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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
4
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.
7
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.
8
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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
10
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
14
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
•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?