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Atenção Recomendamos o material a seguir apenas
com o objetivo de divulgar materiais de qualidade
e que estejam disponíveis gratuitamente. Profa.
Cristina Maria Henrique Pinto CFS/CCB/UFSC
O presente arquivo é uma coletânea de figuras e
textos extraídos da coleção em CD-ROM utilizada
em nossas aulas. Interactive Physiology, da
Benjamin Cummings.
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Você pode também dar baixa de resumos dos
CD-ROMs, não apenas de Digestório mas de
diversos outros assuntos de Fisiologia Humana.
Arquivos em .pdf e/ou .doc, com textos e
ilustrações. Siga o link abaixo http//www.aw-bc.
com/info/ip/assignments.html E escolha entre os
seguintes assuntos Muscular Nervous I Nervous
II Cardiovascular Respiratory Urinary Fluids
Electrolytes Endocrine e Digestive system
Veja também aulas online (DEMO dos CD-ROMs)
sobre Cardiovascular system Endocrine system
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Digestive System PARTE 1 Anatomy Review and
Control of the Digestive System
Profa. Cristina Maria Henrique Pinto -
CFS/CCB/UFSC monitores Vinicius Negri Dall'Inha
e Grace Keli Bonafim (graduandos de
Medicina) Este arquivo está disponível em
http//www.cristina.prof.ufsc.br/md_digestorio.htm

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Veja estas aulas online, com animações e diversos
recursos
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Anatomy Review Digestive System Graphics are
used with permission of Pearson Education Inc.,
publishing as Benjamin Cummings
(http//www.aw-bc.com) Introduction   The
digestive system consists of two components the
alimentary canal (a.k.a. digestive tract) and
accessory organs.
  After food is ingested and then processed in
the digestive tract, undigested food leaves the
system as feces.
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• Goals
• To identify the organs and circular muscles
  (sphincters) of the digestive tract.
• To list the structures found in a representative
  section of the wall of the digestive tract
• To recognize the accessory organs of the
  digestive system.
• To describe the general function for each organ
  of the digestive system.

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The Wall of the Digestive Tract  A typical
section of the digestive tract reveals four main
layers. From inside (the lumen) to outside they
are o Mucosa o Submucosa o Muscularis
(externa) o Serosa (a.k.a. visceral
peritoneum) LABEL THESE LAYERS BELOW  
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• Different regions of the digestive tract wall
  have unique structures that are related to the
  specialized functions of those regions.
• The mucosa is subdivided into three layers.
  From the lumen
  
• outward they are

oA simple columnar epithelium densely
populated with goblet cells. o A lamina
propria connective tissue layer containing blood
and lymphatic vessels o  A smooth muscle sheet
called the muscularis mucosa

• The mucosal epithelium functions in both
  secretion of digestive substances and in
  absorption of nutrients.

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• Goblet cells secrete mucus (a hydrated mucin
  protein), while other mucosal epithelial cells
  secrete digestive fluids and other substances
  such as water and salts.
• Enteroendocrine cells of the mucosa produce
  hormones that are released into the blood via the
  capillaries of the lamina propria.
• Nutrients are transported (absorbed) through the
  epithelial cells and into either the capillaries
  (most nutrients) or lacteal lymphatic vessels
  (fats).

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• The mucosal epithelial cells are mitotically
  active, thus the epithelium is replaced
  approximately every three to six days.
• The function of the double-layered muscularis
  mucosa is to aid in digestion and absorption by
  moving the mucosal villi in the small intestine.
• Blood and lymph vessels as well as an intrinsic
  network of neurons (the submucosal plexus) are
  located in the submucosa.
• The muscularis externa contains two sheets of
  muscle (circular and longitudinal layers)
  throughout most of the alimentary canal wall (the
  stomach has three layers). The fibers in the two
  layers are arranged at right angles to each other

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• The myenteric plexus is a network of neurons in
  the muscularis externa it is in close
  communication with the submucosal plexus, and
  together, the two plexuses comprise the enteric
  nervous system.
• The outermost layer of the digestive tract wall
  is the serous fluid-producing serosa, which both
  lubricates and reduces friction of the digestive
  tract within the ventral body cavity.

