Exam 4: Lecture 50: Avian Ventilation Physiology

Question 1

Birds belong to the class

Answer 1

Aves

Question 2

Birds are _____ (endothermic/exothermic)

Answer 2

-Endothermic

Question 3

Birds have a ___ chambered heart

Answer 3

4

Question 4

T/F: Birds don’t have lungs

Answer 4

FALSE!
-Birds have lungs (with air sacs)

Question 5

Why is it important to know that birds can fly?

Answer 5

-Flying is metabolically expensive

Question 6

How does Anser indicus sustain MO2 (maintain oxygen uptake) during flight at high altitude?

Answer 6

-V/Q matching
-Coordinated integration of convective & diffusive steps
-High affinity Hb
-High [myoglobin]
-High capillary density
-Blunted hypoxia-ventilation response
-Summation: Well-matched (D/BQ)

Question 7

How does V/A matching help birds maintain oxygen uptake during flying at high altitudes?

Answer 7

-4 chambered heart
-Efficient convective gas flow
-Cross-current gas exchange
-Parabronchus not diffusion limited
-High membrane diffusion capacity

Question 8

What is the shape of the Hb-O2 dissociation curve and why is that important?

Answer 8

-Sigmoidal shape
-Slope of the line is steepest at sharp increase in O2 saturation w/out much change in partial pressure of O2

Question 9

T/F: Birds will experience more of a right shift in the Hb-O2 dissociation curve than mammals

Answer 9

TRUE

Question 10

Why is there a right shift in the Hb-O2 dissociation curve in birds?

Answer 10

-Flying is expensive!
-High-altitude hypoxia is a challenge for aerobic metabolism
-Allosteric cooperative binding
-Hb; Homotropic & heterotrophic interactions

Question 11

What are the 5 respiratory structures in birds?

Answer 11

1. Evaginations of the body (gills)
2. Invaginations of the body (lungs)
3. Series of tubes originating from the body surface & reaching all tissues (trachea); conducting structures (if present)
4. Gas exchange surfaces (integument)
5. Cardiovascular coupling mechanism

-1,2,3 and 4 require adequate ventilation of the gas exchange areas

Question 12

Adequate ventilation of the gas exchange areas requires

Answer 12

-Muscles & in many cases these muscles serve multiple roles like feeding or locomotion

Question 13

Where are avian lungs located?

Answer 13

-Located cranio-dorsally within coelom (fused abdominal-thoracic cavity)

Question 14

Do birds have a diaphragm?

Answer 14

-No diaphragm
-Immune compartmentalization (BALT)

Question 15

What is the branching of the avian lung structures?

Answer 15

-Primary mesobronchus: series of four secondary bronchi, medioventral, mediodorsal, lateroventral, laterodorsal

Question 16

What do we call the tertiary bronchi in the lungs?

Answer 16

-Parabronchi

Question 17

The left and right lungs occupy ____ position

Answer 17

dorsal

Question 18

Are the lungs in avians lobed?

Answer 18

-No

Question 19

How are the avian lungs divided?

Answer 19

-Functionally divided into paleopulmonic (all birds) and neopulmonic systems

Question 20

Conducting airways =

Answer 20

Dead space ventilation (no gas exchange)

Question 21

What are the airsacs that you can find in birds?

Answer 21

-Cranial & caudal (pairs, except clavicular)

Question 22

What are the characteristics of the air sacs in avians?

Answer 22

-Compliant = change V/ change P
-Poorly vascularized (essentially VD)
-Air sac diverticula

Question 23

What is shown in this graph?

Answer 23

-Compliance curve of mammalian lung

Question 24

What do the cranial air sacs in birds do?

Answer 24

-Receive gas from the parabronchi so their PO2 & PCO2 are very near end-tidal values

Question 25

What do the caudal air sacs in birds do?

Answer 25

-Contain mixture of re-inhaled dead-space gas and fresh air

Question 26

What are the major differences in avian respiratory system than mammalian?

