SBI3U_Mod8 by Hadjer Mallem

RandomPerson — 2013-11-01 23:58:10 UTC

Introduction to the Digestive System

RandomPerson — 2013-11-02 00:00:25 UTC

The digestive system is by far one of the most important organ systems in the human body. It is responsible for providing necessary nutrients to the body and releases wastes and unused nutrients out of the body so that all the other systems function properly. That's without saying that the digestive systems relies on other organs systems to function efficiently. For the mere purpose of this assignment imagine that you are on a piece of food about to start it's journey through some random person's body....

The Mouth

RandomPerson — 2013-11-02 00:26:03 UTC

As we all now, consuming food starts at the mouth. The piece of food is broken down by mechanical digestion, or in other words through using teeth to physically breakdown the food through chewing. Saliva amylase helps moistens and break down the complex carbohydrates in the food and turn it into a bolus, primarily with aid from the tongue. Bolus is a fancy Greek word for ball, because of it's round shape that can hardly be recognized as the same food the person had in the beginning. Saliva forms a coating around the bolus so that it can be easily swallowed to the esophagus and activates the taste buds. The tongue is responsible for providing an even balance of mechanical digestion by the teeth, provides pleasant and at times terrible tastes of the food to the person and assists in pushing the food back to be further digested.

The Esopagus

RandomPerson — 2013-11-02 01:35:11 UTC

After the Food is swallowed, it enters the esophagus, a muscular tube that uses peristalsis or muscular contractions to transport food from the mouth to the stomach. The fluid or food will go down involuntarily due to the muscle contractions as apposed to the voluntary mechanical movement of swallowing and chewing. The movement through the esophagus happens in any position. The bottom rings of muscles have to be considerably strong, the muscles in the esophagus weakens a regurgitating of food and acid will travel back through the esophagus (this is also known as heartburn and can be extremly unconfortable).

The Stomach

RandomPerson — 2013-11-02 01:35:46 UTC

Interesting Videos on Peristalsis

RandomPerson — 2013-11-02 02:08:02 UTC

http://www.youtube.com/watch?v=uux1hkoPi4A
http://www.youtube.com/watch?v=HWUjHfKeFSk
http://www.youtube.com/watch?v=fryok536LpA

Fun Facts about Digestion!

RandomPerson — 2013-11-02 02:19:03 UTC

It takes approximately 20 h to several days for food to be digested in your body.

Your digestive tract is approximately 6.5 to 9 metres long.

Peristalsis can happen even when you're upside down
The stomach can expand to store 1.5 Litres of food
PH levels in the amounts are fairly neutral in the esophagus and then goes down to 2-3 and sometimes even 1 in the stomach.
Most digestion occurs in the duodenum
The small intestine is 7 metres long and relatively small in diameter, that's way taller that an an average human being!
.

Teeth and Salivary Glands Diagram

RandomPerson — 2013-11-02 21:57:23 UTC

Path From the Esophagus to the Stomach

RandomPerson — 2013-11-02 22:01:04 UTC

Stomach

RandomPerson — 2013-11-02 22:58:53 UTC

In order for the food to enter the stomach it must pass by the cardiac sphincter, which is like a circular drawstring shaped muscle that opens and contracts. When the cardiac sphincter relaxes food is let into the stomach while contractions prevent the food from entering the stomach. Once the food passes the cardiac sphincter it enters the J shaped stomach, whose superior ability to digest protein, store and breakdown food relies solely on its structure. It has numerous ridges that is able to expand to allow maximum food storage and digestion. The exterior of the stomach is covered by epithelial tissues, followed with three layers of smooth muscles that cross at different angles; this allows for more efficient food digestion, the synchronization of the muscle movement throughout the system is controlled by nerve cells. The inner most layer mucosa contains millions of cells that produce gastric juices. Gastric juices are made up of hydrochloric acid, pepsinogen and mucous. A digestive hormone (gastrin) released by the stomach to control the amount of gastric juices in the stomach. The hydrochloric acid (HCl) kills harmful substances (pathogens) that enter the stomach and aid in the process of turning pepsinogen into pepsin. The function of pepsin is to breakdown long chains of amino acids which make up proteins, into smaller chains of amino acids. Alkaline mucous provides a protective layer surrounding the interior of the stomach so that it isn't digested by the powerful chemicals with low PH levels ranging from 2 to 3. The layer of mucous also serves as a protection for the protein in the stomach from being broken down by the pepsin. After the food the protein in the food has been digested it must pass through the pyloric sphincter, which regulates the amount of food and gastric juices leaving the stomach.

