Anatomy

I am Your Dog’s Heart

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With Valentine’s Day around the corner, we dedicated this Daily Dog Discovery to the dog’s heart. We often take this organ for granted, but this amazing powerhouse does a remarkable amount of work to keep your dog and his body in good working order. We are talking about one of most miraculous “machines” that’s capable of working non-stop, ticking relentlessly for many years of the dog’s life. While a dog’s heart is built in a similar fashion to the human heart, heart disease affects dogs differently than in people. Let’s take a look at what your dog’s heart has to say.

dog heart diseaseLet Me Introduce Myself!

Hello, it’s your dog’s heart talking! Just like the human heart, I am not very impressive looking. People like to imagine me as a Valentine’s day heart, but I am instead just an egg-shaped muscle of an unappealing red/brownish color that’s housed within the thorax.

More than criticizing my looks though, people should look at me for what I accomplish on a daily basis with no down times. What can I say? I am a workaholic “at heart.”  You think I am exaggerating? Here are some impressive dog heart facts about what I do every single day.

  • On an average day, I pump about 4,000 liters of your dog’s blood.
  • At rest, I beat between 70 to 120 times a minute. That’s more frequent than the human heart which beats an average of 70 to 80 times a minute.
  • I beat roughly 144,000 times per day.
  • I work all day and all night and only rest in those brief split second between beats.

I Transport Bloodheart anatomy

As you may know, I am responsible for moving blood through your dog’s blood vessels. To do so, I am equipped with four chambers, two upper ones known as the left and right atria and two lower ones, known as the right and left ventricles. Here’s a quick review of what I do. When my right atrium receives blood that’s low in oxygen but high in carbon dioxide (a waste product)  from the body, it’s pumped into the right ventricle and then into the pulmonary artery so that the lungs can replenish the blood with oxygen. This oxygen-rich blood then travels through the pulmonary vein and goes back to the heart by entering the left atrium. Here the blood is then pumped into the left ventricle which forcibly pumps the blood through the entire body through the aorta. This cycle keeps repeating over and over for the rest of your dog’s life.

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stethWhen Things Go Wrong

You may be familiar with clogged arteries which are a common cause of heart attacks in humans, but when it comes to dogs, arteriosclerosis and heart attacks are actually quite rare. That doesn’t mean that dogs are free from heart disease though. A common form of heart disease seen in dogs is heart failure. This happens when my valves or muscles give out and no longer work as they should. When this happens, one side of me may be overloaded with work and I cannot keep up, so I might have to give up and eventually fail. I don’t fail out of the blue though, it’s usually a process taking months or years. I may give signs of trouble by making affected dogs cough when they’re exercised or excited or right after sleeping.  Affected dogs may appear to get tired more easily and may even faint. These symptoms are proof that I am no longer providing adequate circulation (oxygen for the tissues) to meet the needs of the dog’s body.

Luckily, most vets will notice problems especially if I let out a “murmur” that they’ll hear with the stethoscope. Next, x-rays will show if I am getting too worked out. If I appear enlarged, that’s a sign that I am doing too much. Medications can help me pump more efficiently and help dogs remove excess fluid from the lungs. The vet may recommend a diet low in sodium so to decrease the buildup of fluids. Hopefully, your dog won’t ever go through all of this, but it’s good to keep this in mind so to recognize early signs of trouble especially as your dog ages. Two conditions in particular are known for making me fail, degenerative valvular disease (DVD) when my valves fail to seal properly (a condition common in small dog breeds) and dilated cardiomyopathy (DCM), when my heart muscles weaken, (a condition common in large and giant breeds).

About 10 percent of all dogs seen in primary care veterinary practices have some form of heart disease. This percentage continues to grow as dogs get older. Up to 75 percent of senior dogs experience some form of heart disease. ~Drake Center for Veterinary Care

puppy murmursA Word About Murmurs

I  am known to make a typical “lub-dub, lub-dub” sound that your vet is familiar with. The “lub” sound means that the valves controlling the flow of blood from the upper chambers to the lower chambers close, while the “dub” sound means that the valves controlling blood going out of the heart close.  However, at times, when your vet listens to me with a stethoscope, he may hear an extra noise that sort of sounds like water flowing through a hose. What’s that? It’s a murmur. Not always this is a bad thing. It just means that the blood makes a whooshing noise as it flows through me.  Heart murmurs are quite common in puppies. According to VCA Animal Hospital, they’re often found in young, large breed puppies as early as 6 to 8 weeks of age, but they usually go away by time these pups reach 4-5 months of age. These murmurs are usually benign. Only in some cases they’re a sign of a structural problem.

References:

  • Healthy Hearts for Dogs, Heart Facts, retrieved from the web on February 8th, 2016
  • Merck Veterinary Manual: Resting Heart Rates, retrieved from the web on February 8th, 2016
  • Pet Education: Heart Failure (Mitral Valve Insufficiency) in the Dog, by Race Foster, retrieved from the web on February 8th, 2016
  • Heartworm Society: Prevention, Diagnosis, and Management of Heartworm  Infection in Dogs, retrieved from the web on February 8th, 2016
  • Veterinary Team DVM360: How periodontal disease can affect pets’ organs, by Mary L. Berg, BS, RVT, RLATG, VTS (dentistry), retrieved from the web on February 8th, 2016
  • Your Dog’s Heart: Heart Health Tips, retrieved from the web on February 8th, 2016

Photo credits:

Diagram of the human heart, Wikipedia, CC BY-SA 3.0

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I am Your Dog’s Trachea

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Also known as the windpipe, your dog’s trachea plays a vital role in the passage of air. You might not be aware much of this structure until it gives signs of problems such as when it triggers episodes of coughing and exercise intolerance. As with many other body parts, taking good care of your dog’s trachea goes a long way in preventing problems, especially if you own a small dog. So today we’ll be introducing the dog’s trachea and learn more about this structure which, as many other dog body parts, certainly deserves some attention. Let’s see what the dog’s trachea has to say.

tracheaIntroducing Your Dog’s Trachea

Hello, it’s your dog’s trachea talking! You likely already know about me, I am that short, fairly rigid tube that extends from your dog’s larynx, right down the neck area and then ends right by the thorax where I divide into two primary bronchi that enter the lungs. I am basically shaped like an upside down letter Y. Structurally, I am just a tube made of  fibrous tissue and smooth muscle kept open by several C-shaped cartilage rings. If it wasn’t for these rings, your dog’s trachea would collapse each time your dog took a breath because of the vacuum created by inhalation. My main function, as mentioned, is to carry air to the bronchi, which in turn supply your dog’s lungs.

