CAR week + 8 : Exotics adaptions and non-mammalian respiration

How does the structure of an avian heart compare to a mammalian heart?

• 2 circuits

• 4 chambers

• ventricles are slightly connected

• heart is much larger in proportion to the body due to high metabolic demands of flight

Outline turtle and lizard heart structure

• 2 circuits

• 5 chambered hearts

• oxygenated and deoxygenated are mixed to some extent

• proportionately smaller due to low metabolic demand

outline crocodile hearts

• 2 circuits

• 2 chambers

outline fish hearts

• 1 circuit and 2 chambered

• blood goes from gills → body → heart

• heart is found close to the head to be close to the gills

outline frog hearts

• 3 chambers: 2 atria and one ventricle

• RA receives deoxygenated and LA oxygenated from the lungs

• ventricle is partially divided but classed as 1 ventricle, helps to separate to some extend but not fully

• frog is semi aquatic: when young, needs skin for respiration in water, when an adult the lungs are the primary site for gas exchange so circulatory system becomes more efficient

outline this radiograph:

1. what species

2. what do we notice about proportions?

3. what is a disadvantage to this body structure?

4. in which species do we see this layout?

1. rabbit

2. green = heart - rabbit has very small thorax proportional to abdomen, heart is very cranial

3. any thing can affect lungs and heart from the abdomen, e.g. reproduction as thoracic cavity is so small

4. hind gut fermenters

What species is this radiograph from and what is important to recognise about it?

• rabbit

• it’s large compared to thoracic space, sits vertically against sternum and is very cranial - anatomical location in relation to techniques we may perform

1. what species

2. what are the numbers

1. rabbit

2. 2= cardiac silhouette

3. = trachea

4. where trachea bifurcates to go into different bronchi

5. caudal vena cava

What species and what are the numbers

1. rabbit

2. 1 = diaphragm 2 = cardiac silhouette

3. = mediastinum which is larger in rabbits

What species radiographs are these and how do they compare to rabbits

1. guinea pigs

2. vast majority of body is still abdomen, very small areas for thorax. Shared amongst hind fermenters

what are the 4 common species that have small thorax: abdomen?

• rabbit

• guinea pig

• dengues

• chinchillas

What species is this thorax and what can we note about it?

• ferret

• longer thorax and heart is very caudal and close do the diaphragm

What species radiograph is this and what can we identify?

• bird

• blue = lungs

• red = heart

• rest = Gi tract - due to no diaphragm

What species and what can we identify here?

• bird

• blue = lungs

• red = heart

In which view must we take tortoise radiographs for the lungs? Can we view the heart?

• cranio-caudal

• lateral

• not VD as shell is too thick

• no we can’t view the heart due to shell

How do we perform a radiograph on a snake

• use a doppler to identify where the heart is

• use this as a guid for positioning for radiograph

• Snakes also have air sacks

Identify the temperature, heart beat and breathing rate for:

• rabbit

• 38.5-40

• 130-325

• 30-60

Identify the temperature, heart beat and breathing rate for:

• chinchilla

• 34.9-37.9

• 200-240

• 40-80

Identify the temperature, heart beat and breathing rate for:

ferret

• 37/8-40

• 200-400

• 33-36

Identify the temperature, heart beat and breathing rate for:

guinea pig

• 37.5-39.5

• 230-380

• 40-120

Identify the temperature, heart beat and breathing rate for:

rat

• 37.5-39.5

• 250-450

• 70-120

Identify the temperature, heart beat and breathing rate for:

syrian hamster

• 37-39

• 250-500

• 50-135

Identify the temperature, heart beat and breathing rate for:

• gerbil

• 37-39

• 260-450

• 70-130

Identify the temperature, heart beat and breathing rate for:

• mouse

• 36-38

• 300-800

• 70-220

How do we measure heart rate in a lizard

• use a doppler

• place it over jugular or heart

how do we measure BP and ECG:

• bird

• snake

• around the wing under GA/sedation

• snake around the tail - use sphygmomanometer

where do we take blood sample from a rabbit

• jugular (last choice as stressful)

• cephalic

• saphenous

• lateral and medial MARGINAL ear vein = auricular vein

How do we take blood from hedgehogs/guineapigs

• caudal vena cava

• insert needle into thoracic inlet and put needle b/w clavicle and first rib - where you feel a dip either side of clavicle

• keep at a 30-40degree angle and point towards the opposite hip

• remain superficial and have blood flush in - don’t go deeper, just move side to side (especially in guinea pigs, as heart is so cranial)

For animals with tails, where can we take blood samples?

