Digestion-Where does it begin

ORIGINAL: kennel_keeper

Mastication (the act of chewing, biting, or crunching food bits) IS a integral part of digestion.

Papillion made an excellent point in that digestion and absorbtion are two different things. Absorbtion of nutrients occurs (for the most part) in the small intestine, but digestion occurs all along the digestive tract, which INCLUDES the mouth and continues to the anus.

Also, dogs DO salivate, which helps to begin the digestion process by moistening the food bits for swallowing. It is really irrelevant if the saliva contains amylase or not, digestion DOES start in the mouth.

Of course since dogs don't chew....

Paula

Why start a thread asking what others think if you're already sure of what you think

 
It's not what she thinks, it's what she knows and it's for educational purposes. Just like Anne offers her tidbits and knowledge in the training section, KK offers the what she has learned from caring for wild animals and studying nutrition, both practically and from her studies at the university. It's okay to have opinions, it's better to have opinions based on scientific fact and logic.
 
It looks like we're splitting a hair. If a person wants to say that digestion starts with the presence of amylase, they can say that, though getting the food does start with it entering the mouth. From what I have seen, both dogs and humans can process a starch, though for a human, it may start in the mouth with amylase. We could get even more technical and say ain't nuthin's absorbed 'til the nitrogen is released.
 
Now, if dogs get amylase from the pancreas and can process starch, doesn't that make them functional omnivores, though may choose to eat meat at one time and non-meat at another time?

dogs don't chew....

 
My dog does, as best as he can. He doesn't have as much lateral mastication as a cow but he will crunch and grind kibble before he swallows.
 
Someone else also mentioned the difference in the coronoid process involving the zygomatic arch and the hinge of the mandible. This makes a difference in how the massiter muscle group can attach and how much hinge "play" is possible.

If I were to apply the criteria that simply by breaking the food up into smaller pieces in the mouth, regardless of the presence of digestive enzymes, digestion is begun, then by simply cutting up raw meat in a bowl with a little water I am witnessing digestion?

Let's start with the definition of digestion.  According to Meriam Webster On line dictionary,
"the process of making food absorbable by dissolving it and breaking it down into simpler chemical compounds..."

Therefore, by this definition, simply adding moisture to smaller pieces of food is NOT digestion since it does not reduce the food into 'simpler chemical compound'. Saliva with no amylase just makes the food slippery and smaller, it does not simplify its chemical make up.

So NO. In dogs, digestion does not begin in the mouth.

Paula

My dog chews pretty much also. She does not need to chew her kibble to get it down  because it is small and she has a big mouth,, but she does chew it.
 
And I sure HOPE that all that slobber that comes from her mouth is there for some purpose!! LOL! She salivates when she smells things that smell good to her...just like a human except she drools and slobbers from it. Are you saying that there no purpose for saliva in dogs as there is in humans?

ORIGINAL: dyan

My dog chews pretty much also. She does not need to chew her kibble to get it down  because it is small and she has a big mouth,, but she does chew it.

And I sure HOPE that all that slobber that comes from her mouth is there for some purpose!! LOL! She salivates when she smells things that smell good to her...just like a human except she drools and slobbers from it. Are you saying that there no purpose for saliva in dogs as there is in humans?

Saliva is also a lubricant right, and a vehicle . Just that in dogs it does not have salivary amylase. So it's not useless by any means. Oh and I think it has some anti-microbial properties. That would make sense considering what they eat.

Paula

Saliva is also a lubricant right, and a vehicle

 
You got THAT right!  Did you ever slide across the floor on dog slobber?  No kidding,,,one of us is going to kill ourselves in our kitchen with Bubblegum around.  LOL!

ORIGINAL: dyan

Saliva is also a lubricant right, and a vehicle

You got THAT right!  Did you ever slide across the floor on dog slobber?  No kidding,,,one of us is going to kill ourselves in our kitchen with Bubblegum around.  LOL!

 
 
[]

Let's start with the definition of digestion. According to Meriam Webster On line dictionary,
"the process of making food absorbable by dissolving it and breaking it down into simpler chemical compounds

So, salivating and chewing doesn't help that? Nor would I think preparing the meat is part of digestion. What's in a dog's saliva? I'm sure it's not just water.

