science

• Food


  Any substance which, when absorbed into your body tissues, yields materials for the production of energy
• Nutrition


  The process by which organisms obtain and use food
• Getting energy from food

  1. Food molecules have chemical bonds that contain energy called potential energy

  2. As these bonds are broken, energy is released
• Nutrients for Energy


  • Carbohydrates
  • Fats
  • Proteins
• Carbohydrates

  • Food nutrients that mainly supply energy
  • Digestion of most carbohydrates ends up with their simplest form called glucose
  • The process of glucose breakdown in cell respiration provides the cell with its usable energy or ATP
• Forms of starch (a polysaccharide type of carbohydrates)


  • Bread
  • Cakes
  • Cookies
  • Potato chips
  • Rice
• Adult males need about 2500kcals per day
• Adult females need about 2000kcals per day
• Fats


  • Food nutrients in the form of carbohydrates that are not utilized at once to sustain your body's energy needs are converted into fats
  • Fats also become a very important structure of your cell membrane called phospholipids
• Proteins


  • The primary role of proteins in your body is to form a large part of your body cells
  • The other major functions of proteins include growth and repair of the body cells
• Enzymes


  Examples of proteins that speed up some chemical processes in the body
• Water


  The amount of water that your body needs varies depending on environmental conditions and the nature of your body activity
• Minerals

  • Serve as regulators of the human body
  • Minerals dissolved in the fluids of the body regulates many of the body processes
• Vitamins

  • Organic substances that are present in very small amounts in food
  • They aid in normal growth and different body activities
• Water- and Fat-Soluble Vitamins

  • B1 (thiamine)
  • B2 (riboflavin)
  • Niacin
  • B12
  • E (tocopherol)
  • K
  • C (ascorbic acid)
  • A
  • D
• Digestion


  • The process of reducing food to smaller molecules that the body can absorb
  • The main functions are to break up the big pieces of food into particles and to break the particles into the molecules that can dissolve in the body fluids and pass through the cell walls, for cells to utilize
• The Digestive Tract

  • Mouth
  • Esophagus
  • Stomach
  • Small intestine
  • Large intestine
  • Anus
• Accessory organs assisting the digestive tract

  • Salivary glands
  • Pancreas
  • Liver
  • Gallbladder
• Stages of Digestion

  1. Mechanical

  2. Chemical
• Mechanical digestion


  Takes place within the mouth and the stomach to break down mechanically by biting, cutting, tearing, grinding, and mashing large bits of food into a fine mixture
• Chemical digestion

  Enzymes are needed to hydrolyze and break down starch into glucose molecules, proteins into amino acids, and fats into fatty acids and glycerol
• Saliva


  Secretion of the glands located at different areas within your mouth that lubricates the food and secretes ptyalin (an enzyme also known as salivary amylase that converts starch to maltose)
• Salivary glands

  • Parotid glands
  • Submandibular glands (Submaxillary glands)
  • Sublingual glands
• Mouth


  The beginning of the digestive tract where saliva mixes with the food to begin to break it down into a form your body can absorb and use
• Esophagus


  • Receives food from your mouth when you swallow
  • The epiglottis is a small flap that folds over your windpipe as you swallow to prevent you from choking
• Stomach

  • A hollow organ that holds food while it is being mixed with stomach enzymes that continue the process of breaking down food into a usable form
  • Cells in the lining of your stomach secrete a strong acid and powerful enzymes that are responsible for the breakdown process
• Small Intestine


  • Made up of three segments - the duodenum, jejunum, and ileum
  • A 22-foot long muscular tube that breaks down food using enzymes released by the pancreas and bile from the liver
• Pancreas


  • Secretes digestive enzymes into the duodenum that break down protein, fats and carbohydrates
  • Also makes insulin, passing it directly into the bloodstream
• Liver


  • The main job within the digestive system is to process the nutrients absorbed from the small intestine
  • Bile from the liver secreted into the small intestine also plays an important role in digesting fat and some vitamins
• Gallbladder


  Stores and concentrates bile from the liver, and then releases it into the duodenum in the small intestine to help absorb and digest fats
• Large Intestine


  Also called the colon, it is a 6-foot long muscular tube that connects the small intestine to the rectum and is responsible for processing waste so that emptying your bowels is easy and convenient
• According to researchers from the Duke University Medical Center, the appendix does have a key function - it produces and stores good microbes for the human gut
• Rectum


  A straight, 8-inch chamber that connects the colon to the anus and receives stool from the colon, lets you know that there is stool to be evacuated (pooped out) and holds the stool until evacuation happens
• Anus


  The last part of the digestive tract, a 2-inch long canal consisting of the pelvic floor muscles and the two anal sphincters (internal and external)
• Some common conditions that affect the digestive system

  • Constipation
  • Diarrhea
  • Heartburn
  • Ulcers
  • GERD (gastroesophageal reflux disease, or chronic acid reflux)
  • Lactose intolerance