GASTRO-INTESTINAL

PHYSIOLOGY

Mr D.R Siwale (MSc. Human physiology, BSc

Biological sciences, BSc Human Biology,
Dip.Ed.)
SECRETORY FUNCTION OF THE
GIT
Functional Anatomy of the Mouth
• Mouth is otherwise known as oral cavity or
buccal cavity. It is formed by cheeks, lips and
palate. It encloses the teeth, tongue and
salivary glands.
• Mouth opens anteriorly to the exterior through
lips and posteriorly through fauces into the
pharynx.
• Digestive juice present in the mouth is saliva,
which is secreted by the salivary glands.
 Function of Mouth
• 1. Ingestion of food materials
• 2. Chewing the food and mixing it with saliva
• 3. Appreciation of taste of the food
• 4. Transfer of food (bolus) to the esophagus by
swallowing
• 5. Role in speech
• 6. Social functions such as smiling and other
expressions.
Salivary Glands
• Major glands are:
• 1. Parotid glands
• 2. Submaxillary or
submandibular
glands
• 3. Sublingual glands.
 Classification of salivary glands
• Salivary glands are classified into three types, based
on the type of secretion:

• 1. Serous Glands

• 2. Mucus Glands:

• 3. Mixed Glands
 PROPERTIES AND COMPOSITION OF SALIVA „
PROPERTIES OF SALIVA

• „ 1. Volume: 1000 mL to 1500 mL of saliva is

secreted per day and it is approximately about
1 mL/minute.
• 2. Reaction: Mixed saliva from all the glands is
slightly acidic with pH of 6.35 to 6.85
• 3. Specific gravity: It ranges between 1.002
and 1.012
• 4. Tonicity: Saliva is hypotonic to plasma.
 Composition of saliva
• „ Mixed saliva contains 99.5% water and 0.5% solids.
Function of saliva
 Formation of Saliva
• It is formed in a two-step process that involves
several transport mechanisms.
• The first step is the formation of an isotonic
plasma-like solution by the acinar cells.
• The second step is modification of this
plasma-like solution by the ductal cells.
Mechanism of salivary secretion. Initial saliva is produced by acinar cells (1) and subsequently
modified by ductal epithelial cells (2). ATP, Adenosine triphosphate.
 Cont’d…
1. The acinar cells secrete the initial saliva, which
is isotonic and has approximately the same
electrolyte composition as plasma. Thus, in
initial saliva, osmolarity, Na+, K+, Cl−, and HCO3−
concentrations are similar to those in plasma.
2. The ductal cells modify the initial saliva. The
transport mechanisms involved in this modification
are complex, but they can be simplified by
considering events in the luminal and basolateral
membranes separately and then by determining
the net result of all the transport mechanisms.
 Cont’d…
• The luminal membrane of the ductal cells contains three
transporters:
• Na+ -H+ exchange, Cl−- HCO3 − exchange, and H+-K+ exchange.
• The basolateral membrane contains the Na+-K+ ATPase and Cl−
channels. The combined action of these transporters working
together is absorption of Na+ and Cl− and secretion of K+ and
HCO3 −.
• Net absorption of Na+ and Cl− causes the Na+ and Cl−
concentrations of saliva to become lower than their
concentrations in plasma, and net secretion of K+ and HCO3 −
causes the K+ and HCO3 − concentrations of saliva to become
higher than those in plasma.
• Because more NaCl is absorbed than KHCO3 is secreted, there
is net absorption of solute.
• TABLE: Digestive enzymes of saliva
 REGULATION OF SALIVARY SECRETION
• „Salivary secretion is regulated only by
nervous mechanism.
• Autonomic nervous system is involved in the
regulation of salivary secretion.
• „ NERVE SUPPLY TO SALIVARY GLANDS
• Salivary glands are supplied by both
parasympathetic and sympathetic divisions of
autonomic nervous system.
Cont’d..
Parasympathetic fibers
• Parasympathetic Fibers to Submandibular and
Sublingual Glands: Parasympathetic preganglionic
fibers to submandibular and sublingual glands arise
from the superior salivatory nucleus, situated in pons.
• After taking origin from this nucleus, the preganglionic
fibers run through nervus intermedius of Wrisberg,
geniculate ganglion, the motor fibers of facial nerve,
