CHAPTER 8
DIGESTIVE SYSTEM AND NUTRITION
OVERVIEW OF DIGESTION
a. Ingestion, digestion, movement
b. Wall of digestive tract
b. Wall of digestive tract
FIRST PART OF DIGESTIVE TRACT
a. Mouth
b. Pharynx and Esophagus
THE STOMACH AND SMALL INTESTINE
a. Stomach
b. Small Intestine
c. Obesity
THREE ACCESSORY ORGANS AND REGULATION OF SECRETIONS
a. Three Accessory Organs
b. Secretions
THE LARGE INTESTINE AND DEFECATION
a. Functions
b. Disorders
NUTRITION AND WEIGHT CONTROL
a. Obesity
b. Classes
c. Minerals
d. Vitamins
b. Classes
c. Minerals
d. Vitamins
e. Nutritious Meals
f. Eating disorders
f. Eating disorders
OVERVIEW OF DIGESTION
The processes of digestion require ingestion, digestion, movement, absorption and elimination. See illustration at left.* All parts of the tract have four layers, the mucosa, sub mucosa, muscularis and serosa.
FIRST PART OF THE DIGESTIVE TRACT
The mouth, the pharynx, and the esophagus are in the first part of the GI tract.
In the mout
h, teeth chew the food and saliva contains salivary amylase for digesting starch, and the tongue forms a bolus for swallowing.
h, teeth chew the food and saliva contains salivary amylase for digesting starch, and the tongue forms a bolus for swallowing.The air passage and food passages cross in the pharynx. When swallowing the air passage is blocked off by the soft palate and the epiglottis, food enters esophagus and peristalsis starts. The esophagus moves food to the stomach.
THE STOMACH AND SMALL INTESTINE
The stomach and small intestine complete the digestion of food.
The
stomach expands and stores food, it mixes food with the acidic gastric juices. The duodenum of the small intestine receives bile from the liver and pancreatic juice from the pancreas. The pancreas produces enzymes that digest starch, protein, and fat. The intestinal enzymes finish the process of chemical digestion. Nutrient molecules are absorbed at the villi in the walls of the small intestine. The nutrients absorbed at the small intestine can affect our health. The intake of too much sugar or fat can result in obesity which can lead to diabetes or cardiovascular disease.
stomach expands and stores food, it mixes food with the acidic gastric juices. The duodenum of the small intestine receives bile from the liver and pancreatic juice from the pancreas. The pancreas produces enzymes that digest starch, protein, and fat. The intestinal enzymes finish the process of chemical digestion. Nutrient molecules are absorbed at the villi in the walls of the small intestine. The nutrients absorbed at the small intestine can affect our health. The intake of too much sugar or fat can result in obesity which can lead to diabetes or cardiovascular disease.THREE ACCESSORY ORGANS AND REGULATION OF SECRETIONS
The three accessory organs that send secretions to the duodenum via ducts are the pancreas, liver, and gallbladder.
The pancreas produces pancreatic juice, that has digestive enzymes in it.
The 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 level.
The gallbladder stores bile. The secretions of digestive juices are controlled by the nervous system and by hormones. Gastrin is produced by the lower stomach. It stimulates upper stomach to secrete pepsin. Secretin and CCK produced by the duodenal wall stimulate the pancreas. This secretes its juices and the tells the gallbladder to release bile.
THE LARGE INTESTINE AND DEFECATION
The large intestine include the cecum, which is the blind end of the large intestine, the rectum and the anal canal.
The large intestine absorbs water, salts, and some vitamins, forms feces and carries out defecation.
Disorders of the large intestine include diverticulosis, irritable bowel syndrome, inflammatory bowel disease, polyps and cancer.
NUTRITION AND WEIGHT CONTROL
The nutrients released by the digestive process should provide us with adequate energy, essential amino acids and fatty acids and all necessary vitamins ad minerals.
Obesity is on the rise mainly for poor food choices or eating too much food. Obesity is associated with many illnesses like diabetes 2 and cardiovascular disease.
In this illustration*, it shows what to eat and what to minimize in order to have good health.
There are different classes of nutrients. 1. Carbohydrates, are necessary but simple sugars and refined starches cause a rapid release of insulin the can lead to diabetes type 2.
2. Proteins supply essential amino acids. 3. Lipids - unsaturated fatty acids, omega 3, are protective against cardiovascular disease - saturated fatty acids lead to plaque.
Vitamins and minerals are also required by the body in certain amounts.
Some eating disorders are, anorexia nervosa and bulimia nervosa.
Other abnormal eating practices are binge-eating disorder. Muscle dysmorphia is when one thinks their body is underdeveloped.
Eating healthy is a way to fight many diseases and to make it through our busy lives.
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