1. Chapter 42 Continued
Respiratory System

2. Gas
Exchange
Moist membrane

3. Comparative Study Protists: entire cell surface
Worms: long, thin shape maximizes surface area; stay in moist area to keep exchange surface wet
Animals with gills: aquatic animals; H2O has lower O2 concentration than air
Sea star: dermal gills over whole body
Polychaete annelids: parapodia -- extensions from each segment
Fish, mollusks: finely-divided membrane in localized area

4. Respiratory surfaces are:
• evaginations
• invaginations
Which are each of these?

5. Ventilation Movement of medium over exchange surface
Fish expend a large amount of energy for this
Blood vessel design enhances exchange
Countercurrent exchange strategy extracts more oxygen from water by diffusion.

7. Countercurrent vs. concurrent flow

8. Insect tracheal system
Gases diffuse faster in
air than in water;
Don’t have to ventilate
surfaces as thoroughly
Respiratory surface are
continually desiccated

9. Lungs Highly vascularized evaginations
Land snails: internal mantle is respiratory surface
Spiders: booklungs
Frogs: simple balloon-like lungs; limited surface area; positive pressure breathing
Mammals: highly subdivided; very large surface area

11. Negative pressure breathing
Intercostal
muscles

12. Lung Air Volumes Determined using a spirometer
Tidal: normal, quiet ventilation; 500 ml
Vital capacity: max. air lungs inhale/exhale ml
Residual: remaining air following forced exhalation; about 350ml

13. Avian ventilation: most complex method; one-way air flow
- no gas exchange in air sacs
> act as bellows to keep air moving
Parabronchi:
parallel tubes

14. Control Centers • Medulla oblongata / Pons • O2 concentration affects
- Monitors pH of blood and
cerebrospinal fluid
• increase in CO2 decreases pH;
medulla increases tempo and depth
of breathing
• O2 concentration affects
breathing only if it’s in a
severely low concentration
• aortic and carotid sensors
stimulate centers to pick up
rate and depth of breathing
• Inhalation: neg. feedback affected by stretch receptors in lungs

15. Diffusion of Gases Partial pressures
PO2 = partial pressure of oxygen; O2 = 21% of atmosphere; therefore PO2 = 160 mm Hg
(0.21 x 760 mm Hg = 160 mm Hg)
PCO2 = 0.23 mm Hg ( x 760 mm Hg)
Gases diffuse from areas of high partial pressure to areas of low partial pressures

16. Blood arriving at lungs has lower PO2 and a higher PCO2
than air in alveoli
Systemic capillaries: gradient
favors diffusion of CO2 into
blood

17. Respiratory pigments
Carry oxygen in most organisms because oxygen is not very soluble in water
Contain metal atoms; give color to the pigments
Hemocyanin: arthropods and mollusks
Metal atom is copper; imparts a blue color
O2 dissolved directly in plasma; no cells

18. Hemoglobin
Four subunits; contain one heme protein each; iron atom in center of each heme
Binding of O2 to Hb is reversible
Oxyhemoglobin (HbO2)
The first bound O2 induces shape change in Hb which increases affinity for next three O2 (cooperativity)
Unloading of O2 from one heme induces conformational change in others which stimulates unloading from the other three

19. Dissociation curve reveals cooperativity
• heme groups change conformation as O2
loads/unloads; a change in affinity for O2
Bohr shift reveals a decrease
in oxygen affinity for Hb if pH
decreases (important for
release of O2 in peripheral
tissues)

20. Carbon Dioxide transport
Transported in three different forms
Dissolved in plasma (7%)
Bound to Hb -- carbaminohemoglobin -- (23%)
As bicarbonate ion -- HCO3– (70%)
Carbonic anhydrase facilitates conversion to bicarbonate once CO2 diffuses into RBC
Assists in buffering blood
Bicarbonate diffuses out of RBC in exchange for a chloride ion (Cl–): chloride shift
H+ attach to Hb and other proteins: results in the dissociation of O2 from Hb

21. Cl-
Cl-

22. Deep-diving mammals/oxygen
Seals, dolphins, whales
Weddell seals
Can store 2X amt. of oxygen as human/kg. of weight
More myoglobin concentration in muscles than humans have
Seals have 70% O2 load in blood vs. 51% in human
5% O2 in lungs vs. 36% in human lungs
Seals have 2X blood/kg as human; also large spleen (24 liters!!)
Human spleens stores about 200 ml blood (50 ml - 1,000 ml)
Myoglobin stores 25% O2 vs. 13% in humans
Adaptations support large O2 reserve

23. More diving adaptations
Adaptations to conserve oxygen
Diving reflex
Slows pulse and O2 consumption
Blood rerouted mostly to brain, spinal cord, sense organs, adrenal glands
Rerouting causes muscles to consume oxymyglobin and shift over to anaerobic ATP production; extends dives.

24. End