The Digestive System

Digestive Organ Function Digestive Organ Function Digest Food Absorb Food Absorb Water Chemicals Present (inc. enzymes) Mouth Pharynx / Esophagus Stomach Liver Gall Bladder Pancreas Small Intestine Large Intestine Rectum Anus Digestive Organ Function Digest Food Absorb Food Absorb Water Chemicals Produced (inc. enzymes) Mouth Pharynx / Esophagus Stomach Liver Gall Bladder Pancreas Small Intestine Large Intestine Rectum Anus

MOUTH The mouth is the beginning of the digestive system, and, in fact, digestion starts here before you even take the first bite of a meal. The smell of food triggers the salivary glands in your mouth to secrete saliva (contains the ENZYME AMYLASE), causing your mouth to water. When you actually taste the food, saliva increases. Once you start chewing and breaking the food down into pieces small enough to be digested other mechanisms come into play. More saliva is produced to begin the process of chemically breaking down food.

PHARYNX & ESOPHAGUS Also called the throat, the pharynx is the portion of the digestive tract that receives the food from your mouth. Branching off the pharynx is the esophagus, which carries food to the stomach. The act of swallowing takes place in the pharynx. The food then enters the esophagus. The esophagus is a muscular tube. Food is pushed through the esophagus and into the stomach by means of a series of contractions called peristalsis.

STOMACH The stomach is a hollow organ, or "container," that holds food while it is being mixed with enzymes that continue the process of breaking down food into a usable form. Cells in the lining of the stomach secrete a strong acid and protease enzymes that are responsible for the breakdown process. When the contents of the stomach are sufficiently processed and have changed to the consistency of liquid or paste, they are released into the small intestine.

LIVER The liver has multiple functions, but its main function within the digestive system is to process the blood containing the nutrients absorbed from the small intestine. Bile made in the liver and secreted into the small intestine also plays an important role in digesting fat. In addition, the liver is the body’s chemical "factory." It takes the raw materials absorbed by the intestine and makes all the various chemicals the body needs to function. The liver also detoxifies potentially harmful chemicals found in the blood.

GALL BLADDER The gallbladder is a storage sac for excess bile. Bile made in the liver travels to the small intestine via the bile ducts. If the small intestine doesn't need it, the bile travels into the gallbladder where it awaits the signal from the intestines that food is present. Bile serves two main purposes: First, it helps absorb fats in the diet. Secondly, it carries waste from the liver that cannot go through the kidneys.

PANCREAS Among other functions, the pancreas is the chief factory for digestive enzymes. These are secreted into the first segment of the small intestine. These enzymes break down protein, fats, and carbohydrates. The pancreas also makes insulin, secreting it directly into the bloodstream. Insulin is the chief hormone for metabolizing sugar. Carbohydrate enzyme – carbohydrase Fat enzyme – lipase Protein enzyme - protease

SMALL INTESTINE The small intestine is a 22-foot long muscular tube (split into 3 sections) that breaks down food using enzymes released by the pancreas and bile from the liver. Peristalsis is also at work here, moving food through and mixing it with digestive secretions from the pancreas and liver. The first part is largely responsible for the continuous breaking-down process, with second and third part mainly responsible for the absorption of nutrients into the bloodstream. Contents of the small intestine start out semi-solid, and end in a liquid form after passing through the organ. Water, bile, enzymes, and mucous contribute to the change in consistency. Once the nutrients have been absorbed and the leftover-food residue liquid has passed through the small intestine, it then moves on to the large intestine.

LARGE INTESTINE The large intestine is a 6-foot long muscular tube that connects the small intestine to the rectum. The large intestine is a highly specialised organ that is responsible for processing waste so that emptying the bowels is easy and convenient. Stool, or waste left over from the digestive process, is passed through the colon by means of peristalsis, first in a liquid state and then ultimately in a solid form. As stool passes through the large intestine, water is removed. It normally takes about 36 hours for stool to get through the large intestine. The stool itself is mostly food debris and bacteria. These bacteria perform several useful functions, such as synthesizing various vitamins, processing waste products and food particles, and protecting against harmful bacteria. When the last section of the large intestine becomes full of stool, or faeces, it empties its contents into the rectum to begin the process of elimination.

RECTUM The rectum is an eight-inch chamber that connects the colon to the anus. The rectum: Receives stool from the large intestine. Lets the person know there is a stool to be evacuated. Holds the stool until evacuation happens. When anything (gas or stool) comes into the rectum, sensors send a message to the brain. The brain then decides if the rectal contents can be released or not. If they can, the sphincters relax and the rectum contracts, expelling its contents. If the contents cannot be expelled, the sphincters contract and the rectum accommodates so that the sensation temporarily goes away.

ANUS The anus is the last part of the digestive tract. It is a 2-inch long canal consisting of the pelvic floor muscles and the two anal sphincters (internal and external). It consists of the muscles that line the pelvis (pelvic floor muscles) and two other muscles called anal sphincters (internal and external).

Three different enzymes break down the three main food groups: Amylase Carbohydrates  Sugars Produced in: Salivary Glands / Pancreas /Small Intestine Protease Proteins  Amino Acids Stomach / Pancreas / Small Intestine Lipase Fats  Fatty Acids + Glycerol Pancreas / Small Intestine

Digestive System Election Prepare a 1 minute persuasive talk. What does your organ do? Why does that make it the most important organ? Could the body cope without it? Purpose in the digestive system Reason why it is the most important