At first glance the digestive system appears to have a very simple task of taking in food, digesting it, absorbing nutrients and then excreting the waste, and while everything is in good working order, we never even give it a second thought.
It is in fact an incredibly complex structure with a vast number of tasks to undertake. The more the gut is studied the more we realise the vital role it plays in achieving optimum health, disease prevention and stabilising our dogs emotional state.
Digestive process
Although the teeth are needed to some extent to bite, crush and tear off food the actual process of digestion doesn`t really start until it reaches the stomach. With no digestive enzymes in the saliva to kick start it off, food needs to quickly get where the real work begins, which is in the stomach.
Oesophagus:
Is a long muscular tube that runs down the neck, passes through the diaphragm and uses strong contractions to push food directly into the stomach.
Stomach:
The stomach lies at the front of the abdominal cavity, tucked just behind the liver and acts like a big mixing bowl.
Any incoming food is first subjected to an acid bath of around ph1, this immediately gets to work breaking down protein and also killing any harmful bacteria.
The walls of the stomach are lined with a thick mucous which provides protection from the strong acid as well as stopping the stomach from literally digesting itself.
As the stomach expands with food, a peptide hormone called gastrin is released, which in turn triggers more hydrochloric acid and digestive enzyme production.
To aid digestion even further the surface of the stomach is a mass of wrinkles and folds which expand and contract to grab food particles and perform a churning or chewing like action.
At this point the thick soup like constancy of partly digested food and secretions is known as chyme.
The food has now been in the dogs stomach for anywhere between five and ten hours and its next destination is the duodenum, the first section of the small intestine.
Pancreas
The pancreas is a small gland, which sits next to the stomach and is attached to the small intestine, here it transports digestive enzymes through two excretory ducts into the duodenum.
The enzymes it produces are amylase to help digest starch , lipase to digest fats and trypsin and chymotrypsin to deal with the protein.
Enzymes are needed to break down food into tiny molecules and allow the absorption of nutrients into the cells of the intestines which then go on to be released into the bloodstream.
It also produces and secretes the hormones insulin and glucagon that regulate blood sugar levels. The higher the concentration of sugar in the diet the more insulin is secreted into the bloodstream and the harder the pancreas has to work.
Liver
The liver is the largest gland in the body and the only organ that has the potential to regenerate after disease or injury.
Its many crucial jobs include producing bile to assist the small intestine in breaking down and absorbing fats and to process the nutrients that are absorbed by the small intestine.
Its other roles include storing vitamins and minerals, acting as a filter for toxins in the bloodstream and as a glycogen store for when extra energy is needed.
Small intestine
The small intestine is made up of three sections, Duodenum, Jejunum (longest) and the ileum (shortest)
On receiving the nutrient rich chyme from the stomach, it is joined by secretions from the liver, gallbladder and pancreas to further assist in the digestion process.
The small intestine is lined with millions of tiny finger like projections called the Villi, these act to increase the surface area in order to trap and absorb as many nutrients as possible.
Most of the absorption of nutrients takes place in the small intestine, which are then released into the bloodstream to travel throughout the body to be utilised by the cells.
The final and shortest part of the small intestine is called the Ileum, here the food gets broken down even further in preparation to enter the cecum, the first section of the large intestine.
Large intestine :
The large intestine is made up of the cecum, colon and rectum.
Its purpose is to remove water from the faeces, keep electrolytes in balance and to prepare and temporarily store any indigestible matter for excretion.
But there is much more activity going on in the colon than just that and although not a glamorous area of interest, it does deserve our full care and attention.
The large intestine has a high concentration of bacteria referred to as the Microbiome.
Microbiome.
The microbiome is a collection of microbes made up of bacteria, viruses and fungi that we all have in our gut for efficient digestion, absorption of vital nutrients and to build a strong immune system.
Our dogs would have acquired their unique bugs from their mother at birth and developed others depending on the environment they lived in and the food they ate.
The delicate balance of the microbiome can easily be disrupted by medication such as antibiotics, periods of stress and anxiety and a poor, unsuitable diet.
When everything is in balance these good bugs work hard to extract as much nutrition as possible out of the food that is consumed and to ensure the smooth running of the whole gastrointestinal tract.
The bacteria are also responsible for assisting in hormone production such as serotonin, which occurs in the highest concentration thorough out the lining of the gut.
A thriving, balanced microbiome is absolutely essential for the dogs ability to resist or fight disease, control inflammation in the body and for a positive influence on their mental wellbeing.
Rectum and anal glands.
The faeces are then ready to be expelled along with the indigestible matter and dead red blood cells that it contains.
Ideally the dogs stool will be quite firm, which will press on the anal glands as it is passed, causing the glands to naturally empty.
Emotions and the Gut
The gut is very sensitive to emotions, and I am sure we have all experienced the butterflies in the stomach, stomach cramps, that tight feeling in our guts or acid indigestion which can come on in a split second when we are nervous, excited, fearful or anticipating a particular event.
If this is a brief episode, it is unlikely to have any lasting health effects, if on the other hand it is a regular occurrence with little respite then the impact on the gut and therefore the health is huge.
There is a major factor in the link between gut health and emotions in the form of the enteric nervous system also referred to as the ENS.
The ENS consists of millions of nerves lining the gut and specialists often call it the “second brain” as it has complex pathways to relay information back and forth from the gut to the brain as they interact.
It is capable of shutting down the digestion in times of acute stress such as in a fight or flight situation.
Stress can be caused by many factors such as separation anxiety, excessive ball throwing so the dog is on a constant adrenaline high, inappropriate exercise for the dogs age or mobility, inability to cope in a stressful household and pain, illness or disease.
Whilst these are mainly emotionally based reactions that can be witnessed as the dog exhibiting certain behaviours, a poor quality, inappropriate diet, exposure to toxins or chemicals can also cause the body stress, which may not show any visible signs immediately but develop over time into disease or outwardly noticeable changes in health and behaviour.
A gut that isn`t functioning correctly can manifest as the dog showing anxious, edgy or reactive behaviour which in turn triggers the release of stress hormones into the blood stream such as adrenalin and in the case of cortisol increase the level of glucose in the blood and will over time adversely affect the adrenal glands.
Immunity and the Gut
The gut forms between 70 - 80% of the immune system and has a vital role in regulating immunity, protecting our bodies from invaders such as allergens and pathogens and controlling inflammation.
The food we choose for our dogs and the lifestyle choices we make for them will have either a negative or positive effect on their overall gut health, ability to utilise the nutrients in the food they eat, the essential fuel to grow and repair their body and to thrive well into their senior years.
Caroline Hearn MICHT. Dip. ICAT MIAAT- Canine & Equine sports & holistic therapist