Digestion

• Phases Include

1. Ingestion

2. Movement

3. Mechanical and Chemical Digestion

4. Absorption

5. Elimination

Digestion • Types

– Mechanical (physical)

• Chew

• Tear

• Grind

• Mash

• Mix

– Chemical • Enzymatic reactions to improve digestion of

– Carbohydrates

– Proteins

– Lipids

Digestive System Organization

• Gastrointestinal (Gl) tract – Tube within a tube

– Direct link/path between organs

– Structures • Mouth

• Pharynx

• Esophagus

• Stomach

• Small intestine

• Large Intestine

• Rectum

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Mouth • Teeth mechanically

break down food into small pieces. Tongue mixes food with saliva (contains amylase, which helps break down starch).

• Epiglottis is a flap-like structure at the back of the throat that closes over the trachea preventing food from entering it.

Esophagus • Approximately 10” long

• Functions include:

1. Secrete mucus

2. Moves food from the throat to the stomach using muscle movement called peristalsis

• If acid from the stomach gets in here that’s heartburn.

Stomach • J-shaped muscular bag that stores the food

you eat, breaks it down into tiny pieces.

• Mixes food with digestive juices that contain enzymes to break down proteins and lipids.

• Acid in the stomach kills bacteria.

• Food found in the stomach is called chyme.

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Small Intestine • Small intestines are roughly 7 meters long

• Lining of intestine walls has finger-like projections called villi, to increase surface area.

• The villi are covered in microvilli which further increases surface area for absorption.

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Small Intestine • Nutrients from the food pass into the

bloodstream through the small intestine walls.

• Absorbs:

– 80% ingested water

– Vitamins

– Minerals

– Carbohydrates

– Proteins

– Lipids

• Secretes digestive enzymes

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Large Intestine • About 5 feet long

• Accepts what small intestines don’t absorb

• Rectum (short term storage which holds feces before it is expelled).

Large Intestine • Functions

– Bacterial digestion

• Ferment carbohydrates

• Protein breakdown

– Absorbs more water

– Concentrate wastes

Accessory Organs

• Not part of the path of food, but play a critical role.

• Include: Liver, gall bladder, and pancreas

Liver

• Directly affects digestion by producing bile

– Bile helps digest fat

• filters out toxins and waste including drugs and alcohol

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Gall Bladder

• Stores bile from the liver, releases it into the small intestine.

• Fatty diets can cause gallstones

Pancreas

• Produces digestive enzymes to digest fats, carbohydrates and proteins

• Regulates blood sugar by producing insulin

Fun Facts

• HOW LONG ARE YOUR INTESTINES? At least 25 feet

in an adult. Be glad you're not a full-grown horse -- their

coiled-up intestines are 89 feet long!

• Food drying up and hanging out in the large intestine

can last 18 hours to 2 days!

• In your lifetime, your digestive system may handle

about 50 tons!!

On a sheet of paper, write the name of each

colored organ:

• Light Green:

• Red:

• Pink:

• Brown:

• Purple:

• Dark Green:

• Yellow:

How’d you do?

• Light Green: Esophagus

• Red: Stomach

• Pink: Small Intestine

• Brown: Large Intestine

• Purple: Liver

• Dark Green: Gall Bladder

• Yellow: Pancreas

References and Links

• Your Digestive System and How It Works – Digestive system diagram comes from this site

• The Real Deal on the Digestive System

• Pancreas: Introduction and Index

• Your Gross and Cool Body - Digestive System

Excretory System

Excretory System

•Why do our bodies need to filter waste from the body?

–Maintain homeostasis

– Removal of harmful materials

– Removal of excess fluids, chemicals, minerals, vitamins, salts, and other wastes from the blood

Organs of the Excretory System

• Kidneys = filter

blood that has

collected wastes

from cells

Organs of the Excretory System

• Kidneys = filter blood that has collected wastes from cells

– Nephrons = filters inside the kidneys – Produce urine (sterile waste fluid, 96% water)

Organs of the Excretory System

• Ureters = tubes that

lead from each kidney to bladder

Organs of the Excretory System

• Urinary bladder =

muscular organ that

holds urine

Organs of the Excretory System

• Urethra = tube that carries urine from the bladder out of the

body

Where is urine stored until the body is ready to eliminate it?

1. Kidneys

2. Ureters

3. Bladder

4. Urethra

Functions of Excretory System

• Rids blood of

wastes (urea)

Functions of Excretory System

• Rids blood of

wastes (urea)

• Controls blood

volume by removing

extra water

produced by cells

Functions of Excretory System

• Rids blood of

wastes (urea)

• Controls blood

volume by removing

extra water

produced by cells

• Balances salts and

water so cells can function properly

Which is not a function of the excretory system?

1. Removes wastes from the blood

2. Removes excess water from the blood

3. Removes carbon dioxide from the blood

4. Removes excess salt from the blood

Other Excretory Organs

• Skin = releases perspiration (water

and salts) to cool off the body

Other Excretory Organs

• Lungs = release carbon dioxide from the body

Which system does not include an excretory organ?

1. Excretory system

2. Integumentary system

3. Cardiovascular system

4. Respiratory system

Excretory System

• How did the Filter It investigation model our excretory system?

• What are some advantages of the model?

• What are some limitations of the model?