Anatomy

I am Your Dog’s Anterior Cruciate Ligament

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Not many people are aware that their dogs have cruciate ligaments. Dog owners often unexpectedly end up discovering this structure the very first time when they are at the vet because their dog is exhibiting rear leg limping that doesn’t seem to be getting any better. This body part is often underestimated and lives mostly in the shadow, yet, it plays a very important role in a dog’s ability to happily romp around. Today is dedicated to this fundamental structure which deserves more attention. So let’s have the dog’s cruciate ligament walk the red carpet today and put him on the spot of honor.

acl dogIntroducing Your Dog’s Cruciate Ligament

Hello, it’s your dog’s cruciate ligament talking! Actually, to be correct, we are actually two: the “anterior cruciate ligament” (ACL) and the posterior cruciate ligament” which is also known as the caudal cruciate ligament (CCL). However, you’ll hear vets talking about the anterior cruciate ligament much more because it’s the ligament that is more likely to cause trouble. So in this article, me, the anterior cruciate ligament (yes, the troublemaker!) will do the most talking. If you take a look at my name, you may notice how the word “cruciate” derives from the Latin word “cruciatus” which means “cross.” The word ligament, on the other hand, derives from the Latin word “ligamentum” from ligare  which means “to bind.” What does this all tell you? It tells you that I am a ligament made of fibrous tissue and that the term cruciate is used to refer to the fact that the anterior cruciate ligament and the posterior cruciate ligament criss-cross each other like the letter “X” as seen in the picture.

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I Am A Stabilizer

My main job is to connect one bone to another so to stabilize (‘bind”) an important joint–in this case, we’re talking about the dog’s knee joint to be exact. Both me and my fellow posterior cruciate ligament basically work as a team holding together the femur and the tibia which make up the dog’s knee joint. Your hardly notice my hard work, but rest assured, I am very important! I basically keep your dog’s tibia from slipping forward, while my fellow posterior cruciate ligament keeps the tibia from slipping backwards.

When Things Go Wrongrottweiler cruciate ligament

When all goes well, I help stabilize your dog’s knee joint so your dog can romp around happily without the tibia bone slipping forward and causing an abnormal range of motion, but sometimes accidents happen. How do I rupture in the first place? It’s often an accident. Your dog may have taken a bad step or his leg may have gotten caught in a hole. Dogs who are overweight may be more susceptible to me rupturing especially when they jump off a bed or truck. Large breed dogs are more likely to suffer from my rupture.

If I get torn, things start getting complicating. The knee no longer stabilized, develops an abnormal range of motion and the dog feels pain. Rear-leg limping is the most evident sign of trouble and dogs may engage in sloppy sits (sitting with both legs out to the side) and they may “toe touch” (keep only the tips of the toes in contact with the floor) when standing. Dog owners may delay the vet visit assuming their dog just got a sprain, but it doesn’t get any better after a few days. I am not a fast healing structure, and I can only heal in two ways: a long period of rest (conservative management) or an expensive surgery.

“Almost all dogs with ACL problems sit to the side, even when sitting for a treat. Sometimes the lameness comes on quickly but often it’s a gradual progressive problem.”~Colorado Canine Orthopedics and Rehab

How does the vet test me to check if I am torn? There’s a very specific test called the “drawer sign.” The vet will basically move the dog’s leg a certain way to see if the knee joint feels unstable. The vet basically feels the tibia bone slipping forward, which is the most distinctive sign when I am torn and no longer keeping things together. However, don’t trust this test blindly, if your dog is tense or if the tear has been there for a while, the joint may appear stable, leading to a possible misdiagnosis. For this reason, some vets will opt to have this test done under sedation. X-rays may help provide some hints to rule out bone cancer and check if any secondary arthritis may have set in, because you see, when I am no longer there to stabilize things, the dog’s bones start slipping and rubbing against each other which can lead to arthritic changes down the road.

 As seen, I am an important structure! What can dog owners do to prevent me from rupturing? Well, you can’t really keep dogs in a safety bubble, but there are some things that may help. According to the American Kennel Club Canine Health Foundation, keeping your dog lean and active is a good way to help keep me in good shape as good muscle tone is important!

I hope this has helped you understand me better!

Kind regards,
Your Dog’s ACLDog Pawprint
References:
  • American Kennel Club Canine Health Foundation, Stabilizing the Stabilizer, retrieved from the web on Match 16th, 2016
  • Colorado Canine Orthopedics and Rehab, Clinical Signs of Canine ACL Tear, retrieved from the web on March 16th, 2016
  • Vet Specialists, Dog Cranial Cruciate Ligament Disease, retrieved from the web on March 16th, 2016
 Photo Credits:

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Stunning Dogs With Two Colored Eyes

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Beyond being the windows to the soul, dog eyes can come in several stunning colors. While the majority of dogs have dark brown eyes, some can also have amber eyes, copper eyes and blue eyes. In some cases though, dogs may have eyes of different colors, meaning that they have one eye of a color and the other one of another. These dogs aren’t really rare or unusual per se’, but we can’t deny that they can be quite intriguing looking dogs! One may wonder if there are any problems with these eyes, but generally there’s nothing wrong with the eyes of these fellows other than being different. Certain dog breeds are more prone than others to develop two eyes of different colors. Today we discover exactly how dogs develop two different colored eyes and what breeds are mostly affected.

Eye color is a matter of melanin
Eye color is a matter of melanin

The Effect of Melanin

Melanin is a pigment that gives color to a dog’s eyes, coat and skin. The color of a dog’s eyes depends on the concentration of melanin found in the dog’s iris, the pigmented structure surrounding the dog’s pupil. The more concentrated the melanin, the darker the eyes will be. When dogs present with eyes of different colors, the concentration of melanin differs between the eyes, therefore, it is not distributed uniformly. So for example, in a dog with a blue eye and a brown one, the brown eye has a higher concentration of melanin while the blue one will have considerably less.

Did you know? The scientific term for having two eyes of a different colors is “complete heterochromia.” Some breeders though like to refer to it as being “bi-eyed.”

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husky eyes
Complete heterochromia in husky.

A Matter of Genes

The phenomenon of having eyes of two different colors is mostly because of genetics. In other words, it’s a trait that can be passed down from one generation to the next.  As mentioned, certain dog breeds are more likely to develop this trait compared to others. As appealing as having two colored eyes can be though, in certain dogs breeds it’s frowned upon and considered a fault in the show ring.

Dog Breeds With Two Different Colored Eyes

  • Siberian husky: we are used to seeing these dogs with blue eyes, but some fellows can have a blue eye and a brown one. This is acceptable in the American Kennel Club’s standard; indeed the standard states “eyes may be brown or blue in color; one of each or parti-colored. “
  • Australian shepherd: as with the Siberian husky, at times one may stumble on an Aussie with two colored eyes.  According to the United States Australian Shepherd Association,  Australian shepherds that boast a blue  or red merle coat may sometimes have a blue eye and a brown eye.
  • Louisiana Catahoula leopard dogs:  this all American dog breed that sports intriguing looking coats may also sometimes sport intriguing looking eyes  of a different color.
dog nuclear sclerosis
Bluish-grey haziness in nuclear sclerosis

Possible Eye Problems

There is a reason why in the introduction we said “generally” there is nothing wrong with dogs with two eyes of different colors. The word generally is in italics because there are sometimes exceptions to the rule. In this case though, the eyes generally aren’t of different colors to start with.

