Download Bile

By:
M.H.Dashti
Lecture 3
Physiological functions of esophagus:
Esophageal sw allow ing
Upper esophageal
sphincter closes again
Primary Peristalsis pushes
food
down by contraction of
circular fibers behind the
bolus
longitudinal fibers in front
of bolus shorten the
distance of travel
Travel time is 4-8 seconds
for solids and 1 sec for
liquids
Lower sphincter relaxes
as food approaches
Secondary peristaltic:
central or enteric reflexes
Pressure
changes in
pharynx
pharynx
,esophagus
&
esophageal
sphincters
during
swallowing
LES is controlled
by :
Parasympathetic
preganglionic fibers
via ENS stimulatory &
inhibitory neurons
Vagal
nucleus
Post ganglionic
Sympathetic
Neurons
Cholinergic
sympathetic
which inhibit
Vagal neurons
ENS neurons
+ -+ and directly
stimulate lower ENS
+
+
esophageal Cholinergic
sphincter
NANC neur
Neuron L.E.S. MUSCLE
VIP,ATP,NO
1:Achalasea : LES fails to open
distension of esophagus feels like chest pain or heart attackTreatment :Air balloon ,Myotomy sympathectomy
2 : GERD/ hiatus hernia: LES
fails to close
post- prandial heart burn, regurgitation at 1
hour
Avoiding a large meal (fatty foods) and lay down or Bending,
smoking , alcohol & coffee, tomatoes, onions & mint
taking H2 blocker 60 minutes before eating
neutralize existing stomach acids with Digel
Size when empty?
large sausage
stretches due to rugae
Receptive relaxation due to
oblique muscle
Physiologically, it is divided into
(1) the orad portion, comprising
about the first two thirds of the
body,
(2) the caudad portion,
comprising the remainder of the
body plus the antrum.
Two types of tubular
glands:
1- oxyntic glands
(gastric
Gastric glandular cells & their secretions
Paracrine
cells
(not shown)
1-Entrochromafin
cells
produce
Histamine
2- D cells
secretes
Somatostatin
Secrete alkaline
mucin
,rennin
Regulation of gastrin
secretion
Stimuli that increase
gastrin secretion
Luminal: Peptides and
amino acids, Distention,
Neural: Increased vagal
discharge via GRP
Blood-borne: Calcium,
Epinephrine
Stimuli that inhibit gastrin
secretion
Luminal: Acid, Somatostatin
Blood-borne: Secretin, GIP,
VIP, Glucagon, calcitonin
Functions of the
gastrin
stimulation of gastric
acid and pepsin secretion
stimulation of the growth
of the mucosa of the
stomach and small and
large intestines (trophic
action).
Stimulation of gastric
motility
Stimulation of insulin &
glucagon secretion;
however, only after a
protein meal, and not
after a carbohydrate meal
(Glucagon stimulating
intestinal factor )
Helicobacter pylori & Gastritis
cytokines
Stimulated by: Prostaglandins
& parasympathetic vagal stimulation
Inhibited by : Sympathetic nerve stimulation,
Bile salts , Alcohol & Citric acid
Secretin , VIP &
-adrenergic
agonists act via
CAMP
Ach Gastrin &
cck act via IP3 &
Ca2+
Mechanism for
Potentiation
effect of H+ is
not known
Pepsinogen
& Gastric
lipase
type I
type IItypeIII
type I : mixing waves, based
on BER (3/min)
type II : More vigorous
churning waves
(peristalsis)
type III :Intense waves
(slow emptying)
Intestinal Phase
Nervous inhibition by
local, prevertebral
& central reflexes
Myenteric
plexus
duodenum
antrum
Pyloric sphincter
Sub mucosal
plexus
Regulation of Gastric
Emptying
Rates of gastric emptying
depends on:
1- Gastetic motility
2- Pyloric sphincter status
3- Type of ingested
meals
Chem ical Digestion & absorp tion in the Stom ach
Protein digestion begins
HCl denatures (unfolds) protein molecules
HCl transforms pepsinogen into pepsin that breaks
peptides bonds between certain amino acids
(aromatics)
Rennin in infants digests casein
