Hello everybody. This is reptiles, and there's actually 22 lectures this, this is reptiles 1, and then there's reptiles 2. This goes through some basic anatomy and physiology and normal things that you might expect to find before reptiles too goes into specific examples of clinical conditions and procedures that you might see or be able to perform in either snakes, tortoises, or lizards.
So it's a lot, it's a lot to ask to cover general reptiles in 2 hours. So this doesn't go into, lots of specifics in terms of anaesthesia or surgery, anything like that. It's a general overview that you might see in general practise.
Also, if you add in there about 7,000+ reptile species. Obviously across that big ranging tax so there's numerous variations in both anatomy, physiology, everything like that. You can see the picture on the right, you know, sea turtles to terrestrial lizards to desert lizards to, you know, crocodiles.
You can imagine there's a huge variation and certainly too much to cover over in 2 hours. So this is really a general overview to give you some idea of what to expect. And then, as I say, for reptiles too, that goes into more common species that you might see in general practise.
So I made this lecture for a class in the US, so looked up some numbers. There's about 3 million pet reptile households across the states at the moment, about 70 million dogs, about the same cats, but reptiles is almost catching up to horses. So it's probably the same in the UK as well, and I think The take home point from that is that if you're in small animal practise, you may be asked to see the occasional pet reptile.
It's not an uncommon first pet for kids. People buy them and think they're relatively easy to keep, which is not true, but people buy them for the small kids as like a starter pet. It's either that or a hamster, it seems to be.
And I think this is true. It's poor education regarding care and ownership. You know, you can just go and pick one of these animals up and they need a lot of very specific husbandry things which are sometimes not conveyed.
People don't fully understand exactly how they function. So probably I would suggest maybe 80 to 90% of problems that you'll see in practise are husbandry related or I should say husbandry deficiency related. So to keep this concise, reptiles 1 is the 1st 2 general anatomy, general physiology, and then reptiles 2, we'll go into specific examples of snakes, Gillonia, which is tortoises and turtles and lizards.
So taxonomy wise, there's 5 different orders of reptiles and I bolded the 3 that we're gonna go into. So Uhidia is snakes, Celonia, as I said, is tortoises and turtles, and Sauria is lizards. I'm not really going to go into crocodilians or sennodontia.
You know, not commonly seen, I think that's fair to say, and the Tuatara is the only species, and that's a New Zealand reptile, you know, you're not going to see that in practise. So the bold ones are the ones we're going to concentrate on here. So, first glance from the outside is integument.
They all have this layer of dry skin which is scaled and the scales are made from keratin. It forms either scoots or scales. It scoots if you're a tortoise, there's parts of the shell.
Underneath that, they have a lipid layer which conserves water, very few dermal glands. And if you look at this picture here, this is a side view of a snake post-surgery, and this is how you close them post-surgery. So this is an inverting horizontal mattress pattern.
If you do inverting or even appositional patterns, you get scale to scale, which doesn't heal very well. So that's something to take into account should you ever do surgery on a reptile. So this very thick skin is for protection, so it's that also has a caveat that it's less sensitive to stimuli.
So if you have something like a hot rock, which people use, it's a heated rock within reptiles bavarians. They're often more prone to contact burns because they'll just fall asleep and burn without realising. It could become a problem.
These grey boxes you see here, this is from a book that I'll show you at the end. This is a book that has a lot of these cool little clinical tips in there which are helpful and I think helpful for anyone going into general practise in reptiles. And this one is that sutures should be left in place for about 6 weeks as opposed to our mammal species, which is probably a couple.
Every species goes through ecdysis, which is shedding in a snake that's normally one piece, and that's the species that that that that you classically think of when you think of shedding skin, that whole snakeskin that's come off. In both lizards and tortoises, they'll shed it in multiple pieces rather than one whole piece. So if Aysis is normal shedding, dissectysis is abnormal shedding, and we'll talk about that.
When they do shed, this is a, this is a snake that's going into shed. This picture on the right, you can see this hazy eyes and this kind of dull coat, and the picture on the left really demonstrates the contrast between the old skin, which is a dry, kind of hazy, skin versus the new shiny skin coming through. And that's because lymph fluid is actually in that space between both the old and the new, and it helps it kind of cleave away.
So they are more vulnerable to parasites and infection during that time. And you can see here, you see this picture on the right, this, this hazy eye thing, people will call and say, my snake's got hazy eyes. It's generally going into shed, and that's really an important thing to be aware of.
