Ch 46 Gas Exchange

Question 1

Is the solvent for oxygen destined for aerobic cellular respiration.
• either already dissolved in water
• or from air passing over a moist surface

Answer 1

Water

Question 2

Pros and Cons of Acquiring oxygen from the air

Answer 2

• Pro: Air has a higher concentration of
molecular oxygen than does water
• Pro: Oxygen diffuses faster through air than through water
• Pro: Air is less dense and less viscous than water (less energy needed to move air over gas exchange surface)
• Con: However, gas exchange via direct contact with air requires protection for respiratory surfaces from drying

Question 3

Gas Exchange structures in Aquatic animals are

Answer 3

Gills

– thin projections of body surface

Question 4

Gas exchange structures in echinoderms

Answer 4

– dermal gills that project from body wall

• no active ventilation

Question 5

Gas exchange structures in Chordate

Answer 5

– gills usually internal, along edges of gill slits in the pharynx

Question 6

Gas exchange structures in many terrestrial animal

Answer 6

Lungs
– ingrowths of the body surface
– to protect moist surfaces

Question 7

Gas exchange structures in bony fish

Answer 7

Swim bladders

– homologous with vertebrate lungs

Question 8

Gas exchange structures in lungfish

Answer 8

Gills and lungs

– or only lungs for gas exchange

Question 9

Gas exchange structures for amphibians and reptiles

Answer 9

– have lungs with some ridges or folds that increase surface area

Question 10

• The most efficient respiratory system in vertebrates
– 2 cycles of inhalation and exhalation; one-way flow of air through lungs
• Gas exchanged through walls of parabronchi
• tiny, thin-walled tubes open on both ends
• air passes through lungs; not held in lungs
• air sacs to control air movement; not for gas exchange
Air crosses lungs through both inhalation and exhalation.

Answer 10

Gas exchange in birds

Question 11

• Includes lungs and system of airways
• Each lung is covered with a pleural membrane (a serous membrane)
• Air passes through nostrils, nasal cavities, pharynx, larynx, trachea, bronchi, bronchioles, alveoli
– and back again

Answer 11

Human Respiratory System

Question 12

• Inhalation: diaphragm (and sometimes other muscles) contracts
– expanding chest cavity
• Membranous walls of lungs move outward along with chest walls
– lowering pressure within lungs
• Air rushes in through air passageways
– until pressure in lungs equals atmospheric pressure
• Forced exhalation
– internal intercostal muscles push diaphragm up and ribs down

Answer 12

Mechanics of Breathing

Question 13

• 300 million tiny air sacs for gas exchange in lungs
• resulting in large inner surface area of lungs
• lined with extremely thin epithelial cells
• only 2 thin cell layers between air and blood

Answer 13

Structure of Alveoli

Question 14

O2 and CO2 exchange between alveoli and blood by

Answer 14

Diffusion

Question 15

Determine direction and rate of diffusion

Answer 15

Concentrations

Question 16

Respiratory pigment in vertebrate blood

• bright red=oxygenated, dark red= deoxygenated

Answer 16

Hemoglobin

Question 17

≈ 99% of oxygen in human blood is transported as

Answer 17

Oxyhemoglobin

Question 18

Diffusion of O2 into plasma will cease at 0.25mL of O2 per 100mL

Answer 18

– Without hemoglobin

Question 19

Whole blood can carry 20mL O2 per 100mL

Answer 19

-With hemoglobin

Question 20

• ≈ 30% combines with hemoglobin
• ≈ 10% is dissolved in plasma
• ≈ 60% of CO2 is transported in plasma as bicarbonate ions
– However, RBCs facilitate bicarbonate creation

Answer 20

CO2 Transport