Where do you think digestion begins? The mouth or where?
Actually digestion begins in the brain. The sight and smell of food activates the salivary glands to start producing saliva.
The cranial nerve (#10) – the vagel nerve communicates to the stomach to start producing HCL and to the pancreas to start producing insulin and get ready to produce enzymes. It tells the gallbladder contact when it needs to contract and to start releasing bile. It tells the small intestine to start producing hormones for digestion.
The paras
ympathetic response allows us to start salivating. In the mouth- as we release salivary amylase to help break down the carbohydrates. If we don’t start to breakdown the starch into smaller parts in the mouth then the digestion will be impacted later on in the digestion process. Remember the parasympathetic nervous system is the “rest and digest” nervous system … so we need to be “resting” while we are eating in order to “digest” our foods properly or else a chain of events will occur. The teeth breakdown the food- mechanical processes begin but we need to actually chew our food to allow for proper digestion or breakdown of the carbohydrates in the mouth (chew 20-30 times per bite!)
The stomach- minimal carbohydrate digestions. Salivary amylase is completed by the time the food or bolus reaches the stomach. Carbohydrates are exposed to the acid in the stomach but digestion doesn’t begin as much until move down south into the small intestine. Once the stomach has food (bolus) arriving, the hormone Gastrin is released in the stomach to stimulate the gastric glands to release pepsinogen (inactive form of pepsin) and hydrochloric acid (HCL) to breakdown protein. The digestion of carbohydrates starts in the mouth and then finishes in the small intestines- not the stomach.
When the bolus becomes chyme in the stomach then the food (now chyme) moves into the start of the small intestine- the duodenum where lots of digestion steps occur.
- In the small intestine the hormones Secretin and CCK ( cholecytokinin) are released in small amounts.
- The pancreas will receive a message from the hormone CCK from the first part of the small intestine- the duodenum- to stimulate the release of digestive enzymes.
- Also CCK will stimulate emptying the bile (required for fat digestion) from the gallbladder (storage unit for bile made in the liver).
- The hormone Secretin is released in the duodenum as well to signal the secretion of sodium bicarbonate from the pancreas to raise the Ph levels in the small intestine (stomach is highly acidic in order to breakdown food- bolus- into chyme and more processes!).
- The release of Secretin in the small intestine-duodenum- also stimulate the digestion of fat by secreting bile in the gallbladder to the liver into the duodenum.
When the chyme goes into the beginning of the small intestine (duodenum) pancreatic amylase is released to digest the carbohydrates (polysaccrides into disaccarides into monosaccrides). Brush border enzymes are released from the lining and complete the breakdown of the disaccraches into forms of glucose. (Enzymes as: fructase- fructose, Maltase- maltose, lactase-lactose). The remains from the carbohydrate digestion, after the nutrients were absorbed into the bloodstream in the small intestine, gets passed into the large intestine into the feces. Water and nutrients will be absorbed
“Any remaining sugars are acted upon by brush border enzymes. Brush border enzymes are special enzymes found on the microvilli of the small intestine that complete digestion. We previously learned that microvilli are tiny, hair-like projections that increase the surface area of the small intestine and therefore increase nutrient absorption. Because there are so many microvilli, the epithelial cells appear to be fuzzy, like the bristles of a paint brush, leading some anatomists to refer to them as the brush border, hence the name.
Absorption “Now that all the carbohydrate molecules have been hydrolyzed into their simplest monosaccharide form, they can be absorbed out of the digestive tract and into your bloodstream. The digested sugars pass into the microvilli of the epithelial cells and then enter the capillaries found in the wall of the small intestine. The absorbed substances are now in the bloodstream, and with the exception of a quick detour to the liver, they are ready to be transported to your body cells.”
-http://study.com/academy/lesson/carbohydrate-digestion-and-absorption-process-end-products.html#transcriptHeader
-Boundless. “Hormones of the Digestive System.” Boundless Anatomy and Physiology Boundless, 07 Nov. 2016. Retrieved 08 Dec. 2016 from https://www.boundless.com/physiology/textbooks/boundless-anatomy-and-physiology-textbook/digestive-system-23/phases-of-digestion-226/hormones-of-the-digestive-system-1110-6772/
-www.nutritionaltherapyassociation.com