These snakes can't see very well. They will generally strike to try to bite a lot more easier than a snake that can see properly. So snakes aren't normally that aggressive, but when they can't see or they get spooked, they could, they could strike out.
So be aware if you see this in practise. So I mentioned dysagiasis, and that's abnormal shedding, so that's when in a snake in particular that that it doesn't come off in one piece. Usually it's 90% of the time I'd say it's from inappropriate husbandry being too dry.
So there's just not enough humidity in their, in their enclosure. And that's why it's important to become aware of what they really require and get the owners to monitor that thing. You can also see it in skinny animals are hyperprotemic because they can't produce the necessary enzymes to get rid of that shed and put the lymph fluid in there to get rid of that old skin.
And a big thing for a lot of animals, particularly snakes, is retained spectacles. So in the previous slide we saw those hazy eyes. That's because there's a there's a spectacle over the front of the eye.
So snakes don't have eyelids. They have this transparent spectacle which lives over the cornea, and when they develop a new skin, the old spectacle should come away. Now what you Probably the most common dysectiasis issue in snakes is a retained spectacle, and that's when the old one doesn't come away.
And sometimes you can end up with two or three retained spectacles there. So it's important to get the owners to check that skin and make sure the spectacles have come away. You can look at it with a slit lamp on the thermoscope and try and determine if there's multiple spectacles there, but it can be difficult to really, really pick that up, you know, to separate it from the cornea.
Obviously they have different colours. So there's a chameleon on the top right it changes colour, we all know that's a rainbow bower on the bottom right, that's kind of this iridescent species, whether it's for camouflage or sexual display or thermoregulation, they have chromatophores in their skin, which, which can cause colour changes. So that's it for skin.
Moving on to skeletal structure. Particularly snakes, a kinetic skull, so they have a lot of elastic cartilage and this quadrate bone. This quadrate bone is really important for the snakes to ingest large prey, so the top jaw and the bottom jaw will articulate with that and allow that jaw to open wide.
So that's what. Say, oh, snakes, you know, their jaws disarticulate. They don't, they just slide up and down the quadrate bone, if you will.
So that allows that kind of jaw to open wide. The lower jaw is also not fused, so that can separate, and again, provide a bigger surface area to eat larger prey. I've definitely seen fractures of the quadrate bone, and CT is helpful.
Difficult on radiographs to pick out fractures there because it's just small little piece. CT is certainly the superior imaging modality to pick that up. They have a very flexible backbone, so they don't need to support.
Their backbone off the ground like dogs or cats because their belly is normally on the ground whether that's a snake or a lizard or you know a tortoise often kind of sits on the ground. So flexibility is really important. We divide that into pre-sacral, sacral, and caudal areas of the, of the backbone.
And they, they don't have a diaphragm. So it's just one salomic cavity. So, you know, if you see some, if you hear someone say a thoracic or abdominal or a lumbar description, it's relatively invalid.
You know, you know what they mean, but there's no diaphragm, so there's no thoracic cavity. The cardiovascular system is a little bit different, so I got just some pictures of hearts on here, which you all know. So you'll know the one on the left, the four chambered classic Mean heart, and turtles and snakes and lizards have got this kind of set up.
And then crocodilians I included here because they're a little bit different. I know I said we wouldn't talk about crocodiles, and look, slide 6 or 7. I'm already telling lies, but here's a crocodile situation and we'll talk about that.
So most reptiles, picture B, turtles snakes, and lizards have got a 3 chambered heart, which is 2 atria, and essentially one ventricle. So you can see here in the mammal, you can see my arrow on the screen that this, this, The wall between the ventricles here separates left and right. Here in the in the lizards and the snakes, this is not complete, so it allows mixing of blood.
Crocodiles have a cool function where this ventricular wall can actually move up and down and it articulates up here so they can produce for tubers, but they're actually a three chambered animal, which is pretty interesting. What that does, it allows you allows animals to shunt blood to or away from the lungs. So if they're an animal that's going to hold its breath, particularly for diving, you know, if it's an aquatic turtle, they can shunt blood away from the lungs.
There's no point in that animal sending blood to its lungs which doesn't have fresh oxygen or fresh air in there, and just goes to the major organs where the oxygenated blood is required. Think about this in terms of gas anaesthesia. We usually don't gas reptiles down, simply because they have the ability to breath hold, which we'll talk about, but also they can shun blood away from the lungs.
