Download Digestion

Chapter
38
Digestive &
Excretory
Systems
What’s this pic saying?
Digestion
Where does all the energy come
from for all everything in your
body like nerve impulses (signals)
& muscle contractions?
Digestion
• *Breakdown of food into small molecules
• Two main reasons for this
– *Energy; turn glucose  ATP*
– *Nutrition - need building materials for new
cells, new tissues, and tissue repair*
• DNA from your food is broken down into
nucleotides – reassembled into your DNA’s code
during DNA replication
• Protein-rich meats are broken down into amino
acids – reassembled during translation to make
more proteins
• Lipids for cell membranes (phospholipid bilayer)
Nutrition - Building Blocks from Food
Nutrients
***Water
***Carbohydrates
***Lipids (fats)
***Proteins
Function in Body
Makes up the bulk of blood, lymph, and cytoplasm
Essential for most cellular processes
Helps regulate body temperature, blood pressure
Main energy source for the body.
Used to create cell membranes, myelin sheaths, &
hormones.
Provides support, protection, insulation for body organs.
Long-term energy storage.
Growth & repair of structures like skin & muscle.
Regulate movement of molecules into cells (protein
pumps & protein channels).
Vitamins
Organic molecules that help regulate chemical reactions –
called coenzymes (allow the enzyme to actually bind to its
substrate)
Minerals
Inorganic nutrients used to make bone, teeth, hemoglobin,
and help neurons function: Ca, Fe, Mg, Na, K
The Gastrointestinal Tract
• Alimentary canal - *a single tube that runs
from mouth to anus*
• Organs/parts:
– mouth, pharynx, esophagus, stomach, small
intestine, large intestine
• Glands:
– Salivary glands, pancreas, and liver
– add their secretions to the digestive system
The Digestive System
Pharynx
Mouth
Salivary
glands
Esophagus
Liver
Gallbladder
(behind liver)
Stomach
Pancreas (behind stomach)
Large intestine
Small intestine
Rectum
Basic Steps of Digestion
1. *Break down food from macromolecules to
smaller molecules (polymer  monomer)
•
•
Mechanical – physically make smaller pieces
Chemical – breaking bonds to make smaller
molecules
2. *Absorb small molecules into the blood.
3. *Distribution to the rest of the body cells
(“internal transport system”)
Mouth
• Mechanical
– teeth cut & grind food
• *Chemical
– salivary glands secrete
salivary amylase
– *Breaks down
polysaccharides into
monosaccharides
• *Rear part of throat*
– Accommodates both
food & air from mouth
and nasal passages
• Tongue pushes food
toward it
– Bolus – chewed
clump of food and
enzymes
• Epiglottis
– Small flap of cartilage
– closes so food doesn’t
enter respiratory tract
Pharynx
Esophagus
• *Muscular tube that
connects pharynx
with stomach*
• Peristalsis is the
muscular contractions
that push food to
stomach
*Stomach– HCl (hydrochloric acid) helps
breaks food into smaller pieces protein digestion
• Also makes the stomach acidic to
• Mechanical
activate other enzymes
– Mucus – secreted to help protect
lining of stomach from the acid
– Mixture is now churned into
chyme
• Chemical
– *Pepsin begins the breakdown of
proteins into amino acids*
• Activated by the HCl
• 8 essential amino acids are found
in meats, fish, eggs, milk – vegans
must be sure to eat various plant
groups to get these
• valve at bottom of stomach
opens to release chyme into
small intestine
Small Intestine
• 3 parts (it can be 7 meters long!)
– Duodenum  Jejunum  Ileum
• Both mechanical & ***chemical digestion*
• *Enzymes added by the pancreas & liver*
• Where *absorption of nutrients,
vitamins, & minerals
happens*
The Liver and the Pancreas
Liver
Bile duct
Gallbladder
Pancreas
Duodenum
Pancreatic
duct
To rest of small
intestine
*Liver & Pancreas Release into the
Small Intestine to digest*
• From the liver…
– Bile = Mechanical
Digestion
– Emulsifies fats - acts
like a detergent to
break large fats into
smaller ones that the
lipase can chemically
break down
– Bile is stored in
gallbladder until
needed
• From the pancreas …
– Releases sodium
bicarbonate (NaHCO3) to
neutralize acidic stomach
secretions
– Chemical Digestion
• Amylase – resumes
carbohydrate digestion
• Trypsin – continues
protein digestion
• Lipase – completes fat
digestion
– Also regulates blood sugar
levels
*Small Intestine=most
absorption of nutrients*
• Most absorption of
nutrients to blood occurs
in the jejunum & ileum
• Inner surface is a series
of folds called villi and
microvilli that increase
surface area used for
absorption
– have lots of capillaries
running over them to do
this (like the alveoli in the
lungs)
*Large Intestine (colon)=remove
water*
• Chyme is now almost
devoid of nutrients
– Only water, cellulose, &
undigestible material left
• *Large Intestine takes out
extra water
• E. coli colonies live here
off the undigestible
materials
– produces vitamin K
• *Undigestible materials
are compacted, collected
in rectum, & expelled
through anus
The Digestive Enzymes
Site
Enzyme
Role in Digestion
Mouth
Salivary amylase
Breaks down starches into
disaccharides
Stomach
Pepsin
Breaks down proteins into large
peptides
Small intestine
(from pancreas)
Amylase
Continues the breakdown of
starch
Trypsin
Continues the breakdown of
protein
Lipase
Breaks down fat
Maltase, sucrase, lactase
Breaks down remaining
disaccharides into
monosaccharides
Peptidase
Breaks down dipeptides into
amino acids.
