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

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