Sometimes dog owners may notice how one of their dog’s eyes start assuming a bluish tint or a cloudy look. When this happens, it’s important to report these changes to the vet. Medical conditions affecting the eye that may cause color changes or changes to the appearance of the eye include cataracts, nuclear sclerosis, glaucoma, anterior uveitis and corneal dystrophy. These are eye disorders that are known to possibly cause blue eyes in dogs, explains veterinarian Dr. Becker.

Other Types of Heterochromia

Sectoral heterochromia in dog
Sectoral heterochromia in dog

As discussed earlier, complete heterochromia is having one eye color that is different from the other, but many may not be aware that there is another form of heterochromia in dogs known as “sectoral heterochromia.” In this case,  within one eye, there is one color that is of a completely different color from the rest of the eye. This can sometimes be seen in the Australian shepherd, border collie, Welsh corgi,  Catahoula cur and great dane. It can also be found in other dog breeds that are known to also have the merle trait. An exception is the Siberian husky, which does not carry the merle trait but that may at times sport  two  different colors within the same eye.

 

Did you know? According to an ancient Native American legend dogs who had two different colored eyes were known as having”ghost eyes” because they were capable of seeing simultaneously heaven with the blue eye and earth with the brown eye.

 

References:

  • American Kennel Club: Siberian Husky Breed Standard, retrieved from the web on May 14h, 2016
  • Pet Education: Heterochromia: Eyes of Different Colors in Dog by Race Foster DVM, retrieved from the web on May 14th, 2016

Photo Credits:

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I am Your Dog’s Uterus

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The dog’s uterus plays very important roles in the intact female dog’s body. This reproductive organ is similar in many ways to the uterus in women, but it’s also different in many other ways. When we think of the dog’s uterus, we often think about its ability to carry puppies, but since many dogs are spayed, dog owners often don’t think about this organ much. Regardless, learning more about a dog’s uterus can be fascinating, and in owners of intact dogs it can also be helpful so to learn how to recognize early signs of trouble that warrant a vet visit.

uterus dogIntroducing Your Dog’s Uterus

Hello, it’s your dog’s uterus talking! Many dog owners do not deal with me much. Once puppies reach a certain age, I am removed along with the ovaries in a procedure known as “ovariohysterectomy.” If that sounds a tad bit complicated, no worries, you can call it spay surgery or simply getting the dog “fixed.” Those though who decide to keep me for personal choice or reproductive purposes, will probably get to know me a whole lot.

If you look at me, I am a hollow muscular organ with a Y-shaped structure. Unlike the human uterus which is like a big sac because it’s mostly meant to carry one baby, I am shaped differently so the puppies are aligned nicely in a row along my uterine horns. To better understand my anatomy, take a look at the picture. The arms of the “Y” are my long uterine horns with the ovaries located at the end of each horn, the shorter part of the “Y” is my body and the very base of the “Y” is where the cervix is located. For the most part, the cervix is closed so to prevent pesky bacteria from climbing up and reaching me. In certain circumstances though such as when your dog is in heat or during birth and 3 weeks after giving birth, the sphincter of the cervix is temporarily open, explains veterinarian Margaret Root Kustritz, in the book “The Dog Breeder’s Guide to Successful Breeding and Health Management.”

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Did you know? There is an alternate option to spaying which involves leaving the uterus intact and only removing the dog’s ovaries. The procedure is known as  an “ovariectomy” and can be done through laparoscopy, a less invasive type of surgery. Not many vets offer this though.

I Carry Puppiespuppy

When dogs get pregnant, the fertilized eggs travel through the long oviducts and then descend all the way down to me where they implant and start developing into puppies. Then, once the pups are ready to be born, I will help push them out.  You may think of me just as a receptacle, but I don’t just sit there and carry puppies. When the puppies are in me, I have to stretch and develop along with the pups, and then once they’re born, I have to return to my initial pre-pregnancy size. Call that easy!

I also help out developing the puppy’s placentas, those life-sustaining structures that attach to my lining and keep the pups alive and nourished as they develop inside me. While I am mostly quiet during those 63 days of pregnancy, when the big day comes, boy do I get to work! I must contract powerfully so to open the now locked cervix and push out those pups and their placentas. Wheeeew… that’s quite a task! My job is still not done though, my contractions must continue even after all that work so to stop that annoying post-partum bleeding and get rid of any excess fluids.

Did you know? Once an ovum is fertilized, it’s known as a “zygote ” and by the time the zygote is ready to implant in the uterus lining, it’s known as a blastocyst. 

When Things Go Wrongdog pain goes away at the vet

Even though I am quite a simple structure, I am prone to several problems. When vets remove me during a spay surgery, sometimes things can go wrong. When it’s time to give birth, I may encounter some difficulties.  Also, as I age and go through several heat cycles, I am more likely to thicken and become vulnerable to problems. Unlike humans though, dogs do not go through menopause, (yes, no doggy hot flashes!) so hormones keep being produced even into old age.

Surgical Complications

When a dog is in heat, I can become enlarged compared to a dog who is not in heat.  If you are planning to spay your dog and your dog is in heat, expect veterinary receptionists to give you a bit of a hard time. Things get more complicated when I am swollen. This is why vets recommend waiting or charge more  for spaying a dog who is in heat than one who is not.

While a spay surgery is really routine surgery, sometimes, in rare cases, things can get a bit messed up. Some of my  tissue may be left behind and this can create problems. When this happens, the dog can’t bleed or get pregnant, but she may still develop others signs of a heat cycle, explains veterinarian Chris Bern.  Deja vu, anyone? When this happens, it’s known as Ovarian Remnant Syndrome in Dogs. In some rare instance, these ovarian and uterine tissue remnants can develop what is known as “stump pyometra.”

cryingHormonal Abnormalities

When a dog is left intact (not spayed), there are risks that I can get infected at one time or another, especially in dogs over the age of six. Here’s what happens. As dogs go through several heat cycles without getting pregnant, my lining tends to thicken and cysts that release fluids may form. Now, consider that progesterone levels stay high for about 2 months following heat regardless if the dog is pregnant or not (that’s why it’s so hard telling a real pregnancy from a false pregnancy). These high levels of progesterone inhibit my muscles from contracting and expelling bacteria, thus creating the perfect grounds for a secondary bacterial infection.

This is when dogs get in trouble and develop what is known as pyometra, a condition that happens about two to eight weeks after the heat cycle. If the cervix is open, pus will drain out from me and make its way outside. This is when dog owners notice the abnormal discharge under the tail. If the cervix is closed, the pus will not have an outlet, thus it will collect in the dog’s abdomen causing it to enlarge and be very painful. Due to all the fluid accumulating in me and diseased tissues, I may go from weighing just a few pounds (as seen in an average-sized dog) to weighing even up to four pounds, warns Dr. Becker! No wonder why people have compared me to a stuffed venison sausage when this happens! With all this trouble going on, affected dogs get severely ill very rapidly, drinking more, acting lethargic and sometimes vomiting or having diarrhea. But wait, the worse has to come…If treatment isn’t sought quickly, I risk rupturing, spilling out my contents into the abdomen which can result in a fatal septic peritonitis or acute kidney failure. Yes, you don’t want to mess with me when I get so sick, see your vet at once!

