Compendium Review II

Table of Contents

Digestive System and Nutrition

The organs of the digestive system are located within a tube called the gastrointestinal tract (GI tract.)


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Ingestion occurs when the mouth takes in food. Digestion can be mechanical or chemical. Mechanical digestion occurs when the food is divided into pieces, Chemical digestion begins in the mouth and is not completed until food reaches the small intestine. Movement fo the GI tract contents along the digestive tract is very important in orider for the tract to fulfill other functions. Absorption occurs as unit molecules produced by digestion cross the wall of the GI tract and enter the cells lining the tract. Elimination occurs as indigestible wastes pass through the anus in the form of feces.

The wall of the gastrointestinal tract has a mouth and an end. The lumen is the central space that contains water. The first layer of the wall next to the lumen is called the mucosa. The second layer of the GI wall is the submucosa. The third layer is the muscualris which contains 2 layers of smooth muscle. The fourth layer is the serosa. The appendix is a worm-shaped blind tube projecting from the first part of the large intestine on the right side.



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The mouth, the pharynx, and the esophagus are in the first part of the GI tract.

• Mouth- receives food and begins process of mechanical and chemical digestion

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• Pharynx-the food passage and air passage cross in the pharynx, where swallowing begins

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• Esophagus-muscular tube that takes food to the stomach, because other avenues are blocked off, peristalsis pushes the food along the esophagus and continues in all organs of the digestive tract
  

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The stomach and small intestine complete the digestion of food.

• Stomach- thick walled, j shaped organ, that is continuous with the esophagus above and the duodenum of the small intestine below, stores food, initiates digestion of protein and controls movement of chyme into small intestine, has 4 layers

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• Small Intestine- digestion is completed in the small intestine, enzymes needed to digest food are secreted to the small intestine via the pancreas and duodenum, bile is brought from liver and gall bladder to for fat emulsification, nutrients are absorbed into the vessels of the villus and are carried to the cells by the bloodstream

http://www.acm.uiuc.edu/sigbio/project/digestive/late/small_intestine.jpg

3 accessory organs of the digestion system:

• Pancreas-a fish shaped, spongy, gray pink organ that stretches across the back of the abdomen, produce pancreatic juice which contains sodium bicarbonate and digestive enzymes for all types of food, also secretes the hormone insulin into the blood

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• Liver- largest, major metabolic gland in the body, filters blood removing toxins, stores iron and different vitamins, along with glucose, makes plasma proteins and helps regulate cholesterol, produces bile
• Gallbladder-stores bile
  

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Liver disorders

• Jaundice-bile pigments leak into blood
• Hepatitis-inflammation of the liver caused by virus
• Cirrhosis-fatty liver which turns to scarred tissue

The large intestine includes the cecum, the colon, the rectum, and the anal canal. The large intestine is larger in diameter than the small intestine, but shorter in length. The cecum is the blind end of the large intestine and has the appendix protrude from it. The colon includes the ascending colon, the transverse colon, the descending colon, and the sigmoid colon. The large intestine absorbs water, but does not absorb nutrients. TI does however absorb intestinal floral. The large intestine forms feces. Defecation is the process in which the body rids itself of feces.


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Disorders of the colon and rectum

• Diarrhea
• Constipation
• Diverticulosis
• Irritable Bowel Syndrome
• Inflammatory Bowel Disease (colitis)
• Polyps and Cancer

Obesity is being grossly overweight and is on the rise throughout the world. Obesity is defined as through a body mass index (BMI) of 32 or greater. The BMI is a percentage of body fat or adipose tissue.


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The USDA has recommended servings of different food groups for a healthy diet:



A nutrient is a component of food that performs a physiological function in the body. 3 types of nutrients:

• Carbohydrates-simple or complex sugars and starches
• Proteins-digested to amino acids which cells use to synthesize cellular proteins
• Lipids-fats, oils and cholesterols

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Minerals are divided into major and trace. The major minerals are constituents of cells and body fluids and are structural components of tissues. Trace minerals are parts of larger molecules.


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Vitamins are organic compounds (other than carbs, proteins, or fats) taht the body uses for metabolic purposes. Many vitamins are portions of coenzymes. Some vitamins are water soluable, some are fat soluable.



Eating disorders

• Anorexia Nervosa-severe psychological disorder characterized by an irrational fear of getting fat that results in refusal to maintain a healthy body weight

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• Bulimia Nervosa-a person binge eats then purges to avoid gaining weight. The cycle may occur several times a day.
  

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Citations:

Bulimia Nervosa. (2008) http://www.4women.gov/faq/Easyread/bulnervosa-etr.htm

Mader, S. (2008) Digestive System and Nutrition. Human Biology 10th ed. (p 143-168)

Your Digestive System. (2008) http://digestive.niddk.nih.gov/ddiseases/pubs/yrdd/