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: