DIGESTIVE SYSTEM & NUTIRTION
DIGESTIVE SYSTEM
a. Overview
b. wall of the digestive tract
c. where digestion begins and ends
d. complications with poor nutrition
e. disorders of the liver, colon
NUTRIRION
a. weight control, obesity
b. nutrients and vitamins
c. food guide pyramid
d. eating disorders
I think the digestive system is one of the more interesting system in our bodies. The digestive system consists of many organs working together. The digestive system is also referred to as the GI tract (gastrointestinal tract). It starts with the mouth because this is where ingestion begins. Our mouths contain saliva and enzymes that help, along with our teeth, break down food and turn it into a bolus. The bolus is a soft ball of broken down food that can be easily swallowed. This might also be considered digestion because of the breakdown of food. All parts of the digestive tract contains digestive enzymes that hydrolyze foods to molecular nutrients for our bodies to absorb. The GI tract has three main functions; movement, this is due to peristalsis. Peristalsis is involuntary muscle at work. Food must has to pass along form organ to organ and peristalsis makes that happen. Another function of the GI tract is absorption, this happens when the food has been broken down into molecules and can be absorbed by the body. The third function is elimination; the molecules that can not be digested are eliminated form our bodies by defecation.
Wall of the digestive tract
The digestive tract is made up of long tube and starts with the mouth and ends with the anus. This tube is made up of layers. It starts with the mucosa or mucous membrane. This is responsible for secreting mucous and protecting the wall for the digestive enzymes. The second layer of the tract wall is submucoa. This layer contain connective tissue with blood vessels, lymphatic vessels and nerves. Theses vessels carry the nutrients absorbed by the mucosa. The third layer is the muscularis and is made up of smooth muscle. This covers the tube by crossing over it and running along side of it. The fourth layer, is the serosa layer which secretes serous fluid.
www.mednote.co.kr/images/stomach.gif
Where digestion begins and ends
Digestion, as I said above, really begins in the mouth because this is where we start to break down the food with our saliva and enzymes. Or as the the book says the mechanical and chemical digestion. Our saliva is created by the salivary glands in our mouths. When we start to chew food the salivary glands are activated and the glands release saliva through ducts. The saliva is made up of mucous and water and contains an enzyme call salivary amylase. This particular enzyme speeds up the breakdown of food. Our teeth and tongue play a role in digestion. Obviously, the teeth help cut and chop the food, but the tongue helps with chewing and swallowing the bolus that is created after you have chewed the food enough. The tongue also contain our taste buds. The swallowing of food involves the pharynx and the esophagus. When we swallow, food enters the esophagus, but a lot of other stuff is happening while you are swallowing. This takes probably a split second. The soft palate is in our mouths, moves back to close off the nasal passages, and the trachea moves up under the epiglottis to cover the glottis. The glottis is the opening to the larynx (voice box)and serves as our airway. Everyday people choke or think that the food went down the wrong pipe, well this possible. It can go into our nasal cavities or into the trachea. Sometimes, food can be aspirated and go into the lungs. I talked about peristalsis in the beginning of my compendium because this is really how food goes through all the organs and even when defecation takes place. The bolus continues thru the esophagus on its way to the stomach. As the bolus makes it way to the stomach, it encounters a sphincter. The is called the gastroesophageal sphincter. Sphincters are muscles that encircle tubes and act as valves; they close when contracted and open when relaxed. Similar to the heart valves. When the sphincter is relaxed it allows the bolus to pass through into the stomach. When the bolus enters the stomach (which has a high acidic of 2 due to hydrochloric acid) it continues with digestion. The stomach also has layers like the GI tract, and the mucosa layer has millions of gastric glands that produce gastric juices that help with more breakdown of the bolus into proteins. These gastric juices contain an enzyme called pepsin that digests proteins. When food leave the stomach it is turned into a thick liquid, called chyme. Chyme enters the small intestines slowly, not all at once. The chyme enter the small intestines through another sphincter called, pyloric sphincter and this allows the small amounts of chyme to enter at a time. Digestion is completed in the small intestines. Here, in the small intestines are different enzymes to digest all types of food. The enzymes are secreted by the pancreas, liver and gallbladder. These three organs are the accessory organs working with digestive system that release their enzymes. We will start with the pancreas, most pancreatic cells release pancreatic juices which enter the duodenum (the beginning of the small intestine). The pancreatic juices contain sodium bicarbonate and enzymes. Pancreatic amylase digests starch, Trypsin digests protein, and Lipase digests fats. The pancreatic enzymes I just named begins and an intestinal enzyme finishes the digestion of carbohydrates to glucose. Glucose is our bodies main source of energy when broken down. The liver filters our blood, but when it comes to digestion the liver make plasma proteins that helps regulate cholesterol in the blood. It produces bile salts that are made from cholesterol. Bile is stored in the gallbladder and is released during digestion. Bile emulsifies fats and that is when it breaks up fat droplet into water. Nutrients are absorbed in the small intestines. The mucosa is modified for absorption. The mucosa contains tiny projections called villi with extensions called microvilli which increases the surface area of the small intestines and helps with the absorption of nutrients. What ever can not be ingested in the small intestines is passed into the large intestine. The main function of the large intestine is absorb water, which helps form feces. Not enough water absorbed, dehydration can occur. The large intestines consists of the cecum (a blind sac), the colon, rectum and the anus. The colon includes the transverse colon (across the abdomen), the ascending colon (traveling up), and the descending colon (goes down). The large intestines also absorbs vitamins produced by bacteria. The large intestine is feces is formed. Ridding the body of feces is another way to maintain homeostasis!
