Name ______
Digestive System Research & Maniken Activity
(60 Informal & 10 formal based on 3 randomly selected questions to be graded on correctness and completion of your Body System Organizer and Maniken. All answers must be hand-written in complete sentences on a separate sheet of paper!)
Rubric
Completion à 60 Informal Points
One question from topics #1-4 in Part 1 à 3 Formal Points
One question from #5 in Part 1 à 3 Formal Points
One conclusion question à 3 Formal Points
Completion of Body System Organizer and Maniken Clay Build à 1 Formal Point
Introduction
During his or her lifetime, the average person eats his/her way through at least 20 tons of food. Meats, vegetables or sweets - whatever your diet, that’s 40,000 pounds! Our digestive system works to turn this enormous amount of food into substances that the body can use for energy and for growth and repair. But what actually happens to these foods once they enter our bodies? How does the body process each tasty bite and harness the power locked in the food?
The digestive system works like an assembly line in reverse. Carbohydrates, fats and proteins are progressively broken down into smaller molecules that can be used by the body. This system extracts needed nutrients and gets rid of any unnecessary wastes. Structurally, the digestive system consists of the long tube, the gastrointestinal (GI) tract that serves as the direct pathway for what you eat and excrete. Along the way, various accessory organs help with the mechanical breakdown and the chemical digestion of food. Mechanical digestion involves physically mashing or tearing the bites of food we put in our mouths. We normally think of mechanical digestion occurring in the mouth, but there are other features of your GI tract that also help mash up your food. As what you consume is being smashed, chemical digestion also begins. Enzymes break fats, carbohydrates and proteins into their building blocks so they can be used by the body. Once these molecules are broken down, they can become the raw material for the production of the body’s energy currency, adenosine triphosphate (ATP).
In this activity, you will research the digestive system and build a model of the human digestive system on your Maniken. Each structure and organ along the path has unique properties that make it ideal for its function. For example, the stomach is both muscular to help churn and break apart food, and elastic to expand and contract with the pressure of a big meal. Specific enzymes target macromolecules along the way and the progressive process of digestion makes sure food is broken down and absorbed to create usable energy. After all your research is done, on your own, you will uniquely decide how to build an accurate representation of this system on your Maniken®.
Procedure
Part 1: Research the Digestive System
Research each of the following topics and questions and give as much detail as possible when answering the questions. Write your answers on a separate sheet of paper; all answers must be handwritten. Be sure to use complete sentences.
1. Oral cavity, pharynx, (must also include accessory organs such as salivary glands, tongue, and teeth)
A. What is the oral cavity and what does it contain?
The oral cavity is the first part of the digestive tract. It contains the mouth, teeth, gums, the bony roof (hard/ soft palate), the floor of the mouth (under the tongue), and cheeks (buccal mucosa). The main function is to begin the process of digestion. It receives and chews food, and mixes it with saliva to begin the swallowing process.
Both mechanical (chewing) and chemical (enzymes breaking down food) digestion begins here.
B. What is the function of the salivary glands?
The function of the salivary glands is to produce saliva which begins the breaking down of the food chemically and moistening it to make it easier to swallow. The salivary amylase is responsible for breaking down the carbohydrates. This is why if you put a cracker in your mouth and do not chew or swallow it will become soft and mushy.
C. What is the function of the tongue?
To move food in the mouth, swallowing and chewing. It also contains thousands of taste buds which are nerve-like cells that connects into the brain which transmits taste signals.
D. What is a bolus?
Small rounded mass of chewed food at the moment of swallowing.
E. Where are the soft and hard palate located and what are their functions?
Both palate are located in the roof of the mouth. The hard palate is in the anterior part and the soft palate is at the back part of the mouth. The hard palate holds the roots of the teeth and helps with mastication (vocabulary word for chewing.) When food is swallowed, the soft palate rises up and blocks off the entrance to the rear nasal passage. It also helps pushing the food making it easier to swallow.
F. What mechanical and chemical digestion occurs in the oral cavity?
The chemical digestion occurs when the enzyme in the saliva (amylase) breaks down carbohydrates. While the teeth breaks down the food mechanically through masticating.
G. What mechanisms are in place to make sure food does not “go down the wrong tube” and into the windpipe?
The epiglottis is located behind the tongue to seal off the windpipe during eating so that the food isn't accidentally inhaled and stops it from entering the trachea (prevents choking).
2. Esophagus and Stomach
A. What is peristaltic movement and how does it function in the esophagus?
Constriction and relaxation of muscles in the esophagus, stomach and intestines that occur in wavelike contractions to move food from the mouth to the stomach.
B. Does any digestion of food occur in the esophagus?
Inside the esophagus, there is no digestion, only in the mouth, stomach, and intestines.
C. What are the primary functions of the stomach?
Break down food by churning as well as killing off bacteria.
D. What is chyme and how does the stomach mix this material?
Dense semi-fluid that is composed of partially digested foods and food secretions.
E. What role does the stomach play in decontaminating the incoming food matter?
Low, acidic pH (pH = 2) to kill bacteria.
F. What cells in the stomach function to form enzymes and acids?
Chief cells in the stomach produce the enzyme pepsin, which functions best at a low pH and breaks down proteins.
G. Why doesn’t gastric juice digest the inside of the stomach?
The digestive juices in the stomach consist mainly of hydrochloric acid (HCI), a strongly acidic solution as you saw on the PH Scale. This stuff can dissolve some metals!
