2 Flashcards
Muscles of mastication are:
Muscles of mastication are: masseter, lateral &
medial pterygoid, buccinator and temporalis
muscles.
Most of the muscles of mastication are
innervated by the motor branch of the …………………….
and the mastication
process is controlled by
Most of the muscles of mastication are
innervated by the motor branch of the fifth cranial nerve (trigeminal N.) and the mastication
process is controlled by nuclei in the brain stem.
The important from Chewing
1-digestion of all foods,
but especially important for most fruits and raw vegetables because these have indigestible
cellulose
2- grinding the food to a very fine
particulate consistency prevents excoriation + increases the ease with which food is
emptied from the stomach into the small intestine,
3- Digestive enzymes act only
on the surfaces of food particles; therefore, the rate of digestion is absolutely dependent on the
total surface area exposed to the digestive secretions.
SWALLOWING OR DEGLUTITION
It is initiated voluntary and completed involuntary. It has 3 stages:
The entire process occurrs in less than ،،،،،،،
seconds.
- Buccal Stage (Voluntary)
- Pharyngeal Stage (Involuntary )
- Esophageal Stage (Involuntary)
N.B. The entire process occurrs in less than 2
seconds.
The food is “voluntarily” squeezed or rolled
posteriorly into the pharynx by pressure of the
tongue upward and backward against the palate.
What this stage?
Buccal stage (Voluntary)
Pharyngeal stage (Involuntary) As the bolus of food enters the posterior mouth and pharynx, it stimulates “……………
epithelial swallowing receptor
areas” all around the opening of the pharynx, especially on the tonsillar pillars
Pharyngeal stage (Involuntary) impulses from these pass to the brain stem to initiate a series of automatic pharyngeal muscle contractions as follows:
- The soft palate is pulled upward to close the posterior nares,
2 . The palatopharyngeal folds on each side of the pharynx are pulled medially to approximate each other. - The vocal cords of the larynx are strongly approximated, and the larynx is pulled upward and to be closed by the epiglottis.
- Temporary apnea.
Pharyngeal stage (Involuntary) swallowing center is present in ……………………
The motor impulses from the swallowing center to the pharynx and upper esophagus that cause
swallowing are transmitted successively by
medulla and lower pons.
5th , 9th , 10th and 12th cranial nerves and even a
few of the superior cervical nerves.
Esophageal stage
The esophagus normally exhibits 2 types of peristaltic movements:
primary peristalsis and
secondary peristalsis.
Primary peristalsis of Esophageal stage
simply continuation of the peristaltic wave that begins in the pharynx and
spreads into the esophagus during the pharyngeal
stage of swallowing.
Secondary peristaltic waves Esophageal stage
result from distention
of the esophagus itself by the food; these waves
continue until all the food has emptied into the
stomach.
Esophageal stage
They are initiated partly by:
They are initiated partly by:
GIT that
swig blow to esophagus did
1. intrinsic neural circuits in the myenteric nervous
at system and partly by;
2. reflexes that begin in the pharynx and are then transmitted through vagal afferent fibers to the
medulla and back again to the esophagus through
glossopharyngeal and vagal efferent nerve fibers.
The musculature of the pharyngeal wall and upper 1/3 of the esophagus is………. are controlled by
striated muscle. are controlled
by skeletal nerve impulses from the glossopharyngeal somatic
and vagus nerves.
In the lower 2/3 of the esophagus the musculature is
……………strongly controlled by the
smooth muscle, strongly controlled by the vagus nerves acting
through connections with the esophageal myenteric
nervous system.
At the lower end of the esophagus, extending upward about 3 centimeters above its junction with the stomach, the esophageal circular muscle functions as a …………
broad sphincter.
