Chapter 24
The Digestive and Urinary Systems
Section 1 The Digestive System
Objectives:
•Compare mechanical digestion with chemical
digestion.
•Describe the parts and functions of the
digestive system.
Major Functions of the Digestive System
• Break down ingested food
• Put nutrients into the bloodstream
• Remove waste from the body
Organs of the Digestive System
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Mouth- teeth, salivary glands, tongue
Esophagus
Stomach
Small Intestine
Large Intestine
Pancreas
Accessory
Liver
Organs
• Gall bladder
Mouth
• Digestion begins here!
• Teeth and tongue are used in mechanical
digestion- physical breakdown of food
• Saliva and enzymes begin chemical
digestion- chemical breakdown of food
Esophagus
• Muscular tube that connects mouth to stomach
• Moves food downward by peristalsis, or
muscular contractions
• Epiglottis seals off windpipe during swallowing
to prevent choking
Stomach- Mechanical and
Chemical Digestion
• Muscular pouch that expands to hold your
food
• Hydrochloric acid (HCl) and the enzyme
pepsin combine to form gastric juice
• A gummy coating of mucus protects the
stomach lining from the strong chemicals
• Chyme, a thick liquid containing partially
digested food, is produced here
Pancreas
• Makes digestive enzymes
• Makes hormones that regulate sugar levels
Small Intestine
• Most chemical digestion occurs here!
• Inner surface is covered in villi and microvilli,
millions of tiny finger-like projections that
absorb nutrient molecules from the chyme
• The villi create a large surface area so
as many nutrients as possible can be
absorbed
• Longest portion of the digestive tract
Liver
• Makes bile to break up fat
• Stores nutrients
• Breaks down toxins
Gallbladder
• Temporarily stores bile and releases it into
the small intestines
Large Intestine
• No digestion occurs here
• Water is absorbed from remaining food
• Waste material, feces, is prepared for
elimination from the body
Rectum
• Stores feces until they can be expelled
through the anus.
Section 2 The Urinary System
Objectives:
•Describe the parts and functions of the urinary
system.
•Explain how the kidneys filter blood.
•Describe three disorders of the urinary
system.
The Urinary System
• Excretion is the process of removing waste
products from the body.
• The urinary system removes waste products
like carbon dioxide from the body.
The Kidneys as Filters
• The kidneys are a pair of organs that
constantly clean the blood.
• Your blood cycles through your kidneys
about 350 times a day.
• Inside each kidney are nephrons,
microscopic filters that remove waste from
the blood. (especially urea)
Water In, Water Out
• The balance of fluids in the body is
controlled by chemical messengers called
hormones.
• Sweat and thirst
• Antidiuretic hormone (ADH)-signals the kidneys
to make less urine
• Diuretics-cause the kidneys to make more urine
Urinary System Problems
• Bacterial infections-bacteria in the bladder; if
spreads to kidneys, then permanent damage
can be caused to nephrons
• Kidney stones-when salts and other wastes
collect inside the kidneys and form stones;
can interfere with urine flow
• Kidney disease-can be caused by damage to
nephrons; dialysis used as treatment to filter
blood