“In the past, we thought pyometra was simply a uterine infection, but today, we know that it is a hormonal abnormality, and a secondary bacterial infection may or may not be present.”~Dr. Marty Smith

Bacterial Infections

Remember how I said that the cervix is usually closed, but during a heat cycle or after giving birth it tends to remain open? Well hear me out.. During a dog’s heat, the cervix is open so to allow sperm to go through, but along with the sperm, bacteria may make its way up to me. After the heat, the cervix tightly closes, trapping the bacteria inside. When bacteria invades me, dogs develop what is known as “metritis.” How is metritis different from pyometra? Unlike pyometra, metritis is not caused by a hormonal abnormality. Also, metritis is likely to develop right after the dog gives birth and sometimes after abortion or breeding, explains veterinarian Dr. Bari Spielman. I often get infected when right after birth there are retained placentas or dead fetuses. Now you know why most vets recommend a check up the first 24-48 hours after your dog gives birth.

puppyUterine Inertia

Sometimes, for one reason or another, I may get sluggish, and unable to contract enough to push the puppies out.  When I act this way, you know you have to get help as fast as you can as I can’t perform my pushing duties. What causes me to not contract as I should? Dr. Lopate a member of the American College of Theriogenologists explains in the book “Management of Pregnant and Neonatal Dogs, Cats, and Exotic Pets” that this can be due malnutrition or conditions such as hypocalcemia, fatigue or some other systemic disease. When I fail to contract with sufficient force, the condition is known as primary inertia; whereas, in secondary intertia, my contractions are first vigorous but then they decrease in vigor. Often the problem is due to how the puppy is positioned, or if the puppy is too large and the birth passage to narrow. That’s the price to pay for those breeds with large heads! At the first signs of trouble, your best bet is to touch basis with your vet. Your vet may give your dog a shot to jump start me and get me back to work or he may need to do a C-section.

As seen, I am more than just a receptacle that holds puppies until they are born, I perform quite some complex roles.  If you own an intact female, it’s imperative that you contact your vet as soon as possible at the first signs of trouble with me. And if your dog is pregnant and nearing delivery, please do me a big, big favor, will you? Keep your vet’s phone number handy, and get help as soon as you can so that I can do my work and safely deliver that batch of puppies you have been waiting for. Your dog, the pups and me will thank you.

Respectfully yours,

Your Dog’s Uterus.Dog Pawprint

 

Disclaimer:  this article is not to be used as a substitute for professional veterinary advice. If your dog is having health problems, please consult with your vet at once.

 

References:

  • Pet Place, Structure and Function of the Female Canine Reproductive Tract, retrieved from the web on May 2nd, 2013
  • Pet Education, Anatomy and Function of the Reproductive System in Dogs, by Dr. Race Foster, retrieved from the web on May 2nd, 2013
  • VCA Animal Hospital, Pyometra in Dogs, retrieved from the web on May 2nd, 2013
  • Management of Pregnant and Neonatal Dogs, Cats, and Exotic Pets, By Cheryl Lopate, Wiley-Blackwell; 1 edition (13 July 2012)
  • Clinical Anatomy and Physiology for Veterinary Technicians, 3e 3rd Edition by Thomas P. Colville DVM MSc (Author), Joanna M. Bassert VMD (Author), Mosby; 3 edition (April 2, 2015)

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I Am Your Dog’s Stomach

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You may not pay much attention to your dog’s stomach other than when your dog brings food back up from there or when you watch him wolf down food like if there was no tomorrow, but your dog’s stomach is sure a fascinating body part. We often take a dog’s stomach for granted when it’s often doing loads of work, from storing food to preparing it for its further journey down the lower digestive tract. So today’s spot of honor is dedicated to Rover’s stomach, so let’s listen to what our dog’s stomach has to say!

Introducing the Dog’s Stomachstomach

Hello, it’s your dog’s stomach talking! Ever wondered where that whole bowl of food your dog ate goes? In his stomach of course! You see, when your dog eats food, it travels from his mouth down to the esophagus where it then reaches a valve-like structure that’s known as the cardiac sphincter or antrum cardiacum. Just like a valve, this muscular sphincter opens and closes as needed. In between meals, the valve is closed, but when your dog eats or drinks, the valve opens so to allow food and water to reach me. Once the food reaches me, the valve closes again, but it can sometimes be forcefully opened when I am full of air (as it often happens when your dog eats too fast!) and the air pressure forces the valve to open causing your dog to burp. When food makes it past the cardiac sphincter, it finally reaches me and then it’s my turn to go to work!

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dog eatingI am Storage Unit

I am a sac-like structure located between the esophagus and duodenum (small intestine) and one of my main goals is to store your dog’s food. When your dog eats, I tend to distend and act as a reservoir, but I am also contracting in the meanwhile so to help mix up and churn the food. As food is ground up, the parts that are mostly liquefied (chyme) are sent to the duodenum for further digestion, while the larger parts remain inside me awaiting to become a more liquid form. This explains why liquid medications or poisons are more readily absorbed compared to solid or semisolid foods.

Did you know? According to veterinarian Race Foster, once ingested, most food leaves the dog’s stomach within twelve hours.

I Aid in Digestion

My interior surface is lined up with several folds known as “gastric folds.” These folds are responsible for grinding up the food your dog wolfs down for breakfast and dinner. On top of that, I secrete acids and enzymes to help break down the food further.  The acid I produce is known as hydrochloric acid and it’s very strong! It is thanks to this acid that your dog can digest things that you may not be able to. You would think this acid I produce would harm me, but thankfully, I have a protective lining of mucus that prevents me from auto-digesting myself.

Once I have started the preliminary digestive process, the partially digested food can then be sent to the duodenum (where the main part of the digestion occurs) through the pyloric sphincter. Like the cardiac sphincter, the pyloric sphincter acts as a valve, opening and closing to regulate the flow of food that reaches the duodenum.

When Things Go Wrongdog pain goes away at the vet

Despite being a simple storage sac that can grind up food and initiate the digestive process, many things can go wrong with me. I can get irritated and inflamed, I may produce too much acid, my protective layers may be affected and I can develop growths and dangerous cancers. On top of that, dogs can swallow things that are unable to pass through me, leading to debilitating blockages.

Gastritis

Gastritis comes from the ancient Greek word gastḗr, meaning “belly” and itis meaning inflammation. There are many things that can cause me to get inflamed. As in humans, viruses and bacteria, ingestion of spoiled food, abrupt dietary changes, certain medications and overeating can irritate me and cause a bout of gastritis. Affected dogs will be vomiting, refuse food and act lethargic. While in several instances the issue is short term and I recover after being fasted (yes, I too benefit from some rest at times!) and offered a dog upset stomach bland diet, repeated episodes of vomiting are often a red flag that there’s some underlying problem that needs addressed. 

Presence of Ulcers

As discussed above, when a dog’s cardiac sphincter works well, the valve opens when food and water needs to reach me and then remains in the closed position at other times. However, sometimes the valve can weaken or become damaged, and when this happens, it doesn’t open and close as it should causing some of my acid to seep through and reach the esophagus, causing an esophagitis (yes, now it’s his turn to get irritated.)