I’m a Self-Cleaning Structurepoodle

While my main role is to transport air into and out your dog’s lungs, I am also responsible for protecting your dog’s airway from irritating substances. You see, my surface is lined up with motile cilia, several hair-like structures, which, as it happens in the nasal passages, are responsible for trapping any dirt and debris out of the lungs.

For example, if your dog was exposed to lots of dust and contaminants as you were sweeping the floor, I would produce an increased amount of mucus to help trap all those the foreign particles preventing them from reaching the lungs. The mucus is then moved up towards the larynx so that when it reaches the pharynx, your either dog swallows it into the stomach or it’s coughed up as phlegm to clear the passageway.

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dog collapsed trachea
The white arrows indicate a normal-sized trachea, whereas, the black arrows mark the collapsed trachea.

When Things go Wrong

While I am a fairly rigid in structure, unfortunately sometimes things go wrong. See, in a dog with a healthy trachea, the airways remain nicely open. Imagine me as an agility tunnel. However, when things go wrong, I might weaken overtime, become misshapen and then, I might eventually collapse.

When I collapse, for sake of an example, you can imagine me as an agility chute, also known as a “collapsed tunnel.” When I cave in or collapse, the air has difficulty passing through so I cause the poor dog to develop a goose-like honking cough as a response. This cough can be noticed more when the dog is exercising, coughing, eating or acting excited. Pressure from the collar on me when the dog is being walked can also trigger coughing. And to keep me in good shape, you must also watch what training tools you use. According to the Pet Professional Guild, tracheal and esophageal damage along with neurological problems and many other issues may result from the use of choke or prong collars.

Sometimes, other than coughing, I may also cause trouble breathing, panting, exercise  intolerance and bluish gums which can be very scary symptoms! Some dogs are more predisposed than others in getting a collapsed trachea. Keep in mind that Yorkies, Pomeranians, Chihuahuas, pugs and poodles are some dogs that are particularly vulnerable, especially when they age.

Some Preventive Measures

A harness is better than a collar.
A harness is better than a collar.

Preventing me from collapsing would sound like a good idea as there is really no 100 percent effective treatment once I collapse. Some surgeons have had some luck in using stents for keeping me open, but according to veterinarian Dr. Eric Barchas these are prone to failing over time. There are several things that can be done though to slow things down. Even though there’s likely a hereditary component at play in collapsed trachea of dogs, genetics are just one piece of the puzzle. Most dogs with collapsed trachea do not show symptoms until a secondary problem arises and contributes in complicating matters, explains Robert Prosek a board certified veterinarian specializing in internal medicine. So here are a few things that can be done to prevent further complicating matters.

  • Keep your dog in good shape as obesity predisposes to problems.
  • Keep your dog away from cigarette smoke.
  • Keep your dog’s heart healthy as an enlarged heart can push against me and the bronchi.
  • Prevent your dog from getting too stressed or overexcited
  • Use HEPA air filters to minimize exposure to irritants
  • Protect me from respiratory conditions such as chronic bronchitis
  • Protect me by using a harness instead of a collar
  • Holistic veterinarians may suggest maintaining my integrity by using cartilage builders. Examples are glucosamine, chondroitin, MSM, eggshell membrane, and cetyl myristoleate (CMO), explains veterinarian Karen Becker. Consult with your vet.

Did you know? Dog’s have an Adam’s apple too! It’s basically the larynx which sits in the front of the neck just below the dog’s chin, explains Dr. Forsythe, a veterinarian working for Broadway Veterinary Hospital & Wellness Center in Sonoma, California.

References:

  • Clinical Anatomy & Physiology for Veterinary Technicians, Thomas Colville DVM, Joanna M. Bassert VMD, Mosby Inc.  St Louis, MO, 2002
  • Marck/Merial Manual for Pet Health, Home Edition, Merck and Co. INC. Whitehouse Station, NJ, 2007

Photo credits:

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Ten Fascinating Facts About Dog Paws

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We often take a dog’s paws for granted, but those paws are quite fascinating body parts that are worthy of being discovered! For a lifetime of walking on rocks, snow and asphalt, those dog paws are sure a work of art on their own considering how many pairs of shoes us common mortal humans must go through throughout our lives. Whether you own a Labrador, great dane or a Chihuahua, those paws are certainly remarkable yet, often, ho-hum, so underestimated. So today is the day to give an all paws up as we celebrate dog paws. So here are some fresh, fascinating facts about your dog’s paws we just fetched and thought to share.

dog paws 101) Tough & Thick-Skinned 

Think you are thick-skinned? Well, a dog’s paws are far more thick skinned than you, literally… Indeed, turns out that the outer surface of a dog’s paw pads boast the toughest AND thickest skin in the body. The foundation of your dog’s paws is composed of thick layers of fat and connective tissue and it comprises five, (yes five!) layers of skin. For dog geeks, the layers include, the following: the deepest layer known as the stratum basale, next, comes the stratum spinosum, followed by the stratum granulosum, the stratum lucidum, and finally, the outermost layer, which is the stratum corneum.

2) Not What You Think

We often compare our dog’s paws to our hands and feet, but turns we often confuse some body parts for others. First off, an important clarification: humans are plantigrades, meaning that we walk on the soles of our feet; whereas, dogs are digitigrades, meaning that they walk on their toes. When we see things from this perspective, we notice that when it comes to anatomy it makes a whole lot of difference. So turns out that those paws don’t really correspond to our hands and feet  as we might think if we take a look at these illustrations.  At a closer look, we’ll notice how the bones that correspond to our wrists and ankles are set much higher than we would think.