Since dogs do produce amylase and can digest starch, I would think that shows an omnivorous capabillity. But it was suggested that dogs not having salivary amylase was a sign of being carni. Looks like a dichotomy to me.

[linkhttp://www.bio.davidson.edu/Courses/anphys/2000/Hatfield/Hatfield2.htm#digestion]http://www.bio.davidson.edu/Courses/anphys/2000/Hatfield/Hatfield2.htm#digestion[/link]
 
[linkhttp://www.seefido.com/html/the_digestive_system.htm]http://www.seefido.com/html/the_digestive_system.htm[/link]
 
[linkhttp://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/20100.htm&word=digestive%2ctract]http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/20100.htm&word=digestive%2ctract[/link]
 
Here's Wiki's spin on digestion.
[linkhttp://en.wikipedia.org/wiki/Digestion]http://en.wikipedia.org/wiki/Digestion[/link]

Overview
Digestion occurs at the multicellular, cellular, and sub-cellular levels, usually in animals. This process takes place in the digestive system, gastrointestinal tract, or alimentary canal.
Digestion is usually divided into mechanical manipulation and chemical action. In most vertebrates, digestion is a multi-stage process in the digestive system, following ingestion of the raw materials, most often other organisms. The process of ingestion usually involves some type of mechanical manipulation. Digestion is separated into five separate processes: 1) Ingestion: Placing food into the mouth, 2) Mechanical digestion: Mastication, the use of teeth to tear and crush food, and churning of the stomach. 3) Chemical digestion: Addition of chemicals (acid, bile, enzymes, and water) to break down complex molecules into simple structures, 4) Absorption: Movement of nutrients from the digestive system to the circulatory and lymphatic capillaries through [linkhttp://en.wikipedia.org/wiki/Osmosis]osmosis[/link], [linkhttp://en.wikipedia.org/wiki/Active_transport]active transport[/link], and [linkhttp://en.wikipedia.org/wiki/Diffusion]diffusion[/link], 5) Elimination: Removal of undigested materials from the digestive tract through [linkhttp://en.wikipedia.org/wiki/Defecation]defecation[/link]. Underlying the process is muscle movement throughout the system, [linkhttp://en.wikipedia.org/wiki/Deglutition]deglutition[/link] and [linkhttp://en.wikipedia.org/wiki/Peristalsis]peristalsis[/link].

 
 

Are you saying dogs have no salivary amylase?  In highschool a while back for AP biology we did an experiment where we tested human, dog and horse saliva for salivary amylase and they all came back positive.  Course we could've totally messed it up as we weren't very trained as scientists.  I guess I should've flunked that assignment!  Lol

ORIGINAL: kennel_keeper

[linkhttp://www.bio.davidson.edu/Courses/anphys/2000/Hatfield/Hatfield2.htm#digestion]http://www.bio.davidson.edu/Courses/anphys/2000/Hatfield/Hatfield2.htm#digestion[/link]

[linkhttp://www.seefido.com/html/the_digestive_system.htm]http://www.seefido.com/html/the_digestive_system.htm[/link]

[linkhttp://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/20100.htm&word=digestive%2ctract]http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/20100.htm&word=digestive%2ctract[/link]

Here's Wiki's spin on digestion.
[linkhttp://en.wikipedia.org/wiki/Digestion]http://en.wikipedia.org/wiki/Digestion[/link]