While as mentioned I have a protective layer of mucus that prevents me from digesting myself, sometimes when I produce too much acid or my local protective force weakens, or both, the acid I produce may manage to harm me, predisposing me to ulcers. What can cause me to produce too much acid or weaken my protective mucosa? Certain conditions such as mast cell tumors, stress or the administration of anti inflammatories, pain killers and corticosteroids, just to name a few. Affected dogs will typically vomit, lose their appetite and there may be fresh of digested blood in it.

Pyloric Stenosis

As with the cardiac sphincter, the pyloric sphincter may also malfunction. In this case, after undergoing repeated muscle spasms its passage may become narrow, triggering what is known as pyloric stenosis. This condition is more common in small nervous dogs in which it may cause them to occasionally regurgitate partially digested food within two hours of eating. In severe cases, dogs may regurgitate more often leading to weight loss.

Bloat and Torsion

Perhaps, one of the problems I am mostly associated with is bloat which most commonly affects large dogs with deep chests. When I fill up too much with air, I tend to dilate and if I fill up too much, I risk twisting on my axis leading to a potentially life threatening torsion that can cause shock and death if not treated immediately. Affected dogs develop a swollen belly, they may be dry heaving, retching and pacing anxiously. This is a medical emergency!

Foreign Bodies

Dogs can eat the strangest things, and sometimes foreign bodies such as balls, buttons or bones can get lodged somewhere in the gastro-intestinal tract. When something gets stuck inside me, it’s important to take prompt action as foreign bodies can cause me lacerations, erosions and even perforations. When help is sought quickly, vets may retrieve the ingested object through endoscopy, via a tube inserted in the dog’s esophagus with attachments that reach me and allow the foreign item to be grasped. If this option isn’t feasible, the foreign object may need to be removed surgically.

Stomach Cancer

Sadly, I can also get cancer. According to veterinarian Dr. Rance K. Sellon, the most common stomach tumor affecting dogs is adenocarcinoma, followed by lymphosarcoma and smooth muscle tumors (leiomyomas, leiomyosarcomas). Usually, stomach cancer happens mostly in middle-aged to older dogs that present with chronic vomiting, loss of appetite and weight loss. Like in the case of a blockage, the tumor may grow so big that food cannot pass through me so it’s vomited back up, which leads to weight loss as the dog is no longer able to receive food as it should.

The above are just a few of the many things that can go wrong with me.  I hope this article has helped you understand me better. As you have seen, I do quite a whole lot! If you wish, you can compare my workload to a washing machine, where food is loaded up, rinsed with acids and enzymes and then tumbled out to the intestinal tract. You may want to keep me in good shape so that I don’t make your dog sick and lose his appetite! Keep an eagle eye on your dog to ensure he doesn’t ingest things that he shouldn’t, feed him a easily digestible diet and report to your vet promptly if something seems amiss. Me and your dog will thank you!

Respectfully yours,

Your dog’s stomach.Dog Pawprint

Disclaimer: this article is not meant to be used as a substitute for professional veterinary advice. If your dog has a stomach problem, please see your vet promptly.

References:

  • Pet Education, Pyloric Stenosis, By Race Foster, retrieved from the web on April 25th, 2016
  • DVM 360, Gastric ulcer disease in dogs and cats (Proceedings), by Rance K. Sellon, DVM, PhD, DACVIM, retrieved from the web on April 25th, 2016
  • DVM360, Gastric neoplasms in dogs and cats (Proceedings) by Rance K. Sellon, DVM, PhD, DACVIM, retrieved from the web on April 25th, 2016
  • Pet Education, Gastritis and Stomach Inflammation in Dogs, by Race Foster, retrieved from the web on April 25th, 2016

Photo credits:

  • Outline of stomach, showing its anatomical landmarks.Henry Vandyke Carter – Henry Gray (1918) Anatomy of the Human Body (See “Book” section below) Bartleby.com: Gray’s Anatomy, Plate 1046 This is a retouched picture, which means that it has been digitally altered from its original version. Modifications: vectorization (CorelDraw). The original can be viewed here: Gray1046.png. Modifications made by Mysid. Public domain.

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Do Dogs Have a Collarbone?

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Among the many fascinating facts about dogs one that is truly amazing is the way the shoulders of a dog are structured. It is thanks to the way the dog’s shoulders are designed that dogs are able to romp around with great  stride length and flexibility. On top of walking on their toes, dogs have a special shoulder design that plays a major role in canine locomotion making them the amazing runners they are. So today’s we’ll be discovering how dog’s shoulders are designed compared to us, and what makes them truly remarkable.

collarboneShoulder Design in Humans

When we look at the anatomy of the human shoulder, we notice that it is composed of three bones: the collarbone (clavicle), the shoulder blade (scapula) and the upper arm bone (humerus). It is thanks to these three bones and their associated muscles, ligaments and tendons, that we are able to lift, push, pull and swing our arms. The fact that the shoulder is the most mobile joint in the human body is a double-edged sword considering that this mobility is also what makes us more prone to dislocations. Now you know why it seems like baseball players get so many shoulder injuries!

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The collarbone, is the only horizontal bone in our body. See the red bones in the picture? It’s that thin, long bone that’s located at the base of the neck and that’s highly visible in thin people as the lack of fat causes a visible bulge in the skin. This is because, unlike most bones that are covered with muscles, this bone is only covered by skin. As seen in the picture, we have two clavicles, one per side in each shoulder. They are both responsible for connecting our right and left arms to the trunk of our body.

Shoulder Design in Dogsdog clavicle

Dogs being a cursorial species, don’t have a need to lift, push or pull objects or swing their arms as we do, so their shoulder design is for the most part crafted for what predators need the most: speed and agility. Along with a dog’s spine which is capable of bending and stretching with every stride and the powerful hind legs providing forward propulsion, the dog’s shoulders are designed to increase stride length. Unlike humans, the dog’s shoulders are somewhat disconnected from the rest of the skeleton, which is why many people refer to them as “floating shoulders.” However, no body part really floats alone as a particle suspended in space. While the dog’s scapula is not attached to any bones at the top, there are several muscular and ligamentous attachments.

rottweiler dog foodA Rudimentary Collarbone

While humans, have a collarbone connecting the arms to the trunk of the body, dogs have just a rudimentary collarbone that does not articulate with the rest of the skeleton. Darryl Millis and David Levine in the book “Canine Rehabilitation and Physical Therapy” mention that a dog’s collarbone is an oval plate that measures about one centimeter or less in length and 1/3 in centimeter wide. This structure is mostly made of cartilage and it doesn’t appear in x-rays. Because of the lack of a fully developed collarbone, dogs are capable of a greater stride length so that they can run and leap, an evolutionary advantage that allowed them to be successful predators. While your dog today is fed food in shiny bowls and no longer hunts for food, you surely have admired his fascinating locomotion as he chases and leaps up for the ball you just tossed!

Did you know? Just because your dog’s collarbone is rudimentary, doesn’t mean it’s useless! According to a study, the dog’s clavicle provides muscle stability and protects the nerves and blood vessels that supply the front legs.

