Case 1 - Yaffas Flashcards
what is the enteric nervous system a part of
the autonomic nervous system found in the GI tract
what is the ENS involved in
coordination of reflexes
what are the two main plexuses of the ENS
submucosal and myenteric plexus
where is the submucosal/Mesissner’s plexus dound and what does it control
lies in the submucosa and controls mainly gastrointestinal secretion and local blood flow
where is the myenteric plexus and what does it control
lies between the longitudinal and circular muscle layers and controls motility
what does the myenteric plexus secrete
secretes vasoactive intestinal polypeptide
what are the resulting inhibitory signals of this useful for
inhibiting some of the intestinal sphincter muscles that impede movement of food
what do the sensory neurones of the ENS report on
mechanical and chemical conditions
what do the motor neurones of the ENS control
through intestinal muscles, control peristalsis and churning of the intestinal contents
what does the presence of bolus of food in the mouth initiate
reflex inhibition of the muscles of mastication which allows the lower jaw to drop
what does this drop initiate
a stretch reflex of the jaw muscles that leads to rebound contraction
what does this rebound contraction lead to
causes raising of the jaw to cause closure of the teeth but it also compresses the bolus again against the lining of the mouth, which inhibits the jaw muscles once again, allowing the jaw to drop and rebound another time
what does this lead to
physical breakdown of the food whcih is important for the digestion of many carbohydrates
what is the rate of digestion absolutely dependent on
the total surface area exposed to the digestive secretions
what happens after the voluntary phase
the bolus of food enters the posterior mouth and pharynx
what happens in the pharynx
it stimulates the epithelial swallowing receptor areas all around the opening of the pharynx, especially on the tonsillar pillars
what is the soft palate muscle contraction
the soft palate is pulled upward to close the posterior nares, to prevent the reflux of the food into the nasal cavities (nasopharynx)
what happens to the palatopharyngeal folds
pulled medially to approximate each other. in this way, the folds form a sagittal split, thought which the food must pass into the posterior pharynx. this slit performs a selective action , allowing food to pass with ease
what happens to the vocal cords
the larynx vocal cords are closed, and the larynx is pulled upward and anteriorly by the neck muscles. these actions, cause the epiglottis to swing backward over the opening of the larynx.
what does the upward movement of the larynx also do
pulled up and enlarges the opening to the oesophagus. At the same time, the upper 3-4cm of the oesophageal musclular wall, called the UOS relaxes, thus allowing food to easily and freely move from the posterior pharynx into the upper oesophagus. Between swallows, this sphincter remains strongly contracted, thereby preventing air from going into the oesophagus during respiration. The upwards movement of the larynx also lifts the glottis out of the mains stream of food flow, so that the food mainly passes on each side of the epiglottis rather than over its surface; this still adds another protection against entry of food into the trachea.
what happens once the larynx is raised
the pharynxgoesophageal sphincter becomes relaxed, the entire muscular wall of the pharynx contracts, beginning in the superior part of the pharynx, then spreading downward over the middle and inferior pharyngeal areas, which propels the food by peristalsis into the oesophagus.
what are the four stages of swallowing
cephalic stage
oral stage
pharyngeal stage
oesophageal stage
what are the two involuntary stages of swallowing
the pharyngeal and oesophageal stages
what does the upper oesophageal sphincter consist of
the cricopharyngeus muscle, the adjacent inferior pharyngeal constrictor, and the proximal portion of the cervical oesophagus
what is the UES innervation by
the vagus nerve
what innervates the musculature acting on the UES to facilitate its opening during swallowing
5th, 7th and 12th cranial nerves
what happens to allow the UES to open
the cricopharyngeus muscle has to relax. this occurs due to cessation of vagal excitation