chorda tympani branch of facial nerve and lingual
branch of trigeminal nerve and finally reach the
submaxillary ganglion.
• Postganglionic fibers arising from this ganglion supply
the submaxillary and sublingual glands.
• Parasympathetic Fibers to Parotid Gland
• Parasympathetic preganglionic fibers to parotid
gland arise from inferior salivatory nucleus situated
in the upper part of medulla oblongata. From here,
the fibers pass through the tympanic branch of
glossopharyngeal nerve, tympanic plexus and lesser
petrosal nerve and end in otic ganglion.
• Postganglionic fibers arise from this ganglion and
supply the parotid gland by passing through
auriculotemporal branch in mandibular division of
trigeminal nerve.
Parasympathetic Fibers to Submandibular
and Sublingual Glands
Function of Parasympathetic Fibers
• Stimulation of parasympathetic fibers of
salivary glands causes secretion of saliva with
large quantity of water.
• It is because the parasympathetic fibers
activate the acinar cells and dilate the blood
vessels of salivary glands.
• However, the amount of organic constituents
in saliva is less. The neurotransmitter is
acetylcholine.
• SYMPATHETIC FIBERS
• Sympathetic preganglionic fibers to salivary glands
arise from the lateral horns of first and second
thoracic segments of spinal cord.
• The fibers leave the cord through the anterior
nerve roots and end in superior cervical ganglion of
the sympathetic chain.
• Postganglionic fibers arise from this ganglion and
are distributed to the salivary glands along the
nerve plexus, around the arteries supplying the
glands.
• Function of Sympathetic Fibers
• Stimulation of sympathetic fibers causes secretion of
saliva, which is thick and rich in organic constituents
such as mucus.
• It is because, these fibers activate the acinar cells and
cause vasoconstriction.
• The neurotransmitter is noradrenaline.
• REFLEX REGULATION OF SALIVARY
SECRETION
• Salivary secretion is regulated by nervous
mechanism through reflex action. Salivary
reflexes are of two types:
• 1. Unconditioned reflex.
• 2. Conditioned reflex.
 EFFECT OF DRUGS AND CHEMICALS
ON SALIVARY SECRETION
• Substances which increase salivary secretion
• 1. Sympathomimetic drugs like adrenaline and
ephedrine.
• 2. Parasympathomimetic drugs like
acetylcholine, pilocarpine, muscarine and
physostigmine.
• 3. Histamine
• Substances which decrease salivary secretion
• 1. Sympathetic depressants like ergotamine
and dibenamine.
• 2. Parasympathetic depressants like atropine
and scopolamine.
• 3. Anesthetics such as chloroform and ether
stimulate the secretion of saliva. However,
deep anesthesia decreases the secretion due
to central inhibition
 Disorders affecting Salivary secretion
• HYPOSALIVATION:Reduction in the secretion
of saliva. It is of two types.
• 1. Temporary hyposalivation occurs in: i.
Emotional conditions like fear. ii. Fever. iii.
Dehydration.
• 2. Permanent hyposalivation occurs in: i.
Sialolithiasis (obstruction of salivary duct). ii.
Congenital absence or hypoplasia of salivary
glands. iii. Bell palsy (paralysis of facial nerve).
• HYPERSALIVATION: Excess secretion of saliva. Physiological
condition when hypersalivation occurs is pregnancy.
• Hypersalivation in pathological conditions is called ptyalism,
sialorrhea, sialism or sialosis.
• Hypersalivation occurs in the following pathological conditions:
• 1. Decay of tooth or neoplasm (abnormal new growth or
tumor) in mouth or tongue due to continuous irritation of
nerve endings in the mouth.
• 2. Disease of esophagus, stomach and intestine.
• 3. Neurological disorders such as cerebral palsy, mental
retardation, cerebral stroke and parkinsonism.
• 4. Some psychological and psychiatric conditions.
• 5. Nausea and vomiting.
• OTHER DISORDERS: salivary secretion is
affected by other disorders also, which include:
• 1. Xerostomia
• 2. Drooling
• 3. Chorda tympani syndrome
• 4. Paralytic secretion of saliva
• 5. Augmented secretion of saliva
• 6. Mumps
• 7. Sjögren syndrome.
THE STOMACH

