Download Nutrient Absorption

Nutrient Absorption
Digestive, Respiratory, and
Circulatory Systems
Working Together
• Nutrition
 The Vital Nutrients
• - Six basic kinds of nutrients can be found:
–1. Carbohydrates
»Main source of energy
–2. Fats
»Used to store energy
–3. Proteins
»Form part of muscles and many cell
structures, including the cell membrane
Ca
Mg Cr
–4. Minerals
»Serve as structural materials
Vitamin D
–5. Vitamins
Vitamin C
B
»Needed for growth and metabolism
–6. Water
»Facilitates chemical reactions, helps
dissolve materials and helps
maintain the body’s temperature
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Following the Digestion of a
Meal
Functions of the Digestive System
• Main function is to disassemble the
food you eat into its component
molecules so that it can be used as
energy (ATP) by your body.
All of these organs work together to break down
food into simpler compounds that can be
absorbed by the body.
Four Stages of Digestion
1. Ingestion- the act or process of taking food or
other substances into the body.
2. Digestion- the process of converting food to an
absorbable form by breaking it down to simpler
compounds.
3. Absorption- the process of moving water and
solutes from outside of the cell into the interior.
4. Elimination-the process of the body ridding itself
of any indigestible material.
Digestion/Absorption Summary
• Digestion begins as soon as you start eating. Enzymes in
your saliva start the process of converting food into
energy.
• Via mechanical and chemical mechanisms, large nutrient
molecules are broken down into smaller ones that your
intestine absorbs into the blood stream.
• Cells then take up these nutrient molecules and use them
to build new molecules and provide their cellular energy
needs.
• Cells can also store the molecules for later use.
 The Mouth
- The disassembly line STARTS at the
mouth
• What happens when you chew?
– Your tongue moves food around & helps position
it between your teeth
– Chewing is a form mechanical digestion = the
physical process of breaking down food into
smaller pieces. This prepares food for chemical
digestion
– Chemical digestion = the process of changing
food on a molecular level through the action of
enzymes
• Chemical Digestion begins in
Mouth
• Saliva in mouth contains digestive
enzymes, called amylase, which
breaks down starch into smaller
molecules
• In the stomach, amylase continues to
digest food for about 30 min.
Starch
• Swallowing Your Food
• Chewed food becomes a ball and is
swallowed
• Swallowing forces food into throat and then
to the esophagus = a muscular tube that
connects the mouth to the stomach
– Food moves through the esophagus by
peristalsis = a series of involuntary smooth
muscle contraction along the walls of the
digestive tract
Peristalsis
• The epiglottis = a flap of cartilage that closes
over the opening to the respiratory tract as
you swallow, keeping food out
– After food passes, epiglottis opens again
– If you talk or laugh as you swallow, food may
enter the upper portion of the respiratory tract
– Your response is to choke & cough, forcing food
out of the respiratory tract
 The Stomach
Stomach = a muscular pouchlike
enlargement of the digestive tract
• Muscle Churning
– The walls of the stomach are composed of 3
layers of involuntary muscles
– When the muscles contract, they work to
physically breakdown food, creating smaller
pieces
– The pieces mix with digestive juices produced
by the stomach
• Chemical Digestion in the stomach
• The lining of the stomach contains
millions of glands that secrete a
mixture of chemicals called gastric juice
• Gastric juice contains pepsin &
hydrochloric aced
– Pepsin = an enzyme that begins the
chemical digestion of proteins in food
• The lining of the stomach secretes mucus
that forms a protective layer b/t it and the
acidic environment of the stomach
• Food remains in stomach for about 2-4 hrs
• When food leaves it is the consistency of
tomato soup (YUMMY!)