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dog corn chip feet3) That Frito Feet Smell

Did a whiff of your dog’s feet ever made you crave Fritos, popcorn or Doritos? Turns out, the Frito Feet Mystery in dogs has finally been solved! If you’re looking for the source of the smell, you should point your finger towards a strain of Gram negative bacteria known as proteus. Proteus is likely to be held responsible for causing your dog’s famous snack food smell, explains  Dr. Robert J. Silver, a Colorado-based veterinarian in an article for the Huffington Post.  Do your dog’s feet smell too much like Fritos? Here are some tips for dealing with a bad case of dog smelly feet: Dog Frito Feet Treatment.

newfoundland4) If it Looks Like A Duck…

If your dog’s feet look like a ducks’… he’s not a duck. Sure there are many dog breeds with webbed feet, but dogs don’t have completely webbed feet like ducks, swans or geese do. If dogs really had webbed feet in the same way as ducks, they would have a hard time walking on certain surfaces and would end up “waddling” like a duck. Sure, most dogs have some skin in between their toes, but this characteristic doesn’t make them officially “webbed” in the real sense of the term, just as we aren’t considered “webbed” just because we have skin found between the fingers. While all dogs have some degree of “webbing,” it’s true though that certain breeds with a history of  working in water have more webbing in their paws than others. Here is a list of them: dogs with webbed feet.

dog sweaty paws5) Clammy Paw Pads

If you have ever noticed your dog leaving humid paw prints on the vet’s examination table, you weren’t seeing things. Just like humans get clammy hands, dogs may sweat from their paws, especially when they are stressed or nervous. It’s a common myth that dogs don’t sweat. Unlike humans though, who tend to sweat profusely from sweat glands distributed over a large percentage of the body, dogs sweat discreetly from a few sweat glands located on their noses and paw pads. These sweat glands though have a minor role in cooling dogs down, which is why dogs must rely on vaporizing water from their respiratory passages as their primary method to dissipate heat, according to Muller and Kirk’s Small Animal Dermatology.

carpal pad6) A Braking Device

If you take a close look as your dog’s front legs, you may notice a mysterious pad hanging around the wrist area. Often referred to as “carpal pads” or “stopper pads, ” these foot pads on the back of the dog’s front legs are not there for decoration. Turns out, they actually have several functions. One of them, as the name implies, has to do with the dog’s ability to stop. When a dog canters, there’s a moment when the carpal pad of the front leg touches the ground. During this time, should the dog turn or stop suddenly, the carpal pad along with the dewclaw provides extra traction, and should the dog stop, they’ll work as a braking device, explains veterinarian Chris Zink. Additionally, those stopper pads keep dogs from sliding when walking on steep, slippery slopes and provide an extra cushioning effect when the dog lands after a jump the moment the dog’s leg touches the ground.

7) Getting Cold Feet

Ever wondered how your dog manages to romp happily on the snow without getting cold feet? Well, we must once again thank again those remarkable paws. There are several good reasons why dog feet won’t freeze when running on the snow. One of them is the structure of the dog’s feet themselves, the thick skin, along with the thick layers of fat protect them from the cold, but there’s more. Dogs have a higher temperature than us (101.5 Fahrenheit), and therefore, their paws are significantly warmer, explain D. Caroline Coile and Margaret H. Bohman in the book “Why do Dogs Like Balls.” Last but not least, several Northern dog breeds have hair between their toes that’s snow and ice resistant. The oils in the hairs repel snow, as water and oil don’t mix, so they help protect the pads of these pooches’ feet. However, consider that paws, albeit tough, are still vulnerable. Dog paws  get frostbite too, not to mention damage and cracks from walking on rock salt.

dewclaw dog8) No Thumb Twiddling

You won’t find Rover twiddling his thumbs or sending text messages, but dogs have a structure that is similar to our thumbs. These are called dewclaws and they’re found high up the dog’s leg. However, depending on the breed of dog, he may or may not have them. Some breeders remove them when the puppies are very young. While these dewclaws are far from being effective as our opposable thumbs, they do have several functions. Consider that each dewclaw is attached to five tendons, which are each attached to a muscle. The dewclaws provide support to Rover’s lower legs, so when he makes those tight, swift turns as seen in the sport of agility, his legs are prevented from getting twisted or injured, further explains Christine Zink. As a bonus, those dewclaws help him grasp objects such as toys, bones and sticks so he can chew on them and may come handy when he has to scratch a sudden itch, climb up or remove some foreign item stuck in his teeth!

9) Pooches with Unique Paws

The six toes of the lundenhund
The six toes of the lundehund

Not all dogs paws are created equal. Other than some dog breeds having webbed feet, there are several dogs with unique feet that are worth mentioning. Perhaps the most amazing of all, are the paws of the Lundehund dog breed which sports six toes. Other remarkable paws are seen in the great Pyrenees dog boasting double dewclaws on the same paw (which by the way are considered part of the breed standard.) The Akita instead is known for having what are known as “cat feet.” According to the American Kennel Club, these feet are neat and round, with high-arched toes closely held together. What’s so special about them? These feet require less energy to lift off the ground. Hare feet instead are found in greyhounds. The two centered toes, which are longer than the others, allow them to attain faster speeds.

imprint dog paw10) A Paw is Forever

Dog paws hold a special place in our hearts. We watch our puppies prance on those paws, we hold them in our hands, and when our dogs are no longer with us, we want to remember those precious paws. Dog paws are so cherished, that many dog owners decide to make imprints of their dog’s paws before saying farewell transforming them into a precious, one-of-a kind keepsake. Several companies now offer keepsakes made of clay or metal so dog owners can immortalize those paws.

Dog paws are amazing, aren’t they? Despite being tough, don’t forget about them so protect them from being punctured from sharp objects, burnt by hot asphalt and irritated by ice or road salt. Remember to regularly inspect those paws, keep those nails nicely trimmed and keep the feet moisturized when they become cracked and dry. Your dog and his precious paws will thank you!