So even, so even if they are breathing, there's no blood, actually go in there to take up the isofluoride or see fluoride, whatever you're using. So that's important in terms of gas anaesthesia. They have something called a sinus spinosis that gets the deoxidated blood from the circulation before it enters into the right atrium.
And they have two aorta. Single ventricle has got 3 chambers, so there's the cava venosum, the cava arteriosum, and the cava pulmonale. So CV, CA and CP.
And what this, what this means is you've actually got 3 chambers within essentially a single ventricle, you know, because it's left and right and not totally separate with this wall. Now, although it's a mixture of blood, It looks like it in, in reality, because of contraction timings and movement of those ventricular walls and movement of the valves, and also there's a big pressure differential of blood coming in versus blood leaving. Actually, the deoxidated blood and oxidated blood doesn't mix completely.
So I imagine this, the way I best imagine this is if you've got, if you've got two hose pipes going, one one's kind of coming out really slow and one's coming out very fast. If you join those two streams of water, the high pressure stream kind of stays by itself and disperses the lower pressure stream. So if that high pressure stream is the is the oxygenated blood.
It disperses the dioxinated and stays by itself, so it doesn't completely mix as if you pour in both hose pipes into a bucket. Does that make sense? Probably not the best way to think about it, but that's how I deal with it.
So in terms of pathway, you get deoxygenated blood comes from the right atria into the carbovinosum, which is right atria into here. Then oxidated from the left atriy into the corpus arteriosum, so you see this blood comes in and goes down here, so the high pressure. The atri then contract, causing those valves to hinge, and deoxygenated blood is forced because it's low pressure from the CV into CP.
So it pushes the low pressure pooled blood out the way first. So this low pressure, deoxygenated blood is here and is kind of pushed this way by contraction before this high pressure blood moves. Which forces blood into pulmonary artery.
So the valves close and oxygen as blood flows into back into flows into CV for the first time and into the aorta and goes to the rest of the body. So that's something to think about in terms of, kind of, you know, we always say that they mix blood and that's true, but it's not a completely Book it situation, if that makes sense. So this muscular ridge also is a little feeder for the matriculate from the the septum here and that reduces mixing between the two blood compartments as well.
They can shunt it depending on pulmonary resistance. So during peak respiration, the pulmonary resistance is low, so deroated blood flows to the lungs. So if you think back to those pressures, it goes back to that situation again.
And you not some starvation, so if it's a dying turtle or if it's a snake that's swallowed a sheep or something, pressure increases due to vasoconstriction, so that alters those valves and the muscular ridge, so blood is actually diverted away from the lungs. And that is what you call a right to left shunt. So as we mentioned, you can get problems when you use gas.
Also, if you've got an animal with chronic pneumonia, you've got less blood flow through those lungs, you've got higher pressure in that system, so blood may be diverted away when it's needed. So that's the circulatory, that's the heart. In terms of blood films, they have nucleated red cells, which you may or may not have seen before.
And if you do in-house slide exams, and they generally have a longer lysis, a longer lifespan than mammals, sorry, and these are, these are normal red cells. This is what you call a heterophil, so H is heterophil, and that's basically the same as a neutrophil. They have other white cells called Azorrophils, which we only see in reptiles.
We think they're similar to monocytes, they are in appearance, and they also have eos, besos, lymphocytes, and monocytes as well. It's important to note that if you take a blood sample from a reptile, generally don't put it in EDTA. It does produce lysis if you put it in EDTA, so it's going to ruin a lot of clinical pathology results.
So put it in a lithium heparin tube that prevents clotting, prevents and preserved cell morphology. So that's a, that's a useful tip because sometimes they're difficult to blood sample and you really don't want to put it in the wrong tube and ruin it. They have a well developed lymphatic system with big reservoirs, no lymph nodes, so if you feel a swelling in the neck, it's not a lymph node.
They do have lymph hearts which will pump lymph around the system. And depending where you take blood from, and we'll talk about this, particularly in terms of tortoises and turtles, lymph dilution of blood samples is relatively common. So if you see a low PCV and a low white cell count, especially during your sample, if you see a clear fluid coming in there, be suspicious that you've got some lymph dilution and be prepared to factor that into your clinical thinking.
Moving on to the respiratory system, intubation is relatively simple in all these species. And they have lungs just like we do for cases exchange, but also they use them for buoyancy, display, and vocalisation. They don't have alveoli, they have faveoli, essentially not a huge difference to alveoli in terms of what, you know, we need to know from a clinical standpoint, just know it's a little bit different to alveoli.
