Transcript Gastrointestinal Physiology

Gastrointestinal
Physiology
Tanveer Raza MD MS MBBS
[email protected]
Introduction

Gastrointestinal system

Portal through which nutritive
substances, vitamins, minerals, and
fluids enter the body
Tanveer Raza MD MS MBBS
[email protected]
Introduction

Digestion


Complex food particles are broken
down to simple form (absorbable units)
Absorption

Products of digestion and the vitamins,
minerals and water cross the mucosa
and enter the lymph or the blood
Tanveer Raza MD MS MBBS
[email protected]
Introduction
 Alimentary
 Digestive
tract
tract
Tanveer Raza MD MS MBBS
[email protected]
Introduction

Alimentary tract

Mouth to Anus
Tanveer Raza MD MS MBBS
[email protected]
Introduction

Gastrointestinal tract

Stomach to Anus
Tanveer Raza MD MS MBBS
[email protected]
Physiologic Anatomy
Parts of digestive system

Mouth or buccal cavity with
tongue

Oropharynx

Oesophagus

Stomach

Small Intestine

Large Intestine
Tanveer Raza MD MS MBBS
[email protected]
Parts of digestive system




Mouth or buccal cavity with tongue
Oropharynx
Oesophagus
Stomach

Small Intestine
 Duodenum
 Jejunum
 Ileum

Large Intestine
Tanveer Raza MD MS MBBS
[email protected]
Parts of digestive system

Mouth or buccal cavity with tongue
Oropharynx
Oesophagus
Stomach
Small Intestine

Large Intestine











Caecum
Ascending Colon
Transverse Colon
DescendingColon
Sigmoid Colon
Rectum
Anal Canal
Tanveer Raza MD MS MBBS
[email protected]
Parts of digestive system

Accessory parts
Teeth
 Salivary glands
 Liver
 Pancreas
 Gall Bladder
 Other digestive glands in the wall of the
digestive tract

Tanveer Raza MD MS MBBS
[email protected]
Parts of digestive system

Accessory parts

Teeth

Salivary glands
 Major Salivary Glands
Parotid
 Submandibular
 Sublingual

 Minor




Salivary Glands
Liver
Pancreas
Gall Bladder
Other digestive glands in the wall of the digestive tract
Tanveer Raza MD MS MBBS
[email protected]
Cross Section of Intestinal wall

From outer surface inward




Serosa
Muscular layer
 Longitudinal
 Circular
Submucosa &
Mucosa
Sparse bundles of smooth muscle fibers (mucosal
muscle) lie in the deeper layers of mucosa
Tanveer Raza MD MS MBBS
[email protected]
Cross Section of Intestinal wall

Muscular layer
 Arranged in bundles
 Within
each bundle
 Fibers connected through gap junctions
 Low resistance movement of ions
 Electrical signals travel easily

Each muscle layer functions as a
syncytium
 Excitation
of one layer excites the other
Tanveer Raza MD MS MBBS
[email protected]
Cross Section of Intestinal wall
 Resting

membrane potential
Voltage can change to different levels
less negative
-56mv
Depolarization
At rest
more negative
Hyperpolarization
Tanveer Raza MD MS MBBS
[email protected]
Cross Section of Intestinal wall
Resting membrane potential
 Depolarization of membrane

Less negative

More excitable

Factors
I. Stretching of muscle
II. Stimulation by Acetylcholine (Ach)
III. Stimulation by Parasympathetic nerves
IV. Stimulation by several GI hormones
Tanveer Raza MD MS MBBS
[email protected]
Cross Section of Intestinal wall

Resting membrane potential

Hyperpolarization of membrane



More negative
Less excitable
Factors
 Effect of norepinephrine or epinephrine
 Stimulation of Sympathetic nerves
Tanveer Raza MD MS MBBS
[email protected]
Enteric Nervous System
Enteric Nervous System
Tanveer Raza MD MS MBBS
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Enteric Nervous System

In GIT wall, from Esophagus to Anus

Two plexuses
1.
2.
Myenteric or Auerbach’s plexus
Submucosal plexus or Meissner’s
plexus
Tanveer Raza MD MS MBBS
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Enteric Nervous System


Connected to and influenced by

Sympathetic Nervous System

Parasympathetic Nervous System
Receives sensory nerve endings
Tanveer Raza MD MS MBBS
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Enteric Nervous System
Myenteric or
Auerbach’s plexus
Submucosal
plexus or
Meissner’s plexus
Outer plexus
Inner plexus
Between
longitudinal and
circular muscle
layers
Controls GI
movements
In submucosa
JEJUNUM
Cross section
Controls GI
secretion and
Local blood flow
Tanveer Raza MD MS MBBS
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Enteric Nervous System

Neurotransmitters




Acetylcholine (Ach)
 Most often excites
GI activity
Norepinephrine (NE)
 Almost always
inhibits GI activity
Adenosine
triphosphate
Serotonin

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Dopamine
Cholecystokinin
Substance P
Vasoactive intestinal
polypeptide
Somatostatin
Leu-enkephalin
Metenkephalin
Bombesin
Tanveer Raza MD MS MBBS
[email protected]
Autonomic Nervous System

Sympathetic

Spinal Cord T5-L2

Postganglionic neuron
 Celiac
ganglion
 Mesenteric

ganglion
Inhibits GI activity
Tanveer Raza MD MS MBBS
[email protected]
Autonomic Nervous System

Parasympathetic

Cranial: Vagus

Sacral:
 Pelvic
 Sacral

2nd, 3rd & 4th
Postganglionic neurons
 Myenteric
& Submucosal
plexuses

Effect
 Mainly
Excitatory
Tanveer Raza MD MS MBBS
[email protected]
Thank You