Fat digestion continues
gastric lipase ( tributirase ) splits the triglycerides in
milk fat
most effective at pH 5 to 6 (infant stomach)
Absorption of Water ( especially if it is cold ) ,
Electrolytes , Some drugs (especially aspirin)
By:
M.H.Dashti
Lecture 4
Secretions
2 types of glands
1- Brunner s glands- from
pyloric to Oddi sphincter
Secreting Alkaline mucus
-Stimulated by
parasympathetic
-Inhibited by sympathetic
-?stress related ulceration
2- crypts/glands of Lieberkuhn
between villi
Exocrine from Enterocyte
Endocrine: Gasterin (G),
Secretin (S) , cck ( I ),GIP ( K )
,VIP ( v ) ,Motilin ( mo )
Digestive enzymes not
secreted from small intestine
except enterokinase secreted
from duodenal mucosa
Crypt of Lieberkuhn
Enterocyte
(Digestive ,
absorptive &
secretary cells
with brush border)
Villus
under local
nervous control
some minor
hormonal
control cells
(VIP
Mucous
(simple
goblet cells)
,secretin,
CCK )
Endocrine cells
(secrete hormones for
control of gut function)
Paneth cell
(have Secretory granules
of lysozyme)
Cyclic
GMP
GC
Guanylin
Or E-coli toxin
Small
intestine
secretes 1 L/
day of
day
ofiso
iso
osmotic
alkaline
secretion
stimulated by
guanylin (
secreted by
enterocytes
from pylorus
to the rectum )
& heat stable
E-coli toxins
via cystic
fibrosis
regulated cl
channels
(
CFTR )
Fat H+
S cells
stomach
Secretin
Bile S.I.
HCO3-
Stomach
stomach
duodenum
CCK
I cells
Bile
S.I.
Peptides +
Amino acids ,
pancreas
Fat
Enzymes
Insulin
Glucagon
GIP (Gastric Inhibitory peptide ) from k cells
Stimulated by carbohydrates in duodenum
Stimulate insulin secretion (E. I. S. F )
VIP ( Vasoactive Intestinal Peptide )
Stimulated by H+ in duodenum
Inhibits gastric acid secretion & Stimulates
intestinal secretions
VIPoma
Motilin
Stimulated by H+ in duodenum
Co-related to Migratory Myoelextric Complex ( MMC
)
Mixing (Segmentation) Contractions
BER ( 12-9/min), influenced by local
local mixing of chyme with intestin
Weak peristalsis in comparison to the stomachtraveling 3-5 cm, chyme remains in SI for 4 to 5
hours
a local reflex influenced by gastroenteric reflex & hormones(
enhanced by gastrin, CCK, insulin, motilin, and serotonininhibited by secretin and glucagon )
Peristaltic rush: a local reflex highly influenced
by the central reflex due to intense irritation.
Interdigestive ( migratory ) myoelectric
complexes ( MMC ):
An intense central reflex ,slowly propagated from
the stomach to the terminal ileum every 75-90
minutes in fasting associated with the release of
moyilin
Controlled by
pressure differences
and Neural events
Ileo -colic & colonoileal reflexes
Ileo- gastricic &
gastro-ileal reflexes
Ileal break
Ileo- gastricic reflex
along with the
secretion of
Oxyntomodulin &
neurotensin from the
ileum
Components: water&
eledtrolytes
Cholesterol , TG, FA & PL
(Lecithin )
bile salts = Na & K salts of
bile acids
( 50% cholic
acid, 30%
chenodesoxycholic acid,
15% desoxycholic acid &
5% lithocholic acid all
conjugated to glycine or
taurine )
bile pigments (bilirubin)
Alkalinephosphatase
0.5-1 Lof bile/day is
secreted
yellow--green in color
yellow
& pH 7.6 to 8.6
Bile p rod u ction &
secretion
~
enterohepatic
circulation
Gallstones & jau nd ice
Calcium bilirobinate due to
glucoronidase activity of bacteria
Cholesterol stones due to
increased Cholesterol/PL ratio
Bile
regulation
Choleretic
agents su ch
as secretin,
vagal
stim u lation
& bile salts
recycling
controls the
bile
secretion
cholagogu es
agents e.g.
CCK & Ach
controls the
gallblad d er
em p tying
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