• The Upper Part of the GI Tract
• Ingestion occurs in the mouth.
• Chemical digestion (saliva w/amylase for starch
  digestion) and mechanical digestion (teeth
  tongue) occur in the mouth.

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• The lining of the oral cavity and pharynx is a
  stratified squamous epithelium mucosa.

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• The partially digested bolus of food is moved
  from the mouth to the esophagus, and then the
  stomach.
• There is a transition in the esophagus wall from
  striated (skeletal) to smooth muscle, from the
  upper to lower portions, respectively,.
• The muscular stomach is involved in chemical
  (mostly protein) and mechanical digestion, as
  well as storage of food.

• The cardia, fundus, body, and pyloric (w/antrum)
  regions are specialized areas of the stomach.

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• The muscularis externa layer of the stomach wall
  is unique in that it has three sheets of muscle
  (circular, longitudinal, and oblique).

• The stomach can expand greatly because of
  internal folds called rugae.

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• Once food is mixed with gastric juices in the
  stomach it is called chyme, which is then moved
  from the pylorus to the duodenum of the small
  intestine.
•  

• The Lower Part of the GI Tract
• The majority of chemical digestion and virtually
  all-nutrient absorption occur in the small
  intestine.
• The three regions of the small intestine are the
  duodenum, jejunum, and ileum

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• The three modifications of the inner wall of the
  small intestine that function to increase surface
  area are (from macroscopic to microscopic) the
  plicae circularis (circular folds), villi, and
  microvilli
•  

 
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• The intestine aids the body in its defense
  against pathogens by secreting antibacterial
  enzymes and antibodies (immunoglobulins) and by
  providing specialized sites in the ileum
  (lymphoid nodules called Peyers patches) where
  leukocytes can fight pathogens
• The large intestine absorbs water, salt, and
  vitamin K
• The large intestine includes the cecum, appendix,
  colon, rectum, and anal canal

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LABEL THESE AREAS BELOW

• Three bands of smooth muscle called taeniae coli
  cause the outer portion of the colon to be
  puckered into pockets called haustra
• Epiploic appendages are fat storage areas located
  on the outside of the colon

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• The final section of the digestive tract, the
  anus, is lined with stratified squamous
  epithelium
• Feces are composed of indigestible food,
  bacteria, inorganic substances, and sloughed off
  epithelial cells from the digestive tract wall

• Sphincters
• Sphincters regulate the passage of food from one
  region of the digestive tract to the next, and
  finally, out of the body as feces
• The sphincters of the digestive tract, from mouth
  to anus, are the
• Upper esophageal sphincter or UES (circular
  skeletal muscle an anatomical sphincter)
• Lower esophageal sphincter or LES (a
  physiological sphincter)

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• Pyloric sphincter (circular smooth muscle)

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• Ileocecal sphincter or valve (circular smooth
  muscle)

• Internal anal sphincter or IAS(circular smooth
  muscle)
• External anal sphincter or EAS (circular
  skeletal muscle)
• The UES prevents air from entering the esophagus
• The LES prevents acid reflux from the stomach
  into the esophagus

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• The pyloric sphincter regulates passage of chyme
  from the stomach into the duodenum
• The ileocecal valve regulates passage of chyme
  from the ileum to the large intestine
• The IAS is under involuntary control when
  relaxed, it produces the urge to defecate
• The EAS is under voluntary control when relaxed,
  it allows for defecation.

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• Accessory Glands
• The accessory glands that produce secretions to
  aid in digestion are the salivary glands (3
  pair), liver, and pancreas.
• Salivary glands moisten food, cleanse and protect
  the mouth, and produce amylase to begin enzymatic
  digestion of starch

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• The liver produces bile, which emulsifies fats to
  increase their surface area for subsequent
  chemical digestion by lipases bile is stored in
  and released from the gall bladder into the
  duodenum

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• The pancreas is the main digestive
  enzyme-producing exocrine organ in the body. It
  releases a host of digestive enzymes into the
  duodenum via the pancreatic duct it also
  produces bicarbonate to neutralize the chyme from
  the stomach