References:

  • Canine Rehabilitation and Physical Therapy, by Darryl Millis, David Levine, Saunders; 2 edition (March 30, 2014)
  • McCarthy, P.H. and Wood, A. K., Anatomic and radiologic observations of the clavicle of adult dogs, Am. J. Vet. Res. 49:956–959, 1988

Photo credits:

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I am Your Dog’s Pineal Gland

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Just like humans, dogs have a pineal gland, a small gland that not many people may be aware of, but that carries many important functions. Also known as pineal body, conarium or epiphysis cerebri, the pineal gland is present in almost all animals and it plays an important role in their lives. Getting to know the pineal gland better can help us better understand how much dogs rely on this small brain structure, however, this gland’s secretory activity is still only partially understood. So let’s discover today what we currently know about a dog’s pineal gland by listening to his story!

dog pineal glandIntroducing Your Dog’s Pineal Gland

Hello, it’s your dog’s pineal gland talking! There are chances you have never heard about me before and that’s OK, I am not too popular, but hopefully today you’ll become more familiar with me and my importance. I am quite tiny, just imagine that in humans I am roughly 1 cm in length, whereas in dogs I measure just about 1 mm long. Since I am tucked  at the base of your dog’s brain just outside of the blood brain barrier, it’s not like I am advertised much. You may perhaps stumble on pictures of me in some anatomy or veterinary textbooks but otherwise, I sort of live in the shadow.

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If you look at the meaning of my name, you’ll find that the word “pineal” comes from the Latin word pīnea ‎ meaning pine cone. I am called this way because some people think that I am shaped like a small cute pine cone. The fact that I am a gland means that I secrete hormones that are meant to be sent into your dog’s bloodstream. Indeed,  along with other important glands like the thyroid gland and the pituitary gland, I am part of your dog’s endocrine system. Not too long ago, people thought I was pretty useless and were fast to categorize me as some vestigial structure, reminiscent of an evolutionary past, but there’s a renewed interest in me, which is very good news for me, you and your dog!

I am a the Hormone of Darknessdog pineal gland function

I am a gland responsible for providing information about the amount of sunlight  received during the day and therefore play a role in those wake and sleep cycles, also known as “circadian rhythms.” I basically tell bears when it’s time to hibernate and it’s likely my fault if people feel like crawling into bed early during those long, wintry days making them feel lethargic and depressed! You see, when you and your dog sleep, I produce what is known as melatonin, a hormone that provides information about the daily onset of darkness and that’s responsible for regulating the sleep cycle. My production of this hormone is maximized during a good night of sleep in a quiet, completely dark room. On top of that, melatonin offers even more benefits: it can support a good immune function in your dog and protect his cells from the damage of free radicals.

“Melatonin is involved in the circadian rhythm and acts as a free-radical scavenger.” ~ Dr. Megan Whelan

idea tipDid you know? On top of helping regulate sleep, melatonin is also known for having anticancer effects, explain Dr. Demian Dressler, and Dr. Susan Ettinger on the Dog Cancer Blog.

 

CaptureWhen Things Go Wrong

When I produce melatonin in normal quantities, your dog is happy and healthy. As the photosensitive ganglion cells  in your dog’s eyes detect light, this information is sent to the suprachiasmatic nucleus, a small region of the brain in the hypothalamus that communicates with me. When it’s daytime, I inhibit my production of melatonin so you can carry on with your daily tasks without getting too groggy, but when nighttime falls, my production of melatonin goes in high gear so I can make you and your dog ready for bed time (as long as you have kept your dog busy during the day!) Problems start though when for one reason or another, I stop producing adequate amounts of melatonin as needed. This can wreck havoc on your dog’s body causing disruptions to your dog’s “internal clock.”

Studies in humans say that a common reason for me slowing down is aging.  According to Colorado State University, as I age, I tend to develop calcium deposits (brain sand) which is common in older animals. Due to the aging factor, older dogs suffer from disruption in their sleep and wake cycles, which explains why they’re often pacing restlessly at night. According to veterinarian Dr. Nicholas Dodman, melatonin can be given under the guidance of a vet to dogs with sleeping disorders or elderly dogs suffering from cognitive dysfunction triggering disrupted sleep (sundowner syndrome.)

Other than helping in sleep timing,  I am also responsible for several other biological effects that vary with the seasons  such as reproduction, behavior, coat growth and those changes in coat colors seen in animals that camouflage. Some dogs are prone to light-responsive alopecia, which means they tend to lose hair when I don’t get enough sun exposure as it may happen in certain areas with long, dark winters.

“Light responsive alopecia is logically more common in those areas of the country with dark winters such as the Midwest, the Plains states, parts of New England and Canada.” ~ Dr. Alice M. Jeromin, veterinary dermatologist.

idea tipDid you know? The pineal gland is sometimes referred to as the ‘third eye” because it responds to light and day length.

 

As seen, I am quite an important gland! Luckily, unlike some other glands, I am not a frequent site for tumors. The National Canine Cancer Foundation mentions that pineal tumors are extremely rare in dogs.  I hope this article has helped you understand me better! Send pats to your dog!

Yours truly,

Your dog’s pineal gland Dog Pawprint

 

References:

  • Sack RL, Lewy AJ, Erb DL, Vollmer WM, Singer CM (1986). “Human melatonin production decreases with age”. J. Pineal Res. 3 (4): 379–88. doi:10.1111/j.1600-079X.1986.tb00760.x. PMID 3783419.
  • Colorado State University, The Pineal Gland and Melatonin, by R. Bowen, retrieved from the web on April 18th, 2016.
  • Dvm360, Seasonal affective disorder can be culprit for canine hair loss, by Alice M. Jeromin, retrieved from the web on April 18th, 2016.
  • Pet Place, Melatonin for cats and dogs, by Dr. Nicholas Dodman, retrieved from the web on April 18th, 2016.
  • The MSPCA–Angell, Melatonin for Primary Immune-Mediated Thrombocytopenia (ITP), by By Megan Whelan, retrieved from the web on April 18th, 2016

Photo credits:

Wikibooks, Anatomy and physiology of animals pineal gland, By Ruth Lawson. Otago Polytechnic.Creative Commons Attribution 3.0 Unported license.

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Five Fascinating Facts About A Dog’s Neck

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We often take our dogs’ necks for granted, but those necks do so much! A dog’s neck main function is to support the dog’s head and protect the spinal cord. Sure, a dog’s neck is not as impressive as the neck of a giraffe, but it carries many roles and there are some interesting facts about a dog’s neck that are ready to be discovered! Here are fives fascinating facts about a dog’s neck.

dog 1) Dogs Have the Same Number of Vertebrae Than a Giraffe.

How can it be? Sure, a dog’s neck appears much shorter than the neck of a giraffe, but both dog and giraffe have only 7 vertebrae, which is also the same number of vertebra humans have. The dog’s first vertebrae is called the atlas and you must thank this bone if your dog is able to raise his head and lower it down. Next in line is the axis, the vertebra that allows your dog to rotate his head laterally. The remaining five vertebrae are quite similar in structure. What mainly makes the difference between the neck of a dog and the neck of a giraffe? According to San Diego Zoo, a giraffe’s vertebrae can measure over 10 inches long, so add those vertebrae up and you have an explanation for the giraffe’s impressive 6-foot neck!

Did you know? The first vertebra’s name “Atlas” derives from a Titan giant who in Greek mythology was known for holding the world on his shoulders. Just like the giant, the atlas holds up your head and the head of your dog!