• from the lateral tail vein

where can we take blood from in birds

• medial metatarsal vein - birds larger than pigeons

• jugular - small birds

• basilic (ulnar) vein

where do we take blood samples from in reptiles

• ventral tail - ensure caudal to cloaca in snakes

• dorsal tail vein

• jugular vein (be careful)

• subcarapacial sinus (tortoises)

• intracardiac: only if patient is completely still and heart can be held still (with thumb and index finger)

• ventral abdominal vein in patients w. very thin skin and pale skin

what is special about bird and reptile blood cells

• nucleated

what leucocytes do reptiles and birds have that mammals don’t

• heterophils (aka neutrophils)

• azurophils (monocytes in birds) - monocyte equivalent in smallies

We have a tortoise presented by an owner who thinks it’s dead… it’s very cold, what should we do?

• warm up and see if a heart beat is then detected.

• They’re not dead until they’re warm and dead

Why should we have a veterinary consult before allowing a tortoise to hibernate

• ensure the tortoise isn’t showing signs of illness that may prevent a healthy hibernation including nasal discharge, swelling of the eyes or limbs, any changes inside the mouth.

• a faecal parasite screen may be advised too.

• reproductive activity needs to be assessed

Why can we hibernate tortoises in a fridge

• constant cold temperature

• ensures safety from predators

• do need to open door often though to ensure there’s enough O2

when do tortoises start preparing for hibernation and when should they go into hibernation

• late august

• november

what is another word for hibernation

• brumation

how long should tortoises hibernate for

• 8-10 weeks if small

• up to 16 weeks if large

How do we wake up a tortoise from hibernation

• remove from cold area and expose to a UV/basking lamp

• ensure they’re in a calm, quiet environment

• once they start stirring, provide with water and if awake enough, bathe in lukewarm water, place back in enclosure and slowly increase temperature back to normal

• should start to eat food over the next 10-14 days

why may a PCV of a tortoise coming out of hibernation be very high?

• dehydrated due to being in hibernation

• blood is very concentrated in cells.

What structures does water have to pass through for the fish to complete respiration?

• gill filaments

• lamellae: primary and secondary

• gill rakers

• operculum

How would we keep a fish breathing during surgery?

• place into anaesthetic bath with suitable concn so it’ll be absorbed through gills and enter bloodstream

• use a syringe to pass water and then anaesthetic over the gills

What functions are affected if gills are damaged?

• osmoregulation

• nitrogeneous excretion

• pH regulation

• hormone production affected

what are the main physiological functional differences b/w mammal and fish respiration

• gills are more effective gas exchange system due to use of counter current

  • means exchange occurs constantly, unlike in lungs where an equilibrium is reached

What 2 physical properties of water do fish have to overcome in terms of respiration?

• low O2 content in water

• water is thicker than air

How do fish overcome:

• low O2 content in water

• water being thicker than air

• counter current flow to maintain gradient

• movement through water to maintain flow over the gills

why would a bird/reptile with coelomic mass/fluid accumulation in the cavity have laboured/troubled breathing

• they don’t have a diaphragm therefore fluid/mass pushes onto lungs so they can’t inflate, meaning other mechanisms need to be adopted to stimulate respiration

why do tortoises (chelonians) move limbs and head in laboured breathing?

• they have a pseudodiaphragm which isn’t a muscle but a large sheet of tissue attached to front and back legs

• means they can breathe by moving limbs, by forcing air movement 

what enables snakes to breathe whilst swallowing very large prey?

• they can extend the glottis to the side of their mouth whilst eating

• glottis is a vertical air slit so air can pass through, allowing respiration whilst eating