HUBS1404 Lecture Notes - Lecture 8: Brush Border, Intestinal Gland, Goblet Cell
26 Oct 2018
School
Department
Course
Professor
Small Intestine
Length (approx. 7 metres)
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To maximize absorption of nutrients
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Circular folds - plicae
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Villi
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Has a blood vessel and lymphatic vessel to absorb all the nutrients and such
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Microvilli (brush border)
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Forms a hairy like surface
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Small Intestine Structural Adaptations
Goblet cells - mucus
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Intestinal crypts
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Enteroendocrine cells - secrete secretin and CCK
•
Stem cells divide to replace lost cells
•
To keep the villi protected
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Lysozyme secreting cells
•
Intestinal juice - stimulated by distension, hypertonic/acidic chyme; slightly alkaline; isotonic with plasma; watery
mucous; enzyme poor; mucous secreted by goblet cells and duodenal glands
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Small Intestine Secretions
Arrival of acidic, hypertonic chyme (partially digested food)
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Chyme is hypertonic, so if too much enter duodenum, blood would lose volume due to osmotic shift of water
into intestine
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Chyme pH needs to be increased to allow digestive enzymes to work
-
Bicarbonate is secreted to neutralize the acid that is coming in the duodenum
-
Must control rate of chyme entry - the
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Partially digested CHOs & proteins - more enzymes to complete digestion
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Enzymes both from pancreas and on brush border. Bile from liver
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Mixing from pancreatic and bile salts is important
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3-6 hour journey across huge surface area to allow water & nutrient absorption
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Digestive Processes: Small Intestine
The Arrival of Chyme in the Duodenum Regulates Stomach Emptying and Stimulates Pancreatic and Biliary Activity..
Completion of chemical digestion
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Enzymatic breaking of bonds
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Absorption
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Duodenum:
The blue coloured bit
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Remainder of digestion takes place
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Jejenum and Ileum
The pink coloured bit and orange coloured bit
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Undergoes absorption processes
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A smaller length of smaller intestine is given
-
completion of digestion and majority is given
for absorption
Digestive System 2
Wednesday, 2 November, 2016
9:21 PM
HUBS1404 Page 11.1
CCK & secretin stimulate different pancreatic secretions..
CCK & secretin also regulate stomach emptying …
CCK empties the gall bladder…
Secretion increases volume and bicarbonate content of bile…
Chyme enters duodenum. Fat in chyme causes
release of CCK & acid in chyme causes release of
secretin
1.
The more fat that comes in, the more CCK
secreted
-
Secretin is stimulated by the presence of acid
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CCK stimulates pancreatic enzyme
secretion & secretin stimulates pancreatic
bicarbonate and water secretion
2.
CCK is going to stimulate the pancreas to
increase its production and secretion,
which is going to cut up the food
components
-
More secretin stimulates more secretion
of bicarbonate and water, to neutralize
-
the acid
CCK stimulates gall bladder to contract and sphincter
of Oddi to relax, allowing bile to flow into the
duodenum
4.
CCK gets the gall bladder to contract its bile to flow
down the bile duct and into the duodenum
-
The duct from the pancreas and gall bladder joins as
it enters the duodenum, called the sphincter of Oddi
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Bile is needed in digestion and absorption of fats
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Parasympathetic stimulation during cephalic and
gastric phases have also caused some gall bladder
contraction
While we were thinking of food, the parasympathetic
system stimulates the gall bladder
-
Secretin also stimulates bicarbonate and water
5.
Both CCK and secretin inhibit and enzyme and acid secretion and
peristalsis in stomach
3.
Regulate the rate of which the stomach empties to get a nice feed of
chyme at a rate the duodenum can cope with
-
Whatever is left in the stomach could still be digested but the enzymes
in the stomach then wouldn't be increased
-
HUBS1404 Page 11.2
Secretion increases volume and bicarbonate content of bile…
Accessory Organs of Digestion
system stimulates the gall bladder
Secretin also stimulates bicarbonate and water
secretion in liver -> greater volume of alkaline bile
5.
To neutralize the acid level that is entering the
duodenum
-
Liver produces bile
→
Major function in digestion
-
Gall bladder stores and concentrates bile
→
Gall bladder also takes water out of the bile
-
The longer it stores the bile, the more
concentrated the bile becomes
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Pancreas (exocrine portion) produces
digestive enzymes & bicarbonate
→
The duct of digestion that produces the
enzymes that are going to complete the
rest of digestion in the small intestine
-
Also producing bicarbonate to neutralize
the acid
-
Bilirubin is the
breakdown/waste product
after breaking down/recycling
haemoglobin
The pigment that can't be
recycled and is mixed in the
bile
-
Bile acids are able to work
well due to hydrophobic and
hydrophilic sides
Polar and non-polar sides that
allows them to surround
little fat globules (lipids)
-
So that lipids can be carried
through an aqueous solution
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Proteases has either -ogen or
pro- attached to it as it's inactive
HUBS1404 Page 11.3
Document Summary
The pink coloured bit and orange coloured bit. A smaller length of smaller intestine is given completion of digestion and majority is given for absorption. Has a blood vessel and lymphatic vessel to absorb all the nutrients and such. Intestinal juice - stimulated by distension, hypertonic/acidic chyme; slightly alkaline; isotonic with plasma; watery mucous; enzyme poor; mucous secreted by goblet cells and duodenal glands. Arrival of acidic, hypertonic chyme (partially digested food) Chyme is hypertonic, so if too much enter duodenum, blood would lose volume due to osmotic shift of water into intestine. Chyme ph needs to be increased to allow digestive enzymes to work. Bicarbonate is secreted to neutralize the acid that is coming in the duodenum. Must control rate of chyme entry - the. Partially digested chos & proteins - more enzymes to complete digestion. Enzymes both from pancreas and on brush border. Mixing from pancreatic and bile salts is important.