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2) Mother Dogs Carry Pups By the Scruff of Their Neckpuppy mother

We often see mother cats carrying their litter of puddy- tats by the scruff of the neck, but did you know mother dogs carry their pups the same way? Without the luxury of baby strollers, mother dogs have to resort to their most ancient means of transportation if their desire is to move a litter of pups from point A to point B. If you ever watched a mother dog carry her pups by the neck, you may have noticed how the pup gets limp like a strand of overcooked spaghetti. Why is that? This behavior is reminiscent of the past and might have helped grant a pup’s survival, even though today it might not have much survival value. In the olden days, pups were raised in a den and it was imperative that pups were kept safe. When mother dog stumbled on any stranded pups it was crucial to move them from the great outdoors back to the safety of the den. 

Upon being lifted off the ground, the pups go instinctively limp because this ups their chances for survival. Struggling was maladaptive because doing so could have caused the pup to get hurt and it could have irritated the mom with the pup risking being left behind. Non-struggling puppies who made the task easy as pie instead had higher chances of being quickly brought to safety. This evolutionary advantage has therefore persisted and is why we still see it occur as of today even though our pups nowadays live in our homes instead of dens, explains Stanley Coren.

Warning: just because momma dog carries her pups this way doesn’t mean we should handle them the same way. “Scruffing” is likely to cause pain in puppies because flexor dominance does not persist in puppies” warns Karen Overall. Also, puppies are no longer carried this way by momma dog after a certain age. And definitively, scruffing should never be used as a way to discipline puppies!

ewe head dog3) Some Dogs have an Ewe Neck.

According to the American Kennel Club, dogs with an ewe neck have a neck that has a topline that is concave rather than convex.  The bottom of the neck is instead convex making it look like an upside down neck. It’s called this way because it resembles the neck often seen in a female sheep, known as “ewe.” In many dog breeds an ewe neck is considered a fault. According to the Borzoi Club of America, the presence of an ewe neck in the borzoi is indication of a weak neck that interferes with the ability to hold prey.

 

 

 

4) The Lundehund  Can Bend His Neck Backwards

Norwegian lundenhund
Norwegian lundenhund

The Norwegian Lundehund dog breed is as special as it can be. On top of being equipped with 6 toes on each foot and being able to close his ears so to protect the ear canals from dirt and moisture, the Lundehund has special neck joints that allows him to bend the neck backwards along his spine (a quality seen only in reindeer!) which turns extra handy when he must turn in a very tight passage. This extraordinary breed was selectively bred to hunt for puffins and their eggs which required him to hunt off the rocky coasts and narrow passages of Værøy island, Norway.

plott hound5) The Neck is a Delicate Piece of Machinery

Despite what you may have heard, a dog’s neck is not as tough as you may have thought. Chronically pulling on your dog’s collar may lead not only to stress on the neck, but in the long run, potential for a lifetime of painful disc disease and shoulder ailments, explains veterinarian Dr. Patty Khuly.  Not to mention tracheal problems which are common in small dogs.

The neck and cervical spine contain the spinal cord, from which the nerves of the front legs originate.  The thyroid gland which is responsible for regulating the whole metabolism of a dog’s body is also located in the neck, points out veterinarian Dr. Dobias. Choke, prong and shock collars can cause irreversible damage to your dog, he warns. He recommends avoiding collars and using instead front-attachment harnesses which don’t put strain on a dog’s neck and throat.

“Sometimes it seems no one ever explained that the neck is a delicate piece of machinery through which all things flow.” ~Dr. Patty Khuly

References:

  • San Diego Zoo Animals, Mammals, Giraffe, retrieved from the web on April 15th, 2016
  • Norwegian Lundehund Club of America, Homepage, retrieved from the World Wide Web on April 15th, 2016
  • Pet MD, Collar Safety, Collar safety in dog training and in real life: A veterinarian’s take, retrieved from the World Wide Web on April 15th, 2016
  • Dr. Dobia’s Natural Healing, Choke, Prong and Shock Collars Can Irreversibly Damage Your Dog, retrieved from the World Wide Web on April 15th, 2016
  • Manual of Clinical Behavioral Medicine for Dogs and Cats, By Karen Overall, retrieved from the World Wide Web on April 15th, 2016

 

Photo Credits:

-Wikipedia, Picture of a Norwegian Lundehund, N UCH Ålvisheims Hårek, by Karen Elise Dahlmo, CC BY-SA 3.0

-Wikipedia, Plott Hound, DTabCam – Own work, GFDL

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I am Your Dog’s Lymph Nodes

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Just like us, dogs have several lymph nodes in their bodies, and just like us, they are prone to getting them inflamed or infected in certain circumstances which leads to their enlargement. Becoming aware of your dog’s lymph nodes can help you understand early signs of trouble so that you can report them promptly to your vet. Just as women are often instructed to perform breast self-exams, it’s not a bad idea for dog owners to get accustomed to how their dogs feel so they can readily recognize any suspicious lumps and bumps. So today, the dog’s lymph nodes will be the star of the day, so  let’s see what they have to tell us!

dog lymphatic systemIntroducing the Dog’s Lymph Nodes

Hello, it’s your dog’s lymph nodes talking! We are special  bean-shaped structures that are distributed on your dog’s body in various places. While we are scattered around in many places, we are mostly concentrated in clusters mostly found around your dog’s neck area, armpit area and inguinal area. You don’t normally feel us or perhaps you barely feels us when you pet your dog, which is a good thing! The fact that you barely feel us though doesn’t make us insignificant; rather, it’s an important sign that we are doing a very good job! As for size, expect us to be typically less than 1/2 inch in length on average, but the size really ultimately depends on the type of dog you are dealing with. Oh, and if you ever hear somebody calling us “lymph glands,” consider that’s incorrect. Unlike glands, we don’t secrete any substances!

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We are part of your dog’s lymphatic system, an extensive drainage network composed by several thin tubes (lymphatic vessels) which carry lymph, a colorless watery fluid that is similar to plasma. Where does this fluid come from? Basically, lymph fluid leaks out into surrounding tissues from your dog’s circulatory system. Oh, but don’t worry about this leakage! This is perfectly normal. After collecting lymph fluid and then sending it through us, the lymphatic system then returns this lymph fluid to the circulatory system. This is a good thing. If the lymphatic system didn’t return that fluid, it would quickly build up in the dog’s body’s tissues causing swelling.

We Act Like Filterslymph node

While your dog’s liver  and kidneys do a good job in filtering and getting rid of toxicity, us lymph nodes are responsible for filtering and removing any germs, foreign particles, fungi or damaged cells. You see, when the lymph fluid passes through us, it’s our job to filter it before it’s returned to the bloodstream. With the help of  T lymphocytes and B lymphocytes, white blood cells responsible for fighting infections by attacking with specific antibodies, and macrophages, special white blood cells that engulf and digest any foreign substances, we are able to rid the lymph fluid of anything that shouldn’t be there so that when the lymph fluid is returned to the circulatory system, it’s as pure as it can be!

old dogWhen Things go Wrong

As mentioned, you should barely detect us at all, but sometimes when we encounter something in the lymph fluid that shouldn’t be there, we will put up a fight. This causes us to swell up, which means that we are battling and trying to do our job the best we can. When we swell up, the condition is known as “lymphoadenopathy” which literally means enlargement of the lymph gland. Along with us becoming enlarged, we may cause other symptoms in dogs  secondary to our enlargement such as problems swallowing when we we swell in the neck area, difficulty moving when when swell  by the armpit, constipation when we swell by the inguinal area. When we swell, it’s important to consult with a vet to identify what is causing us to swell up in the first place.