PART 3
Stomach….
The function of the stomach
• 1. Mixes saliva, food, and gastric juice to form
chyme.
• 2. Serves as a reservoir for food before release
into small intestine.
• 3. Secretes gastric juice, which contains HCl,
pepsin, intrinsic factor and gastric lipase.
• 4. Secretes gastrin into blood.
GI secretion in the stomach
Secretion of Hydrochloric acid by parietal cells
Function of serotonin, gastrin and histamine
secreted by the enteroendocrine cells

Serotonin:
• i. it Is an inhibitory substance.
• ii. Inhibits impulses of pain sensation in
posterior gray horn of spinal cord
• iii. Causes mood depression and induces sleep
• iv. Causes vasoconstriction.
Histamine:
• i. It is an excitatory neurotransmitter
substance
• ii. Histamine released from tissues causes
vasodilatation and enhances the capillary
permeability for fluid and plasma proteins
from blood into the affected tissues. So, the
accumulation of fluid with proteins develops
local edema
• iii. In GI tract, histamine increases the motility.
 Cont’d…
• Gastrin:
• Increases gastric secretion and motility
• Stimulates islets in pancreas
Composition of gastric juice
 Enzymes of the Gastric juice
ENZYME ACTIVATOR SUBSTRATE END PRODUCTS

Pepsin HCL PROTEINS Proteoses,

Peptones,
Polypeptides

Gastric Lipase ACID Medium TRIGLYCERIDES Fatty acids and

Glycerol
Gastric amylase ACID Medium STARCH Dextrin and
Maltose
(negligible
action)

Gelatinase ACID Medium GELATIN & Peptides

COLLAGEN
Urase ACID Medium UREA Ammonia
 Describe the physiological basis of the 3
phases of Gastric secretion
• The three phases of gastric secretion;
• 1. Cephalic phase.
• 2. Gastric phase,
• 3. Intestinal phases

• The secretion of gastric juice is controlled by

both nerves and hormones.
• Stimuli in the brain, stomach, and small intestine
activate or inhibit gastric juice production.
Cephalic phase
 Cont’d….

• Secretion of gastric juice by the stimuli arising

from head region (cephalus) is called cephalic
phase
• This phase of gastric secretion is regulated by
nervous mechanism. The gastric juice secreted
during this phase is called appetite juice
• Gastric secretion occurs even without the
presence of food in stomach.
• Two types of reflex regulate the cephalic phase:
Unconditioned reflex and Conditioned reflex.
Gastric phase
 Cont’d…

• Secretion of gastric juice when food enters the

stomach is called gastric phase.
• This phase is regulated by both nervous and
hormonal control.
• Gastric juice secreted during this phase is rich
in pepsinogen and hydrochloric acid.
Intestinal phase
 Cont’d…
• Intestinal phase is the secretion of gastric juice
when chyme enters the intestine.
• Intestinal phase of gastric secretion is regulated
by nervous and hormonal control.
• Chyme that enters the intestine stimulates the
duodenal mucosa to release gastrin, which is
transported to stomach by blood. There it
increases gastric secretion.
• Gastric secretion is inhibited by two factors:
Enterogastric reflex and Gastrointestinal (GI)
hormones.
 Disorders that can affect Gastric secretion?