And they have smooth muscle within the lung lining which helps inspiration and expiration. So clearly no, obviously no diaphragm, so they need to kind of help themselves a little bit more. Here's a picture of the glottis.
So you can see the snake here is very rostral, very easy to get to. Tilonia a little bit further back. My top tip for integrating those is when they're asleep, push your thumb underneath the soft portion between the two branches of the mandible.
And then you kind of elevate that glottis, which is relative, sometimes far back in turtles and sometimes kind of fleshy. And then you can see it. If you don't do that, when you try and intubate, it just pushes it backwards and can make it difficult, especially if your tube is a little bit big.
So push underneath with your thumb, and then lizards are relatively simple as well, you can see it there, letter A, that cap. They have 3 different lung types. Again, this is academic as opposed to clinical, but just to make you aware of the different things that they may have, which conveys into, Respiration efficiency.
So the unicameral are the very prehistoric reptiles, that's essentially a Tesco bag that just fills clothes. Poi camera is a little bit more advanced, so they've got a few air sac dilations there as well. And then multicameral is much more like the mammalian lung that we might see.
So it's a multi-chambered lung. So 3 different types. We mentioned they don't have a diaphragm, so the whole body cavity is named the salomic cavity.
Some species have a septum, but it's easier to think of that just don't have, don't have a diaphragm and, and deal with that. So the negative pressure is created by body muscles, so, you know, legs going in and out, actual body muscles creates that negative pressure to take it into the lungs. Also, I think this picture's interesting.
It shows a cut through section of a tortoise, and you can see here's the lungs in situ, all the rest of the GI organs and stuff and the heart have been removed, but you can see this is an enclosed box. So if you ever do intracellumic fluid therapy, be careful because you put too much in and you're right next to the lungs, you can compress them or drow them fairly easily. So be careful of that.
Some of them have got some of them have got accessory methods, so if you're a soft shelled aquatic turtle, you might be able to respi through your skin. A lot of snakes have got a tracheal lung, and the tracheal lung is there. So when they swallow large prey and it compresses their lungs, they can still respray through the small tracheal lung.
They can perform More more anaerobic metabolism than mammals, and we'll talk about that in metabolism. They're overall pretty tolerant of hypoxia. One interesting point is that respiration rate is driven by temperature, not PCO2 like mammals.
. And actually high PO2 depresses respiration. So just that flow through of oxygen, you know, even without actually taking a physical breath that you can see and count, just passive oxygen into the lungs is about all they need. So that's important if you anaesthetize an animal.
If you, if you keep them intubated and keep them on oxygen as opposed to room air. And wait for them to take a breath. They're gonna be breathing for they're, they're not breathing for quite a while because they just don't need to.
So they've got that high 02 going into the lungs just by passive, you know, flow through. They don't need to actually take a breath. So that, so I would recommend, you know, once you've got an animal off anaesthesia, get them onto room air as fast as you can, you know, as, as safely.
Keep them intubated, you can use an Ambi bag if you, if you need to, and that'll drive their own respiratory drive, to help them recover. Keep them warm as well, so the warmer they are, the, the, the faster they'll breathe. Obviously if they get cold, they're not gonna breathe.
In terms of digestion, There's 3 different types of teeth. So Arodont is a lot of lizards, and this is his first picture. They're just attached to the crest of the of the mandible or maxilla.
And once it hits adult size, those arodont teeth do not regrow. So if they lose them, that's it, they're done. So be, be careful if you see a lizard that you know has arodont teeth, that if you break the teeth through an oral exam or forcing the mouth open, you know, those teeth are not going to come back.
If you're a snake and the other types of lizards, you have luridon teeth and they're attached to the inner wall, and they have a limited ability to regrow. I think it's a little bit dependent on species and age, but they're attached to the inner wall of the mandible and maxilla. And then the most advanced teeth that we see in crocodiles and there's a ficodon, they actually have a bony socket, much like mammals, and they'll regrow through life.
So they'll fall out and replace them throughout their whole life. So those are So you don't worry about crocodile teeth falling out. They don't really chew, you know, especially if you're a snake, you know, if you're a tortoise, you chew on veggies and stuff, you know, you swallow a lot of things whole, especially if you're a snake.
So they have oral glands to help with lubrication. Obviously some snakes have got venom glands, and hopefully not ones you see in general practise. The venom gland lives up here, and it's this area here.
