GASTROINTESTIN
AL PHYSIOLOGY
TOPICS THAT COVER
INTRODUCTION TO ORGANS OF GIT
CROSS SECTION OF GIT
ORGANS AND FUNCTIONS OF GIT
BREIF NOTES ON SMALL & LARGE INTESTINE & FUNCTIONS
SYMPATHETIC & PARASYMPATHETIC NERVES-ORIGIN AND SUPPLY TO ORGANS
NERVE SUPPLY
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
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Small Intestine PARTS:1. Duodenum : C- shaped and 25cm in length2. Jejunum : 25 meters long3. Ileum : 3.5 meters long
Gastric chyme (Duodenum) Mixes Pancreatic, bile and Succus entericus absorbed
Small Intestinal Villi
Imp: 4. Movements of Small Intestine helps in Mixing, Digestion and Absorption of Food stuffs.
2. Peristaltic activity : Helps in movement of Undigested and unabsorbed food into Large Intestine
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Large IntestineDivided into1. Caecum : Blind ended sac which opens from Lower part of Ileum.
Ileocaecal valve allows inflow but not outflow of intestinal contents.
2. Appendix: Worm shaped and in humans it is Vestigial.
3. Ascending Colon: Extends from the Caecum upto the Right side of the abdomen up to Liver. On reaching liver it forms Right Hepatic Flexure
4. Transverse Colon: Right Hepatic Flexure to Left Splenic Flexure.
5. Descending Colon: Extends from Left Splenic Flexure to Pelvic Inlet
6. Sigmoid Colon: Begins at Pelvic Inlet and joins Rectum in front of Sacrum
7. Rectum: Descends in front of sacrum by piercing Pelvic floor. It continues with anal canal in the perineum.
8. Anal Canal: Opens to Exterior through anus . It is guarded by two sphincters.
FUNCTIONS
1. Mostly Absorbs Water and electrolytes.
2. Remaining called Faecal matter. It is lubricated by the mucus secreted
from the large intestine.
3. Faecal matter is stored in Sigmoid Colon till expelled by the process
called Defaecation.
PARASYMPATHETIC NERVES TO GIT
Cranial Nerve Site of Connection Site of ganglion Cells
Structures supplied
1. Vagus 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. S2, S 3,S 4 Segments of 2,3,4 of sacral Nerves
Hypogastric ganglia Rest of Large Intestine
SYMPATHETIC NERVES TO GIT
Organs Supplied Site of Connection Site of ganglion Cells
Structures supplied
Viscera of Abdomen T6- L2 Upper abdominal Ganglia
Along the Blood Vessels
Pelvic Viscera L1- L2 Hypogastric ganglia Along the Blood vessels in the hypogastric Nerves
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
ABSORPTION:
Transports Nutrients & Electrolytes to Circulation.
EGESTION:
Undigested food pass into rectum with various secretions.
Other functions:
• hormones - • erythropoises- intrinsic factor, vit B12, extrinsic factor & folic acid •Excretion of waste products (stercobilin etc.,).•Maintains water and electrolyte balance .
NERVE SUPPLY:
A. EXTRINSICB. INTRINSIC
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
INTRINSIC or ENS
MYENTRIC PLEXUS SUB MUCOSAL PLEXUS ( MEISSNER’S )
(FROM EXTRINSIC N.S.)
MOTOR FUNCTION (↑TONE,RYTHMICAL CONTRACTION,CONDUCTION OF WAVES ALONG GUT)
SENSORY FUNCTION (Control of exocrine & endocrine secretions in GIT)
PARASYMPATHETIC NERVES TO GIT
Cranial Nerve Site of Connection Site of ganglion Cells
Structures supplied
1. Vagus 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. S2, S 3,S 4 Segments of 2,3,4 of sacral Nerves
Hypogastric ganglia Rest of Large Intestine
SYMPATHETIC NERVES TO GIT
Organs Supplied Site of Connection Site of ganglion Cells
Structures supplied
Viscera of Abdomen T6- L2 Upper abdominal Ganglia
Along the Blood Vessels
Pelvic Viscera L1- L2 Hypogastric ganglia Along the Blood vessels in the hypogastric Nerves
NERVE SUPPLY:
A. EXTRINSICB. INTRINSIC
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
INTRINSIC or ENS
MYENTRIC PLEXUS SUB MUCOSAL PLEXUS ( MEISSNER’S )
(FROM EXTRINSIC N.S.)
MOTOR FUNCTION (↑TONE,RYTHMICAL CONTRACTION,CONDUCTION OF WAVES ALONG GUT)
SENSORY FUNCTION (Control of exocrine & endocrine secretions in GIT)
MASTICATION
Mastication / Chewing: Definition
Actions takes in Mastication
Chewing reflex
Muscles of Mastication
Functions
CHEWING REFLEX1. Voluntary response 2. Opening and closing of Jaws
DEGLUTITION
ACTIONS TAKES PLACE IN ORAL PHASE:
1. Mastication
2. Moistening
3. Movement of Bolus
ORAL PHASE:
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Deglutition (swallowing)• Sequence
– Voluntary stage• Push food to back of mouth
– Pharyngeal stage• Raise
– Soft palate– Larynx + hyoid– Tongue to soft palate
– Esophageal stage• Contract pharyngeal muscles• Open esophagus• Start peristalsis
APPLIED PHYSIOLOGY
1. ACHLASIA CARDIA: “LES” fails to relax. NM disorder Absence of Peristalsis
2. AEROPHAGIA:unavoidable swallowing of air with food and liquids
3. GERD:Incompetence of LESCause- Reflex of Acidic gastric contents into
Esophagus
4. DYSPHAGIA:Difficulty in swallowing
5. BULBAR PARALYSIS:
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