Transcript File

The Digestive System
The Basics of Nutrition
Heterotrophs (can NOT synthesize organic nutrients)
Digestion involves:
• ingestion:
• digestion:
• egestion:
The Basics of Nutrition
Nutrient: any substance that provides energy for
growth and repair:
Food molecules must be digested into subunits
( Monomers ) that can diffuse through cell
membranes
Structure of Digestive System
• Continuous tube extending from mouth to
anus- Also called ALIMENTARY TRACT
• Accessory organs attached along the way
LineRider
• LineRider
Organs of Digestive System
Alimentary Tract
1. Mouth – “oral cavity”
2. Pharynx – “throat”
3. Esophagus
4. Stomach
5. Small intestine
6. Large intestine – “colon”
Organs of Digestive System
Accessory Organs
1. Liver
2. Gall Bladder
3. Pancreas
4. Appendix
5. Salivary Glands
The Mouth
• Ingestion occurs here
• Contains teeth, tongue, and salivary glands
• Both chemical and mechanical digestion occur
here.
• Only Starch get digested in the Mouth
The Mouth
– Chemical:
Salivary amylase is an enzyme in saliva that
breaks down Starch.
– Mechanical:
Teeth grind food increasing surface area for
more efficient enzyme action
• saliva also lubricates the food by adding water
and mucus
The Food we swallow is called a bolus
Pharynx
•
•
•
Back of the throat
Where openings to trachea and esophagus
meet
Epiglottis: flap of connective tissue that
closes over the trachea when swallowing
Esophagus
•
•
tube that connects the oral cavity with
stomach
Peristalsis: muscular contractions that
squeeze food towards the stomach
A Phone Call at 12am
The opening from the esophagus into the
stomach is a ring of muscle called the cardiac
sphincter
Stomach
•
muscular organ that mechanically and
chemically digests food.
•
Only Protein get digested in the stomach
Stomach
•
Lined with cells that secrete:
1. Mucus to protect stomach lining
2. Protease ( Pepsin ) to chemically digest Protein
3. Hydrochloric acid (HCl)
 HCl has several functions
- lowers the pH in the stomach (pepsin works
best at pH 2)
- helps to kill microorganisms ingested in the
food
Stomach
Strange things in kids stomachs
Chyme
The food coming out of the stomach is a soupy
mixture called chyme
Most of the chemical digestion of
food occurs in the the duodenum the first 25 cm of the SI
Villi
VILLI - finger-like projections lining the
small intestines for increased surface area
FYI: (size of tennis court)
• Absorption and diffusion of
nutrients into the bloodstream occurs
here
A CLOSER LOOK at Villi
Digested end products are taken into the villi
by active and passive transport
Each villus contains :
Lacteal - pick up fatty acids
and glycerol
Veins, arteries and
capillaries - pick up
nucleotides, amino acids,
and monosaccharides
Accessory Organs
Pancreas
• Pancreas:
1. Produces enzymes and release them into
the Small Intestines:
Enzymes breaks down carbohydrates, lipids,
and proteins
• Pancreas:
2. Produces sodium bicarbonate – neutralizes
stomach acid
3. Produces hormones that regulate blood
sugar levels (Endocrine Hormones)
Pancreatic juice
contains:
proteases - digest proteins
lipases - digest lipids
amylases - digest carbohydrates
Gall Bladder
• Small, non-vital organ –
storage of bile
• Bile – emulsifies fat
• Tucked on underside of liver
Gallbladder
The gallbladder releases bile into the Small
Intestines
Bile is NOT an enzyme - its function is to break
down fat globules by a emulsification
Emulsification: mechanical digestion
of fats molecules dissolved into smaller
droplets
The Liver
• Largest internal organ
Liver
• Functions:
Produces Bile: Which breaks down fats
Produces Urea (from breakdown of proteins)
Filters out harmful substances
Removes Biliubin ( from dead red blood cells )
Produces and removes Cholesterol
Bile is produced in the liver then stored in the
gallbladder
Appendix
• Pouch located where small and large intestines
meet
• A vestigial organ:
– Non-vital
– Thought to house important bacteria needed for
balance in body
– Could possibly play a role in immunity
• All indigestible waste at this point – no
nutritional value
• Known as the colon
• Regulates water concentration of fecal matter
before EGESTION through the RECTUM and
ANUS
• Function is to reabsorb most of the water that
was not picked up by the SI
• Too much or too little water can be
problematic…
A large colony of bacteria known as E. Coli
lives in the LI
They Help produce vitamin K - needed for
blood clotting
1. Erosion of the
stomach lining by
digestive enzymes
or acid due to lack
of protective
mucus.
Ulcers
• a hole in the stomach lining
• cause: bacterium – Helicobacter pylori
• Large intestine is
difficult to empty
due to too much
water being
reabsorbed in the
colon – waste
hardens.
• Cardiac sphincter
stretches and stomach
acid splashes walls of
esophagus.
• Burning and pressure in
chest
• Caused by overeating,
acidic foods, or
caffeinated beverages
• Not enough water is absorbed out of
waste before egestion
• Usually caused by bacteria
• Results in watery feces
• Could cause SEVERE DEHYDRATION
• Inflammation of the
appendix
• Could be very
dangerous if it
ruptures
• Accumulation of
hardened cholesterol in
the gall bladder
• Hepatitis (Inflammation/ Infection of the liver)
• Type A , B, & C
• Cirrhosis
• Distorted or scarred liver as a result of chronic
inflammation or drinking and drug use
Question #1
The principal function of the large
intestine is to:
1.Produce salivary amylase
2.Produce bile
3.Store bile
4.Reabsorb water from feces
Question #2
Choking on food is most likely
caused by an interference with the
proper functioning of the
1. Diaphragm
2. Oral cavity
3. Esophagus
4. Epiglottis
Question # 3
What is the role of teeth in digestion?
1. They break down food mechanically,
increasing the surface area of the food for
enzyme action.
2. They break food down mechanically,
stimulating enzyme synthesis in the food.
3. They break down food chemically, aiding in
the movement of food down the esophagus.
4. They break down food chemically, mixing
saliva with the food for easier digestion.
Question # 4
In the human body, hydrochloric acid is
responsible for the low pH of the
contents of the
1. Lungs
2. Kidneys
3. Pancreas
4. Stomach
Question # 5
In humans villi that absorb small, soluble
nutrients into the bloodstream are found in
the
1. Large Intestine
2. Small Intestine
3. Esophagus
4. Stomach
Question # 6
Bile is a secretion produced by the liver,
which aids in the emulsification of
1. Lipids
2. Proteins
3. Sugars
4. Starches
Question #7
Feces is usually about 40% water and 60%
solid matter. Reducing the water
content to 20% would most likely result
in
1. Diarrhea
2. Ulcers
3. Gallstones
4. Constipation