GIT Flashcards
Salivary glands
Saliva is a thin watery fluid secreted by three pairs of salivary glands which
1)parotid
2)submandibular and
3)sublingual.
Secretion of saliva is a reflex process and is regulated by superior and inferior salivatory nucleus.
There are three types of stimulus which cause secretion of saliva.
1) presence of food in mouth
Presence of food in mouth stimulates tactile receptors and afferrent impulses are carried through lingual, glossopharyngeal and vagus nerve tu superior and inferior salivatory nucleus. These nucleus send secretomotor impulses to salivatory gland causing secretion of saliva by acinar cells. Superior salivatory nucleus send impulses to sub mandibular and subblingual glands through submandibular ganglion. Inferior salivatory nucleus sends impulses to parotid gland through Otic ganglion.
2) site smell or thought of food causes secretion of saliva which originates impulses in higher centres of brain such as appetite centre of hypothalamus or visual or smell centre. This is conditioned reflex.
3) stimulus arising from other parts of gastrointestinal tract
Irritation of oesophageal mucosa causes Oesophagosalivatory reflex end of gastric mucosa causes gastro salivatory reflex.
4) resting secretion
Small amount of saliva is secreted by salivary glands in resting state due to release of acetyl choline by nerve endings.
Cutting of chorda increases salivary secretion called as paralytic secretion of saliva.
Salivary secretion can be innovated by drugs like atropine.
Process of deglutition
Deglutition or swallowing is a reflex process in which food bolus passes from mouth into pharynx, oesophagus and stomach.
Oral stage
In this process food is passed backward by tongue into pharynx by pressure of tongue against soft palate and contraction of intrinsic muscles of tongue.
Pharyngeal stage
In this process food passed through the pharynx into oesophagus.
1) Approximation of palatopharyngeal fold
2) Initiation of pharyngeal deglutition receptors.
3) Receptive relaxation of upper Oesophageal Sphincter.
Movements protecting respiratory tract:
1) Contraction of tensor palate and levator palate.
2) Food entering into larynx and lower resp. tract prevented by stopping respiration and approximation of true and false vocal cord and hyoid bones and larynx pulled upwards.
Oesophageal stage
Pharyngeal peristaltic wave continues into oesophagus as primary Oesophageal peristaltic wave and movement of bolus is accelerated by gravity. If food gets stuck myentric plexus gets activated causing appearance of secondary peristaltic wave. Then there is relaxation of lower Oesophageal Sphincter.
Regulation of gastric secretion
Occurs in 4 phases controlled by cephalic and basalic phase.
1) Cephalic phase