And that's, there's a muscle that actually compresses that venom gland and squirts venom. So they can so venomous snakes can do what we call dry bites, which is when the no venom comes through, but obviously you don't know if you get bit by something, if it's a dry bite or not. So there's a couple of these quiz questions thrown in here.
So everyone knows venomous snakes, but the venomous lizards, that is true. There's the Mexican beaded lizard, all the, . Healer monster, some people would argue is a venomous lizard.
I think it depends what you read. They've got such a horrible bacteria laden bite, you know, you could call it venomous, but I don't think it's actually a true venom, like it is with the Mexican beaded lizard. Obviously, you know, everything about reptiles is slower, so GI transit time is slower.
Particularly in herbivores and especially if they're sick. Carnivore's got a pretty simple digestive system and herbivores got a larger colon and secum. So if they're sick or the temperature's low, the GI transit time is massively reduced even further.
So if you're given animal oral medications, either via a tube or force feeding them, think about the, the medication may just sit in that stomach for a long time. So, and all of a sudden, if things start moving again as temperature increases, they might get a big whoop of drugs that have been sat in the stomach for ages. At the back end they have a cloaca, which is divide which is which internally is divided into three sections.
There's the coprodum and the uro and the proctoiumium. The coprodeum collects faeces from the rectum and the colon. The urodium, the urs empty into there, and, and, and the bladder opens into the urodium.
The Proctodaium is what the mixing chamber, so that's where everything kind of mixes before it leaves to the outside world. And these are pictures of cloiers just on some bearded dragons underneath here, you can see the shape and size of that. So if you're a desert species such as bearded dragons, it's important for water conservation, and they can actually reserve water through the bladder, or they can hold faeces in here and reserve water that way.
In the kidneys, they don't have a loop of Henley. So, they can't concentrate their own urine. Bladders, bladders are found in tortoises and some lizards, but otherwise it just generally collects in the cloaca.
It's not sterile. It's obviously mixed in that uridum Procterdaum area with a lot of faeces, so. It's not a sterile procedure.
It's not like they, we can diagnose a UTI very often. I'm gonna talk a little bit about the renal portal system, which may be a totally academic thing, but I think it's probably important to be aware of. So different to mammals, the reptilian kidneys got dual afferent blood supply.
So it's got renal arteries just like we do, but it's also got a renal portal vein which enters the kidney, the tubules, so bypasses glomerulus, and that comes from the back legs and it enters the kidneys in here, so you can see this vessel coming from the, the back leg of this lizard going into the kidney, as well as the renal arteries. So 22 different blood supplies. The purpose of that is to allow kidney perfusion after glomerular filtration rate or GFR has been reduced, so it prevents kidney necrosis.
So it's an adaptation to You know, lack of fluids or dehydration. There is a valve system in place, so it's not constantly open. We think it's controlled by stress or hydration level, and that will obviously allow blood to bypass the kidney from the renal portal vein.
So this valve, this vein coming in here, you can see it's also got a branch that goes up. Up towards the rest of the body that can close off so blood doesn't go into the kidneys right of the renal portal vein. And we've got no real easy clinical hands-on way of knowing whether it's open or closed, you know, in terms of holding a reptile and working out what's going on at that time.
So people worry about cural administration of drugs, and I think this is a topic that's a little bit open still. So there's two, there's two worries with giving drugs into the back legs. If the renal portal system happens to be open, if those valves are open from the renal portal veins, and it goes straight to the kidneys, potentially, does that lead to increased excretion of that drug, so you get less .
You know a lower pharmacokinetic level that alters the pharmacodynamics of that drug, and so does it ever reach therapeutic levels. And if it's a nephrotoxic drug, it does it hit the kidneys at a big toxic dose, you know, instead of being diluted through the body before actually getting to the kidneys. So that's what people worry about with the renal portal system.
And I think consider the drug in question. So ammicain is probably the drug that springs to mind for a lot of people in terms of renaloxicity. It's secreted by the glamerulus only and the renal pulse system bypasses this, so technically amicain should be safe in terms of being more nephrotoxic and in terms of being more excreted.
So I think consider it in terms of the actual drug and It's probably safer just to give drugs in the cranial third of the body. I mean, you don't have to give them in the back legs. So I guess avoid it if you can.
But don't worry about it too much if you're forced to give in the back legs. In terms of reproductive system, the male's got two testicles. They, they're all internal.