References:

  • Clinical Anatomy and Physiology for Veterinary Technicians, by Joanna M. Bassert and Thomas P. Colville,  Mosby; 2 edition (December 21, 2007)
  • Peak Performance EBook: Coaching the Canine Athlete, Canine Sports Productions, 2011
  • Why Do Dogs Like Balls?: By D. Caroline Coile, Margaret H. Bonham, 2008, Sterling Publishing Co. Inc, NY

Photo Credits:

Wikipedia,Paw (dog) showing pads, A: Claw, B: Digital Pads, C: Metacarpal Pad, D: Dew Claw, E: Carpal Pad by Amos T Fairchild, GNU Free Documentation License,

Wikipedia, Foot of a Norwegian Lundehund. Picture taken by myself, User:ZorroIII, Creative Commons Attribution-Share Alike 3.0 Unported license.

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I am Your Dog’s Blood Brain Barrier

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Today is Monday’s Marvels and what’s more marvelous than a special barrier that protects the dog’s brain from potentially harmful substances? Owners of a sub-population of collies and several other herding breeds, in particular may be well aware of the risks their dogs may be susceptible to due to the way their blood brain barrier is structured, but this is something that certainly may interest owners of any other types of dogs as well. As we marvel at this structure, we can gain more insights on how the blood brain barrier works and gain more information about possible problems. So let’s see what our dog’s blood brain barrier has to say so we can get more acquainted with this structure. So let’s welcome today the dog’s blood brain barrier!

Let Me Introduce Myself!

Hello, you may not know me well, but you sure need to thank me for protecting something as important as your dog’s brain! I might not be popular as the brain, but I sure need a place of honor for ensuring your dog’s brain is shielded from potential dangers. I take no offense if you have never heard about me before, but my job today is just this, introducing myself and letting others become aware of my noble duties. While time ago, it was suggested that I was present only in an immature form in young animals, today studies have instead indicated that my sophisticated structure is actually already somewhat operative at birth! I am just quite permeable in neonate puppies according to veterinarian Kit Kampschmidt. This means that neonates are more vulnerable to the toxic effects of certain drugs, which is why most vets are cautious in medicated those youngsters unless strictly necessary!

Warning, Restricted Area

What’s my day like as a blood brain barrier? My main role is allowing the entry of essential nutrients such as glucose and several amino acids while blocking certain substances from reaching the brain. To be more precise, I have a network of blood vessels lined with tightly wedged endothelial cells that form a nearly impermeable boundary responsible for restricting the passage of certain substances from the bloodstream to your dog’s brain. Hey, if you rarely hear about brain infections, it is thanks to me! Indeed, I effectively protect the brain from harmful substances such as toxins and bacteria. At the same though, as mentioned, I must grant access to important sugar and amino acids. These latter successfully gain access courtesy of special transport systems that move them across the barrier and into brain tissue as needed.

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When Things go Wrong

As effective as I am in restricting access to the brain, I must admit, I am not invincible. Sometimes cancers or bacteria break me down which allows small compounds that normally wouldn’t come through to gain access. When this happens, this can be bad news. Since my barrier is effective at preventing the passage of foreign substances, I may prevent certain life-saving drugs from reaching the brain. Antibodies meant to the fight the bacteria are also too large to make it through my barrier, so really only a few selected antibiotics are able to pass. Administering them directly into the cerebrospinal fluid may seem like a good option, but it’s quite a tortuous trip to reach all those tight interstitial passages to the brain. One good thing though is that when I am inflamed, I become more permeable, which increases absorption of certain antibiotics, but you must be careful too as this also means that the brain becomes more vulnerable to the infiltration of bacteria and viruses.

The Issue with Collies

Owners of collies/collie mixes and other herding dogs are likely aware of the problems associated with giving these dogs the heartworm drug ivermectin. The issue with ivermectin toxicity observed in collies was first noticed in the 1980s. What’s the problem in these dogs? You see, ivermectin is toxic to pesky parasites, but it is thanks to me that most breeds aren’t affected. As a barrier, I prevent this drug from reaching your dog’s brain, but since parasites do not have a blood brain barrier, this drug affects them without poisoning your dog. You must therefore thank me for allowing this form of “selective toxicity.”

However, it was discovered that a sub-population of collies (along with several other herding breeds, see quote below) had a tendency to accumulate high concentrations of ivermectin in brain tissue which caused them severe neurological symptoms. Why? Turns out, such dogs lack a functional blood-brain barrier, explains Katrina L. Mealey a board certified veterinarian specializing in internal medicine and clinical pharmacology. The issue is the result of an altered multi-drug-resistance gene (MDR-1) which makes their blood brain barrier more permeable. It’s estimated that about 3 out of every 4 collies in the United States have the mutant MDR 1 gene, explains Dr. Joey, a board-certified veterinarian.

Affected breeds include Australian Shepherds, Collies, McNabs, Longhaired Whippets, Silken Windhounds, English Shepherds, German Shepherd Dogs, Old English Sheepdogs and Shetland Sheepdogs. ~Dr. Marty Becker

Ivermectin at high doses isn’t the only drug these dogs are sensitive to, according to Washington State University, other problem drugs include loperamide (Imodium), acepromazine and several chemotherapy and antiparasitic agents agents. Fortunately, today there are tests that can screen for multidrug sensitivity. One of them is offered by Washington State University.  The old adage of “white feet, don’t treat” which refers to not treating scotch collies due to the risks associated with their “leaky blood brain barrier”, has now transformed into “white feet, test to see if you can treat” says Patricia Dowling in an article published on Can–Vet Brand Animal Health Products. So if you own a collie or other affected breed and are wondering about risks associated with giving certain medications, consult with your vet and ask about getting your dog tested.

Drugs to watch for: The tranquilizer acepromazine; the pain medication butorphanol; the anti-cancer drug doxorubicin, vinblastine and vincristine; the antibiotics erythromycin and rifampin;  the anti-parasitic drugs ivermectin (in high doses), milbemycin, moxidectin and selamectin; and the anti-diarrhea drug loperamide (Imodium).~Dr. Marty Becker

I hope this article may have helped you understand me better! You know, not many people are aware of me and I thought I deserved to at least be acknowledged. The best part is that I am not exclusive to dogs, so today you have also learned something about yourself as well! Thank you for listening and enjoy the rest of your day!

