WEEK 8: 8.3 Salivary Glands, Oesophagus & Stomach Flashcards
(73 cards)
What are different components of the mouth that play a role in ingestion?
hard palate
soft palate
uvula
palatine tonsil
tongue
duct of salivary gland
muscular lips
What are the 3 steps involved in mastication (chewing)
- grind and break up food into small sizes (increases surface area of food for salivary enzymes)
- mix with saliva
- stimulate taste buds (reflex increased in secretion)
What is saliva made up of?
water, electrolytes, protein, mucus
amylase (break polysaccharides into maltose)
lingual lipase (start fat digestion)
lysozyme (antibacterial)
bicarbonate buffer (neutralise acids and prevent dental decay)
What is the function of saliva?
breaks down food particles, washes particles away, acts as a solvent for taste
What is the usual type of secretion of saliva?
slow, continuous basal secretion
What two reflexes cause periods of increased secretion?
simple reflex
conditioned reflex
explain the difference between the simple and conditioned reflex?
in the simple reflex, pressure and chemoreceptors in the mouth activate the salivary center in the medulla, stimulating the autonomic nerves, which stimulate the salivary glands and increase salivation. however, in the conditioned reflex, the same process occurs but thinking of food, seeing food, smelling food activate the cerebral cortex activate the salivary centre in the medulla instead
Explain the voluntary oral stage of swallowing
the tongue pushes portion of food to be swallowed to back of oral cavity, by elevation and retraction against hard palate
explain the involuntary pharyngeal stage
breathing stops and airways are closed
soft palate and uvula lift to close nasopharynx
larynx elevates (causing epiglottis to be bent over), vocal cords close
explain the involuntary oesophageal stage
pharynx muscles contract - force bolus into oesophagus
while swallowing, larynx lifts, and upper oesophageal sphincter relaxes
sphincter closes as bolus passes
swallowing centre triggers peristalsis to push food down
lower sphincter relaces as food approaches
what are the two sphincters in the oesophagus and what are their functions?
pharyngoesophageal (upper): prevents excess air entering GIT
gastroesophageal (lower): keep out stomach contents to prevent heartburn
What is primary peristalsis
it is preceded by pharyngeal phase and controlled by the swallowing centre
What is secondary peristalsis?
occur without pharyngeal phase if oesophagus is distended eg. if food is stuck, and is characterised by stronger force
why does the oesophagus secrete mucus?
for lubrication and protection - to lessen damage from sharp sides of food
What structures make up the upper GIT?
oral cavity
pharynx
esophagus
stomach
small intestine:
duodenum
jejunum
ileum
what is the foregut supplied by?
celiac trunk
what is the foregut made up of?
esophagus
stomach
part of duodenum
pancreas
liver
gallbladder
Where does the esophagus travel through?
the neck, thoracic cavity and into the abdomen
what two layers of muscle of the muscularis externa does the esophagus consist of?
external longitudinal layer of muscle
internal circular layer of muscle
they allow efficient directional movement of food
which atrium of the heart does the esophagus travel behind?
left atrium.
at what level does the esophagus enter the diaphragm at?
level T10
what are the two types of muscle that the esophagus consists of?
striated and smooth muscle
What kind of peritoneal is the stomach
intraperitoneal
