GSATROINTESTINAL PHYSIOLOGY INTRODUCTION

9. ORGAN FUNCTION
MOUTH & OROPHARYNX CHOPPING, LUBRICATING, AND
PROPELS FOOD.
ESOPHAGUS CONDUIT TO STOMACH
STOMACH AS RESERVOIR & STARTS
DIGESTION BY SECRETING
ENZYMES (PROTEASES, ACIDS)
SMALL INTESTINE ABSORPTION OF NUTRIENTS
LARGE INTESTINE ABOSRPTION OF FLUIDS AND
ELECTROLYTES
FUNCTIONS OF ORGANS THAT ARE PRESENT IN GIT

12. LAYERS OF GUT
I. MUCOSA
1. SURFACE
EPITHELIUM
2. LAMINA
PROPRIA
3. MUSCUARIS
MUCOSA
Two Thin layers of
Smooth Muscle.
Localised
Movements
Glands, Blood
Vessels, Nerve
fibers etc.,
Simple Epithelium.
Squamous to tall
Columnar Cells.
LAYER
DIVISION
CONTAINS

13. Submucosal Plexus or Meissner’s Plexus
Contains Blood vessels, Lymphatics, network of
Nerve Fibers
II. SUB MUCOSA

14. LAYERS OF GUT
III. MUSCLE COAT
Thick Layer of Smooth Muscle
Outer Longitudinal Muscle
fibers
Inner Circular Muscle Fibers
LAYER
MADE OF
CONTAINS
Aurbach’s Plexus or Myenteric Plexus

15. IV. SEROSA
Outer most layer
•Attaches to the surrounding
GUT

17. PARASYMPATHETIC NERVES TO GIT
Cranial Nerve Origin Site of ganglion
Cells
Structures
supplied
Cranial
Parasympathetic
Segments
Medulla
Dorsal N. of 10th
Nerve
 Myenteric Plexus
 Meissners Plexus
Almost all parts of
GIT upto proximal
2/3rd and distal 1/3rd
transverse colon
2. Sacral
Parasympathetic
segments
Segments of 2,3,4 of
sacral Nerves
Hypogastric ganglia Rest of Large
Intestine

19. SYMPATHETIC NERVES TO GIT
origin Nerves Preganglionic
fibers relay
Post ganglionic
fibers
T5 – L2 spinal
segments
Splanchnic
nerves
Coeliac and
Autonomic
ganglia
Runs Along the
Blood Vessels
Structures
supplied
All
portions
of GIT

20. NERVE SUPPLY:
A. EXTRINSIC
B. INTRINSIC

21. EXTRINSIC NERVOUS SYSTEM
SYMPATHETIC (mainly post ganglionic) PARA SYMPATHETIC
(preganglionic)
INHIBITORY STIMULATORY
(+)Parasympathetic causes:
↑ motility, relaxation of sphinter,secretions from GIT and intestine
(+)Sympathetic causes:
↓ motility, contraction of Sphinters, secretions from GIT

22. INTRINSIC or ENS
MYENTRIC PLEXUS SUB MUCOSAL PLEXUS
( MEISSNER’S )
MOTOR FUNCTION
(↑TONE,RYTHMICAL CONTRACTION,CONDUCTION OF WAVES ALONG GUT)
SENSORY FUNCTION
(Control of exocrine & endocrine secretions in GIT)

23. FUNCTIONS OF DIGESTIVE SYSTEM:
 INGESTION INVOLVES
FOOD IN MOUTH MASTICATION MOISTENING BY SECRETIONS
DEGLUTITION
 DIGESTION BREAKDOWN INTO SMALL PARTICLES BY ENZYMES
Eg: STARCH AMYLASE MONOSACCHARIDES
PROTEINS PROTEASES DIPEPTIDES & A A .
FATS ESTERASES & LIPASE MONOGLYRIDES & FFA

24.  ABSORPTION:
Transports Nutrients & Electrolytes to Circulation.
 EGESTION:
Undigested food pass into rectum with various secretions.
Other functions:
• intrinsic factor, vit B12, extrinsic factor & folic acid
•Excretion of waste products (stercobilin etc.,).
•Maintains water and electrolyte balance .