The right ones are closely associated to vena cava, the left is closely associated with the adrenal gland. They've got extra cloa or hemipes, and basically the hemipenis is basically like a slip and slide for semen. It doesn't actually do much other than allow semen to get into the female.
So you can, you can amputate the hemipes. Functionally, the animal will be just fine, reproductively, it will not, which is something to think about if you're taking blood samples from the tail, you know, could you damage the hemipes? Is this a breeding animal?
Do you want to be careful about that? The answer is yes. So be aware of the hemipenis in terms of reproduction, but in terms of normal bodily functions, staying alive day to day, it's not an essential organ.
Females have got two ovaries. Again, the right one is close to show to the vena cava and the left of the adrenal glands. So if you do space, obviously this is not a spa, there's an ruptcy.
I would hate to do this surgery, . If you do that, be careful that you don't disrupt a large blood vessel or an important gland. And they have after those ovaries, they have an infindibulin uterine tube isthmus, uterus and vagina before you hit the outside world.
And they can be different in the way they produce babies. So there's oviparous, which is the egg, an egg laying animal, and they lay these soft leathery eggs which are water resistant, allows gas exchange. They're not hard shelled chicken egg, or they are viviparous, which is live young, which is this one here.
There's a live birth in a snake. And then obviously this is from Indiana Jones, for those that remember. So the quiz question, are we as males in the reptile world, are we relatively useless for some species?
Yes, we are. Some species can produce by something called parthenogenesis, which is when just females produce babies without a male around. It's been proven in geckos, Komodo dragons.
Some species of boas are bo snakes, so are we destined? To end the endocrine system, yes, they have one. There's not much different here in terms of mammals versus reptiles.
So the thyroid is metabolic rate control for shedding and growth. Again, it's temperature dependent, so you can see temperature keeps coming up as an important thing. They have a parathyroid gland, which is the same function as mammals to produce parathyroid hormone.
And obviously we know about calcium deficiencies in reptiles, and that's where this kind of comes in. They have adrenal glands, which you mentioned are next to the gonads and the kidneys, so be careful if you do space. They have a pineal gland, which likely plays a role in thermal regulation in terms of where to move to to bask and things like that.
They've got 12 cranial nerves. Not the brightest of things. They can train, they can learn, and they can target train, they can learn to some degree, but obviously it's pretty limited in comparison to, to mammals.
Crocodiles have got an external ear. The rest have not got an external ear. They've got this tympanic membrane as the outer level.
So this is being a dragon ear, it's basically just a hole in the head with a tympanic membrane inside. Snakes and chameleons don't have a tympanic membrane. So this is a bearded dragon ear, it's a crocodilian.
And they only have one middle ear bone, which is the columnella, and that actually connects to the quadrate bone which you remember back to the skull radiographs, that's the that's the bone that allows the jaw to articulate. They have a Jacobson's organ which is on the rostral cavity of the, the ros the roof of the oral cavity. And that's why you see snakes in particular, using the tongue tips to explore the environments, and sense what's going on around them.
I should probably delete this line. I think people know the eyes are the primary receptor for vision, but it's true, spectacles we mentioned in terms of dysectiasis or ecdysis in snakes. Also some lizards have got spectacles, so no eyelids.
Pino gland is secondary, that senses light. They have sclero articles, which are bones kind of around the back of the eye which hold it in place, particularly in lizards and chlodia. And all the eyes have got lenses, so they can focus the different distances.
Interestingly, the iris is controlled by skeletal muscles, so this is similar to birds. So, mammals, it's smooth muscle, so it's involuntary, skeletal muscle is a voluntary control. So if you need to dilate, you can't use atropine.
You've got to use rockuronium or something like that, some skeletal muscle blocker. So snakes never blink, true or false. That's actually true, because they don't have eyelids.
We know that, snakes in particular can sense heat, so they have these infrared receptors called pits, which are these red arrows here. They can sense the warm prey and therefore they can hunt in darkness. That's why when a snake is going into shed and can't see it very well, it relies more on its pits and its heat sensing, and can strike.
Pretty richly innervated by numerous branch numerous cranial nerves, the ophthalmic mandibular and maxillary branches. And actually temperature variations of 0.003 °C it can detect, which is kind of incredible, more than the best thermal cameras, I think.
So it's almost 1/6 sense that they have. So that's general anatomy. So I think if you have any questions, I guess there's a way to do that.
You can reach out or reach out to webinar people. We'll talk about reptile physiology. So the metabolism, as you might expect, pretty slow, about 20% of the rate of mammals, affected a lot by temperature, but also by species, the diet, predation, behaviour, all those things come into play for different speeds of reptile metabolism.