Small intestine
Glucagon=hey your glucose is gone
Insulin- sends sugar into cells for cell resp.
Excretion
How do we get rid of the other
wastes we create in every
chemical reaction?
A filter you may be familiar
with
• Have you ever seen a waterpurification system attached
to a faucet?
• This system removes
impurities from water such as
arsenic or other chemicals
that can be harmful to
people. Water passes
through the filters in the
system; the impurities are
trapped on the surface of the
filters. Eventually, the water
that comes out of this purifier
is free of the impurities.
Your Body’s Filter
• 1. Your body has its own system for
filtering blood. Why might the blood in your
body need to be filtered?
• 2. What organ(s) do you think filters your
blood?
• 3. How do you think the filtered materials
leave your body?
What kind of waste do we make?
• Excess water, salts, carbon dioxide, and
urea
– Urea is made from nitrogen of proteins that
we’ve broken down for energy
• Excretion means getting rid of waste
•Filter
•Detoxify stores glycogen- make
bile
•Releases enzymes and hormone
insulin
•Protein digestion
The Excretory System
• Skin
– excretes excess H20 and
salts (some urea)
• Lungs
– excrete CO2
• Liver
– turns excess amino acids
into urea
• *Kidneys
– *Filters blood of toxins
– *Removes excess water
– *Regulates pH of blood
Kidneys - main excretory organs
• 2 bean-shaped organs
– size of a closed fist
• Renal artery – enters each
kidney with unfiltered blood
(full of toxins)
• Renal vein - leaves each
kidney with filtered blood (rid
of toxins)
• A ureter leaves each kidney
carrying waste filled fluid
(urine) to urinary bladder for
storage
• The urethra is a duct that
releases urine from the
bladder to the external
environment
How the Kidney Filters
•
*Made up of nephrons***
– *Each is a separate little filtering system (1 million)
1. *Blood enters kidney through the renal artery
2. *Blood flows into the nephron in small arteries and is
filtered
– Water, salts, urea, glucose & amino acids are filtered out (the
filtrate) in the Bowman’s capsule
– Salts, amino acids, fats, sugars are removed from filtrate by
active transport and put back into the blood (reabsorption)
3. * (Filtered fluid now called urine) & flows through a duct
called the Loop of Henle
– Urine gets concentrated when water moves back into blood via
osmosis
4. *Urine empties into the ureter that leads to the bladder
for storage
5. *Purified blood leaves through renal vein to return the
body
Structure of the Kidneys
Kidney
Nephron
Bowman’s
capsule
Cortex
Capillaries
Glomerulus
Medulla
Renal
artery
Renal vein
Ureter
Collecting
duct
Vein
To the bladderArtery
To the ureter
Loop of Henle
Renal artery  glomerulus  Bowman’s capsule  Loop of Henle  Ureter  bladder
FYI Kidney Dialysis
Blood in tubing flows
through dialysis fluid
Blood pump
Vein
Artery
Used dialysis fluid
Shunt
Air detector
Dialysis
machine
Fresh
dialysis
fluid
Compressed
air
The digestive enzymes in the table function in some organs
to perform the chemical digestion of food. The major
organs of the digestive system are the esophagus, large
intestine, mouth, pharynx, small intestine, and stomach.
A. List these six organs in the order in which food passes
through them.
B. Identify which of these organs is primarily responsible for
absorbing nutrients from digested food.
C. Describe the functions of two of the organs listed other
than the one you identified in part (b).
• Milk is an important part of many people’s diets. When the word milk
is mentioned, most people think of dairy milk derived from cows.
Many people, however, cannot drink dairy milk because of lactose
intolerance. Individuals with this condition are unable to digest a
component in the milk called lactose.
Lactose is the sugar in dairy milk. It is a disaccharide made from the
sugars glucose and galactose.
Lactose-intolerant individuals lack the enzyme lactase, which is
needed for the digestion of lactose sugar.
• Many lactose-intolerant individuals drink soymilk instead of dairy
milk. Soymilk is produced from soybeans (the seeds of the soybean
plant) and is a nutritious substitute for dairy milk. Soymilk contains
protein, calcium, and other essential nutrients just as dairy milk
does.
• The table below compares some of the nutrition information for a
serving of dairy milk and a serving
of soymilk.
• Dairy Milk and Soymilk Nutrition Information Chart
The digestion of dairy milk or soymilk provides the body with important
nutrients
1. Describe how the digestive system converts the carbohydrates, proteins,
and fats in dairy milk or soymilk into nutrients that can be used by cells.
Include the body parts and organs involved.
2. Describe how the nutrients in the digestive system are made available to
cells throughout the body after digestion has occurred. Include the body parts
and organs involved.