Small Intestine - Duodenum

RandomPerson — 2013-11-03 01:47:46 UTC

There are three parts to the small intestine the duodenum, where MOST of the digestion takes place, jejunum and ileum (where not so much digestion, but absorption takes place). The food passes through the pyloric sphincter in a fairly acidic state that cannot be supported by the weak structure of the small intestine, for that reason that Pancreas has an important role to play in adjusting the PH levels in the food before it reaches the small intestine. The primary function of the pancreas is to create insulin which regulates the blood sugar in the body, however it does have other purpose linked to the digestive system. When HCl enters the duodenum from the stomach is simulates the prosecretin (an inactive form) into secretin (active form). The secretin is then absorbed and transferred through the blood stream to the pancreas by the blood vessels. Secretin simulates the release of pancreatic fluids. The HCO3 (Bicarbonate ions) that is then produced by pancreas neutralizes the hydrochloric acid coming from the stomach to about 9 on the PH level so that the inner wall of the duodenum is not damaged. Other secretions of the pancreas produce enzymes that promote digestion of the three major components in food, proteins, carbohydrates and lipids. Trypsinogen, a protein digesting enzyme, is also produced by the Pancreas.

Once in the small intestine an enzyme called enterokinase converts the inactive trypsinogen enzyme into trypsin (an active enzyme). The responsibility of trypsin is to breakdown the long chains of polypeptides into shorter-chain peptides from the partially digested protein from the stomach. Finally erepsins (a group of enzymes that are secreted from the small intestine and the pancreas) finish off the protein breakdown by turning the short chained peptides into separate amino acids.

On the other hand amylase enzymes aid in the breakdown in carbohydrates and lipases help in the breakdown of lipids. Amylase enzymes continue breaking down carbohydrates which have partially been broken down by the salivary amylase in the mouth if you recall. They are further broken down disaccharides which by the help of disaccharide enzymes, referred to as disaccharidases, is further broken down.

And you may have guessed that lipids come next... yes you're right! Lipases the enzymes that help digest lipids, there are two types that are responsible for the breakdown of two groups. The Pancreatic lipase breaks down fats into glycerol and fatty acids, while the Phospholipase are responsible for breaking down phospholipids.

... That practically summarizes most of the food breakdown ...Phew!

Liver, Pancreas and Gall bladder

RandomPerson — 2013-11-03 02:09:21 UTC

Parts of the Small Intestine

RandomPerson — 2013-11-03 03:45:28 UTC

Liver and the Gall bladder

RandomPerson — 2013-11-03 20:24:43 UTC

The function of the liver in terms of digestion is to consistently produces bile, but it has many other functions like removing harmful chemicals and toxins from the body as well as glucose into glycogen and vise versa. Bile salts aid in speeding up digestion in the stomach, when there is no digestion taking place in the stomach bile salts are stored in the gall bladder. When fat is being digested in the small intestine, the liver produces cholecystokinin (CCK) instead. the CCK is then transported to the gall bladder Via the blood stream, where it triggers the release of bile salts. The bile salts further breakdown the food by physical digestion because no chemical bonds are broken. This physical digestion helps increase the surfaces at which the fat digesting enzymes are able to function.

