Functions of the Digestive System • Ingestion (bring food in)

– Occurs when materials enter digestive tract via the mouth• Mechanical processing (Crushing and shearing)

– Makes materials easier to propel along digestive tract• Digestion

– The chemical breakdown of food into nutrients• Absorption

– Movement of nutrients through digestive tract wall into the bloodstream.

– All materials that sustain and build your body come from your nutrition

• Excretion – Removal of waste products from body fluids

Accessory Organs

Figure 16-1

Oral Cavity

• Food first enters the digestive system through the mouth.• In the mouth the teeth break apart the food and saliva mixes

with the food.• Saliva: fluid secreted from salivary glands that contains

enzymes to break apart food, saliva is about 99% water.• Once the food is swallowed it moves down

the esophagus.–Hollow tube that moves food toward the stomach.

• Swallowing causes the epiglottis to close, protecting the airway.– Tissue flap that blocks food from entering larynx

The Stomach• Once in the stomach the food mixes with stomach

acid.– Stomach: organ that stores food- mechanical and chemical

digestion.– Chyme: food mixed with stomach acid.

• The chyme that leaves the stomach moves into the small intestine.– Small intestine: main function is nutrient absorption.

• Chyme moving into the small intestine mixes with fluid from the pancreas, liver and gall bladder.

Accessory Organs• Pancreas: is an organ that releases digestive enzymes,

that break down food into nutrients.– Remember also releases insulin

• Liver: organ that makes bile.– Bile is a fluid that is made to break apart fatty foods.

• Gall bladder: organ that stores bile made by the liver.• Once the chyme, mixes together with enzymes from

the pancreas, and bile from the liver and gall bladder it moves through the small intestine.– What allows for the nutrients to be absorbed is intestinal

villi.

Small Intestine

• Intestinal villi: increase surface area inside the intestines which increases nutrient absorption.

Large Intestine• Processed food leaves the

small intestine and moves through the large intestine.– Large Intestine: organ where

water reabsorption occurs.

• Once all the nutrients and water have been removed waste product leaves through the rectum and anus.– Anus: external opening where

waste product is removed.Animation

Disorders• Appendicitis: inflammation of the appendix.• Gall bladder removal: when the gall bladder does

not work properly it can be removed.– The liver will then just make and release bile when

needed.

EXCRETORY SYSTEMPart 2

Main Function Excretory• Main function of the excretory system is the removal of

water and wastes.– While the digestive system removes solid waste the kidneys

remove water wastes from the blood (salts, ions, etc.)

• Main organs: Kidneys– Kidneys: filter the blood and remove waste or drugs in the blood.

• Regulate ion concentration, pH, and blood pressure by controlling how much water is removed and how many solutes are left in the blood.

– Filtration: the process of removing unwanted products from the blood.

– The functional units that filter the blood are called nephrons.

Excretory System

• The fluid that is filtered from the blood leaves the kidneys and then goes through the ureters.– Ureters: tubes that move urine from the kidneys to the

bladder.

• Bladder: hollow organs that stores urine.– Can house up to 2 cups of urine.

• The urine then leaves the bladder through the urethra.

Dialysis• If the kidneys are not

working properly the process of dialysis can be done to work as a “fake kidney”.

• Dialysis:– Removes waste, salt and

extra water.– Keeps safe levels of

certain chemicals in your blood.

– Helps to control blood pressure.