• Gastritis
• Gastric atrophy
• Peptic Ulcers
• Zollinger- Ellison Syndrome
 What are the causes and features of Zollinger-
Ellison syndrome
• ZollingerEllison syndrome is characterized by secretion of excess
hydrochloric acid in the stomach.
• Cause
• This disorder is caused by tumor of pancreas. Pancreatic tumor
produces a large quantity of b. Gastrin increases the hydrochloric
acid secretion in stomach by stimulating the parietal cells of
gastric glands.
• Features
• i. Abdominal pain
• ii. Diarrhea (frequent and watery, loose bowel movements)
• iii. Difficulty in eating
• iv. Occasional hematemesis
 What are the causes and features of peptic
ulcers?
• Ulcer means the erosion of the surface of any
organ due to shedding or sloughing of inflamed
necrotic tissue that lines the organ.
• Peptic ulcer means an ulcer in the wall of
stomach or duodenum, caused by digestive
action of gastric juice.
• If peptic ulcer is found in stomach, it is called
gastric ulcer and if found in duodenum, it is
called duodenal ulcer.
 Cause of peptic ulcers
• i. Increased peptic activity due to excessive secretion of
pepsin in gastric juice
• ii. Hyperacidity of gastric juice
• iii. Reduced alkalinity of duodenal content
• iv. Decreased mucin content in gastric juice or decreased
protective activity in stomach or duodenum
• v. Constant physical or emotional stress
• vi. Food with excess spices or smoking (classical causes of
ulcers)
• vii. Longterm use of NSAIDs (see above) such as Aspirin,
Ibuprofen and Naproxen
• viii. Chronic inflammation due to Helicobacter pylori
 What are the causes and features of
Gastric atrophy?
• Gastric atrophy is the condition in which the muscles of the
stomach shrink and become weak. Gastric glands also shrink,
resulting in the deficiency of gastric juice.
• Cause
Gastric atrophy is caused by chronic gastritis called chronic
atrophic gastritis. There is atrophy of gastric mucosa including
loss of gastric glands. Autoimmune atrophic gastritis also causes
gastric atrophy.
• Features
Generally, gastric atrophy does not cause any noticeable
symptom. However, it may lead to achlorhydria (absence of
hydrochloric acid in gastric juice) and pernicious anemia. Some
patients develop gastric cancer.
 What are the causes and features of gastritis?
• Inflammation of gastric mucosa is called gastritis.
It may be acute or chronic.
• Acute gastritis is characterized by inflammation
of superficial layers of mucus membrane and
infiltration with leukocytes, mostly neutrophils.
• Chronic gastritis involves inflammation of even
the deeper layers and infiltration with more
lymphocytes. It results in the atrophy of the
gastric mucosa, with loss of chief cells and
parietal cells of glands. Therefore, the secretion
of gastric juice decreases.
 Cont’d…
• Causes of Acute Gastritis
i. Infection with bacterium Helicobacter pylori
ii. Excess consumption of alcohol
iii. Excess administration of Aspirin and other
nonsteroidal antiinflammatory drugs (NSAIDs)
iv. Trauma by nasogastric tubes
v. Repeated exposure to radiation (rare).
 Cont’d..
• Causes of Chronic Gastritis
i. Chronic infection with Helicobacter pylori
ii. Longterm intake of excess alcohol
iii. Longterm use of NSAIDs
iv. Autoimmune disease.
 Cont’d..