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Study Questions on Anatomy Review Digestive
System   1.   Which histological layer of the
digestive tract contains goblet cells for mucous
secretion? 2.  Which histological layer of the
digestive tract is responsible for producing
peristaltic contractions? 3.  Which network of
neurons would you find in the muscularis
externa? 4.   In which histological layer of the
digestive tract would you find lacteals? 5. 
What is the name of the 3rd muscularis externa
layer found only in the stomach?    
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6.  List the three modifications of the small
intestine that increase surface area for
digestion and absorption. 7.   List the regions
of the large intestine. 8.  Which sphincter
allows for defecation and is under voluntary
control? 9.  Which accessory gland is located in
the u-shaped fold of the duodenum and is
connected via a duct to that organ?  
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Topic 2 Control of the Digestive System Graphics
are used with permission of Pearson Education
Inc., publishing as Benjamin Cummings
(http//www.aw-bc.com)
Title Page   The autonomic nervous system,
hormones, and other chemicals control motility
and secretion of the digestive system.
The Autonomic Nervous System
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• Goals
• To list the phases of GI control
• To describe the interaction between the enteric
  and autonomic nervous systems
• To discuss short and long reflexes.
• To list the hormones that control digestion and
  describe the function of each hormone.
•  

Control of the GI tract depends on the location
of food    The sight, smell, taste, and mental
images of food trigger the cephalic phase of
digestion via the vagus nerve (N X) which
includes o    salivation o    gastric juice
production o     gastric contractions
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• Increased volume of food in the stomach and
  subsequent stimulation of stomach stretch
  receptors triggers the gastric phase of digestion
  which includes
• o       gastric juice production
• o       increased gastric motility

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• As food moves into the small intestine
  (duodenum), the chemical composition and volume
  of that food triggers specific reflexes during
  the intestinal phase of digestion which may
  include
• o       pancreatic secretion of bicarbonate
  into the duodenum
• o pancreatic secretion of digestive enzymes
  into the duodenum
• o gall bladder release of bile into the
  duodenum
• segmentation contractions of the small
  intestine

• The small intestine reflexively slows gastric
  emptying to allow for neutralizing, enzymatic
  digestion, and absorption of its contents
•  

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• Parasympathetic and sympathetic nerves innervate
  the GI tract
• Both parasympathetic and sympathetic divisions of
  the autonomic nervous system control digestion by
  contacting the enteric nervous system in the wall
  of the digestive tract
• The parasympathetic division typically stimulates
  digestion while the sympathetic division
  typically inhibits it.
• The vagus and pelvic splanchnic nerves send
  preganglionic parasympathetic fibers to synapse
  with enteric neurons.
• Sympathetic postganglionic innervation of the
  digestive tract is both direct to smooth muscle,
  glands, and blood vessels and indirect via
  synapses with the enteric NS.

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LABEL THE NERVE FIBERS BELOW
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• The enteric nervous system serves the GI tract
• The submucosal and myenteric plexuses are the two
  nerve networks of the enteric nervous system.
• The enteric nervous system controls many
  digestive functions independent of the rest of
  the nervous system, such as lower esophageal
  peristalsis and mobility of the small intestine.
•  

• Reflexes coordinate and modulate digestive
  activity
• Reflexes (stimulus, integration, and response)
  that are totally controlled by the enteric
  nervous system are termed short reflexes.
• Reflexes that involve the CNS as an integration
  center are called long reflexes
• Short and long reflexes can occur simultaneously

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• Larger volumes of food in the stomach produce
  stronger gastric contractions than smaller
  volumes of food.

Small volume ? weaker contractions Large volume
? stronger contractions

Chemical composition of food influences the rate
of digestion lipid rich meals take longer to
digest than carbohydrate rich meals
Lipid rich meal ? Longer
digestion time Carbohydrate rich
meal ? shorter digestion time
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• There are many neurotransmitters in the GI
  tract
• All preganglionic fibers of the ANS release
  acetylcholine (ACh).
• Parasympathetic postganglionic fibers also
  release ACh
• Sympathetic postganglionic fibers release
  norepinephrine

• LABEL THE FIBERS BELOW AND INCLUDE THE
  NEUROTRANSMITTER RELEASED BY THE FIBER

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• Other enteric nervous system neurotransmitters
  include serotonin, vasoactive intestinal peptide
  (VIP), nitric oxide (NO), and somatostatin (SST)
• ACh and substance P stimulate smooth muscle of
  the digestive tract.
• Smooth muscle of the digestive tract is inhibited
  by norepinephrine, VIP, and NO
• Enkephalins released in the submucosal and
  myenteric plexuses slow intestinal motility,
  inhibit intestinal secretion, and contract the
  LES, pyloric and ileocecal sphincters.

