Digestive System

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Digestive System

• A closer look

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Digestive Processes

• In order for our bodies to use the food we eat to
  grow, energize, and repair our cells, 5 digestive
  processes have to occur.
• These include
• Ingestion
• Movement
• Digestion
• Absorption
• Egestion (excretion)

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Digestive Processes

• These processes occur at different locations
  along the digestive tract, which is a continuous
  tube from mouth to anus.
• We are going to discuss what happens at each site
  as we go through the stages.
• It will be useful to copy the following concept
  map and to keep adding to it as we add more
  details to help you stay organized.

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NOTE This should be a straight line in your notes
Small Intestine
Stomach
Large Intestine
Esophagus
Tongue
Rectum/ Anus
Mouth/ Throat
Teeth
Salivary Glands
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Digestive System

• Includes organs which perform digestion tasks
• Digestive Tract (Gastrointestinal Tract, G. I.
  Tract) includes mouth, esophagus, stomach,
  small intestine, large intestine or colon, and
  anus.
• Accessory Structures include, tongue, salivary
  glands, liver, gall bladder and pancreas.

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Digestion

• The process in our bodies that breaks down food
  for use by our cells. This is done in two ways
• Mechanical our teeth chewing through the food
• Chemical enzymes breakdown food into absorbable
  molecules.

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Mouth (where it all begins)
Hard Palate

• Four main parts of the mouth
• Teeth
• Tongue
• Salivary Glands
• Hard and Soft Palates

Uvula
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Mouth

• Teeth (Chewing)
• Mechanical Digestion
• Are covered by enamel, the hardest structure of
  the body
• Their movements slice, tear, grind and mix food
• Incisors snap off pieces of food
• Canine tearing pieces apart
• Premolars molars grind food to a paste

How many teeth in adult humans?
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Tongue

• Floor of oral cavity
• Composed of voluntarily controlled muscle tissue
• Role Guides food during chewing and swallowing
• Major taste buds are embedded here.
• Salty, sweet, sour, bitter

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Salivary Glands

• Release saliva in response to the smell, taste,
  and thought of food
• First example of chemical digestion
• Contains Amylase an enzyme that begins breakdown
  of starch into simple sugars, like glucose or
  table sugar.
• Interesting Fact We secrete about 1-2L of saliva
  per day!

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Hard Soft Palates

• Separate mouth from nasal
• cavity, so food doesnt go up your nose!
• Located at the roof of your mouth.
• Uvula (dangles)
• Just beneath the soft palate
• Prevents food from entering nasal passages by
  raising up.

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Soft Palate
Hard Palate
Tongue
Uvula
Epiglottis
Trachea
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Recap (Mouth)

• Food enters
• Teeth rip, tear, and chew into smaller pieces to
  swallow
• At the same time, Salivary Glands are stimulated
  to release saliva which contains amylase.
• Tongue pushes bolus to back of pharynx (throat)
  and the uvula elevates, closing off the nasal
  passage. The bolus now pushes the epiglottis
  which closes the opening of the larynx,
  preventing the food from entering the wrong tube,
  which results in choking

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Esophagus

• Muscular tube which extends from pharynx (throat)
  to the stomach
• Swallowing initiates peristalsis, a wave of
  contraction which initiates just above the
  bolus (substance) and moves it towards the
  stomach.
• This movement also occurs in the stomach and in
  the intestines.

http//pennhealth.com/health_info/animationplayer/
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Esophagus

• Secretes mucus (along with the rest of the
  digestive tract)
• This lubricant decreases the likelihood of the
  esophagus getting damaged by any sharp edges from
  the food entering.
• Mucus also protects esophagus from acid and
  enzymes in gastric juice if reflux were to occur.

http//digestive.niddk.nih.gov/ddiseases/pubs/gerd
/
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NOTE This should be a straight line in your notes
Small Intestine
Stomach
Mechanical Peristalsis
Large Intestine
Esophagus
Tongue
Rectum/ Anus
Mouth/ Throat
Mechanical Chewing
Chemical Starch/Amylase
Teeth
Salivary Glands
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Stomach

• Separated from esophagus by the Gastro esophageal
  sphincter
• Expandable muscular J-shaped sac that can hold up
  to 2-4 liters of food and liquid
• Secretes mucous to protect lining cells
• Contents are held in the stomach by the pyloric
  sphincter, ring of circular muscle, which
  separates the stomach from upper small intestine

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Stomach

• 3 Functions
• Stores food and releases it gradually into the
  small intestine
• Assist in mechanical breakdown of food by
  peristalsis and contractions of muscular walls
• Chemical breakdown of food by enzymes and other
  substances.

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Stomach

• Secretions (continued)
• Gastrin hormone that stimulates secretion of
  Hydrochloric acid (HCl)
• Pepsinogen inactive form of enzyme is activated
  by HCl and transformed into pepsin which helps
  breakdown proteins into amino acids (smaller
  units).

