Respiration and Circulation in Tetrapods

Question 1

What are the requirements for cutaneous respiration in amphibians?

Answer 1

• low keratinization for efficient gas exchange, but this increases water loss in air
• water/moisture to maintain integument
• blood capillaries close to surface, increased surface area

Question 2

What trend is observed in tetrapod lungs with an increased size and metabolic rate?

Answer 2

Increased compartmentalization

Question 3

Briefly explain the process of the buccal pump within amphibians

Answer 3

Inspiration: cavity expands, air drawn into cavity from outside/lungs
Expiration: cavity contracts, air forced out of nostrils, into lungs
(air into lungs with positive pressure)

Question 4

What is different about the aspiration pump of amniotes compared to the buccal pump of amphibians?

Answer 4

• opposite process, air sucked into lungs from negative pressure
• ribs and intercostal muscles power pump in most reptiles

Question 5

Briefly describe the lungs in birds

Answer 5

• aspiration pump, lung +air sac system
• unidirectional air flow
• flows from dorsobronchus> parabronchus> ventrobronchus
• gas exchange in capillaries in parabronchi

Question 6

Describe the ventilation process in birds

Answer 6

• two cycles, uses lungs and posterior air sacs
• inhale 1: posterior air sacs expand, creates -ve pressure drawing air in
• exhale 1: posterior air sacs contract pushing air into lungs, gas exchange occurs
• inhale 2: anterior air sacs expand, air moves from lungs to air sacs
• exhale 2: anterior air sacs contract pushing air out of body

Question 7

What are other special adaptations in bird lungs, aside from unidirectional airflow?

Answer 7

• cross-current exchange
• large exchange surface
• relatively fixed lung volume, use of air sacs for moving air

Question 8

What gas exchange and concentrations are in each mammals, birds, and fish?

Answer 8

Mammals: ~constant [gas], uniform pool
Bird: increasing [gas], cross-current system
Fish: lower [gas], countercurrent system

Question 9

Briefly explain the pathway of the anuran heart

Answer 9

• two atria, one ventricle
• O2 poor blood from body into RA, then ventricle, goes to lungs and skin through pulmocutaneous artery
• pulmonary veins carry O2 rich blood from lungs to LA, enters ventricle and goes to body
• conus partially divided by spiral valve

Question 10

Briefly explain the structure and pathway of the heart in reptiles

Answer 10

• two atria, partially divided ventricle
• two aortic vessels on left side to body and head
• regular blood flow in air
• under water, most blood bypasses lungs
• gap between ventricles allows O2 poor blood to leave heart through aorta instead of pulmonary artery

Question 11

What two bypasses are present in the fetal heart of mammals

BONUS: why are there two?

Answer 11

• foramen ovale
• ductus arteriosus

fetus doesn’t need blood flow to lungs or liver in womb while connected to umbilical cord, since they won’t work (suspended in fluid, don’t want in lungs) until after birth when passages close