Unit 2 Compendium 2- Digestive System and Nutrition

Table of Contents
I. Overview Of Digestion
II. The First Part of the Digestive Tract
III. The Stomach and Small Intestine
IV. Three Accessory Organs and Regulation of Secretions
V.The Large Intestine and Defecation
VI. Nutrition and Weight Control

I. Overview of Digestion
A. Ingestion- occurs when the mouth takes in food.
1. Mouth- teeth chew food, tongue tastes and pushes food, for chewing and swallowing.
2. Salivary Glands- secret saliva which contains a digestive enzyme for carbohydrates.
3. Pharnyx- passageway where food is swallowed.
4. Esophagus- passageway where peristalsis pushes food to stomach.
B. Digestion- Mechanical and Chemical- breakdown of large nutrient molecules into smaller molecules that can be absorbed.
1. Mechanical Digestion- occurs when food is divided into pieces that can be acted on by the digestive enzymes; occurs primarily in the mouth and stomach.
2. Chemical Digestion- begins in the mouth and is not completed until food reaches the small intestine; produces chyme (thick semifluid mass of partly digested food that is passed from the stomach to the small intestine).
a. Stomach- secretes acid and digestive enzyme for protein; churns, mixing food with secretions, and sends chyme to the small intestine.
b. Liver- major metabolic organ- processes and stores nutrients and produces bile for emulsification of fats.
c. Gallbladder- stores bile from liver and sends it to the small intestine.
d. Pancreas- produces pancreatic juice that contains digestive enzymes, and sends it to the small intestine; produces insulin and secretes it into the blood after eating.
C.Movement- GI tract contents moving along the digestive tract is very important. In order for the tract to fulfill it's other functions, movement must occur.
D. Absorbtion- occurs as unit molecules, produced by digestion, cross the wall of the GI tract, enter the cells lining the tract, and then the nutrients enter the blood for delivery to the cells.
1. Small Intestine- mixes chyme with digestive enzymes for final breakdown; absorbs nutrient molecules into the body; secretes digestive hormones into the blood.
2. Large Intestine- absorbs water and salt to form feces.
E. Elimination- the removal of indigestable wastes through the anus, in the form of feces, by defecation.
1. Rectum- stores and regulates elimination of feces.
2. Anus- outlet of the digestive tract.
F. Wall of the digestive Tract
1. Lumen- the central space that contains water/food being digested.
2. Mucosa- inner mucous membrane layer that is modified according to the digestive organ.
3. Submucosa- broad band of loose connective tissue that contains nerves, blood, and lymphatic vessels.
4. Muscularis- two layers of smooth muscle.
5. Serosa- thin, outermost tissue that is the visceral peritoneum.

II. The First Part of the Digestive Tract
A. The Mouth- recieves food and begins mechanical and chemical digestion.
1. Componants- hard palate, soft palate, uvula, tonsils, salivary glands, tongue, and teeth.
2. The teeth chew the food and break it down for digestion, and the tongue pushes it toward the throat.
a. Teeth- 8 incisors, 4 canines, 8 premolars, and 12 molars.
B. The Pharnyx and Esophagus
1. When you swallow food, the tongue pushes the bolus of food up against the soft palate, which closes of the pharnyx. The epiglottis closes off the glottis so that food enters the esophagus and not the lungs.
2. Peristalsis, a rythmic contraction, pushes the bolus down through the esophagus until it hits the lower esophageal spincter, which relaxes, and the food enters the stomach.

III. The Stomach and Small Intestine
A. The stomach expands and stores food, and then churns, mixing it with the acidic gastric juices.
1. Gastric juices contain pepsin, an enzyme that digests protein.
B. Duodenum- recieves bile from the liver and the pancreatic juice from the pancreas.
1. Bile- emulsifies fat and readies it for digestion by lipase.
C. Pancreas- produces enzymes that digest starch, protein, and fat.
1. Pancreatic Amylase- digests starch.
2. Trypsin- digests protein.
3. Lipase- digests fat.
4. The intestinal enzymes finish the process of chemical digestion.
D. Small nutrient molecules are absorbed at the villi in the small intestine walls.