Yours truly,

The Blood Brain Barrier

Did you know? According to the University of Washington website, the blood brain barrier was discovered more than 100 years ago when a blue dye was injected into the blood stream of an animal. Curiously, all the structures of the animal’s body turned blue except for the brain and spinal cord.

Disclaimer: The article is not intended to be a substitute for professional veterinarian advice, diagnosis, or treatment. If your dog is sick, please see your vet.

References:

  • Clinical Anatomy & Physiology for Veterinary Technicians, Thomas Colville DVM, Joanna M. Bassert VMD, Mosby Inc.  St Louis, MO, 2002
  • Newborn rabbit blood-brain barrier is selectively permeable and differs substantially from the adult, Braun LD, Cornford EM, Oldendorf WH, J Neurochem. 1980 Jan;34(1):147-52.
  • Pharmacogenetics: It’s not just about ivermectin in collies, Patricia Dowling, Can Vet J. 2006 Dec; 47(12): 1165–1168.
  • Brain Facts.org, Society for Neuroscience, The Blood-Brain Barrier
  • Vet Street: Multidrug Sensitivity: What You Need to Know

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I am Your Dog’s Adrenal Glands

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It’s Monday Marvels, and today we will be introducing the dog’s adrenal glands. Like some other dog body parts that for the most part live in the shadow, you likely don’t hear much about the adrenal glands unless they start giving problems. In dogs, the adrenal glands are responsible for secreting important hormones, but sometimes things can get a bit out of whack in the hormonal department. By getting more acquainted with these glands, we can better understand their important role in a dog’s overall state of health and sense of well being. So for Monday’s Marvels let’s see what the adrenal glands have to say.

Introducing Your Dog’s Adrenal Glandsadrenal glands public domain wikipedia

Hello, it’s your dog’s adrenal glands talking!  Our name derives from the fact that we are located right in front of your dog’s kidneys. The term “renal” indeed comes from the Latin word “renes ” which stands for kidneys” while the prefix “ad” comes from the Latin word “near.” Therefore put 2 and 2 together and you’ll figure out that adrenal means “near the kidneys.” At a first glance, if you look at our structure we may look like two glands, one on the left, and one of the right, but actually, we’re made of some  distinct parts. To better give you an idea, imagine a chocolate-covered peanut. The peanut being one part (the adrenal medulla), and the chocolate on top being another, (the adrenal cortex). That’s how we are structured. What are our main functions? We actually have several, so hold tight as here are some.

scared dog fight or flightImplementing the Fight or Flight Response

The adrenal medulla, the inner peanut portion of us,  is responsible for secreting the hormones epinephrine (adrenaline) and norepinephrine (which increases blood pressure) into your dog’s bloodstream. You see, when your dog feels threatened from something, his sympathetic nervous system kicks in, triggering what is known as the “fight or flight response.” Basically, his body gets in a hyper reactive state so it’s ready to spring into action and up his chances for survival. For the sake of comparison, it’s that short-term stress reaction you may feel when you’re camping and see a bear that has come too close for comfort.

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Your dog’s heart will therefore beat faster, his blood pressure rises, the airway passages dilate, blood is sent to the muscles and his senses become more acute. At the same time, his gastrointestinal function decreases, which is why he may not be interested in that slice of baloney you dangle in front of his face when he’s extra worried about something. Even after the scary event has passed, it may take some time for your dog’s body to recover from such an excited state considering that these hormones tend to stick around in the bloodstream for some time.

The Adrenal Cortexadrenal cortex wikipedia public domain

The outer portion of us, the adrenal cortex, comprises several layers, with each layer being responsible for different tasks. To have a better idea, imagine our outer portions as the layers of an onion. My outermost layer is the zona glomerulosa, then, sandwiched somewhere in between is the zona fasciculata, and finally, our inner portion is the zona reticularis. To have a better idea, see the picture on the side. Now, let’s take a closer look at the different roles these layers play, shall we?

  • Raising Your Dog’s Blood Glucose

The zona fasciculata, the middle layer, is responsible for producing glucocorticoid hormones. These hormones include cortisone, cortisol and corticosterone which share the ability to raise your dog’s levels of blood glucose, maintain blood pressure and help the body deal with the effects of stress. Glucocorticoids also act as natural steroids,  suppressing any inflammatory and immunologic responses.

  • Regulating Your Dog’s Minerals and Salts

The outermost layer, the zona glomerulosa, is responsible for regulating the amounts of important electrolytes under the form of minerals and salts in the body. Aldosterone, the main mineralocorticoid hormone, regulates the right balance of salt, potassium and water and helps control blood pressure. You see, when levels of potassium are too high, they must be lowered as potassium can become toxic at high levels, so aldosterone works on keeping its levels under control.

  • Producing Dog Sex Hormones

Finally, the inner most layer, the zona reticularis, is responsible for the production of small amounts of the sex hormones androgen, progesterone and estrogen.

 

dog adrenal diseaseWhen Things Go Out of Whack

While I try to do my best in producing hormones as needed, sometimes things can get out of whack. If my adrenal cortex happens to produce too much cortisol, affected dogs may develop what is known as “Cushing’s disease,” also known as hyperadrenocorticism. In a normal, healthy dog,  a normal amount of cortisol helps the body adapt in times of stress and regulates proper body weight and tissue structure, but too much of a good thing leads to the weakening of the dog’s immune system and a predisposition to infections and disease, explains Ann Stohlman, a veterinarian working for the FDA’s Center for Veterinary Medicine. Why do I produce so much cortisol? Good question! The Merck Manual states that 85 to 90 percent of the time, it’s due to a tumor in the pituitary gland. Less commonly it’s due to either a tumor in my glands or the long term use of steroid drugs.

If instead, my adrenal cortex produces too little adrenal gland hormones, affected dogs may develop what is known as “Addison’s disease,” also known as hypoadrenocorticism. Why do I produce too little of these hormones? In this case, we can blame some auto-immune condition, where the dog’s body mistakenly destroys some of its own tissues, infections in the gland or some form of cancer. When I secrete too little aldosterone, the levels of potassium, sodium, and chloride in the dog’s bloodstream are no longer regulated and we already talked about how toxic potassium can be if there’s too much.