Answer 26

-Lack diaphragm -No pleural cavity (coelomic) -**Inspiration & expiration are both active processes** -**Two cycle breathing** -**Continuous unidirectional airflow across lung** -**During flight, breathing & wing movement are independent** -Lungs are noncompliant

Question 27

Most birds have ____ air sacs

Answer 27

-9 -Some invested into bones (pneumatization)

Question 28

What energy do the mechanisms of ventilation require?

Answer 28

All require energy of varying degrees -Positive pressure -Negative pressure (in birds = reciprocating +/- ventilation) -Passive (diffusion)

Question 29

Skeletal muscles are responsible for ____ ventilation in all vertebrates

Answer 29

active phase

Question 30

What skeletal muscles are responsible for the active phase ventilation in all vertebrates?

Answer 30

-Buccal/pharyngeal/RAM (fish/amphibians) -Costal (Sauropsids) -Diaphragmatic (unique to mammals) -**Coelomic (birds; volant)**

Question 31

The partial pressure of oxygen in the blood leaving the parabronchus can be ______ than that in the gas leaving the parabronchus

Answer 31

higher

Question 32

How is the convective air flow in cross-current gas exchange?

Answer 32

-**longitudinal**

Question 33

What is meant by Q=centripetal in cross-current gas exchange?

Answer 33

-Blood is directed toward central parabronchial lumen

Question 34

The arrangement of parabronchial lung supports capillaries and consists of

Answer 34

-Endothelial cells -Basal lamina -High-density of small-diameter **air capillaries** (**avipulmosaccules = alveoli**) -Small-diameter air capillary epithelium (squamous)

Question 35

The lung is _____ between two functionally distinct sets of air sacs (**Cranial & caudal**); cervical, clavicular, and cranial thoracic & the abdominal

Answer 35

**intercalated**

Question 36

What happens during inspiration?

Answer 36

-Ribs are drawn forward and the sternum is lowered

Question 37

What happens during the expiration active process?

Answer 37

-Air in caudal air sacs flows to lungs as air sacs are compressed -Air in cranial air sacs leaves via trachea

Question 38

Are ribs/sternum in birds active during inspiration or expiration?

Answer 38

-Both

Question 39

There are time-varying resistances in the two cycle ventilation pattern in the

Answer 39

-Mesobronchus -Dosobronchus -Ventrobronchus

Question 40

Do birds have a diaphragm?

Answer 40

-No

Question 41

Is inspiration or expiration in birds an active process?

Answer 41

-Both

Question 42

Explain the **two cycle breathing** that birds do

Answer 42

-Each breath 50% of air in its lungs -Two cycles are required for 1/2 of air to move through the entire system

Question 43

What is the **KEY** adaptation in birds?

Answer 43

-Upright stance: separation of ventilation/locomotion

Question 44

What is unique about some bird bones?

Answer 44

-There is pneumatization of bones

Question 45

Birds have **aerodynamic valving** which means

Answer 45

-Differential distribution of ventilation (variable resistance at branch points of secondary bronchi (parabronchi)) -**Connective momentum**

Question 46

What leads to bird ventilation?

Answer 46

-Bellows-like ventilation of **air sacs; pressure oscillations among air sacs and the atmosphere** lead to ventilation

Question 47

Are birds lungs compliant?

Answer 47

-No they are **non-compliant lungs**

Question 48

How is the blood gas barrier in birds?

Answer 48

-Birds have a **thin blood gas barrier (TBGB)**

Question 49

How is the airflow in birds?

Answer 49

-**Caudal to cranial through paleopulmonic parabronchi during both phases of ventilation**

Question 50

Explain the relationship with airflow and gas exchange in birds

Answer 50

-Uni-directional flow of air with **cross-current gas exchange surface**, and thin blood-gas barrier (connective inertia) -Also found in non-volant ectotherms (American alligator, Nile/saltwater crocodiles, savanna monitors, green iguanas)

Question 51

How is ventilation powered in birds?

Answer 51

-**Ventilation is powered by two sets of hypaxial muscles that have no role in locomotion**

Question 52

Does the morphology of the rib cage in birds change?

Answer 52

-Yes! -The morphology of the rib cage & accessory breathing structures is different in walk/run, drive/fly, and swim