Tanveer Raza MD MS MBBS razajju2@yahoo.com

Introduction
 Gastrointestinal system
 Portal through which nutritive substances, vitamins, minerals, and fluids enter the body
Tanveer Raza MD MS MBBS razajju2@yahoo.com

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 razajju2@yahoo.com

Introduction


Tanveer Raza MD MS MBBS razajju2@yahoo.com

Introduction
 Alimentary tract
 Mouth to Anus
Tanveer Raza MD MS MBBS razajju2@yahoo.com

Introduction
 Gastrointestinal tract
 Stomach to Anus
Tanveer Raza MD MS MBBS razajju2@yahoo.com

Parts of digestive system
 Mouth or buccal cavity with tongue
 Oropharynx
 Oesophagus
 Stomach
 Small Intestine
 Large Intestine
Tanveer Raza MD MS MBBS razajju2@yahoo.com

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 razajju2@yahoo.com

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 razajju2@yahoo.com

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 razajju2@yahoo.com

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 razajju2@yahoo.com

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 razajju2@yahoo.com

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 razajju2@yahoo.com

Cross Section of Intestinal wall
 Resting membrane potential
 Voltage can change to different levels less negative
Depolarization
-56mv
At rest more negative
Hyperpolarization
Tanveer Raza MD MS MBBS razajju2@yahoo.com

Cross Section of Intestinal wall

 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 razajju2@yahoo.com

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 razajju2@yahoo.com

Enteric Nervous System
Tanveer Raza MD MS MBBS razajju2@yahoo.com

Enteric Nervous System
 In GIT wall, from Esophagus to Anus

1.
2.
Two plexuses
Myenteric or Auerbach’s plexus
Submucosal plexus or Meissner’s plexus
Tanveer Raza MD MS MBBS razajju2@yahoo.com

Enteric Nervous System


Connected to and influenced by
 Sympathetic Nervous System
 Parasympathetic Nervous System
Receives sensory nerve endings
Tanveer Raza MD MS MBBS razajju2@yahoo.com

Enteric Nervous System
Myenteric or
Auerbach’s plexus
Outer plexus
Between longitudinal and circular muscle layers
Controls GI movements
Submucosal plexus or
Meissner’s plexus
Inner plexus
In submucosa
Controls GI secretion and
Local blood flow
JEJUNUM
Cross section
Tanveer Raza MD MS MBBS razajju2@yahoo.com

Enteric Nervous System
 Neurotransmitters
 Acetylcholine (Ach)
 Most often excites
GI activity
 Norepinephrine (NE)
 Almost always inhibits GI activity
 Adenosine triphosphate
 Serotonin
 Dopamine
 Cholecystokinin
 Substance P
 Vasoactive intestinal polypeptide
 Somatostatin
 Leu-enkephalin
 Metenkephalin
 Bombesin
Tanveer Raza MD MS MBBS razajju2@yahoo.com

Autonomic Nervous System
 Sympathetic
 Spinal Cord T5-L2
 Postganglionic neuron
 Celiac ganglion
 Mesenteric ganglion
 Inhibits GI activity
Tanveer Raza MD MS MBBS razajju2@yahoo.com

Autonomic Nervous System
 Parasympathetic
 Cranial: Vagus
 Sacral:
 Pelvic
 Sacral 2 nd , 3 rd & 4 th
 Postganglionic neurons
 Myenteric & Submucosal plexuses
 Effect
 Mainly Excitatory
Tanveer Raza MD MS MBBS razajju2@yahoo.com