Did you know? Dogs can be also prone to adrenal fatigue. According to veterinarian Randy Kidd, chronic overstimulation of the adrenal glands may lead to adrenal fatigue and other conditions such as diabetes mellitus or heart failure.

References:

Merck Vet Manual: Disorders of the Adrenal Glands in Dogs

Clinical Anatomy & Physiology for Veterinary Technicians, Thomas Colville DVM, Joanna M. Bassert VMD, Mosby Inc.  St Louis, MO, 2002

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I am Your Dog’s Thymus

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dog thymusFor Monday’s Marvels we would like to introduce the dog’s thymus. We don’t hear much about this organ of the lymphatic system, other than perhaps when there are problems associated with it. Simply because it’s an organ that’s not that popular, we thought that it would be interesting learning more about it and how it affects our dog’s bodies. Our references point to some intriguing tasks carried out by this organ that make our dog’s bodies so interesting to learn about. So here’s what our dog’s thymus has to say.

Let Me Introduce Myself!

Hello, it’s your dog’s thymus talking today! You may not know me well as I am not so popular as other organs such as the liver, heart or stomach, but don’t let my lack of popularity belittle my role in ensuring your dog stays healthy and happy. I play some quite important roles that help orchestrate the immune system so everything runs smoothly and your dog’s body is protected from the harm of any foreign invaders. As a lymphoid organ, I am responsible for the development and deployment of special types of white blood cells the help maintain your dog’s immune function. I am located just above your dog’s heart and right below the trachea. I am born relatively large, but as it happens in humans, I tend to shrink in size with age.

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I protect the fortress from invaders.
I protect the fortress from invaders.

I am an Instructor

My main function is to educate. My trainees are certain blood cells of your dog’s immune system which are known as “T cells.” T-cells are born in your dog’s bone marrow, but then are sent to me for their education, (hence their “T” name.) What do I teach these cells? I coach them on how to distinguish cells that are part of your dog’s body and those who aren’t supposed to be there. Just imagine your dog’s immune system as being protected by a fortress surrounded by walls and many troops. Sometimes, among the troops, there may be invading soldiers who dress up like the troops and try to infiltrate in hopes of gaining access to the fortress. My job is teaching my troops how to identify these invaders so they can be captured and removed before they do harm.

Meet My Troops

Interested in getting more acquainted with my troops? I have different types of soldiers that help protect my fortress and engage in different tasks.  My “helper T cells” work hard cooperating with other types of white blood cells so to develop a strong immune response. My “killer T cells” are specifically trained to detect those foreign invaders such as harmful bacteria. While I try to do my best in training these latter soldiers, not all of them excel in their tasks. In this unfortunate instance, they aren’t given a second chance to make up for their mistakes. I must promptly take action because their mistake can be costly to your dog’s body. So I fire them on the spot and they are gone once and for all. Finally, I have a team of “suppressor T-cells” meant to keep things under control. You see, when invaders arrive, they stir up quite a conflict and things can get out of hand. Their job is to keep things under control.

Puppy’s Best Friend

We love puppies as much as you do. Remember how I mentioned that I am born relatively large and then shrink in size with age? Well, there’s a good reason for this. My role is most important during puppy hood, when puppies need to rely on the immune system the most. When puppies are born, they really don’t have much immunity, so my role is to help kick start the immune system to help these vulnerable beings.

I  also play a role in what is known as “adaptive immunity“, also known as “acquired immunity.” I help make sure that those vaccinations protect your puppy as they should. You see, certain memory t-cells have the uncanny ability to remember exposure to certain foreign invaders. So let’s say the puppy is given a vaccination against distemper. The soldiers with the good memory will remember the distemper antigens so that should these antigens show up in the system, they can fight them promptly and efficiently so your dog can survive and thrive for as long as there is protection (something to obviously discuss with your vet!)

Disclaimer: The article is not intended to be a substitute for professional veterinarian advice, diagnosis, or treatment. If your dog is sick, please see your vet.

References:

Merck Veterinary Manual, Immune System Responses in Dogs

Pet Education, Lymphatic System Anatomy and Function

Pet Education: The Immune System

The Canine Immune System and Disease Resistance, Dr. Jean Dodds, 

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A Look into Dog Hackles

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A black cat with raised hackles is a staple of Halloween decorations, but did you know that dogs have the ability to raise their hackles too? The action of raising hackles is known as piloerection, literally meaning raising of hairs. Cats are known to raise their hackles, but so do porcupines with their thick hairs when they’re frightened by predators. In some sort of way, the action is similar to when we get goosebumps, and as the popular expression goes,  our “hairs stand on end. ” So in this Fascinating Friday, we’ll be taking a look as to why dogs raise their hackles.

Skin anatomy and skin follicle, Wikipedia Commons Public Domain
Skin anatomy and skin follicle, Wikipedia Commons Public Domain

A Lesson in Anatomy

Dogs are equipped with hair follicles that are attached to special muscles called the “arrector pili” which are confined to the dog’s neck, back and tail. When the dog is in a normal, relaxed state, the hair follicles stay at a 30 to 60 degree angle compared to the skin.

Let the muscles contract though and those hair shafts will literally stand up, explains Karen L. Campbell, a board-certified veterinarian specializing in internal medicine and dermatology in the book “The Pet Lover’s Guide to Cat and Dog Skin Diseases.”

 

Getting Worked Up

dog raised hackles
Raised hackles in dog

The arrector pili muscles are innervated by the sympathetic branch of the autonomic nervous system. In our canine companions, contraction of these muscles is elicited by the release of epinephrine as it occurs when the animal feels afraid or excited, further adds Dr. Campbell. The contraction is involuntary, and thus, not under the dog’s conscious control as it’s part of the dog’s fight-or-flight reaction. It can also be seen in animals that are aroused, anxious, uncertain or surprised by the sudden appearance of an unexpected stimulus. An overstimulating play session may also cause raised hackles in dogs while playing.

