2. Syllabus
Essence of digestion and classification of digestive processes;
digestion in oral cavity, mastication, salivation, composition of saliva
and properties.
Digestion in stomach; composition of gastric juice and its properties;
phases of gastric juice secretion; motor function of stomach
Methods of study for gastrointestinal tract function. Influence of diet
regimen on gastric secretion; regulation of gastric motor function;
3. Ingestion of food
Is determined by the intrinsic desire for food called hunger.
The type of food the person preferentially seeks is determined by apetite.
Mastication (Chewing)
Frontal incisors – cutting
The posterior teeth -Molars - chewing
Chewing muscles are innervated by the V cranial nerve
Chewing is controlled by the nucleus in the brainstem
Stimulation of the RF taste center causes rhythmical chewing
activity.
Stimulation of hypothalamus, amygdala and cerebral cortex also cause chewing
Chewing reflex
Presence of bolus of food in mouth cause the reflex inhibition of mastication muscles.
This drop causes the stretch reflex of the jaw muscles that leads to rebound contraction.
Jaw rises to close the teeth, but it also compresses the bolus and the reflex starts again.
4. Swallowing – deglutition
1) Voluntary stage
Voluntary squeeze or roll of a bolus
posteriorly into the pharynx by
pressure of the tongue upward and
backward against the pallet.
2) Pharyngeal stage
Involuntary – posteriorly taken bolus
of food stimulates the epithelial
swallowing receptor areas,
impulses go to the brainstem, in
tractus solitatious via trigeminal
and glossopharyngeal nerves and it
initiates the series of automatic
pharyngeal muscle contractions.
3) Oesophageal stage
7. Swallowing – deglutition
3) Oesophageal stage
Primary peristalsis is the
continuation of the pharyngeal
phase and the wave psses to the
stomach. Time – 8-10sec (in upright
position 5-8 sec due to gravity.)
Secondary peristlsis
13. Functions of the stomach
1. Storage - due to vagovagal reflex
after distention it can enlarge and
store more food up to 0.8-1.5 liter.
2. Mixing movements with the slow
rhythm generated in the walls of
stomach; The contracted pyloric
sphyncter helps mixing the food
stored in the antrum – this is called
retropulsion.
3. Hunger contractions
4. Digestion
5. Absorption
6. Protection
16. Regulation of stomach emptying
1. Gastric factor
Increased volume of food in stomach causes stratchinf and
hence the reflexive emptying, pressure is not chaned.
2. Hormone Gastrin
3.
