m2) 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

11

12 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! (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

13 7. 2. 1. 3. 4. 5. 6.

14 Draw It!

15 Inverse relationship: pressure and volume
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 volume Increase in volume  decrease in pressure 2 environments Thorax & Internal envt of lungs

16 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 expands diaphragm contracts, flattens downwards Abdominal & intercostal muscles contract, raising rib cage increases volume of thorax  decreases P inside thorax  less P pushing on lung tissue Increases lung & alveoli volume b/c less P on it  decrease in P inside lungs (partial vacuum) Air 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 smaller

17 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.

18

19

20

21

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;

25

26 THICKER wall of left ventricle 4 chambers Sup & inf vena cava
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. THICKER wall of left ventricle 4 chambers Sup & inf vena cava L, R AV valves Pulm SL valve Aortic SL valve Pulm art Pulm vein Aorta site for IB diagrams

27 12. 6. 7. 1. 2. 11. 8. 5. 3. 9. 4. 10.

28 DRAW IT!

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

30

31 Vena cava  RT Atrium, certain volume of blood collects
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. 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 All this...in a minute or two!
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!

33

34

35 Artificial heart valves!

36 “Myogenic muscle contraction”
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 contraction” Cardiac muscle spontaneously contracts/relaxes SA node (mass of tissue) = “pacemaker” sends regularly paced electrical signal to initiate atrial contractions HR = 72 bpm ... Signal sent every 0.8 seconds! AV node receives signal from SA node, waits ~0.1 sec, sends another to ventricles (more muscular) for contraction Atria contract, pause, ventricles contract

37 Need faster gas exchange to keep up w/cell respiration
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  ??? Need faster gas exchange to keep up w/cell respiration Medulla (brainstem) senses increase in CO2 Sends 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 node—slows HR back down Adrenaline: adrenal glands secrete it when high stress/excitement (into bloodstream) to SA node, causes it to “fire” more frequently, increase HR

38

39

40 Explain the relationship between the structure and 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 Thin-walled 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

41

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

43

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

45


Download ppt "6.4 Gas Exchange."

Similar presentations


Ads by Google