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There are chances that based on the area of raised hairs, one may deduce information pertaining the dog’s emotional state. Raised hackles by the shoulder area may denote fear, while hackles raised by the tail area may suggest confidence, and in both shoulder and base of tail, they may suggest an ambivalent emotional state and conflict, (Karen London, 2012). Most likely, just as in the cat and in the porcupine, the action of raising those hackles has some adaptive function meant to make the dog appear larger than he really is. But wait there’s more! Alexandra Horowitz in her book “Inside of a Dog, What Dogs See, Smell and Know ” on page 110, explains that those hairs may also release the odor of skin glands located at the base of the hairs.

Raised hackles during rough play
Raised hackles during rough play

Not Necessarily Aggression

It’s not correct to make unfounded claims that dogs who raise their hackles are aggressive. First of all, it’s wrong to label dogs as aggressive from the get-go, as dogs aren’t always in a constant state of aggression. It’s more correct to say that dogs  may act aggressively in certain scenarios versus “dogs are aggressive.” Also, one must identify the stimulus that triggered the hackles to rise in the first place and take note of the accompanying body language before drawing conclusions. The fallacy of stating that dogs who raise hackles are aggressive is counterproductive, as it labels dogs through mere speculation and assumptions. If you are uncertain as to why your dog may raise his hackles, consult with a veterinary behaviorist.

Getting Warmed Up

Jackets have replaced our fur.
Warm coats have replaced our fur.

The sensation of cold has been associated in several animals with the activation of the sympathetic nervous system causing the contraction of the arrector pili muscles. The piloerection in this case is meant to trap air and create a layer of insulation. As the hairs thicken, the amount of subcutaneous fat also increases. In us humans, cold still triggers goose bumps, causing the characteristic bumps and the rising of the hair shafts. Charles Darwin in the book “The Expression of the Emotions in Man and Animals ” classified the appearance of goose bumps as a vestigial reflex though, considering that it has lost its original function since we’re no longer covered in hairs.

In dogs, Steven R. Lindsay in his book “Handbook of Applied Dog Behavior and Training, Procedures and Protocols” discusses about a possible interesting relationship between reactive emotional states and the process of heat production. The findings of several studies conducted on rats found a correlation between psychological stressors and temperature elevations. These increases in temperature may therefore turn out being a useful, non-invasive tool for evaluating the presence of psychological distress in dogs, he suggests.

Did you know? You’re not imagining things when you notice more hair loss in your dog during stressful situations. What happens is that hairs that are in the telogen phase (the resting phase) are more likely to fall out when the arrector pili muscles contract as it happens in stressful situations such as being at the vet, explains board-certified veterinary dermatologist Karen L. Campbell in the book “The Pet Lover’s Guide to Cat and Dog Skin Diseases.”

References:

Alexandra Horowitz in her book “Inside of a Dog, What Dogs See, Smell and Know”, Simon &Shuster, Inc, New York, Ny

Darwin, Charles. (1872) The Expression of the Emotions in Man and Animals John Murray, London

Karen L. Campbell “The Pet Lover’s Guide to Cat and Dog Skin Diseases” Elsevier Health Sciences, 2006

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I am Your Dog’s Liver

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An introduction to your dog's liver.

Today we’ll be sharing some interesting discoveries pertaining a marvelous organ that is often underestimated, the dog’s liver.

For those folks who loved reading stories from Reader’s Digest around the mid 80s’ may remember the author J.D. Ratcliff who wrote compelling articles featuring organs as if they were talking  in first person.

We thought it would be fun to share some interesting discoveries of our dog’s bodies in a similar fashion on a weekly basis.

So we got our dusty veterinary textbooks out and visited several websites  that are posted in the reference section. So here come some interesting facts about a dog’s liver, inspired by Ratcliff’s style and presented under the “I am Rover’s Liver” format.

Let me Introduce Myself!

Hello, it’s your dog’s liver talking. As an organ, you likely don’t know me well as I am tucked deep within your dog’s abdomen, right under the ribs, but don’t expect me to make my presence much relevant even when I am not doing well. I am notorious for causing vague symptoms that may mimic many other conditions. But first let me introduce myself.

My name is liver, and just from the origin of my name, you can tell a whole lot about me. My name comes from the Old English word “lifer” which most likely refers to life. In German, the liver is called “die Leber” and the word “leben” is a German verb that means “to live.”

Even our English word “life” has quite a close resemblance to the Old English word “lifer.” Perhaps, that’s because I sure play a great role in your dog’s life and the life of any living being who hosts me, as I am a vital organ that carries out a wide range of functions which are necessary 24 hours a day.

OK, I'm not that good looking even when served on a plate!
OK, I’m not that good looking even when served on a plate!

I was once considered the largest organ of your dog’s body, but now that many physiologists claim that the skin is an organ too, what can I say, the skin has outranked me, but I come right after with a honorable second place.

From an aesthetic standpoint, my appearance is not much candy for your eyes, as you may attest when you chop up liver treats for your dog’s training sessions.

I am a basically a brownish/red colored blob with several lobes. The real beauty of me relies in my “intelligence” in carrying out many complex tasks. This is not an understatement!

According to veterinarian Race Foster, I am capable of performing more than 1,000 different tasks! It would take a whole book to list them all, so I’ll try to make it short and sweet for you. My main tasks include metabolizing food, storing items for later use and disposing of stuff that aren’t needed or that are potentially toxic. Here’s a rundown of them.

I’m a Filtration System

Loads of blood comes in and out of me on a continuous basis. I am technically a sponge saturated with blood, squeeze me and I’ll secrete droplets of blood. Blood is delivered to me via the hepatic artery which supplies me with oxygen-rich blood straight from the heart that keeps me healthy and happy, but the great majority of the blood supplied to me comes from the portal vein which carries particles of digested food straight from the small intestine.

When blood makes it into my filtration system, I sort it into various components: things that are helpful, things that should be disposed of and things that should be stored for later use, yes, just like dogs who bury bones!

I’m a Chemical Processing Factory factory

After your dog eats his chow, I start working on breaking down and processing all the fats, carbohydrates and proteins. For example, I transform carbohydrates into glucose, break down the amino acid building blocks of protein so to separate the nitrogen and help in the digestion of fats by secreting bile.