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• Hormones modulate digestive activity
• GI hormones are peptides (amino acid based).
• GI hormones include gastrin, cholecystokinin
  (CCK), secretin, glucose-dependent insulinotropic
  peptide (GIP) and motilin.
•  

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• Enteroendocrine cells of the GI mucosa secrete
  the peptide hormones.
• Pyloric antrum G cells secrete gastrin, which
  stimulates HCl production and growth of the
  gastric mucosa
•  

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        CCK is secreted by the I cells in the
duodenum and jejunum.         CCK cause gall
bladder contraction and subsequent release of
bile into the duodenum         CCK causes the
pancreas to release digestive enzymes into the
duodenum         CCK inhibits gastric
emptying         CCK stimulates growth of the
pancreas and gall bladder mucosa  
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• Duodenal S cells produce secretin
• Secretin causes the pancreas, and to a lesser
  extent the liver, to release bicarbonate into the
  duodenum
• Secretin inhibits HCl secretion by the stomach
•  
•  

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• Duodenal and jejunum cells secrete GIP
• When glucose is present, GIP stimulates the
  pancreas to secrete insulin, thus enhancing the
  secretion of insulin

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• Duodenal and jejunum cells secrete motilin during
  the postabsorptive state
• Motilin stimulates GI motility thereby moving
  intestinal contents toward the end of the ileum 
• GI hormones, like all hormones, enter the
  circulatory system, and then return to the target
  organ(s) in this case, back to the GI tract.
• Potentiation of hormones involves the combined
  effect of two or more hormones being greater than
  the sum of their individual actions

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1.      Looking at a picture of strawberry
shortcake with whipped cream would likely trigger
the ______ phase of digestion. 2.      As the
stomach expands, the _____ phase of digestion is
triggered. 3.      Bicarbonate from the pancreas
neutralizes acid chyme entering the duodenum
during the ______ phase of digestion. 4.     
Increasing digestive processes is typically
caused by stimulation from the _______ division
of the autonomic nervous system. 5.      What is
the name of the cranial nerve that contains most
of the pre-ganglionic parasympathetic to the
enteric nervous system? 6.      What are the two
plexuses that comprise the enteric nervous
system? 7. _____ reflexes are controlled by
the central nervous system, whereas _____
reflexes are controlled by the enteric nervous
system
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8.      What does stomach contraction strength
depend upon? 9.     Which would take longer to
digest 6 oz of deep-fried chicken or 6 oz of
whole wheat bread? 10.     Worrying excessively
about the quiz on this material may cause
constipation in some individuals. True or
False? 11. Preganglionic fibers of both the
sympathetic and parasympathetic divisions of the
ANS release the neurotransmitter ____. 12.   
Which ANS fibers release norepinephrine? 13.   
Which ANS neurotransmitter inhibits
digestion? 14.     Which neurotransmitter(s)
released by the enteric nervous system inhibits
gastric motility and causes several sphincters to
contract? 15..     GI hormones are steroids. True
or False?
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16.    List the hormones that influence digestive
activity. 17.  Which hormone stimulates
hydrochloric acid production in the
stomach? 18.  Which duodenal hormone would be
secreted to stimulate the emulsification process
of lipids? 19.    Which organ secretes most of
the hydrolytic digestive enzymes? 20.    Which
hormone would be released to stimulate
neutralization of acidic chyme in the
duodenum? 21.    What is the function of
GIP? 22.    Which duodenal hormone is released
to speed the passage of material through the
lower digestive tract?
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Digestive System continua na parte 2 Motility
Profa. Cristina Maria Henrique Pinto -
CFS/CCB/UFSC monitores Vinicius Negri Dall'Inha
e Grace Keli Bonafim (graduandos de
Medicina) Este arquivo está disponível em
http//www.cristina.prof.ufsc.br/md_digestorio.htm