Hungry for progress – appetite, genes and drugs (HD) – A film by the Wellcome Trust
Be a Nutrition Sleuth
Diving into Digestion
You just ate a hamburger on a whole-wheat bun for lunch. What happens to the food during the digestive process?
Get Real!
How Do Your Eating Habits Stack Up?
What are your less-than-healthy eating habits?
The Top Ten Points to Remember
1. There are five categories of taste-sweet, salty, sour, bitter, and savory (umami)-but there are thousands of aromas and flavors. Hunger and thirst alert you to your basic physical need to take in food and fluid. Appetite is less about physical need and more about the psychological desire to take in foods.
2. Digestion is the process of breaking down food into absorbable nutrients. Digestion takes place in the organs of the GI tract-particularly in the stomach, small intestine, and large intestine.
3. There are both mechanical and chemical aspects of digestion. Mechanical digestion includes chewing and peristalsis. Chemical digestion involves mixing consumed food with enzymes and gastric juices to break it down.
4. Digestion begins in the mouth as chewing breaks down food and mixes it with saliva. Swallowing is a coordinated process that involves the mouth, throat, and esophagus. The stomach mixes food with enzymes and stores it before propelling it into the small intestine, where most digestion and absorption occur. The walls of the small intestine are covered with villi, which greatly increase its surface area and facilitate absorption. The large intestine absorbs water and some nutrients, before pushing waste through the colon and out of the body via the anus. Several sphincters control the entry and exit of food and chyme through the organs of the GI tract.
5. Hydrochloric acid, hormones, enzymes, bile, and bicarbonate are all necessary for efficient digestion. Hydrochloric acid is a gastric juice that helps prepare the food for further digestion. Hormones are chemical messengers that direct activities in the body. Hormones direct enzymes that do the actual work of facilitating reactions. Bile is produced in the liver and stored in the gallbladder and is particularly important for fat digestion.
6. In addition to producing bile, the liver processes and metabolizes several nutrients after they have been digested and absorbed. The liver also stores several nutrients, and plays an important role in detoxifying alcohol. The gallbladder stores concentrated forms of bile. The pancreas produces both hormones and enzymes that play roles in digestion.
7. Body systems other than the digestive system help you use the nutrients you eat. Your nervous system lets you know when you are hungry or thirsty. Your circulatory and lymph systems distribute nutrients to all your cells. The endocrine system releases hormones that regulate the cells’ use of nutrients, and the excretory system filters waste products, such as urea, from the blood and passes them out of the body in urine.
8. Flatulence is the release of intestinal gas from the rectum.
9. Digestive disorders can range from the trivial, such as occasional stomachaches, heartburn, diarrhea, constipation, or hemorrhoids, to the serious conditions of irritable bowel syndrome (IBS), Crohn’s disease, ulcers, and cancer. Heartburn is the layman’s term for the uncomfortable sensation of stomach acid returning to the esophagus or throat. A primary cause of heartburn is poor eating habits and other lifestyle choices. Constipation is a generally benign condition of sluggish colon movements commonly caused by a low-fiber, low-fluid diet. Diarrhea is a potentially serious and distressing condition characterized by frequent, loose, and watery stools. It is often caused by exposure to microorganisms in food or water. IBS and Crohn’s disease can lead to malabsorption and malnutrition. Peptic ulcers are sores or breaks in the lining of the stomach or upper part of the small intestine. Colon cancer begins with polyps on the intestinal lining and is very treatable if caught early.
10. Celiac disease is an autoimmune disorder of the small intestine that can be treated with a gluten-free diet. Celiac disease is not the same thing as gluten intolerance, which does not involve the immune system or damage the wall of the small intestine.
Test Your Knowledge
1. You have an innate preference for sweet and salty foods because
A. Your friends prefer these types of foods.
B. These foods provide plenty of calories and nutrients, which you need for energy and health.
C. These foods are less dangerous than sour or bitter foods.
D. None of the above
2. ______ is the process that breaks down food into absorbable units.
A. Circulation
B. Digestion
C. Absorption
D. Excretion
3. Digestion begins in the
A. Liver.
B. Stomach.
C. Mouth.
D. Colon.
4. The name of the protective tissue that covers the trachea when you swallow is the
A. Esophagus.
B. Tongue.
C. Pharynx.
D. Epiglottis.
5. What causes heartburn?
A. Improper relaxation of the lower esophageal sphincter
B. Improper contraction of the lower esophageal sphincter
C. Improper and rapid swallowing
D. Improper breathing and chest congestion
6. The name of the secretion produced in the stomach that helps break down protein and activates pepsin is
A. Hydrochloric acid (HCl).
B. Amylase.
C. Bile.
D. Gastrin.
7. The sphincter that separates the stomach from the duodenum is the
A. Lower esophageal sphincter.
B. Ileocecal sphincter.
C. Pyloric sphincter.
D. Colon sphincter.
8. The compounds that help break down foods during digestion are
A. Enzymes.
B. Hormones.
C. Proteins.
D. Digestive organs.
9. What is the purpose of the gallbladder?
A. To make bile
B. To modify bile so it becomes liquid
C. To digest bile
D. To concentrate and store bile
10. Which of the following is true regarding the small intestine?
A. The small intestine has a vast digestive surface area.
B. The small intestine has minimal digestive surface area.
C. The small intestine has access to lymph tissue, but not to the bloodstream.
D. The small intestine is unimportant in the process of digestion.
(Answers in next text)