• Features
• Features of gastritis are nonspecific. Common feature is
abdominal upset or pain felt as a diffused burning
sensation. It is often referred to epigastric pain.
• Other features are:
i. Nausea
ii. Vomiting
iii. Anorexia (loss of appetite)
iv. Indigestion
v. Discomfort or feeling of fullness in the epigastric region
vi. Belching (process to relieve swallowed air that is
accumulated in stomach).
PANCREASE

Part 4
Two major functions of pancreas

• Pancreas is a dual organ having two functions:

• (1) Endocrine function.
• (2) Exocrine function.
PANCREASE- anatomy
Description of Exocrine part
Nerve supply to the pancreas

• Pancreas is supplied by both sympathetic and

parasympathetic fibers.
• Sympathetic fibers are supplied through
splanchnic nerve and parasympathetic fibers
are supplied through vagus nerve.
Composition of Pancreatic Juice
Function of the Pancreatic Juice
DIGESTIVE FUNCTIONS OF PANCREATIC JUICE
• Pancreatic juice plays an important role in the
digestion of proteins and lipids. It also has mild
digestive action on carbohydrates.
DIGESTION OF PROTEINS
• Major proteolytic enzymes of pancreatic juice are
trypsin and chymotrypsin.
• Other proteolytic enzymes are carboxypeptidases,
nuclease, elastase and collagenase.
Action of Trypsin
• i. Digestion of proteins: Trypsin is the most powerful
proteolytic enzyme.
• ii. Curdling of milk
• iii. Blood clotting: It accelerates blood clotting
• iv. It activates the other enzymes of pancreatic juice, viz.
• a. Chymotrypsinogen into chymotrypsin
• b. Procarboxypeptidases into carboxypeptidases
• c. Proelastase into elastase
• d. Procolipase into colipase
• v. Trypsin also activates collagenase, phospholipase A and
phospholipase B
• vi. Autocatalytic action: Once formed, trypsin itself
converts trypsinogen into trypsin.
Actions of chymotrypsin

• i. Digestion of proteins: Chymotrypsin is also

an endopeptidase and it converts proteins into
polypeptides
• ii. Digestion of milk: Chymotrypsin digests
caseinogen faster than trypsin. Combination
of both enzymes causes rapid digestion of milk
• iii. On blood clotting: No action.
SUMMARY: Source of digestive Enzyme
Mechanism of Pancreatic secretion
• The enzymatic and aqueous components of pancreatic
secretion are produced by separate mechanisms. Enzymes are
secreted by the acinar cells, and the aqueous component is
secreted by the centroacinar cells and then modified by the
ductal cells.
• Pancreatic secretion occurs in the following steps:
• 1. Enzymatic component of pancreatic secretion (acinar cells).
Most of the enzymes required for digestion of carbohydrates,
proteins, and lipids are secreted by the pancreas. Pancreatic
amylase and lipases are secreted as active enzymes.
• Pancreatic proteases are secreted in inactive forms and
converted to their active forms in the lumen of the duodenum;
for example, the pancreas secretes trypsinogen, which is
converted in the intestinal lumen to its active form, trypsin.
• 2. Aqueous component of pancreatic secretion (centroacinar and ductal cells). Pancreatic juice
is an isotonic solution containing Na+, Cl−, K+, and HCO 3 − (in addition to the enzymes). The Na+
and K+ concentrations are the same as their concentrations in plasma, but the Cl − and HCO3 −
concentrations vary with pancreatic flow rate.
• Centroacinar and ductal cells produce the initial aqueous secretion, which is isotonic and
contains Na+, K+, Cl−, and HCO3 −.

• This initial secretion is then modified by transport processes in the ductal epithelial cells as
follows:
• The apical membrane of ductal cells contains a Cl−-HCO3 − exchanger, and the basolateral
membrane contains Na+-K+ ATPase and an Na+-H+ exchanger. In the presence of carbonic
anhydrase, CO2 and H2O combine in the cells to form H2CO3.
• H2CO3 dissociates into H+ and HCO3 −. The HCO3 − is secreted into pancreatic juice by the Cl−-HCO3
−
exchanger in the apical membrane.

