PAVITHRA M
FUNCTIONS OF GASTROINTESTINAL TRACT
DIGESTIVE SYSTEM-GI TRACT
The Major functions - GI Tract
1.Motility: This refers to the movement of food through digestive
tract through the processes of
a. Ingestion: Taking food into the mouth.
b. Mastication: Chewing the food and mixing it with saliva.
c. Deglutition: Swallowing food.
d. Peristalsis and segmentation: Rhythmic, wavelike
contractions (peristalsis), and mixing contractions in different
segments (segmentation), move food through the
gastrointestinal tract.
2. Secretion: This includes both exocrine and endocrine secretions.
a. Exocrine secretions: Water, hydrochloric acid, bicarbonate,
and many digestive enzymes are secreted into the lumen of the
gastrointestinal tract.The stomach alone, for example, secretes
2 to 3 liters of gastric juice a day.
b. Endocrine secretions: The stomach and small intestine
secrete a number of hormones that help to regulate the
digestive system
3. Digestion:
This refers to the breakdown of food molecules into their
smaller subunits, which can be absorbed.
4. Absorption:
This refers to the passage of digested end products into the
blood or lymph.
5. Storage and elimination:
This refers to the temporary storage and subsequent
elimination of indigestible food molecules.
6. Immune barrier:
The simple columnar epithelium that lines the intestine,
with its tight junctions betweencells, provides a physical
barrier to the penetration of pathological organisms and
their toxins. Also, cells of the immune system reside in the
connective tissue located just under the epithelium to
promote immune responses.
Functions of GI
Layers of GI Tract
Mucosa: It is absorptive and major secretory layer. Goblet cells in mucosa secrete Mucus.
Sub mucosa: Thick,vascular layer. it Contains glands and nerve plexuses.Muscalaris(circular muscle): Segmental contractions ,peristaltic movement. Provides major nerve supply to the entire GI tract.Serosa: Outer complete layer and protective wall of the GI tract.
Oesophagus
The oesophagus is the portion of the GI tract that connects the pharynx to the stomach.
Movement of food from mouth to stomach occurs through the peristaltic movement of oesophagus. Peristalsis is the wavelikemuscular contractions occurs because of the circular smooth muscle contracts behind and relaxes in front to push the bolus along the GI tract. Lower oesophageal sphincher isthick and constriction of it avoidsthe regurgitation of food above.
Structure of stomach J-shaped most distensible part of
GI tract. Notice that pyloric region is the
widest and ends with pyloric sphincter.
Functions The functions of the stomach are
to store food, to initiate the digestion of proteins, to kill bacteria with the strong acidity of gastric juice, and to move the food into the small intestine as a paste material called chyme.
Stomach
Parts Villi and Microvilli
Small Intestine
Duodenum-20 to 30 cmJejunum- next 2/5th Ileum-last part
Intestinal Enzymes
Segmentation-Contractile Activity Empties in Ileocecal valve
Small Intestine
Large Intestine
Cecum-Blind pouch open at one end.Ascending ColonTransverse colonDescending colonRectum
Absorption-Fluid n Electrolyte Balance Defeacation-Rectal Pressure
Large Intestine
Liver
It is positioned below the diaphragm in abdominal cavity.Made up of HepatocytesRole-Bile secretion.DetoxificationSecretion of glucoseSecretion of plasma protein & ketone bodies
Gall Bladder
Bile is stored in the gall bladderSac like organ
Pancreas
Soft glandular organ containing endocrine and exocrine secretion
Endocrine secretion- HormonesExocrine – bile juice containing enzymes and
bicarbonate.
Regulation of Gastric Function (3 Phases)
Regulation of Gastric Function (3 Phases)
Regulation of Gastric Function (3 Phases)
Secretion of pancreatic juice & Bile
It is stimulated by Ach(adrenocortico trophs) production in brain
Trophic effect of the GI tract
Trophic effect of the GI tract is the production of gastrin once digestion starts – gastric mucosa is secreted.
Carbohydrate Metabolism
Lipid metabolism
Protein Metabolism
INTERACTIONS
RECAP
GI FUNCTION