I basically work extra hard in processing all the good stuff that comes in and transform them into easy-to-assimilate forms that the rest of your dog’s body can easily utilize.

When I secrete bile, a substance that aids in your dog’s digestion of fats, the bile is stored in the gallbladder and released into your dog’s small intestine via the bile duct. Bile also helps wipe out bilirubin, which is the residue of old, broken down red blood cells that need to be discarded.

If you ever wondered why your dog’s poop is brown, it’s thanks to the presence of bilirubin which is orange/yellow in color. If I get ill, I no longer can effectively get rid of bilirubin which is why dogs suffering from liver disease sometimes get yellow skin (jaundice) and may have gray-colored stools.

But wait, there’s more. I also make a protein known as albumin, which prevents fluids from the dog’s blood vessels from seeping out. When I get ill though, I may fail to produce enough albumin and fluids may start leaking out into tissues causing ascites, which shows up as abdominal distention.

And what about my ability to manufacture blood clotting factors? If you accidentally cut your dog’s quick as you clip his nails, it is thanks to me that he doesn’t bleed to death. Should I get sick for some reason though, I might be unable to produce these important clotting factors which can make your dog bleed more easily.

I’m a Garbage Disposaltrash

Along with breaking down those carbs, fats and proteins your dog eats, I also try my best to also metabolize any crap I am exposed to such as harmful substances that are added to processed dog foods nowadays. I can do this though only up to a certain extent.

Remember those infamous pet food recalls from 2005/2006 that killed hundreds of dogs? The foods in that case were contaminated with aflatoxins and I couldn’t always keep up and work hard enough to excrete these, so sadly in such cases, I ended up raising the white flag and failing.

Along with getting rid of harmful substances, I am also responsible for metabolizing medications your dog takes. What I do is try to make them easier to excrete. Please make sure you follow your vet’s dosing instructions to a T and read the accompanying package inserts for symptoms suggesting liver or other problems.

If your dog is taking certain drugs that may impair my functionality, your vet may recommend routine blood work just to make sure I am doing OK.

Not all the stuff I dispose of come from bad stuff your dog ingests, some stuff are just part of the body’s normal functioning as in the case of proteins. When I process proteins, I end up with urea, a byproduct that is toxic to the body and should be discarded. So I send this urea to the kidneys, where it’s filtered from the blood and expelled next time your dog urinates.

And what do I do with the remnants of food after all the goodies have been removed? I simply send them off back into the intestine and out of your dog’s body next time he poops.

storageI Am a Storage Unit

While your dog may not take as many vitamins as you do, I play a role in the metabolism and storage of vitamins.

I am responsible for storing several fat soluble vitamins such as vitamins  A, D, E, and K. This is why when a dog goes into liver failure their diet is often supplemented with several vitamins, further explains veterinarian Race Foster. Without these, dogs wouldn’t live much longer.

Along with vitamins, I also store metals such as iron, copper, and zinc in the right quantities so they’re ready when Rover needs them. My storage unit also houses a nice amount of blood. Consider that I store about 15 percent of the total blood in the body.

Should your dog ever lose a large quantity of blood, all sorts of alarm bells go off and within seconds I will send off my reserved supply to try to help as much as I can.

I also store glycogen in case your dog needs it when his blood glucose gets too low. All I need to do is convert the the stored glycogen into glucose to give your dog a quick energy boost.

I Can Regenerate Myselflizard

Perhaps this is my most amazing feature. You might have heard about lizards being able to grow back their tails after losing them, well I am proud to say that us livers are also equipped with similar powers.

When we’re on the surgery table and the vet finds us injured or affected by disease, we can afford to have even up to three-fourths of us removed, and by the end of the year, we can regenerate and grow back to our original sizes.

Also, I am capable of still performing my duties despite 70 to 80 percent of me being damaged. Pretty amazing, huh? This doesn’t mean though that us livers should be taken for granted and neglected! It’s important to take good care of us!

Take Good Care of Me!

As the Canine Liver Disease Foundation explains, my ability to continue to perform my duties despite being damaged by some infection or a massive tumor,  is a double edged sword considering that symptoms may show up only once a disease is well advanced, and possibly, non treatable.

So prevention is worth a pound of cure. To keep me healthy and happy make sure to feed your dog a healthy diet, provide access to fresh water, reduce the amount of toxins he’s exposed to and keep up with health checks as suggested by your veterinarian.

According to Merck Veterinary Manual possible signs denoting liver problems in dogs include loss of appetite, vomiting, stomach ulcers, diarrhea, seizures, fever, blood clotting problems, jaundice, ascites, increased drinking and urination and weight loss. If your dog is not doing well, play it safe and don’t hesitate to have your dog see the vet!

I hope this article has helped you understand me better. You know, I think I am sometimes underestimated and feel a bit in the dark hidden how I am under your dog’s rib cage. Take good care of me and I’ll likely effectively perform my duties so you can enjoy your four-legged companion for many years to come. Yours dearly,

Rover’s LiverDog Pawprint

Disclaimer: The article is not intended to be a substitute for professional veterinarian advice, diagnosis, or treatment. If your dog is sick, please see your vet.

References:

  • Merck/Merial Manual for Pet Health, Merck & Co, INC. Whitehouse Station, NJ USA, 2007
  • Clinical Anatomy & Physiology for Veterinary Technicians, Thomas Colville DVM, Joanna M. Bassert VMD, Mosby Inc.  St Louis, MO, 2002
  • Digestive Disease in the Dog and Cat, James W. Simpson & Roderick W. Else, Blackwell Scientific Publications, Oxford, London, 1991
  • Pet Education, Race Foster DVM, Anatomy & Function of the Liver in Dogs, retrieved from the World Wide Web on January 4th, 2016
  • Canine Liver Foundation, Canine Liver and Anatomy, retrieved from the World Wide Web on January 4th, 2016
  • Tufts University, Feeding the Dog with Liver Disease, September 2014 Issue, retrieved from the World Wide Web on January 4th, 2016