A Digestive Journey: From Food to Poop

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A Digestive JourneyFrom Food to Poop
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Why do we need to eat?

• Food provides us with
• fuel to live,
• energy to work play, and
• the raw materials to build new cells.

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4 Components of Digestion

• ? Ingestion the taking of nutrients
• Digestion the breakdown of complex organic
  molecules into smaller components by
  enzymes
• Absorption the transport of digested nutrients
  to the tissues of the body
• Egestion the removal of waste food materials
  from the body

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A
B
C
D
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Ingestion
A
a
c
b
d
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Teeth

• For Mechanical Breakdown
• Incisors for cutting
• Canines specialized for tearing
• Premolars specialized for grinding
• Molars for crushing

7
Tongue

• Assists with the mechanical breakdown of food
  by pushing the food around while you chew with
  your teeth.
• When you're ready to swallow, the tongue
  pushes a tiny bit of mushed-up food called a
  bolus (bow-lus) toward the back of your throat
  and into the opening of your esophagus.

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Salivary Glands

• Saliva (suh-lye-vuh) is produced in and
  secreted from salivary glands.
• Chewing mixes the food with watery saliva,
  from 6 salivary glands around the mouth and
  face, to make it moist slippery so it is mushy
  and easy to swallow.
• Chemical breakdown of starch by production of
  salivary amylase from the salivary glands, an
  enzyme that begins the breakdown of starch into
  glucose.

Functions of Saliva ?
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Functions of Saliva

• Lubrication Binding binding masticated food
  into a slippery bolus and coats the oral cavity
  and esophagus 
• Solubilizes Dry Food in order to be tasted,
  the molecules in food must be solubilized
• Oral Hygiene oral cavity is almost constantly
  flushed with saliva, which floats away food
  debris and keeps the mouth relatively clean 
• Initiates Starch Digestion amylase begins the
  breakdown of starch into glucose

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Esophagus

• The esophagus (ih-sah-fuh-gus) is a muscular
  tube whose muscular contractions (peristalsis)
  propel food from the back of your throat to the
  stomach.
• But also at the back of your throat is your
  windpipe, which allows air to come in and out
  of your body. When you swallow a small ball of
  mushed-up food or liquids, a special flap called
  the epiglottis (eh-pih-glah-tiss) flops down
  over the opening of your windpipe to make sure
  the food enters the esophagus and not the
  windpipe.

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Teeth Diagram
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Tongue Diagram
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Salivary Glands Diagram
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Esophagus Diagram
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Digestion
B
d
a
e
b
c
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Stomach

• It's a stretchy sack shaped like the letter J
  with thick muscles in its wall that contract to
  mash the food.
• The stomach walls also release gastric
  (gas-trik) juices that assists in the breaking
  down of food and also helps to kill bacteria
  that might be in the eaten food.
• It has four basic functions that assist in the
  early stages of digestion and prepare the
  ingesta for further processing in the small
  intestine 

?
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Functions of the Stomach

• to store the food you've eaten, allowing a
  rather large meal to be consumed quickly and
  dealt with over an extended period of time
• to attack the food in a chemical way, breaking
  down and dissolving its nutrients, it is in the
  stomach that substantial chemical and enzymatic
  digestion is initiated
• to break down the food into a liquidy mixture
  through the vigorous contractions of gastric
  smooth muscle which mix and grind foodstuffs
  with gastric secretions, resulting in
  liquefaction of food, a prerequisite for
  delivery of the ingesta to the small intestine
  and
• to slowly empty that liquidy mixture into the
  small intestine, as food is liquefied in the
  stomach, it is slowly released into the small
  intestine for further processing.

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Pancreas

• The pancreas (pan-kree-us), like the stomach,
  makes powerful digestive juices called enzymes
  which help to digest food further, specifically
  fats proteins (into small peptide fragments
  and some amino acids by the enzyme proteases),
  as it enters the small intestines.
• The pancreas sends pancreatic juice, which
  neutralizes the chyme (the mix of acid and food
  in the stomach), to the small intestine through
  the pancreatic duct.

continued
?
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Pancreas, continued ...

• The pancreas plays a vital role in
  accomplishing both of the previous objectives,
  so vital in fact that insufficient exocrine
  secretion by the pancreas leads to starvation,
  even if adequate quantities of high quality food
  is consumed.
• In addition to its role as an exocrine organ,
  the pancreas is also an endocrine organ and the
  major hormones it secretes - insulin and
  glucagon - play a vital role in carbohydrate
  and lipid metabolism.

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Small Intestine

• The small intestine is the major site for
  digestion and absorption of nutrients.
• It is a long tube that's about 3.5 to 5cm
  around, and it's packed beneath the stomach, if
  stretched out, an adult's small intestine would
  be about 6.7m long.
• The upper part, the duodenum, is the most
  active in digestion, where the digestion of
  carbohydrates, proteins, and fats continues.

continued
?
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Small Intestine, continued ...