An Infection

If we are swollen because of an inflammation or infection, the condition is medically known as “lymphoadenitis. ” Depending on which of us is inflamed, it’s often a tell-tale sign of something going on locally. For instance, if the lymph nodes by your dog’s neck are enlarged, it could be due to a sore throat, if the lymph nodes by the dog’s leg are enlarged it could be due to an infection in the dog’s foot. Why do we enlarge? In this case, we must blame the immune system’s response which involves the multiplication of lymphocytes and the arrival of macrophages, but this is all good as it’s our way of putting up a fight. Luckily, in these cases, once the inflammation or infection has been cleared, the lymph nodes should return to their normal size.

dog enlarged lymph node neckCancer

While our job is to rid the lymph fluid from any foreign particles and other things that shouldn’t be there, cancer cells may sometimes infiltrate and wreck havoc. Where are the cancer cells coming from? In some cases, the cancer starts within us directly. Basically, what happens is that our lymphocytes become cancerous. It may sound ironic that these cells which are meant to be a line of defense, become cancerous, but unfortunately any cells in nearly any part of your dog’s body can become cancerous. When this happens, lymphoma, a cancer caused by the growth of abnormal lymphocytes occurs and this causes us to swell.

“When the numbers of cancerous lymphocytes increase, they form swellings. One of the most common areas that these cancer cells accumulate are in the normal lymph nodes themselves, increasing the size of these normal structures.” ~Dr. Demian Dressler

The Bottom Line

As seen, we are quite important as we filter out all the bad guys! When we get enlarged this may be a sign of many conditions such as viral, bacterial infections, primary immune disorders, tick born diseases, reaction to vaccinations and cancer. For this reason, it’s important to check us out every now and then just to be on the safe side! Because many of us are located close to the surface of the dog’s body, we can be felt through the skin, and can be readily detected when we enlarge. Where should dog owners should check in particular? Veterinarian Dr. Demian Dressler suggests feeling under your dog’s lower jaw just where it connects with the neck area, in the front part of the shoulder area, by the back of the thigh, by the armpit and by the groin where the thigh connects with the abdomen. To see the exact location of certain lymph nodes in dogs that can be easily detected when enlarged, click here or watch the video below for a demo by Dr. Sara. You can also ask your vet to show you.

I hope this has helped you understand us better!

Yours dearly,

Your dog’s lymph glands Dog Pawprint

 

References:

  • Pet Education, Lymphadenitis, Lymphadenopathy & Swollen Lymph Nodes in Dogs, by Dr. Race Foster, retrieved from the Web on April 11th, 2016.
  • Pet Education, Lymphatic System, Anatomy and Function, retrieved from the Web on April 11th, 2016.
  • Dog Cancer Blog, Signs of Dog Lymph Node Cancer, by Dr. Demian Dressler, retrieved from the Web on April 11th, 2016
  • Clinical Anatomy & Physiology for Veterinary Technicians, Thomas Colville DVM, Joanna M. Bassert VMD, Mosby Inc.  St Louis, MO, 2002

 

Photo credits:

Evolution Explains Why Dogs Have Four Toes

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dog four toesHave you ever looked at your hands and feet and compared them to your dogs’? If so, perhaps one of the most prominent contrasting features you may notice is that your hands and feet have five fingers and five toes (that makes you pentadactyl, by the way), whereas, your average dog has only four functional toes. Also, the fingers and toes of your hands and feet are quite long, while your dog’s toes instead are quite short, why is that? For sure, “Mother Nature” must have known what she was doing as she was weighing out the pros and cons of having toes. She then made her final verdict that less was better than more.

“Five is a common number for digital division among vertebrates; and our own hands and feet present these digits in a high degree of perfection.” ~Felter, 1912

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A Matter of Speeddog lung

If we look at the toes of many animals, we may notice that the general standard is to have five toes at the end of a limb. Humans have 5 toes and so do bears, primates, weasels, bats, and several types of reptiles and birds. Some animals such as dogs, foxes, wolves and coyotes though have though four fully functional toes instead of five. What do these four-toed animals have in common? Fossil evidence shows that animals that show a loss of digits are for the most part animals who were required to maintain high speeds for long distances, explains John Buckwalter, Emeritus of Biology at Alfred State College. Such animals are known as “cursorial animals” and they are distinguished for their long limbs, shortened digits and reduced number of toes. Dogs for example have four toes instead of five, and horses (cursorial grazers) have only one (the hoof is simply the distal phalanx of the 3rd digit).

The Recipe for Running

In order to become swift runners, a change in basic physiology was necessary so  several speed adaptations were necessary. While us humans and bears are plantigrades, meaning that we place our whole foot on the ground with a rolling heel-to-toe action, dogs are digitigrades, meaning that they only walk on their digits, a quality that makes them faster and quieter runners as their heels are not required to touch the ground, explains Stanley Coren, in the book “Do Dogs Dream?: Nearly Everything Your Dog Wants You to Know.”

This means that the bones of the dog’s wrist (carpals), palm (metacarpals), sole (metatarsals) and ankle (tarsals) are kept off the ground. We therefore make a mistake when we compare our dog’s paws with our hands and feet. In reality, we are mainly looking at their toes as seen in these illustrations.  Basically, the bones that correspond to our wrists and ankles are set much higher than we would think which explains why many people often confuse the dog’s ankles (tarsal, hock) for the dog’s knee (stifle). However, this doesn’t answer our question:”why do dogs have only four toes?”

” What evolution did to dogs was to rock their legs forward so that their heel would no longer touch the ground. In so doing they became a digitigrade species, meaning that they walk on their digits.” Stanley Coren

dog cursorialLoss of Weight

In us humans, our extra digit, the thumb, played a very important role in our evolution allowing us to manipulate things, but why would a cursorial animal do better with less toes? Dogs didn’t rely much on their digits to manipulate things, but there’s likely an additional reason for having four toes: it’s likely an issue of weight. An extra toe may weigh just a few ounces, but its extra weight on the foot  may ultimately have an impact when it’s carried along for the ride as an animal runs to catch his dinner or runs for his life. So evolution decided that it was in the dog’s best interest to not have a fully developed 1st digit, which is the equivalent of our thumb. Reduced weight is also a plausible explanation also as to why a dog’s legs has concentrated muscle mass at the top, while at the bottom the legs get more slender with a lighter foot. “An increase in limb length adds to stride length, whereas reduction in limb weight especially distally, enhances stride rate.”says  S. M. Kisia in the book “Vertebrates: Structures and Functions.”

“Members of the dog family (canids) have small feet, with usually four digits in contact with the ground. The small size and weight of their limbs requires less energy to move, allowing them to run more efficiently.”~ John Buckwalter,

dog dewclawA Vestigial Remnant….

It would be wrong though to say that the dog has totally lost his fifth toe. In reality, that extra digit is still there but it’s just reduced. You may stumble on it if you take a look at your dog’s foreleg and notice a claw that’s located higher up which doesn’t normally touch the ground as the other toes.

That claw is known as the “dewclaw“and it’s a remnant of that original fifth digit dogs used to have in the past. In technical terms, it’s a vestigial structure, meaning that it has lost its original function and therefore has atrophied.

Note: If you don’t see this fifth digit on your dog’s front feet it likely was removed shortly after birth to give the dog a cleaner look or to prevent it from getting caught on things.