 The Small Intestine
- Small intestine = a muscular tube
about 6 m long
Called “small” because of how narrow
it is (only 2.5 cm in diameter)
- Digestion is COMPLETED here
- First 25 cm of the small intestine
called the duodenum
• Secretions of the Pancreas
• Pancreas = soft, flattened gland that
secretes both digestive enzymes &
hormones
– The mixture of enzymes it releases break
down carbs, proteins, & fats
• Secretions of the Liver
• Liver = large, complex organ that produces bile
• Bile = chemical substance that helps break down fats
– Made by the liver, but stored in the gallbladder
– From the gallbladder, bile passes into duodenum
– Bile causes further digestion by breaking large drops
of fat into smaller droplets
– Gallstones form when bile in the gallbladder
becomes too concentrated due to high levels of
cholesterol in you diet
LIVER
• Absorption of Food
• Liquid food stays in the intestine for 3-5 hrs. as it is
moved through
• As food moves it passes over thousands of tiny
fingerlike structures called villus = a single
projection on the lining of small intestine that
function in the absorption of food
• Now that food is in the form of small molecules, it
can be absorbed directly into the cells of the villi
(plural for villus)
• Food then diffuses into blood vessels of the villus &
enter the bloodstream
* Villi are the link between the digestive system & the
circulatory system
 The Large Intestine
- All indigestible material from a meal
then moves into the large intestine = a
muscular tube that is also called the colon
- Large intestine is only about 1.5 m long,
but it is much wider that the small
intestine ( about 6.5cm in diameter)
• Water Absorption
• As indigestible mixture passes
through the large intestine, water
and salts are absorbed by the
intestinal walls, leaving behind a
more solid material
• This way water in NOT wasted
• Bacteria in the large intestine make
some B vitamins and Vitamin K,
which are absorbed as needed by
the body
–These bacteria also stop harmful
bacteria from colonizing, reducing
the risk of intestinal infections
• Elimination of
Wastes
• After 18-24 hrs in the large intestine,
the remaining indigestible material,
now called feces, reaches the rectum
• Rectum = the last part of the
digestive system
Respiratory/Circulatory Systems
Functions
• Your respiratory system takes in oxygen from the
atmosphere and moves that oxygen into the
blood stream by allowing it to move across the
membranes of the lungs into the blood vessels.
• The circulatory system then carries oxygen to all
the cells in the body and picks up carbon dioxide
waste, which it returns to the lungs.
• Carbon dioxide diffuses from the blood into the
lungs , and you exhale it into the atmosphere.
Digestive Dependence Upon
Respiration
• The digestive tract functions by using
muscular contractions to break up food and
move it along the tract.
• These muscles depend upon oxygen in order
to function.
• Without oxygen, your digestive tract would
stop working.
Respiratory Dependence Upon
Digestion
• Your respiratory tract wouldn’t be able to
function without the products of digestion.
• The process of exhalation is passive; does not
require muscular contraction.
• Contraction of the diaphragm and intercostal
muscles requires fuel.
• This fuel is primarily in the form of
carbohydrates or lipids.
Blood And Energy
• Your body relies primarily on carbohydrates
and fats from the foods you eat for energy.
• The blood transports these chemicals to the
cells of your body through the circulatory
system.
Cellular Dependence Upon All Three
Systems
• The body cells depend upon products of both
the respiratory and digestive systems’
functions in order to maintain themselves
• To produce energy, cells burn nutrient
molecule fuel in oxygen.
• Digestive tract provides nutrient molecules,
while the respiratory tract provides oxygen.
• Circulatory system transports both products to
the cell.
Neural and Hormonal Regulation of
Digestion
• Gastrointestinal activities are coordinated by the
nervous system and endocrine system.
– Stomach secretions are regulated by food and
gastrin.
– The passage of chyme into the duodenum inhibits
stomach contractions.
– Duodenum secretes other hormones that inhibit
stomach emptying and promote bile release and
bicarbonate secretion.
• enterogastrones
Hormonal Control of Gastrointestinal
Tract
Accessory Organs
• Liver regulatory functions
– Liver chemically modifies substances absorbed in
the gastrointestinal tract before they reach the
rest of the body.
• also removes toxins and poisons, and converts them
into less toxic forms
– Liver regulates many compounds such as steroid
hormones, and produces most proteins found in
blood plasma.
Regulation of Blood Glucose Concentration
– After a carbohydrate-rich meal, the liver and skeletal
muscles remove excess glucose from blood and
store it as glycogen.
• stimulated by insulin
– When glucose levels decrease, the liver secretes glucose in the
blood.
» breakdown of glycogen
» gluconeogenesis - process of converting other molecules
into glucose
Actions of Insulin and Glucagon
Glucose Feedback Loop
LOW
HIGH
Blood Glucose
Blood Glucose
pancreas
Insulin
Glucagon
liver
Glucose
Glucose
Target tissue