Complications with nutrition
Some people from lactose intolerance. This is when people do not have the enzyme lactase that digest lactose. There are alternatives for these people because there are products that are made just for the disorder. Also, people with lactose intolerance can eat some diary like cheese and yogurt because the lactose has already been broken down for them. This disorder can cause abdominal cramps, gas and bloating. Another complication, which is much more serious is Diabetes. To much sugar and fat can lead to obesity, which in turn can lead to diabetes 2 and cardiovascular disease. It is stressed in everyday life to eat healthy, meaning eating a lot of fruit, veggies, and lean meats. Balance is really what is about. Wanting a treat once and while is not a bad thing!
Disorders of the liver and colon
You can almost look at person and know that they have some kind of liver disorder because the whites of the eyes and the skin can become jaundice. Jaundice is when bile (stored in the gallbladder, made by the liver) secretes into the blood. One disorder that go along with jaundice is Hepatitis. There are different kinds of hepatitis. There is Hep A which is contracted through the oral-fecal route, Hep B & C are sexually transmitted or body fluids, especially blood. Another disorder of the liver is cirrhosis, which is said to be caused by alcohol abuse. The liver becomes very fatty and the liver tissue is replaced by scar tissue, making it hard for the liver to function properly. It was thought that only alcohol was the cause of cirrhosis, but now is being related to people who are obese. People that are obese tend to eat a lot of fatty foods. The liver is a vital organ, one humans cannot live without. The colon disorders can be very debilitating. Disorders that are common and I believe everyone has suffered from are diarrhea, which is caused by an infection of the lower intestinal tract and nervous stimulation. ie., food poisoning can cause the intestinal wall to be irritated and peristalsis increases. Water is not absorbed as it should be, causing diarrhea. Another common disorder is constipation. The feces are hard to pass thru the anus. This is usually caused by people avoiding going to the bathroom. The one disorder I think can be debilitating is Crohn's disease. My sister has Crohn's and some days she cannot function normally and needs to stay home (alot). Crohn's disease is considered and inflammatory bowel disease and sometimes people can get ulcers in their colons, and that can cause bleeding. some people can hemorrhage (bleed to death).
NUTRITION
Weight control, obesity
Obesity is defined by a persons body mass index (BMI). This is actually taking how much you weigh with your height and see where you fall on the BMI chart. The chart below shows what is healthy and what is considered obese.
Obesity is on the rise in Americans and especially the children. Obesity leads to deadly disorders and diseases.
Nutrients and Vitamins
Nutrients are described as a component of food that performs a physiological function in the body. They provide us with energy, promotes growth and development and regulate cellular metabolism.
Carbohydrates can be simple or complex. Glucose is our #1 source for energy needs and is considered a simple sugar. Carbs are very important to our diets. Complex carbs are broken down into glucose for the use of our bodies. Fats should be included, but in low quantities. Refined foods are the worst for someone diet if too many are consumed. Protein is very important in our diets!!! You can find protein in lean meats, fish, beans, eggs, and on and on. The amino acids in the proteins are what are important for our bodes. All 20 amino acids are needed. The absence of one amino acid can cause the not to work right. Too much red meat is not good for the body because of the high saturated fats. Lipids are fats, oils, and cholesterol. all of which sound bad for you, but if you consume the right kinds and some in moderation it should be fine. I learned that some oils are really bad and others are good for you. One example is the canola, and safflower oils contain polyunsaturated fatty acids which are essential because our bodies don't make. the acids are linoleic and linolenic acids. Some oils are high in saturated fats and that is not good for us. Vitamins are organic compounds that the body uses for metabolic needs. Some vitamins are produce in our bodies and others are taken as a supplement. I believe a lot of people take vitamins to make sure they get the ones that they need because not all of us follow a strict day in and day out diet. A lack of vitamin D can cause ricketts, this is when the bones are deformed and the person look bone legged. Vitamin D is very important to our diet because it helps absorb calcium.
Eating disorders
These can cause a lot of damage to your organs and even death. One example is anorexia when a person literally starves themselves because they have a poor boy image. They damage their organs because their body is not getting the vital nutrients it needs to survive! They are extremely thin, some you can actually see their bones. Bulimia nervosa is another eating disorder is when the person eats a lot of food and the makes themselves vomit. They do this more then once in a day!! They look like average people, unlike people suffering from anorexia.
Conclusion
The systems covered in this unit were interesting. I found it fascinating how things work.
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