IV. Three Accessory Organs and Regulation of Secretions
A. Three accessory organs of digestion send secretions to the duodenum via ducts. The three organs are the pancreas, liver, and gallbladder.
1. Pancreas- produces pancreatic juice, which contains digestive enzymes for carbohydrates, proteins, and fats.
2. Liver- produces bile, destroys old blood cells, detoxifies blood, stores iron, makes plasma proteins, stores glucose as glycogen, breaks down glycogen to glucose, produces urea, and helps regulate blood cholesterol levels.
3. Gallbladder- stores bile, which is produced by the liver.
B. The secretions of digestive juices are controlled by the nervous system and by hormones.
1. Gastrin- produced by the lower part of the stomach, stimulating, via the bloodstream, the upper part of the stomach to secrete pepsin.
2. Secretin and CCK- produced by the duodenal wall, stimulating the pancreas to secrete juices, and the gallbladder to release bile.

V. The Large Intestine and Defecation
A. Large Intestine
1. Consists of the cecum, the colon (ascending, transverse, and descending), and the rectum.
2. Absorbs water, salts, and some vitamins, forms feces, and carries out defecation.
B. Defecation- discharge of feces from the rectum through the anus.
C. Disorders of the Large Intestine
1. Diverticulosis, Irritable Bowel Syndrome (IBS), Inflammatory Bowel Disease, Polyps, and Colon Cancer.

VI. Nutrition and Weight Control
A. Obesity- being grossly overweight; defined by body mass index (BMI).
1. Healthy BMI- 19.1 to 26.4; Overweight BMI- 26.5 to 31.1; Obese BMI- 32.3 to 39.9; Morbidly Obese BMI- 40 or more.
B. Classes of Nutrients
1. Nutrient- a componant of food that performs a physiological function in the body.
a. Carbohydrates- the preferred energy source for the body, but select carbohydrates in whole grains, beans, nuts, and fruits, contain fiber, vitamins, and minerals in addition to carbohydrates.
b. Proteins- sufficient proteins are needed to supply the essential amino acids. Meat and dairy sources of protein may supply unwanted saturated fat, but vegetable sources do not.
c. Lipids- Unsaturated fats, such as those in oils, do not lead to cardiovascular disease and are preferred. Fats and oils contain many more calories per gram than do carbohydrates and protein.
d. Minerals- major and trace- the body contains more than 5 grams of each major mineral, and less than 5 grams of each trace mineral.
d1. Major: Calcium (Ca²+), Phosphorus (PO4³-), Potassium (K+), Sulfur (S²-), Sodium (Na+), Chloride (Cl-), and Magnesium (Mg²+).
d2. Trace: Zinc (Zn²+), Iron (Fe²+), Copper (Cu²+), Iodine (I-), Selenium (SeO4²-), and Manganese (Mn²+).
e. Vitamins- organic compounds (other than carbohydrate, fat, and protein) that the body uses for metabolic purposes, but is unable to produce in adequate quantity.
e1. Fat- soluble: Vitamin A, D, E, and K.
e2. Water- soluble: Vitamin C, Thiamine (B1), Riboflavin (B2), Niacin (Nicotinic Acid), Folacin (Folic Acid), B6, Pantothenic Acid, B12, and Biotin.
C. How to Plan Nutritious Meals
1. Eat a variety of foods from all food groups.
a. Grains- 6 oz. daily
b. Vegetables- 2 ½ cups daily
c. Fruits- 2 cups daily
d. Dairy- 3 cups daily (Ages 2-8, 2 cups)
e. Meat and Beans- 5 ½ oz. daily
f. Oils- small amounts daily
D. Eating Disorders
1. Anorexia Nervosa- a severe psychological disorder characterized by an irrational fear of getting fat, that results in the refusal to eat enough food to maintain a healthy weight.
2. Bulimia Nervosa- eating disorder characterized by binge eating followed by purging, via self induced vomiting or use of a laxative.
3. Muscle Dysmorphia- mental state where a person thinks their body is underdeveloped, and becomes preoccupied with body- building and diet; affects more men than women.