Transcript Human Digestion

First Five
 Describe the differences between:
1. digestion and absorption
2. physical/mechanical digestion and
chemical digestion
3. ingestion and egestion
Announcements
 Turn in the worksheets that were assigned last
week:
 Photosynthesis & Respiration
 Human Digestive System
 Quiz on Monday (3/31) or Tuedsay (4/1):
Digestive system, Respiration & Photosynthesis
 Finish all Coursework by Friday at 4:45 p.m.
 Work times: Mon, Wed, Thurs during LRL;
Mon – Thurs after school until 5:30 p.m.
Human Digestion
Nutrition
Definition:
 Taking in, absorbing and assimilating
nutrients for energy, growth, and tissue
repair
Types of Nutrients
 Micronutrients- vitamins, minerals, & water
 Macronutrients- proteins, lipids, carbohydrates
Four Parts of Nutrition
1. Ingestion
2. Digestion
3. Absorption
4. Egestion
Four Parts of Nutrition
1. Ingestion
taking substances into the body
through the mouth
2. Digestion
3. Absorption
4. Egestion
Four Parts of Nutrition
1. Ingestion
2. Digestion
break-down of large, insoluble food
molecules into small, water-soluble
molecules using mechanical and
chemical processes
3. Absorption
4. Egestion
Four Parts of Nutrition
1. Ingestion
2. Digestion
3. Absorption
movement of digested food molecules
through the wall of the intestine into
the blood
4. Egestion
Four Parts of Nutrition
1. Ingestion
2. Digestion
3. Absorption
4. Egestion
passing out of food that has not been
digested, as feces, through the anus
Human digestive
system
Ingestion takes
place in the mouth
mechanical digestion
teeth break up food
chemical digestion
saliva
 amylase: an enzyme that digests starch
 mucin: a protein present in mucus that
protects soft lining of digestive system and
lubricates food for easier swallowing
 buffers: neutralize acid to prevent tooth decay
 anti-bacterial chemicals: kill bacteria that enter
mouth with food
Esophagus
Food moves through the
Esophagus to the
Stomach by Peristalsis
 Peristalsis: a series of
involuntary wave-like
muscle contractions
which move food along
the digestive tract
Stomach: function
food storage
can stretch to fit ~2L food
disinfect food
HCl [pH 2] kills bacteria
chemical digestion
pepsin: an enzyme that breaks down proteins
Food is further broken down into a thin liquid
called chyme.
Which type of digestion is the
following?
1.
Chewing a saltine? -
2. Saliva breaking the saltine down into molecules of
glucose? 3. Your tongue breaking pieces of a hamburger apart?
4. Pepsin (an enzyme) in your stomach breaking the
hamburger into amino acids?
Accessory Organs
Pancreas
Liver
Gall Bladder
Pancreas
 An organ which secretes both digestive enzymes
(exocrine) and hormones (endocrine)
 Pancreatic juice contains enzymes which digest
all major nutrient types.
• Pancreatic juice
moves through the
pancreatic duct into
the duodenum
(small intestine).
Pancreatic Juice
Digestive enzymes
 amylase
 breaks down starch
 trypsin
 breaks down proteins to polypeptides
 lipase
 breaks down fats to fatty acids and glycerol
Buffers
 neutralize acid from stomach
Liver
 converts excess glucose
(monosaccharide) to glycogen
(polysaccharide) for storage
 converts excess proteins and amino acids
to other substances, such as fats, for
storage
 produces bile for use in digestion
Gall bladder
 Stores bile until needed in the
duodenum (small intestine)
 Moves bile through the bile duct
Bile
 Bile is a bitter, greenish-yellow alkaline
fluid
 stored in the gallbladder between meals
 discharged into the duodenum(small
intestine) upon eating
 aids the process of digestion
 Bile emulsifies lipids
 physically breaks apart large drops of
fat into small drops of fat
Small intestine
Functions:
chemical digestion
absorption of nutrients through
lining
 small intestine has huge surface area
= 300 m2 (~size of tennis court)
Small intestine
Structure: 3 sections
1. duodenum = mostly digestion
2. jejunum = absorption of
nutrients & water
3. ileum = absorption of
nutrients & water
Duodenum
 1st section of small intestine
 acidic food from stomach mixes with
digestive juices from:
 pancreas
 liver
 gall bladder
 the final stages of digestion are
completed in the duodenum
Absorption by Small Intestines
Absorption:
movement of digested food molecules
through the wall of the intestine into the
blood
Absorption by the Small Intestine
 Digested nutrient molecules are small enough to
pass through the wall of the small intestine into the
blood.
 Water, mineral salts, and vitamins are also absorbed
in the small intestine
 Villi
 finger-like projections in the wall of the small intestine
 increase the surface area of the small intestines
 greater surface area provides better absorption of
materials
Absorption by Small Intestines
Villi: finger-like projections that increase
surface area for absorption
VILLI
Large Intestine/Colon
 Functions:
 reabsorption of water
 movement of undigested
solid materials (fibers)
 Structure:
 shorter and wider than the
small intestine
Rectum
Last section of colon
(large intestine)
Eliminates feces
 undigested materials
 mainly cellulose
from plants
 roughage or fiber
mouth
break up food
digest starch
kill germs
moisten food
liver
produces bile
- stored in gall bladder
break up fats
stomach
kills germs
break up food
digest proteins
store food
small intestine
finishes digestion
absorption of
nutrients
contains villi
pancreas
produces enzymes to
digest proteins & starch
large intestine
finishes digestion
absorption of
nutrients
contains villi
Digestive System Classwork
1) Go through the digestive system animation to
visualize how the digestive system works.
http://kitses.com/animation/swfs/digestion.swf
2) Complete Build-A-Body: Digestive System.
-- Build the digestive system
-- Read through the Case Studies to answer the
questions on the handout.
http://www.brainpop.com/games/buildabodydigest
ivesystem/
3) Answer the follow-up questions on the handout.
Finish as homework