Large Intestine

RandomPerson — 2013-11-03 20:48:32 UTC

After the food has finished chemical digestion in the stomach and in the small intestine it heads off to the large intestine or the colon. Most of the absorption already takes place in the stomach where it has been fully digested, but the large intestine does have more absorption to do. The function of the large intestine is to absorb water and nutrients like vitamins, for that reason waste must be stored in the large intestine long enough so that the substances have time to be fully absorbed. E coil a bacteria whose importance is to use waste to synthesize vitamin B and K. Lining the interior of the colon is villi, which are responsible for letting nutrients reach the blood capillaries and lymph vessels so that nutrients is transported throughout the body. Cellulose , long chained chained carbohydrates are unable to be digested by the body, examples include fibre and roughage (such as bran), they do however play an important role in prompting bowel movements within the body. Bowel movements then take over by removing unwanted wastes and toxins from the body. Mucous in the large intestine help the food move towards the rectum. where it will be excreted out of the body.

RandomPerson — 2013-11-03 21:19:44 UTC

Rectum and Anus (AKA the end of the line for the food)

RandomPerson — 2013-11-03 21:20:03 UTC

After the processes of digestion and absorption have been complete, the waste product is stored in the rectum for a period of time until the random person feels like using the... ehm... restroom. It is then that that food is ejected out the anus helped by the mucous of course. Once ejected the system starts all over again when the person puts food into their mouth again... who knew the process of digesting food could be so long and grueling, but our bodies do it every single day. Sometimes even more for other because of the amount of food they eat with the amount of stress that puts on their digestive system.

Resources

RandomPerson — 2013-11-03 21:27:28 UTC

Research sites:

Taylor, Tim . "Digestive System." http://www.innerbody.com. Inner Body. Web. 3 Nov 2013. <http://www.innerbody.com/image/digeov.html>.

NIH Publication, . "Your Digestive System and How It Works." National Digestive Diseases . Clearinghouse , 23 Apr 2012. Web. 3 Nov 2013. <http://digestive.niddk.nih.gov/ddiseases/pubs/yrdd/>.

Enchanted learning, . "Human Digestive System." http://www.enchantedlearning.com. Enchanted learning, n.d. Web. 3 Nov 2013. <http://www.enchantedlearning.com/subjects/anatomy/digestive/>.

Johnson, Kimball. "Your Digestive System." WebMD, 25 Jul 2012. Web. 3 Nov 2013. <http://www.webmd.com/heartburn-gerd/your-digestive-system>.

Mayo clinic staff, . "See how your digestive system works." . Mayo Foundation for Medical Education and Research, 8 March 2011. Web. 3 Nov 2013. <http://www.mayoclinic.com/health/digestive-system/dg00021>.

Images:

N.d. Photograph. n.p. Web. 3 Nov 2013. <https://www.healthbase.com/hb/images/cm/procedures/cancer/large_intestine.jpg>.

N.d. Photograph. n.p. Web. 3 Nov 2013. <http://images.medicinenet.com/images/image_collection/webmd_anatomy/pancreas-anatomy.jpg>.

N.d. Photograph. n.p. Web. 3 Nov 2013. <http://www.healthcentral.com/common/images/1/19221_13626_5.jpg>.

N.d. Photograph. n.p. Web. 3 Nov 2013. <http://stupidstation.s3.amazonaws.com/328/tss_1375279748_1.jpg>.

N.d. Photograph. n.p. Web. 3 Nov 2013. <http://www.uofmmedicalcenter.org/fv/groups/public/documents/images/218479.jpg>.

N.d. Photograph. n.p. Web. 3 Nov 2013. <http://www.cmas.ca/resources/1/cmas%20-%20GIBari%20Logo.jpg>.

N.d. Photograph. n.p. Web. 3 Nov 2013. <http://www.anselm.edu/homepage/jpitocch/genbio/humanteeth.JPG>.