Physiology

Physiology sounds like a textbook term – but it is simply the question: How does my dog actually work? What keeps his heart beating, why does he get sluggish after eating, and why does he pant so strangely when it’s hot? Anyone who understands this roughly will notice sooner if something goes off track.

For dog owners, this basic knowledge is no luxury. A dog that suddenly breathes heavily, even though he was just relaxing on the sofa – that is not a coincidence. That is a signal. And anyone who can contextualise it will act earlier.

Which body systems keep my dog alive?

Seven main systems keep your dog running. Each has its own task – and unfortunately also its typical weak points, which you should know about.

Cardiovascular System: The Pump of Life

A dog’s heart pumps around 7,000 litres of blood through the body daily. Large dog, slower pulse: 60–100 beats per minute. Small dog, faster: up to 160. This is normal – and yet always surprising when you measure it for the first time.

Pale gums, shortness of breath after a few steps or a dog that simply stops in the middle of a walk and doesn’t want to go on – these are not whims. They can be signs of a weakening heart.

Respiratory System: Oxygen In, Toxins Out

Dogs breathe differently than we do. They cool themselves mainly by panting – and can smell through their nose at the same time. This parallel system is quite clever. At rest, 10–30 breaths per minute are normal.

Does your dog breathe more than 40 times a minute without having run beforehand? Then it belongs at the vet, not in the waiting room for tomorrow.

Digestive System: More Than Just Chopping Up Food

A dog’s stomach holds up to 4 litres – proportionally more than ours. The liver produces around half a litre of bile daily, just to digest fats properly. An impressive effort for what some dogs swallow in three seconds.

Yellow eyes or yellow gums point to the liver. A bloated belly shortly after eating can indicate gastric torsion – a real emergency. And faeces that are absent for more than two days are also not worth waiting out harmlessly.

Kidneys: The Filter Plants

The kidneys filter the dog’s entire blood volume about 40 times a day. They regulate not only how much water remains in the body, but also blood pressure and mineral balance.

A dog that suddenly drinks significantly more than usual, or whose urine smells strongly – this can be an early sign of declining kidney function. Can. Not must. But it is worth taking a closer look.

Nervous System: Central Control

A dog’s brain makes up only 1–2 % of its body weight, but consumes 20 % of total energy. The spinal cord transmits signals at up to 120 metres per second – faster than any reaction we can consciously control.

Does your dog suddenly hold his head tilted? Does he walk uncoordinatedly or seem disoriented? Neurological deficits sometimes show subtly – and then very suddenly clearly.

Musculoskeletal System: Bones, Muscles, Joints

Depending on the breed, a dog has 319 to 321 bones – we humans come in at 206. The spine is aligned horizontally, which means entirely different load profiles than for us upright bipeds. This also explains why herniated discs are so common in some breeds.

Stiffness after getting up, a changed gait or a dog that suddenly avoids the stairs – these are not signs of old age that you just have to accept. Often there is more to it.

Immune System: The Body’s Own Army

Around 60 % of a dog’s immune cells are located in the gut. Anyone who knows this understands why persistent diarrhoea strains the entire system – and why dogs are more susceptible to further infections during such phases.

Which values are normal for my dog?

In Switzerland, these reference values help you assess changes – not to self-diagnose, but so you can tell the vet specifically: “This is different from usual.”

Body temperature: 37.5–39.2 °C (measured rectally). Puppies are often about 0.5 °C higher.

Heart rate: Large dogs 60–100 beats/minute, small dogs 100–160 beats/minute.

Breathing rate: 10–30 breaths/minute at rest. Significantly more in heat or stress – that is normal.

Blood pressure: 110–160 mmHg (systolic). Usually only measured at the practice.

Blood sugar: 75–120 mg/dl. Have it determined by the vet if diabetes is suspected.

When does physiology show that something is wrong?

Changed body values are often the very first signs of illness – long before a dog looks visibly sick. A good vet can read from a blood test which organ system is under pressure, even before the dog itself shows signs.

A concrete example: Elevated kidney enzymes in the blood can indicate kidney damage before the dog even starts drinking more. A changed heart rate can point to a heart problem before shortness of breath occurs.

You don’t need to be a vet to benefit from this knowledge. But anyone who knows the basics of physiology notices changes earlier – and can describe much more precisely at the next vet visit what has changed. This is not replacing professional expertise. It is a sensible start.