By: Liam Finley and Sydnay Jordan Nutrition and Digestion By: Liam Finley and Sydnay Jordan

There are three kinds of heterotrophs or organisms that must acquire nutrients in the form of organic material. They are: - Herbivores; feed mainly on plants and algae. - Carnivores; eat mainly animals that eat plants. - Omnivores; eat both plants and animals.

The Four Stages of Food Processing -Ingestion is just another word for eating. -Digestion is the breaking down of food to small nutrient molecules. -Absorption is the uptake of the small nutrient molecules by cells lining the digestive tract. Elimination is the disposal of undigested materials left over from the food we eat.

Physical processes like the chewing and grinding food are examples of mechanical digestion. Chemical digestion is the chemical breakdown of food by digestive enzymes. - Chemical digestion breaks food polymers down to monomers so that they can be absorbed by cells.

Chemical digestion happens safely in some kinds of special compartment in the body. The simplest of the compartments are food vacuoles. Food vacuoles are intracellular organelles filled with digestive enzymes. Simple animals like cnidarians and flatworms have gastro vascular cavities. Gastro vascular cavities are compartments with a single opening that functions as both the entrance for food and the exit for undigested wastes. The majority of animals have digestive tubes with two separate openings, a mouth at one end and an anus at the other.

The human digestive system has a digestive tube called the alimentary canal, or gut. - The alimentary canal is about 9 meters (30 feet) long. It fits in the human body because it folds back and forth over itself. - The alimentary canal is divided into specialized digestive organs. - There are several accessory organs as well that secrete digestive chemicals into the canal.

The mouth functions in ingestion and the beginning steps in digestion. -Chewing food makes it easier to swallow and exposes more food to digestive juices. -Salivary amylase is an enzyme found in saliva which hydrolyzes starch. - The tongue forms food into a ball and helps push it to the back of the mouth so you can swallow.

The Pharynx is an intersection of the food and breathing pathways. The Pharynx opens the trachea (windpipe) which leads to the lungs. When food “goes down the wrong pipe” it triggers a strong coughing reflex that helps keep the airway clear of food.

The esophagus is a muscular tube that connects the pharynx to the stomach. The action of peristalsis is the rhythmic waves of muscular contractions that squeeze the ball of food along the esophagus.

The Stomach is a large organ that can store enough food to sustain us for several hours. The stomach can stretch to accommodate more than half a gallon of food and water. Gastric juice is a digestive fluid that is made up of strong acid, digestive enzymes, and mucus. It is secreted by the cells and lines the stomach’s interior. Pepsin is an enzyme that digests proteins. It breaks the polypeptides of protein into smaller pieces. When the food and gastric juice are mixed and churned in the stomach, it turns into acid chyme. It takes about 2- 6 hours for the stomach to empty. When the stomach is still contracting and it’s empty, it causes the grumbling noises that broadcast your hunger.

The small intestine is the longest part of the alimentary canal and also the major organ for chemical digestion and for absorption of nutrients into the bloodstream. It is also about 20 feet long. The first 25 centimeters of the small intestine is called the duodenum. This is where the acid chyme mixes with enzymes. The pancreas is a large gland that secretes pancreatic juice into the duodenum. Pancreatic juice neutralizes acids that enter the duodenum. Bile is a juice that is produced by the liver and is stored in the gall bladder. Bile contains salts that help digest fats faster.

The Large intestine is also known as the Colon The Large intestine is also known as the Colon. The colon is smaller then the small intestine but it larger in width. The function of the colon is to absorb water from the alimentary canal. Feces are stored in the rectum until it exits the body through the anus.

Human Nutritional Requirements For animals, proper nutrition is key to maintaining homeostasis. A balanced diet helps give the human body the energy needed for cellular work. A calorie is the amount of energy required to raise temperature of a gram of water by 1 degrees Celcius. A kilocalorie is another word for a thousand calories. These are the calories in the foods we eat.

Your metabolic rate is the rate of energy consumption by the body. Your basal metabolic rate is the amount of energy it takes just to maintain your bodily functions. If you take in more calories than you expend, you will gain weight. If you expend more calories than you take in, then you will lose weight.

Food As Building Material Essential nutrients are substances that cannot be made from any other materials and a healthful diet must have the appropriate amounts of all these nutrients. Proteins are built from 20 amino acids. 12 of the 20 can be used in the body for other things but the other 8 are essential amino acids. Animal products like meat, eggs, and milk are all considered “complete” because they provide all the essential amino acids needed. Essential fatty acids also can only be obtained in the diet.

The Eight Essential Amino Acids Methionine Valine (Histidine) – For infants Threonine Phenylalanine Leucine Isoleucine Tryptophan Lysine

Vitamins are organic molecules that are required in the diet for good health. A deficiency in any vitamin can cause serious health problems. Headaches, irritability, vomiting, hair loss, blurred vision, and liver and bone damage are examples of symptoms for a Vitamin A deficiency. Minerals are acquired mainly in the form of inorganic substances. Just like vitamin deficiencies, mineral deficiencies can cause health problems.

Nutritional Disorders The main type of nutritional deficiency is malnutrition. Malnutrition is a deficiency in one or more of the essential nutrients. Under nutrition is caused by the inadequate intake of calories. An undernourished person is not getting enough food to supply basic body needs. Obesity is an inappropriately high body mass index, or ratio of weight to height. Over nourishment helps animals the hibernate but it can cause heart attacks and diabetes in humans.