• Starch and glycogen are broken down into
  maltose.
• Food may spend as long as 4 hours in the small
  intestine and it will become a very thin, watery
  mixture so the nutrients are small enough to
  pass through the lining of the small intestine,
  and into the blood, where they are carried away
  to the liver and other body parts to be
  processed, stored and distributed.

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Liver

• The liver is the largest gland in the body and
  performs an astonishingly large number of tasks
  that impact all body systems.
• For digestion, the liver produces bile, which
  is stored in the gall bladder before entering
  the bile duct into the duodenum.
• Bile emulsifies fats, facilitating their
  breakdown into progressively smaller fat
  globules until they can be acted upon by
  lipases. Fats are completely digested in the
  small intestine, unlike carbohydrates and
  proteins.

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Gall Bladder

• This small bag-like part is tucked under the
  liver.
• It stores a fluid called bile, which is made
  in the liver.
• As food from a meal arrives in the small
  intestine, bile flows from the gall bladder
  along the bile duct into the intestine.
• It helps to digest fatty foods and also
  contains wastes for removal.

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Stomach Diagram
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Pancreas Diagram
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Small Intestine Diagram
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Liver Diagram
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Gall Bladder Diagram
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Absorption
C
a
c
b
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Stomach

• The stomach absorbs some water, specific
  vitamins, some medicines, alcohol.

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Small Intestine

• The net effect of passage through the small
  intestine is absorption of most of the water
  and electrolytes (sodium, chloride, potassium)
  and essentially all dietary organic molecules
  (including glucose, amino acids and fatty
  acids). Through these activities, the small
  intestine not only provides nutrients to the
  body, but plays a critical role in water and
  acid-base balance.
• Most absorption occurs in the duodenum and
  jejeunum (second third of the small intestine).

More ?
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Villi Microvilli

• The inner surface of the intestine has circular
  folds that more than triple the surface area for
  absorption. Villi covered with epithelial cells
  increase the surface area by another factor of
  10. The epithelial cells are lined with
  microvilli that further increase the surface
  area a 6m long tube has a surface area of 300
  square metres.
• Each villus has a surface that is adjacent to
  the inside of the small intestinal opening
  covered in microvilli that form on top of an
  epithelial cell known as a brush border. Each
  villus has a capillary network supplied by a
  small arteriole. Absorbed substances pass
  through the brush border into the capillary,
  usually by passive transport.

More ?
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Villi Microvilli, continued

• Maltose, sucrose, and lactose are the main
  carbohydrates present in the small intestine
  they are absorbed by the microvilli. Starch is
  broken down into two-glucose units (maltose)
  elsewhere. Enzymes in the cells convert these
  disaccharides into monosaccharides that then
  leave the cell and enter the capillary.
• Peptide fragments and amino acids cross the
  epithelial cell membranes by active transport.
  Inside the cell they are broken into amino acids
  that then enter the capillary.

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Large Intestine

• The large intestine is made up by the colon
  (coh-lun), cecum, appendix, and rectum.
• Material in the large intestine is mostly
  indigestible residue and liquid.
• Water, salts, and vitamins are absorbed back
  into the blood, the remaining contents form
  feces.
• Bacteria in the large intestine, such as E.
  coli, produce vitamins (including vitamin K)
  that are absorbed.
• The part of the large intestine called the
  colon, is where the body gets its last chance to
  absorb the water and some minerals into the
  blood.

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Villi Diagram
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Microvilli Diagram
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Large Intestine Diagram
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Egestion
D
a
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Rectum Anus

• As the water leaves the waste product, what's
  left gets harder and harder as it keeps moving
  along, until it becomes a solid, ready to be
  removed from the body.
• The large intestine pushes the poop into the
  rectum (rek-tum), the very last stop on the
  digestive tract.
• The solid waste stays here until you are ready
  to go to the bathroom. When you go to the
  bathroom, you are getting rid of this solid
  waste by pushing it through the anus (ay-nus), a
  ring of muscle and out of the body.

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Rectum Anus Diagram
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Sources
http//www.emc.maricopa.edu/faculty/farabee/BIOBK/
BioBookDIGEST.html http//kidshealth.org/kid/body/
digest_noSW.html http//users.tpg.com.au/users/amc
gann/body/digestive.html http//arbl.cvmbs.colosta
te.edu/hbooks/pathphys/digestion/ http//www.bupa.
co.uk/health_information/html/organ/stomach.html h
ttp//www.nlm.nih.gov/medlineplus/ency/imagepages/
19221.htm http//www.bupa.co.uk/health_information
/html/organ/liver.html http//trms.sheridank12.net
/New20Homepage/Gen.www/Brian20genY/Brian20Image
s/gall_bladder.htm http//www.nlm.nih.gov/medlinep
lus/ency/imagepages/8832.htm http//vanderbiltowc.
wellsource.com/dh/content.asp?ID574