Digestion in intestine. Role of liver and pancreas.

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Digestion in intestine. Role of liver and
pancreas.
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Small intestine
The Small Intestine plays key role in digestion
and absorption of nutrient, 90 of nutrient
absorption occurs in the small intestine
Three subdivisions 1. Duodenum 25 cm in
length, Contains Brunner glands Mixing bowl
that receives chyme from stomach digestive
secretions from pancreas and liver 2.
Jejunum 2.5 m in length, Is the location of
most chemical digestion nutrient absorption 3.
Ileum 3.6 m in length Contains Peyer
patches
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Small intestine

• PHYSIOLOCIAL EVENTS
• 1. Mechanical digestion
• 2. Chemical digestion
• 3. Absorption
• 4. Propulsion

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Small intestine

• 1. MECHANICAL DIGESTION
• In segmentation, nonadjacent
• segments of the intestine
• alternately contract and
• relax, moving the chyme
• forward and then backward
• resulting through mixing. This
• results in the chyme being well
• mixed with the enzymes from
• the liver and the pancreas.

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Small intestine

• In addition, segmentation
• ensures that the chyme well
• move to the plasma
• membrane of the lining cells of
• the small intestine. These
• simple columnar epithelial cells
• have brush border enzymes
• within their plasma membrane
• which complete the chemical
• digestion of the chyme.

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Small intestine

• 2. CHEMICAL DIGESTION
• Chemical digestion in
• the small intestines, is
• the result of the
• intestinal brush border enzymes.

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Small intestine

• 3. PROPULSION
• Propulsion is the result of
• peristalsis. This causes
• adjacent segments to
• alternately contract and
• relax.
• Peristalsis occurs only after
• most nutrients have been
• absorbed. It requires about 2
• hours for undigested material
• to reach the ileocecal valve.

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Small intestines neurological control

• MECHANICAL DIGESTION
• Segmentation is initiated by intrinsic pacemaker
  cells in
• longitudinal smooth muscle layer.
• The rate of segmentation in the duodenum
• is 12-14 contractions/minute.
• Segmentation moves intestinal contents slowly
• and steadily toward the ileocecal valve at a rate
  
• which allows time to complete digestion
• and absorption. The stomach initiates
• the gastroileal reflex, which enhances the force
  of
• segmentation.

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Small intestines neurological control

• CHEMICAL DIGESTION and ABSORPTION
• There is no neurological control within the small
  intestines,
• this is due to the natural of the brush border
  enzymes.

• PROPULSION
• Peristalsis occurs only after most nutrients have
  been absorbed. Peristaltic waves initiated in
  the duodenum begin to sweep slowly along the
  small intestines, moving 10-70 cm before dying
  out. Each successive wave is initiated a bit
  more distally, and this pattern of peristaltic
  activity, migrating mobility complex, continues
  until the undigested food is moved to the ileum a
  2 hour trip. The gastroileal reflex causes the
  ileocecal sphincter to relax.
• Peristalsis is regulated extrinsically by the
  autonomic nervous system. The parasympathetic
  division is excitatory and the sympathetic is
  inhibitory.

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Small intestines hormonal control

• MECHANICAL DIGESTION
• Gastrin stimulates contraction of the smooth
  muscle of the
• small intestines. This results in an increase in
  segmentation.

ABSORPTION is inhibited by Somatostatin.
PROPULSION Perstalsis is stimulated by gastrin.
Also, gastrin relaxes the ileocecal valve, which
allow chyme into the large intestines.
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Large intestine

• PHYSIOLOGICAL EVENTS
• 1. Absorption - vitamins, electrolytes, and
  water.
• Mass movements occur within the large intestines.
  They are
• long slow-moving contractile waves that occur 3
  or 4 times per
• day. Typically mass movements occur during or
  after eating.
• use 9 liters of water every day in digestive
  juices
• gt 90 of water reabsorbed
• not enough water absorbed diarrhea
• too much water absorbed constipation

2. Propulsion - The presence of food in the
stomach activates the gastroileal reflex in the
small intestines. It, in turn, stimulates the
gastrocolic reflex of the large intestines.
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Liver

• Liver functions
• Secterion of bile
• Detoxication of blood (drugs, alcohols)
• Carbohydrate metabolism
• Lipid metabolism
• Protein synthesis
• Fetal RBC production
• Phagocytosis
• Stores
• Gycolgen
• Vitamins (A, D, E, K)
• Fe and other minerals
• Cholesterol
• Activates vitamin D
• Endocrine function

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Bile

• Bile is a yellowish-green liquid that hepatic
  cells secrete
• The liver produces and secretes 250 to 1500 ml of
  bile per day.
• The major constituents of bile are
• water
• bile pigment (bilirubin)
• bile salts
• phospholipids (mainly lecithin)
• cholesterol
• inorganic ions (Na, K, Ca, Mg, Cl, SO4, PO4,
  H2CO3.

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Gallbladder

• The gallbladder is a saclike organ attached to
  the inferior surface of the liver. This organ
  stores and concentrates bile, which drains to it
  from the liver by way of the bile ducts, hepatic
  ducts, and cystic duct, respectively.

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Liver and gallblader control

• NEUROLOGICAL CONTROL
• The gallbladder is regulated
• by the autonomic nervous
• system. The parasympathetic
• division, using the vagus
• nerve, is excitatory and
• the sympathetic division
• inhibits the gallbladder.

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Liver and gallblader control

• HORMONAL CONTROL
• The liver is stimulated by
• secretin to produce bile more
• rapidly. Cholecystokinin
• stimulates the gallbladder to
• contract and
• hepatopancreatic sphincter
• to relax, so that bile can
• enter the duodenum.

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Pancreas

• The pancreas is a large gland lying across the
  posterior abdominal wall. It has 2 secretions
• A digestive secretion (exocrine) poured into the
  duodenum (secretes pancreatic juice), and
• Hormonal (endocrine) passed into the blood
  stream. (The pancreatic islets, or islets of
  Langerhans secrete hormones, insulin and
  glucagon.)

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Pancreatic juice

• Exocrine secretion of about 1500 ml per day.
• Contains water, bicarbonate, and wide variety of
  digestive enzymes. These enzymes include
• amylase, which digest starch
• trypsin, which digest protein
• lipase, which digest triglycerides.
• pancreatic ribonuclease deoxyribonuclease

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PANCREASCHEMICAL DIGESTION
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PANCREASCHEMICAL DIGESTION
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PANCREASCHEMICAL DIGESTION
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PANCREAS CONTROL

• NEUROLOGICAL CONTROL
• The pancreas is regulated
• by the autonomic nervous
• system. The parasympathetic
• Division, using the vagus nerve,
• is excitatory and the sympathetic
• division inhibits the pancreas.

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PANCREAS CONTROL

• HORMONAL CONTROL
• The pancreas is regulated
• hormonally by secretin and
• cholecystokinin (CCK). CCK
• induces the acinar cells to
• secrete the enzymes found in
• pancreatic juice. Secretin
• causes bicarbonate ions to
• form.

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