Overview
Digestion occurs at the multicellular, cellular, and sub-cellular levels, usually in animals. This process takes place in the digestive system, gastrointestinal tract, or alimentary canal.
Digestion is usually divided into mechanical manipulation and chemical action. In most vertebrates, digestion is a multi-stage process in the digestive system, following ingestion of the raw materials, most often other organisms. The process of ingestion usually involves some type of mechanical manipulation. Digestion is separated into five separate processes: 1) Ingestion: Placing food into the mouth, 2) Mechanical digestion: Mastication, the use of teeth to tear and crush food, and churning of the stomach. 3) Chemical digestion: Addition of chemicals (acid, bile, enzymes, and water) to break down complex molecules into simple structures, 4) Absorption: Movement of nutrients from the digestive system to the circulatory and lymphatic capillaries through [linkhttp://en.wikipedia.org/wiki/Osmosis]osmosis[/link], [linkhttp://en.wikipedia.org/wiki/Active_transport]active transport[/link], and [linkhttp://en.wikipedia.org/wiki/Diffusion]diffusion[/link], 5) Elimination: Removal of undigested materials from the digestive tract through [linkhttp://en.wikipedia.org/wiki/Defecation]defecation[/link]. Underlying the process is muscle movement throughout the system, [linkhttp://en.wikipedia.org/wiki/Deglutition]deglutition[/link] and [linkhttp://en.wikipedia.org/wiki/Peristalsis]peristalsis[/link].

Well now we're playing word games. Is it digestion? According to MWebster no. According to Wiki yes.  So  both are right with regards to their own definition. If the OP asked the question within the criteria of his/her own definition the answer would be clearer.

Just re-read the OP;
"Mechanical and enzymatic activity start the process and it continues throughout the alimentary canal. It ends when waste is voided."

More questions than answers I guess because in the dogs - they really don't masticate (chew) like humans do so the first question is; when does bolting become mastication? Secondly, no "enzymatic activity" occurs in the dog's mouth since there is no salivary amylase. 




BTW you shouldn't cite wikipedia as a reference since wiki files are modifiable by any user.  Just thought I'd throw that in there. In one of my classes I've been doing peer reviews and have had to bring that up.

Paula

Well now we're playing word games

So it would seem. Your source is a dictionary, KK's sources involve a vetrinary manual and other articles specifically related. As for citing wikipedia, others source it as if it were the only source and definition to adhere to. But it is not. As you are trying to point out. Yet, I can catch some grief if I point out that wikipedia is not the sum total of knowledge and may not be as accurate as a specific textbook or academic source. Wikipedia is a good source from which to get a general quick idea of something but often, it is not always the complete, final, accurate answer. 

If a vet source points out that mastication is part of the total digestion process, why is that now just word splitting? Someone offered a rebuttal with scientific sources to support enzymatic action was on part of a larger system, all iinclusive of digestion

BTW you shouldn't cite wikipedia as a reference since wiki files are modifiable by any user. Just thought I'd throw that in there. In one of my classes I've been doing peer reviews and have had to bring that up.

As you will notice, Paula, I did use 2 scientific sources PRIOR to Wiki's "spin". I do not hold wiki's definition as 100% credible since I've had to do MANY scholarly presentations and papers and any sources other than science-based ones are not acceptable. In a peer-review, would you accept [linkhttp://www.wonderquest.com/DogSaliva.htm]http://www.wonderquest.com/DogSaliva.htm[/link] as a credible source?
as

As for "chewing", of course dogs don't chew as humans do. They are dogs, but DO use their own form of mastication. Crunching, crushing, biting, whatever you want to call it. "Bolting" (according to your source), is a form of masication. Breaking up food into a managable size in order to swallow it is (in effect) part of the digestion process. It's one of the mechanical processes, as are the muscles of the stomach causing the churning action. Taking food into the mouth (prehension), chewing, crunching, crushing it, to facilitate  "in-gestion" (swallowing) are part of the digestion process.
I have 13 dogs personally, then figure in all the dogs I work with every day (40 or more), they ALL crunch (or chew) their food. If they didn't use some form of mastication, how would RMB clean their teeth????? Or, why offer rec. bones for "chewing"?  

  Secondly, no "enzymatic activity" occurs in the dog's mouth since there is no salivary amylase. 

Again, regardless of the presence of amylase or not, the mechanical process (mastication) is a part of the process of digestion.

OMG!

You asked a question you got answers. Everyone didn't agree. Okay then. Is this really that important? It's not like you were asking proposals to achieve peace in the Middle East.

You say yes digestion in dogs begins in the mouth. I say no digestion in dogs doesn't begin in the mouth.

Now what?

Paula