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Stomach

• Food is gradually converted into a thick liquid
  called chyme which consists of partially digested
  food and digestive secretions.
• Chyme is propelled towards small intestine
• The Pyloric sphincter lets a teaspoon of chyme
  into the small intestine during each contraction
• Takes around 2-6 hours to empty stomach

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NOTE This should be a straight line in your notes
Mechanical Muscle Contractions
Mechanical Peristalsis
Small Intestine
Stomach
Mechanical Peristalsis
Chemical Pepsin (Proteins), HCl
Large Intestine
Esophagus
Tongue
Rectum/ Anus
Mouth/ Throat
Mechanical Chewing
Chemical Starch
Teeth
Salivary Glands
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Small Intestine (S. I.)

• Narrow tube (1-2 inches in diameter)
• Longest part of digestive tract
• Split into three parts duodenum, jejunum, and
  the ileum
• Function to digest food into small molecules and
  absorb into blood stream and lymph vessels.

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Small Intestine (S. I)

• Helped by three other sources
• 1. Liver Has many functions in our bodies. In
  digestion, it produces bile which is stored in
  the gall bladder, then released in the S. I.
• Bile is made up of bile salts, water, and other
  salts and assist in the breakdown of lipids.

http//zap.intergate.ca/images/liver20image.jpg
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Small Intestine (S. I.)

• 2. Gall Bladder stores bile until its needed for
  digestion

http//www.nlm.nih.gov/medlineplus/ency/imagepages
/19260.htm
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Small Intestine (S. I.)

• 3. Pancreas
• Located between stomach and S. I.
• Cells produce pancreatic juice which neutralizes
  the acidic chyme it receives from the stomach
• Digests carbohydrates, proteins, and lipids
• Contains water, sodium bicarbonate, and many
  enzymes
• YouTube - Pancreas - "Weird Al" Yankovic

http//www.nlm.nih.gov/medlineplus/ency/imagepages
/17194.htm
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Small Intestine (S. I)

• Pancreas (contd)
• Enzymes include
• Amylase Carbohydrates
• Lipase Lipids
• Proteases Proteins and peptides

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Small Intestine (S. I.)

• Specialized cells within the wall complete the
  process. At the same time, nutrients are absorbed
  into the blood stream.
• The numerous folds and projections, called villi,
  give the internal surface area a much larger
  surface for absorption.

http//www.udel.edu/biology/Wags/histopage/wagnera
rt/anaglyphpage/anaglyph.html
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Small Intestine (S. I.)

• The area of absorption is also increased by the
  millions of microvilli.

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NOTE This should be a straight line in your notes
Mechanical Peristalsis Bile emulsifies
lipids
Alcohol absorbed
Chemical Amylase-CH2O Lipase-Lipids
Proteases-Proteins
Mechanical Muscle Contractions Peristalsis
(3 layers)
Small Intestine
Stomach
Macro micronutrients absorbed
Mechanical Peristalsis
Chemical Pepsin-Proteins HCl pH-2 (gastric
juices)
Large Intestine
Esophagus
Tongue
Rectum/ Anus
Mouth/ Throat
Mechanical Chewing
Chemical Amylase-Starch
Teeth
Salivary Glands
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Are We There Yet?

• Almost
• While the nutrients are being absorbed by these
  cells, chyme is being mixed back and forth by
  segmentation movements within the small
  intestine.
• When absorption is complete, undigested material
  moves into the large intestine.

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Large Intestine (L. I.)

• Is about 5 feet long and 3
• inches in diameter in adults
• Two parts
• Colon
• (for most of its length)
• Rectum the final 6
• Receives leftovers of digestion water mixture,
  undigested fat and proteins, indigestible fibers

http//www.nlm.nih.gov/medlineplus/ency/imagepages
/19220.htm
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Large Intestine (L. I.)

• Contains large populations of bacteria that
  thrive on the unabsorbed nutrients and are also
  responsible for synthesizing important vitamins
  for the body (B12, riboflavin, K).
• Remaining water, salts, and vitamins are
  reabsorbed by cells in the L. I.

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NOTE This should be a straight line in your notes
Mechanical Peristalsis Bile emulsifies
lipids
Mechanical Muscle Contractions Peristalsis
(3 layers)
Chemical Amylase-CH2O Lipase-Lipids
Proteases-Proteins
Small Intestine
Stomach
Macronutrients absorbed
Mechanical Peristalsis
Chemical Pepsin-Proteins HCl pH-2 (gastric
juices)
Large Intestine
Esophagus
Tongue
Remaining water, salts and vitamins absorbed
Rectum/ Anus
Mouth/ Throat
Mechanical Chewing
Chemical Amylase-Starch
Teeth
Salivary Glands
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Large Intestine (L. I.)

• Leftover material is condensed into semisolid
  feces which are transported to the rectum by
  peristaltic movements.
• Expansion of the rectum stimulates the urge to
  defecate which is initiated voluntarily after age
  2.

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The Facts About Poop

• The Facts About Poop

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