HOW WE USE NUTRIENTS The Digestive System

DIGESTION There are four stages to digestion: INGESTION: eat or taking in food DEGESTION: breaking down food into nutrients ABSORPTION: the uptake of nutrients into the body EGESTION: elimination of waste from the body

DIGESTION MECHANICAL: tearing, ripping and beating down of food There are two kinds of digestion: MECHANICAL: tearing, ripping and beating down of food CHEMICAL: using digestive enzymes to break down food

ORAL CAVITY The oral cavity also contains two kinds of SALIVARY GLANDS: PAROTID: secretes a fluid containing an enzyme that breaks down carbohydrates BUCCAL: secretes mucus which coats the food to prevent it from damaging the digestive tract

ESOPHAGUS A long tube that travels from the mouth to the stomach BOLUS: moisten ball of food Food travels down to the stomach by a process called PERISTALSIS, which is a series of muscle contractions and relaxations.

STOMACH Can hold about 1 L of food Does both mechanical and chemical digestion Contains a chemical called HYDROCHLORIC ACID The acid kills any microbes that may be in the food. The acid also activates enzymes which aid in the breakdown of proteins

STOMACH Also has mucus secreting cells that coat the stomach protecting it from the affects of the acid The food exits the stomach as a thick liquid called CHYME

SMALL INTESTINE Location of the bulk of digestion in the body It is also the location of ABSORPTION in the body Contains millions VILLI which maximizes the surface area of the small intestine for absorption

SMALL INTESTINE The chyme is acted on by three types of digestive juices: BILE: helps the body absorb fats PANCREATIC: contains enzymes that break down nutrients INTESTINAL: works with the other fluids to break down food

LARGE INTESTINE The location of the absorption of water and any other nutrients that the body may need. Produces waste product (poo).

ACCESSORY ORGANS There are organs that help the digestive system, but are not actively involved in digestion. LIVER: produces bile GALL BLADDER: stores bile PANCREAS: produces pancreatic juices

DIGESTIVE SYSTEM AND NUTRTRIENTS Carbohydrates are broken down into GLUCOSE Fats are broken down into FATTY ACIDS Proteins are broken down into AMINO ACIDS Vitamins, minerals and water are not broken down; they are used as is

ABSORPTION OF NUTRIENTS After digestion, the nutrients are absorbed into the bloodstream The nutrients travel to the liver to be processed into forms that the body can use Example: Amino acids can be converted to many different types of proteins Nutrients that are not immediately needed can be stored for future use Example: Excess glucose is converted into glycogen and stored in the liver.

HOW NUTRIENTS ARE USED Nutrients are carried throughout the bloodstream to individual cells They are used for specialized purposes Example: Glucose is combined with oxygen to produce energy Energy is used for AUTOMAIC PROCESSES (breathing, digestion, etc.) and PHYSICAL ACTIVITIES (exercise)

WASTE REMOVAL After absorption some waste material and fibre is left in the small intestine The waste is moved to the large intestine where water, potassium and sodium are removed The waste is stored in the rectum until it is eliminated