• The H+ is transported into the blood by the Na +-H+ exchanger in the basolateral membrane. The
net result, or sum, of these transport processes is net secretion of HCO 3 − into pancreatic ductal
juice and net absorption of H+; absorption of H+ causes acidification of pancreatic venous blood.
Enzymes of the pancreatic juice
Regulation of Pancreatic secretion
Regulation of Pancreatic secretion
 Anatomy of the Gall bladder

Pancreatic juice and bile are secreted into the duodenum. The pancreatic duct joins
the common bile duct to empty its secretions through the duodenal papilla into the
duodenum. The release of bile and pancreatic juice into the duodenum is controlled
by the sphincter of ampulla (sphincter of Oddi).
 Production and storage of Bile
• Bile is continuously produced by the liver and
drains through the hepatic and common bile
ducts to the duodenum.
• When the small intestine is empty of food, the
sphincter of ampulla (sphincter of Oddi) at
the end of the common bile duct closes, and
bile is forced up to the cystic duct and then to
the gallbladder for storage.
3 function of Bile

1. Digestion and absorption of FATS.

2. It acts as the excretory fluid of water insoluble

substance such as cholesterol & bilirubin

3. It helps in absorption of fat soluble substance

such as Vit A, D, E & K

Composition of Bile
Primary and secondary bile acids form Bile SALTS
• The liver conjugates the bile acids with the amino
acids glycine or taurine to form bile salts.
• Bile salts are more effective detergents than bile
acids because of their enhanced amphipathic
nature. Therefore, only the conjugated forms—
that is, the bile salts—are found in the bile.

• Individuals with genetic deficiencies in the

conversion of cholesterol to bile acids are treated
with exogenously supplied Chenodeoxycholic acid.
Biliary System (Enterohepatic Circulation)
•
• Steps 1: Constituents of Bile are continoustly being secreted
• Step2: Bile flows out of the liver and fills the gall bladder
• Step 3: CCK is secreted in response to chyme in the small intestine. The two
action of CCK are; (1) Causes contraction of gall bladder and (2) relaxation of
sphincter of Oddi. The bile salts will emulsify and solubilise dietary lipids.

• Step 4: Bile salt absorption

- Passive diffusion
- Secondary active transport (Na-Bile salt active carrier mediated process).
- De-conjugation of bile salts to bile acids by bacteria in the terminal ileum. Bile
salts are more lipophilic than bile salts
- Passive reabsorption of secondary bile acids …although lithcholic acids is poorly
absorbed.

NOTE: Transport of bile salts in portal blood involves binding to albumin or HDLS
 FUNCTION of GALL BLADDER
1. Store bile
2. Concentrates bile
3. Ejects bile
cont’d Storage of bile

• During the interdigestive periods, the

gallbladder can fill because it is relaxed and
the sphincter of Oddi is closed.
cont’d Concentration of Bile

• The epithelial cells of the gallbladder absorb ions and

water in an isosmotic fashion, similar to the
isosmotic reabsorptive process in the proximal tubule
of the kidney.
Bile concentration in the Gallbladder
cont’d EJECTION of Bile
• CCK has two simultaneous effects that result in ejection of
bile from the gallbladder: (1) contraction of the
• gallbladder and (2) relaxation of the sphincter of Oddi (a
thickening of the smooth muscle of the bile duct at its
entrance to the duodenum).
• Bile is ejected in pulsatile “spurts,” not in a steady stream.
The pulsatile pattern is caused by the rhythmic contractions
of the duodenum.
• When the duodenum is relaxed and duodenal pressure is
low, bile is ejected; when the duodenum is contracting and
duodenal pressure is higher, bile is not ejected against the
higher pressure.
 Liver Physiology (intro)
• The liver receives blood from the portal Veins
from; spleen, stomach, pancrease, small
intestines, colon
• The liver is ideally located to receive
• (a) absorbed nutrients
• (b) to detoxify absorbed substances that may
be harmful e.g drugs and toxins
Splanchnic circulation
 Function of the LIVER
1. Bile formation
2. Bilirubin production
3. Metabolic function
4. Detoxification of substance
Anatomy of the Liver
Path taken by bile from the hepatocyte to the duodenum
Blood supply to the liver
Blood supply to the liver
Cont’d….
5 principle function of the liver
Bile Canaliculus
Acinus
 Types of plasma protein synthesied by the Liver
Plasma proteins synthesized by the liver