And they can switch to ana metabolism fairly easily. So if they switch that vigorous activity, so if they go hunting or running away. It's a big drain on energy resources than aerobics, so we don't want to do it.
If they can, lactate's pretty slow to be eliminated, and it also affects blood pH and decreases the oxygen's affinity for haemoglobin. So it's not a preferred method of metabolism, but they will use it should they have to. So they're exothermics, they can't generate their own body heat, so they need an outside source of heat and this ties back into husbandry, which is primarily the reptiles, the second hour.
They've got much lower energy demand than mammals, but still they need this, this external heat source and so their activity is really limited by the ambient temperature. It's an important concept to know about is the preferred optimum temperature zone or POTZ, depending on the species, and again, this is obviously very species variable. A rule of thumb is 20 to 38 °C, but that varies within species.
And then within that range, each one has a preferred body temperature. Preferred body temperature is a single smaller range within the POTZ. But that varies with current metabolic functions.
So if it's a reproductively active part of the season, if they've just ingested food, if they're having a nap, So that that varies within this. So the POTZ is specific for each species, and then the PBT, the preferred body temperature, varies depending on current metabolic or current activity, current metabolic function. So therefore in captivity they need a temperature gradient and ideally at one end of the Bavarian, it would be the low end of the POTZ and at the other end, it will be the high end.
It does not always possible and obviously it varies for species and day to night and seasons. But the closer people can get to that, the less problems that we'll see with the reptiles, the more successful they'll be at keeping them, raising them, potentially breeding them. Two ways they acquire thermal energy and raiding heat by basking.
So that's heliothermy or sigmathermy is thermic by conduction. So conduction is normally nocturnal animals, so they sleep in the daytime, so they need to get sleep on warm places that's been warned through the daytime to get the heat, whereas heliothermy is usually diurnal reptiles. They can heat up faster than they cool, so they can heat up relatively quickly, and the cardiovascular system helps with that, so they can raise the heart rate to spread that warm blood to the extremities.
They can do a right to left shunt to shunt blood away from the lungs and avoid the cooling from respiration, and they can do peripheral vaso constriction during cooling to reduce heat loss. Osmo regulation, they're taking in water primarily via food, also via drinking, and they lose water via evaporation, respiration, urine and faeces. And also I think a significant portion of that is during the shedding process, especially if you're a snake and it's all at once.
Pretty similar to mammals in terms of body mass, about 70% water, 3/4. 2/3, sorry. And again, no loop of Henley means they can't concentrate urine beyond the value, the osmotic value of blood plasma.
So they got to conserve water somehow, right, because a lot of them are reptile species or they might not be in areas where they've got a lot of water. So methods of water conservation include uric acid production, cloaca absorption. They can decrease GFR.
They have salt glands and the renal portal system which we mentioned. So uric acid waste is a pasty white substance that you're probably seeing. It's excreted with minimal water loss and through the kidney tu also so it's not stopped by dehydration.
If it builds up, they become dehydrated and they get hyperuricemic, which causes gout. So if you were looking for renal function in a reptile, you would not look at BON. You would look at uric acid, BON it's not, not useful.
If it's a carnivorous species, uric acid is going to go up because they just ate a lot of protein. So be aware that a non-fasted sample from a carnivorous reptile might have a high uric acid than what you might expect. Also be aware, reptile may have gout but have normal uric acid levels currently because it's a previous insult that caused a hyperuricemia event.
They can reserve water through the cloaca. So if you put them in a little bath, they'll reserve water through there. They'll hold it in the bladder and resolve it.
And they will drink if you put them in a bath as well. They can reduce GFR in response to dehydration, so that decreases excretion of salts. And then they have salt glands which allow them to get rid of that salt without water.
So these lizard, this lizard here with a white crustiness around its areas, those are salt glands and that's, that's a, that's a water conservation method. In terms of UV, we really need UVA. Within the UVB, sorry, UVA is more for behaviour and reproduction, but UVB, allows them to utilise vitamin D and therefore absorb calcium.
So if they don't have UVB exposure, you can feed them all the calcium you want. They can't, they can't absorb that into their body without without UVB, so they just pass it through and they still become hypocalcemic. Really unfiltered sunlight is the best source, but clearly that's not always easy.
