Chapter 34 Energy and Metabolism I: Digestion

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Chapter 34Energy and Metabolism I Digestion

• By Ara Vehian
• Jennifer Walters
• January 10, 2005

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Digestive Tract in Vertebrates

• AKA the gut
• Digestion breakdown of food molecules and
  absorption into the body
• Tube layers- mucosa, submucosa, muscularis
  externa, serosa
• Wavelike motionsperistalsis
• Sphincters act as valves to control passage of
  food

Peristalsis------?
http//www.emc.maricopa.edu/faculty/farabee/BIOBK/
peristalsis.gif
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The Oral Cavity Initial Processing

• Seizing and Ingestion is accomplished by the
  MOUTH
• Crown of a tooth is covered in enamel, root is
  covered in cement
• Adults have 32 teeth, children have 20
• Incisors-cutting Molars-grinding
• Tongue-used to move and manipulate food in
  mammals
• Saliva-moistens food, so it can be swallowed
  easily, slightly alkaline
• Salivary Amylase- breakdown of starches

Tongue---------------?
http//news.bbc.co.uk/olmedia/1645000/images/_1646
912_tongueruler300.jpg
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The Pharynx and Esophagus Swallowing

• Esophagus is 25 centimeters long in adult humans
• Upper part is striated muscle and lower part is
  smooth
• Peritoneum- a thin layer of connective tissue
  covered by moist epithelium
• Mesenteries- folds of the peritoneum which
  suspend organs

http//www.oncologychannel.com/Images/pharynx.gif
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The Stomach Storage and Liquefaction

• Collapsible, muscular bag
• Holds 2 to 4 liters of food
• Mucus-secreting epithelial cells cover the
  surface of the stomach
• pH of Gastric Juice is between 1.5 and 2.5..VERY
  ACIDIC
• Pepsin-breaks down proteins into peptides
• Gastrin- increases secretion of gastric juices

http//digilander.libero.it/BodyMindCare/kapil/ima
ges/medi/more/horz/stomach-2with20red20light.jpg
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The Small Intestine Digestion and Absorption

• Villi-fingerlike projections
• Microvilli-on surface of individual epithelial
  cells.
• IF SMALL INTESTINE WERE TO BE FULLY EXTENDED, IT
  WOULD BE 6 METERS LONG!!!
• Duodenum- upper 25 cm. concerned with absorption
  of nutrients
• Bile contains a mixture of salts that emulsify
  fats
• Lipases hydrolyze fats into glycerol and fatty
  acids
• Hormones regulate and coordinate digestive
  activities
• Secretin-stimulates pancreas and liver to secrete
  alkaline fluids
• Cholecystokinin- triggers release of enzymes from
  pancreas

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SMALL INTESTINE!!!!!!!!!!!!!!!!!!
http//www.emc.maricopa.edu/faculty/farabee/BIOBK/
humdigest_2.gif
http//virtual.yosemite.cc.ca.us/randerson/Biology
/frog20anatomy20tutorial/NamedJPEGS/Small20inte
stine.jpeg
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The Large Intestine Further Absorption and
Elimination

• Absorption of water, Na, and other minerals
• Harbors a large population of E. coli
• E. coli break down food substances escaped from
  small intestine
• Chief source of Vitamin K
• Appendix is an evolutionary remnant from
  herbivorous ancestors
• The bulk of fecal matter consists of water,
  bacteria and cellulose fibers
• Stored briefly in your RECTUM, eliminated through
  your ANUS

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The LARGE Intestine
http//images.encarta.msn.com/xrefmedia/aencmed/ta
rgets/illus/ilt/0007761a.gif
http//www.hillandthomas.com/fluor1f.jpg
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The Pancreas

• Source of a number of substances essential to
  digestive process
• Secretes an amylase that plays a major role in
  the breakdown of starch
• Endocrine Gland
• Clusters are known as islets of Langerhans whice
  secrete insulin, glucagon, and somatostatin

http//medicalimages.allrefer.com/large/pancreas.j
pg
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The Liver

• 3 pound chemical factory
• Stores and releases carbohydrates
• Processes amino acids
• Manufactures plasma proteins that make the blood
  hypertonic in relation to interstitial fluids
• Important in hormone regulation
• Breaks down foreign substances like alcohol

http//trickytrixie.tripod.com/medical/liver-large
.jpg
http//www.nemc.org/surgery/images/tpimages/liver.
gif
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Regulation of Blood Glucose

• Glucose and other monosaccharides are absorbed
  into the blood from the intestinal tract and are
  passed directly to the liver by way of the
  HEPATIC PORTAL VEIN.
• The liver breaks down excess amino acids and
  converts them to glucose.

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Some Nutritional Requirements

• Vitamins are a group of molecules required by
  living cells that cannot be synthesized by animal
  cells
• Vitamins function as coenzymes
• Minerals are inorganic substances such as calcium
  and phosphorous for bone production, iodine for
  thyroid hormone, iron for hemoglobin, and sodium
  for ion balance

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The Price of Affluence

• 30 of middle aged women and 15 of middle aged
  men are obese
• We consume on average about 20 times the amount
  salt as our bodies need
• Animal fat is a hazard
• Experimentation is also a hazard