“Dewclaws are vestigial remnants of a fifth digit that was reduced in the process of evolution.”~John Buckwalter

With a Purposedog agility role of tail

It would be also wrong to say that a dog’s dewclaws have completely lost their functionality. Turns out, contrary to what we may have heard, those dewclaws at times actually touch the ground, but because it happens when dogs run at high speeds we hardly notice it.  Christine Zink, a veterinarian working with canine athletes, has found that those dewclaws that many people chop off and think of them as useless appendages, actually help prevent torque on the leg especially when the dog is galloping and making tight turns, as often seen in canine sports. Without the dewclaw, there are risks that leg may twist which over time can lead to problems such as carpal arthritis and other injuries to the dog’s  elbow, shoulder and toes!

Did you know? Some dog breeds (like the Great Pyrenees or Briard for example) have one or even two dewclaws on their rear feet as well!

References:

  • MadSci Network, Why do dogs have dewclaws? and why are they only in the front?John Buckwalter, retrieved from the web on April 10th, 2o16.
  • Do Dogs Dream?: Nearly Everything Your Dog Wants You to Know” by Stanley Coren, W. W. Norton & Company; Reprint edition (July 16, 2012)
  • Evolutionary Biology 8/e by Dr. B. S. Tomar, Dr. S. P. Singh. Edition. 9th Revised Edition
  • Chapter 15, Limbs in Mammalian Evolution, by P. David Polly, retrieved from the web on April 10th, 2015
  • Myers, P., R. Espinosa, C. S. Parr, T. Jones, G. S. Hammond, and T. A. Dewey. 2016. The Animal Diversity Web (online).
  •  Vertebrates: Structures and Functions, By S. M. Kisia, CRC Press (April 12, 2010)
  • Course Hero, Mammalian Specializations, Chapter 21,  retrieved from the web on April 10th, 2015
  • Do the Dew(claws)?  by M. Christine Zink DVM, PhD, DACVSMR, retrieved from the web on Aprile 10th, 2016

 

Photo Credits:

Paw and pads in dog by Amos T Fairchild,  CC BY-SA 3.0, edited to add text and adjust size

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I am Your Dog’s Pancreas

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Many dog owners may not be aware of the existence of their dog’s pancreas until one day their dog gets very ill and the vet claims that the dog’s pancreas is inflamed. As with many other organs, the pancreas lives mostly in the shadow, until something goes wrong and dog owners are given an abrupt wake-up call about this organ’s existence. Just as in humans, the pancreas in dogs is a structure that carries some functions that go beyond digestion. So today, let’s take a closer look at a dog’s pancreas and discover some interesting facts coming straight from the pancreases’mouth!

dog pancreasIntroducing Your Dog’s Pancreas

Hello! It’s your dog’s pancreas talking! You may not be too familiar with me, but rest assured, I am working hard each and every day to make sure your dog remains healthy and happy. Where am I located? You’ll find me nearby your dog’s stomach, more precisely, attached to the wall of your dog’s small intestine, right by the duodenum. I am overall a small structure compared to your dog’s stomach, but don’t underestimate me, as I do a whole lot!

I Aid in Digestion

Many people know that I play a role in digestion. Indeed, I produce important enzymes so to help your dog digest protein, starches and fats. To help digest protein, I produce trypsin and chymotrypsin. To help digest starch, I produce amylase. To help digest fats, I produce lipase. I send these enzymes to your dog’s small intestine (right by the duodenum, which lives just next door to me) through a small tube known as the “pancreatic duct.” Once here, these enzymes activate and break down your dog’s food into easy to assimilate molecules which provide nutrients that are readily absorbed by the cells lining your dog’s intestine. Nutrients are then passed from these cells into your dog’s bloodstream and spread out throughout the body where they’re utilized by various tissues.

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I Maintain Normal Sugar Levelsdog pancreas 1

On top of helping your dog digest, I have special islet cells which produce hormones that help keep your dog’s blood sugar at an acceptable level. The glucose-regulating hormones that I produce are known as insulin and glucagon. I secrete these hormones into your dog’s bloodstream. You see, your dog may not eat sweets as you do, but when your dog eats foods rich in starches and carbs, these foods are then broken down into glucose which ends up in the bloodstream. When I produce insulin, the insulin helps remove the glucose from the bloodstream and directs it to the body’s tissues where it can be used as energy for the cells. If those levels of glucose are too high, the other hormone I produce (glucagon) helps store the surplus in the liver and muscles in the form of glycogen.

Small breeds are prone to pancreatitis
Small breeds are prone to pancreatitis

When Things Go Wrong

When I work well, your dog is healthy and happy. Courtesy of my digestive enzymes, your dog can easily digest as my enzymes help break down food into easy to assimilate components. When I become sluggish though, either because of being chronically inflamed or due to some inherited condition, I might not produce enough of these enzymes which may lead to pancreatic insufficiency, also known as  exocrine pancreatic insufficiency or maldigestion syndrome.

What happens in this condition is that all those proteins, starches, and fats are no longer broken down which means they pass through the intestines without being absorbed and they leave the body under the form of feces containing undigested food. This means affected dogs miss out in receiving nutrients big time! These dogs develop diarrhea, start losing weight, their coats become dull and they lose muscle mass. Because food passes into their stools undigested, these dogs may engage in stool eating as the stools taste almost as good as food! These dogs are basically hungry and eating, yet they’re starving themselves of nutrients! Fortunately, treatment is pretty straightforward: borrowing some enzymes from other animals.

I sometimes may become inflamed. This tends to often occur after dogs eat a fatty meal. I am notorious for getting inflamed after the holidays, when dog owners feed their dogs fatty table scraps such as foods prepared in butter, fatty meat and greasy bacon. When  I get acutely inflamed, I cause some pretty scary symptoms such as lack of appetite, vomiting, abdominal pain which causes many dogs to assume a hunched-up position. Basically, what happens here is that instead of my enzymes activating when they reach the small intestine, they activate prematurely as soon as I release them, causing inflammation to myself and my surrounding organs.  In severe cases, my enzymes may even start digesting me! Talk about being in a dangerous situation! My inflammation is therefore not to be taken lightly as I can turn into a life threatening condition. And when I get chronically inflamed with an ongoing, low-grade inflammation, the damage sustained mat cause me to get sluggish in producing enzymes and hormones leading to the pancreatic insufficiency described above and diabetes.

“If a significant number of cells that produce digestive enzymes are destroyed, a lack of proper food digestion may follow. This is known as exocrine pancreatic insufficiency (EPI). If a significant number of cells that produce insulin are destroyed, diabetes mellitus can result.” ~Dr. Ernest Ward

As seen, I carry out several tasks that help your dog stay healthy and in good shape, so don’t take me for granted! I hope this article has helped you understand me better! Best regards,

Your Dog’s PancreasDog Pawprint

References:

  • VCA Animal Hospital, What is Pancreatitis? retrieved from the web on April 4th, 2016
  • Pet Education, Pancreas: Anatomy & Digestive & Endocrine Functions in the Dog, by Dr. Race Foster, retrieved from the web on April 4th, 2016
  • Pet Education, Exocrine Pancreatic Insufficiency (Maldigestion Disorder) in Dogs, by Dr. Race Foster,  retrieved from the web on April 4th, 2016
  • The Whole Dog Journal, Canine Pancreatitis, by Mary Straus, retrieved from the web on April 4th, 2016

Photo credits:

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