Transcript Digestive System Organisms human tree Organ systems stem Organs leaf heart cardiac tissue leaf tissues brain Tissues nerve cell Cells Molecules Atoms DNA molecules Functions of the Digestive System Cells require nutrients obtained from food and oxygen The Digestive.

Digestive System
Organisms
human
tree
Organ systems
stem
Organs
leaf
heart
cardiac
tissue
leaf tissues
brain
Tissues
nerve cell
Cells
Molecules
Atoms
DNA molecules
Functions of the Digestive System
Cells require nutrients obtained from food and oxygen
The Digestive System will:
Disassemble large organic molecules into smaller
component molecules
Transfer these to circulatory system for distribution to
rest of body
Get rid of indigestible material
Different steps of digestion
Mechanical Digestion: Grinding large food particles into
smaller clumps (reducing # molecules per clump)
Chemical Digestion: Breaking larger molecules into smaller
component molecules, by means of a chemical reaction,
using enzymes
Absorption: Smaller component molecules transported
across wall of digestive tract and into blood vessels
Elimination : getting rid of undigested food
Organs involved
in digestion
Two types of organs:
Digestive Tract Organs
Accessory Organs
Components of the digestive system
Salivary
glands
Pancreas
Gall Bladder
Oral cavity
Pharynx
Esophagus
Stomach
Digestive tract
(Muscular tube w/
specialized segments)
Accessory glands
Small intestine (secrete substances
that aid with digestion)
Liver
Large intestine
Oral Cavity:
Mechanical processingchewing
Chemical Digestionsaliva secretion:
carbohydrate digestion
• Epiglottis:
“Lid” that closes over
opening to trachea Prevents food entering
airway
Why is mechanical processing important?
Enzyme must bind to
substrate, so enzyme must
have access to these larger
molecules.
Mechanical processing:
•increases surface area of
food particles
•Exposes more molecules
to enzymes, increases
efficiency.
Swallowing:
Pharynx and
Esophagus:
No mechanical
processing, digestion,
or absorption,
Merely conducts food
to stomach.
If you stand on
your head, will the
food still move to
your stomach?
YES: food moves down by
muscle contractions of the
esophagus (= peristalsis)
Stomach:
Storage for food
Mechanical processing:
churning
Chemical digestion:
protein digestion - enzymes
secreted from stomach wall
hydrochloric acid also
secreted - Lowers pH to kill
pathogens (disease-causing
organisms) and activate
protein enzymes
Small Intestine:
Function:
• Most chemical digestion
occurs in the small
intestines (lipids, nucleic
acids, carbohydrates,
proteins)
• Absorption of nutrients
Small Intestine:
From Accessory Organs:
• Bile
produced in liver
stored in gall bladder
• Pancreatic juices
(enzymes)
Small Intestine:
Digestion
Mechanical - Lipids not water soluble, but enzymes are Bile will break up large groups of lipid molecules
into smaller droplets so enzymes can act on them
(Emulsification)
Bile enters the small intestine through the bile duct
Chemical - Carbohydrate, protein, & lipid digestion
enzymes secreted from pancreas
enzymes located in the intestinal wall
Small Intestine:
Absorption - Component molecules diffuse across
intestinal wall into circulatory system
Villi
(fingerlike
projections)
Increased surface area
for absorption:
Intestinal wall - folded
Villi - Fingerlike
projections of intestinal
wall;
Microvilli - Projections of
plasma membrane of
intestinal cells
Amino acids, glucose, other water soluble nutrients absorbed
into the capillaries
What are lacteals?
• Inside the villi
are vessels of
the lymphatic
system that
absorb the
fatty acids and
glycerol.
Large Intestine (colon):
- Absorbs water;
- Contains lots of bacteria
(mostly E. coli), bacteria digest
some remaining food, bacteria
produce vitamins;
- Responsible for elimination of
undigested food = feces)
Blood leaving
intestines is
transported to the
liver via the
hepatic portal vein
for processing
[molecules
modified, toxins
removed]
The liver Removes
• unwanted or harmful chemicals
(detoxification) including chemicals
produced in the body,
•unwanted chemicals taken into the body
(e.g. carcinogens), and medications.
•Hepatocytes - Liver cells - the liver's main functional
units.
Pancreas
Pancreas
•Main enzyme producing organ of digestive
system
• Pancreatic duct enters the small intestine to
deliver fluid (pancreatic juice) through a small
hole in the wall of the second part of the
duodenum
•Pancreatic juice contains enzymes capable of
digesting all food types - protein, fat and
carbohydrates