Lecture 27 - Reptile & Avian Flashcards
Do reptiles have a diaphragm
No
Do reptiles all have the same kind of heart
No - can be in different spots and have 2 cardiac morphologies (Chelonia & Squamata vs Crocodilia)
Compared to mammals, are reptiles more or less susceptible to adverse effects of hypoxia and changes in blood pH?
Much less susceptible - have great blood buffering systems
Do reptile hearts have pacemaker nodes or purkinje fibers
NO
How are contractions initiated in the reptile heart
Cardiac muscle fibers in sinus venosos - contractions spread from RA to LA then into the ventricles
Can you induce spontaneous contraction in reptile hearts if they’re outside the body
Yes - just touch it at sinus venosus
Reptile heart innervated by
Parasympathetic fibers in vagus nerve (cholinergic)
Sympathetic fibers (adrenergic) (less well developed)
In reptile hearts, are parasympathetic or sympathetic fibers more developed
Parasympathetic! This means sympathetic is less well developed and you don’t see rapid heart rate increases in reptiles
Is reptilian <3 rate slower or faster than birds/mammals
Slower
Reptilian heart rate relationship with body size
Inversely proportional
Reptilian heart rate relationship with body temperature
Directly proportional
Reptilian heart rate relationship with activity level
Directly proportional
Reptilian heart rate relationship with resp rate
Directly proportional
Reptilian heart rate relationship with hypovolemia
Directly proportional
Reptilian heart rate is directly proportional to all factors except ___________ where it’s inversely proportional
Body size
Do chelonians/squamates have a septum to separate R & L ventricle?
No, just have muscular ridges that move to separate some oxygenated and deoxygenated blood
Do crocodiles have a 4 chambered heart
Yes
What is the foramen of panizza in crocodilian hearts
A shunt that separates the L & R aorta
What change opens/closes foramen of panizza
Pressure changes - ie if crocodile is diving/breath holding
In crocodile heart, blood from right ventricle goes to
Left aorta
Blood from right ventricle goes into
Left aorta
What is the cogwheel valve
Also called active valve, can close down
What is shunting in chelonians and squamates
Sending blood left to right during normal respirations
Shunting chelonians and squamates functions
Facilitation of CO2 removal from lungs
Minimize V/Q mismatches
Improve systemic oxygen transportation
Shunting happens right to left during anoxia - true or false
TRUE
When crocodiles are breathing air (above water breathing) what is the pathway of blood (from each ventricle)?
Goes from RA to RV where blood goes to pulmonary artery and small amount goes to L aorta
Goes from LA to LV to R aorta
When crocodiles are underwater or diving/breath-holding, what is the pathway of blood
RA to RV to LA and cogwheel valve shunts, blood wont go through pulmonary artery, instead pushed into L aorta and R aorta
Do reptiles have a diaphragm
No
Do reptiles have symmetrical lungs
Yes - they’re paired EXCEPT snakes where only right lung is present (left lung is vestigial
Reptilian hemoglobin has lower oxygen affinity than mammals therefore
Oxygen delivery to tissues more effective even at low blood oxygen levels
Where does the stimulus to breathe come from in reptiles
Low blood oxygen content
High oxygen tension environments may suppress…
Spontaneous respiratory rate - therefore may not breathe well in O2 Chambers & do NOT want to use 100% O2 during anaesthesia
Do chelonians have incomplete tracheal rings
NO! They are complete <3
Do squamates have incomplete tracheal rings
Yes
Do crocodiles have incomplete tracheal rings
NO! They’re complete
Do birds have a high metabolic rate
Yes so high oxygen demands
Where does the heart sit in the avian body
Tilted slightly to the right
What is unique about bird hearts
They have a unique right AV valve - its a muscular flap, not a valve
Therefore, right sided heart failure is more common in birds
Is the left Av valve in birds unique
It is tricuspid
Birds what is the importance of the renal portal system
Caudal 1/2 of bird - if given any drug that causes renal problems/toxicity, this can be very dangerous as the renal portal system will bring the drug first to the kidneys and then to the circulation, so it causes renal damage
Do birds have a larger or smaller stroke volume compared to mammals
Larger
Is birds’ cardiac output lower or higher than mammals
Higher! 7x greater than dogs or humans relative to size
Birds have increased collagen fibers in their cardiovascular system which means
Stiffer arteries to improve blood flow and maintain high blood pressure
Do birds have a well developed purkinje fibre system
Yes - important because their myocardium is more sensitive to the effects of catecholamines
Do birds have high myoglobin content in muscles
Yes
Can birds shunt blood
No
Avian erythrocytes have
Higher hemoglobin affinity
Are birds more tolerant of blood loss than mammals
Yes - they have higher Hb affinity and high levels of myoglobin in muscles
Do birds have a diaphragm
No
Do birds have incomplete trachea rings
No
Airsacs contribute to _____% of respiratory volume
80
Air sacs act as
Functional bellows
Bird lungs expansion/collapse level
Minimal expansion and contraction during respiration - 20% increase in SA compared to mammals
(Birds) Minute ventilation rates 1.5-2x _______ compared to mammals due to
Greater , due to large tidal volume
Are mammalian or bird lungs more efficient
Birds - 10x more efficient
Why are bird lungs more efficient
Thin blood gas barrier
Cross and counter current flow
Unidirectional air flow
Bird - 2 breaths to get the breath out steps
1st breath - air goes into air sacs
2nd breath - air goes into paleopulmonic parabronchi & out
Respiratory rates of birds lower or higher than mammals
Lower
Is the PaCO2 in birds higher or lower than mammals
Lower
Birds have unique intrapulmonary chemoreceptors in lungs that are
Very sensitive CO2 receptors