The stomach wall is made up mostly of protein, left unprotected the acid would eat right through it. Fortunately for us, the stomach walls have a lining that contains epithelial cells that secrete a protective layer of mucus and bicarbonate.
The mucous is pretty much the same stuff which lines our throat and nose. It sticks to the walls of the stomach to provide a physical barrier so the acid doesn’t touch the stomach itself.
When the cells come into contact with acid, they secrete bicarbonate. Bicarbonate is highly alkaline and very effective at neutralizing acid. This combination of mucous and bicarb is so good at doing its job that when the stomach’s acidity level is high, like PH 2, the stomach lining PH is around 7, or neutral.
H. What are sphincters and how are they related to the stomach?
Sphincters are rings of muscle surrounding and serving to guard or close an opening or tube, such as the anus or the openings of the stomach. The pyloric sphincter allows food to move from the stomach into the beginning part of the small intestine, the duodenum.
I. What mechanical and chemical digestion occurs in the stomach?
The chemical aspect is the breakdown of the food in the stomach with the enzymes such as pepsin. The mechanical aspect is when your stomach is "churning" the food it just digested as it is broken into smaller pieces.
3. Small Intestine and Large Intestine
A. What are the three sections of the small intestine and what role does each section play in digestion or absorption?
-Duodenum, jejunum, and ileum.
-Duodenum first part that connects to the stomach; completes the first phase of digestion where food from the stomach mixes w the enzymes of the pancreas and also the bile of the gallbladder, the enzymes and bile are what help to break down food.
-Jejunum, the middle part, where food goes after it is broken down in the duodenum; nutrients to be absorbed; the walls have circular folds making the surface area large enough to absorb all of the necessary nutrients.
- Ileum; it absorbs bile acids that go back to the liver to be made into more bile and then that is stored in the gallbladder for the duodenum to use.
Made up of three segments — the duodenum, jejunum, and ileum — the small intestine is a 22-foot long muscular tube that breaks down food using enzymes released by the pancreas and bile from the liver. Peristalsis also is at work in this organ, moving food through and mixing it with digestive secretions from the pancreas and liver. The duodenum is largely responsible for the continuous breaking-down process, with the jejunum and ileum mainly responsible for 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, or colon.
B. What is the pH within the small intestine and how is this pH maintained?
The intraluminal pH is rapidly changed from highly acid in the stomach to about pH 6 in the duodenum. The pH gradually increases in the small intestine from pH 6 to about pH 7.4 in the terminal ileum. The pH drops to 5.7 in the caecum, but again gradually increases, reaching pH 6.7 in the rectum.
Sodium bicarbonate maintains PH levels
C. Where do bile and pancreatic enzymes enter the small intestine?
Duodenum
D. How does food move through the intestines?
Peristaltic movement is what forces the food to move through the intestines.
E. What enzymes act inside the small intestine and what are the functions of these enzymes?
F. What is the function of the large intestine in relation to digestion?
The large intestine is the final section of the gastrointestinal tract that performs the vital task of absorbing water and vitamins while converting digested food into feces.
G. What are the three sections of the large intestine and what roles does each play in digestion or absorption?
H. How does the large intestine help maintain a water balance in the body?
Helps maintain a water balance in the body by absorbing water from food back into the body. When water absorption is too great constipation results, but when it is too little diarrhea results.
4. Pancreas, Liver and Gallbladder
A. What are the size and the location of the pancreas?
Flat organ located behind the stomach and is about 6 inches long. The head of the pancreas is on the right side of the abdomen and connects to the duodenum via the pancreatic duct which is the first section of the small intestines.
B. What are the different functions of the pancreas, and how is the pancreas directly related to digestion?
It is part of the digestive system and produces important enzymes and hormones that help break down foods. The pancreas has an endocrine function because it releases juices directly into the bloodstream, and it has an exocrine function because it releases juices into ducts.
Digestive enzymes and make insulin and glucagon. The pancreas produces enzymes that are released into both the stomach and the small intestines that help break down carbohydrates, fats, and proteins.
C. How does the pancreas connect to the rest of the digestive system?
Directly connected to the stomach, small intestines, and the bile duct via the pancreatic duct.
D. What enzymes are produced by the pancreas and what are their functions?
The most important hormone that the pancreas produces is insulin. Insulin is released by the ‘beta cells’ in the islets of Langerhans in response to food.Its role is to lower glucose levels in the bloodstream and promote the storage of glucose in fat, muscle, liver and other body tissues.
‘Alpha cells’ in the islets of Langerhans produce another important hormone, glucagon. This has the opposite effect to insulin, by helping release energy into the bloodstream from where it is stored, thus raising blood sugar levels.Therefore, glucagon and insulin work in tandem to control the balance of glucose in the bloodstream.
Pancreatic proteases which helps digest proteins. Another is pancreatic amylase which digest sugars. Lastly, pancreatic lipase digest fats.
E. How is insulin related to the digestive system?
After food is digested in the small intestine the glucose is released into the bloodstream, when this is detected insulin is released to allow the glucose into cells and out of the bloodstream.
F. What is the size of the liver and where is it located?
Adult liver weighs about 3 pounds and is in the upper-right portion of the abdominal cavity. The average liver is about 7 cm for women and 10.5 cm for men. It is a large gland and very regenerative; it can completely regenerate even if 75% of it is removed.
G. How does the liver function in relation to digestion?
The liver plays an important role in the digestion and processing of proteins, fat and sugar. The liver helps create some of the building blocks of proteins needed for the body known as amino acids. The liver plays an important role in fat digestion as well as the production of fats needed for the function of different organs of the body.