Albumin is quantitatively the most significant, and accounts for the majority of plasma
oncotic pressure.
Acute-phase proteins, proteins synthesized and secreted into the plasma on exposure
to stressful stimuli.
Steroid binding and other hormone binding proteins: Others are proteins that
transport steroids and other hormones in the plasma, and still others are
clotting factors: Following blood loss, the liver replaces the plasma proteins in days to
weeks.
The only major class of plasma proteins not synthesized by the liver are the
immunoglobulins.
What is bilirubin. Show how the liver metabolise and excrete bilirubin?

• Bilirubin is a bile pigment formed as a waste product of the

breakdown of erythrocytes (hemoglobin) and is excreted in
bile rather than urine because of it low solubility in water
Cont’d….
• Hemoglobin is first converted to
biliverdin with the release of iron
and globin.
• Biliverdin is then converted into
bilirubin.
• Bilirubin bind to albumin, which is
transported in blood.
• Bilirubin enters liver cells via a
member of the organic anion
transporting polypeptide (OATP)
family, and then becomes bound to
cytoplasmic proteins.
Cont’d…..

• Inside the hepatocyte Bilirubin conjugates

with glucuronic acid in a reaction
catalyzed by the enzyme glucuronyl
transferase (UDP-
glucuronosyltransferase).
• The glucuronide which is water solube is
secreted into the bile canaliculi through
an active carrier-mediated process known
as multidrug resistance protein-2 (MRP-2).

• In the small intestine, bilirubin

glucuronide is poorly ab- sorbed.
• In the colon, however, bacteria
deconjugate it, and part of the bilirubin
released is converted to the highly
soluble, colorless compound called
urobilinogen.

• Urobilinogen can be oxidized in the

intestine to stercobilin or absorbed by the
small intestine. It is excreted in either
urine or bile. Stercobilin is responsible for
the brown color of the stool
Cont’d… excretion of bilirubin
 Factors that can cause Jaundice
• Jaundice (icterus) is due to accumulation of free or conjugated bilirubin
in the blood, the skin, sclera, and mucous membranes turn yellow. It is
detectable when the total plasma bilirubin is greater than 2 mg/dL
(34mol/L).
• Hyperbilirubinemia may be due to
(1) excess production of bilirubin (hemolytic anemia, etc)
(2) decreased uptake of bilirubin into hepatic cells.
(3) disturbed intracellular protein binding or conjugation,
(4) disturbed secretion of conjugated bilirubin into the bile canaliculi.
(5) intrahepatic or extrahepatic bile duct obstruction.

• When it is due to one of the first three processes, the free bilirubin rises.
When it is due to disturbed secretion of conjugated bilirubin or bile duct
obstruction, bilirubin glucuronide regurgitates into the blood, and it is
predominantly the conjugated bilirubin in the plasma that is elevated.
Describe the mechanism of bile salt secretion?
 Intestinal fluid and electrolyte transport

• About 9 Liters are absorbed by the Intestines.

• Source of these fluids are;
• Diet
• Saliva
• Gastric juice
• Pancreatic juice
• Small intestines
• Disturbances in fluid absorptive mechansim
can lead to excessive fluid loss from GIT called
Diarrhoea
• Mechanism of fluid absorption involves;
- Cellular via membrane
- Paracellular through tight junction
 Diarrhoea
1. ECF volume reduction
2. IV volume decrease
3. Decrease in arterial pressure
4. Loss of HCO3- leads to Hyperchloremic
metabolic acidosis
5. It may lead to hypokalemia
 Causes of diarrhoea
• Decreased surface area of absorption
• Osmotic diarrhoea
• Secretory diarrhoe e.g cholera
THANK YOU

END