Windows will philtre out UVB, normal Windows, so, we really need one of these bulbs that produces UVB so you can see this is labelled UVB here, this Repti Glow. Repti Sun is another good brand. You get what you pay for.
I think that's important to tell people you can buy a $5 UVB in inverted commas bulb, or you can buy a $100 UVB bulb, and probably the $100 bulb is about 20 times better than the $5 bulb. So calcium is a big one. Metabolic bone disease is an issue that we see.
About 99% of the body calcium stored in bone, and the plasma in as calcium is, as with us, the mammals is maintained a very narrow window. This is the same as mammals. I'm not going to go through this.
We know this from mammalian physiology, the parathyroid hormone, and calcitonin are the two main players in keeping plasma ion has calcium within in a very narrow window. If you got a chronic deficiency in calcium, basically you suck all the calcium out of your bones and cause metabolic bone disease. So nutritional osteodystrophies or metabolic bone disease.
In their diets, calcium phosphorus should be about 2 to 1. So beware if you've got an insectivorous animal or just a meatn animal or a herbivorous animal. They're wrong in terms of calcium phosphorus ratios.
So usually we promote calcium intake with dietary supplementation where calcium powders, so people can gut load crickets if they're insects, or they can dust the thing on meat. Or they can dust it into herbivore diets as well to increase their calcium intake. We very rarely see this in snakes, and I think it's because snakes eat whole prey, so they got a whole skeleton that they ingest.
But certainly we'll see it in lizards. They're the poster child. Here's a slider turtle with metabolic bone disease.
So this form was fed meat only, so a lot of demineralization of the bones through the, the shell and also the limb girdles. The pectoral and pelvic girdle, sorry, and the eggs are misshapen. You see those are, that's a calcium deficiency produced in the eggs as well.
So that's metabolic bone disease in a slider. This is a green iguana, which used to be the real known species for it when they were a really popular pet, but you can see a lot of bony loss, especially through the extremities, so you can barely see the digits, you know, the cortex medulla distinction is not very good, very thin cortices. So we've got a lot of bony loss in that greening.
Sometimes they get a wobbly jaw that you can physically, you know, mess, . Touch with your finger and move that jaw. Hibernation wise, we see this in species in temperate climates and high altitudes to survive drop in temperatures.
So it's triggered Physiologically by lower temperature, as opposed to in mammals or things like bears and stuff like that. It's suppose that's a low food trigger. In reptiles, it's a low temperature trigger.
So that lower temperature inhibits appetite, they then generally seek a hibernaculum, which is moisture and freezing resistant. Metabolism slows, their energy source becomes from stored lipids, and then they emerge when temperatures rise again, that increases appetite and makes them wake up. So that's how it would happen in nature.
In terms of captivity, we can manage that, and I think it's probably physiologically normal for them to do it. I don't know of any studies in reptiles, but certainly in mammals. There's been some studies done that look at blood blood profiles of particularly bears, irrespective of whether they are hibernated or not in a captive situation, and their blood actually suggests that they're physiologically hardwired to hibernate in terms of changes in a lot of things like glucose and insulin primarily, but other things as well, thyroid hormones.
And so I think if we don't give them that option of hibernation, that's potentially got long term effects on their health. Saying that hibernation could be a problem. Animals can die during hibernation, and it's important, I think, in practise to do a pre-hibernation check and a post-hibernation check and for owners to be fully aware of how to do it.
So some key points, they shouldn't lose more than 10% of their body weight. So their only body weight lost during hibernation is through water loss through respiration. So owners should weigh them regularly and if they're approaching a 10% body weight, they should wake them up by increasing temperatures.
They should not have anything in the GI tracts, they should stop eating, poop everything out, and be totally clear inside. Until they hibernate just because you're full of bacteria in there and you can cause issues, and you shouldn't hibernate with any diseases, parasites, things like that. Their immune system almost completely shuts down while they're there.
If you blood sample an animal during hibernation or just afterwards, the white cell count is, you know, sunk to almost zero. So if you hibernate them with any diseases, their immunity is shot, and any disease can has a, has a chance to fester and kill the animal during hibernation. So it's a, it's a decision that you've got to take with the owner, to look into that species, make sure it's right, and make sure that they're following all the steps to keep their animal alive through hibernation.
Females are ZW, males are ZZ in terms of sex, and it's generally temperature dependent, which varies among the species, whether males are hot or males are cool or vice versa, with females, but it's generally temperature dependent. So any questions on anatomy physiology, which completes reptiles one? If there is, let me know.
Thanks.