29 Questions
What is the process of cutting and grinding food in the mouth called?
Mastication
Which cranial nerve innervates the chewing muscles?
CN-V (5th cranial nerve)
What is the role of the lower esophageal sphincter?
Preventing reflux of stomach contents into the esophagus
What is achalasia?
A disorder characterized by difficulty swallowing due to esophageal muscle dysfunction
Which nerve controls the movement of the esophagus during swallowing?
Vagus nerve (CN-X)
What type of digestion occurs in the mouth?
Mechanical digestion by teeth and chemical digestion by saliva
What is the primary function of the lower esophageal sphincter (LES)?
To prevent gastric juices from refluxing into the esophagus
What is the physiological basis of achalasia?
Pathology or absence of the myenteric plexus containing VIP & NO in the lower third of esophagus
What is a potential consequence of untreated achalasia?
Severe substernal pain and ulceration of the esophageal mucosa
What is a characteristic feature of gastroesophageal reflux disease (GERD)?
Incompetence of the lower esophageal sphincter (LES) leading to reflux of gastric contents into the esophagus
How does the LES prevent reflux of gastric secretions into the lower portion of the esophagus?
+ve intra-abdominal pressure closure preventing high pressure in stomach from forcing its contents into esophagus
What regulates contraction and relaxation of the circular musculature of the lower esophageal sphincter (LES)?
Nerves, hormones, and neurotransmitters
Which ONE of the following nerves does not transmit signals from the swallowing center to the pharynx and esophagus?
6th
The process of mastication is initiated by:
Inhibition of the muscles of mastication
Which one of the following increases the tone of the lower esophageal sphincter?
Gastrin
Respiratory inhibition occurs in which phase of swallowing?
Pharyngeal
What is Achalasia?
A condition due to high resting pressure at the LES that fails to relax during swallowing.
What are the functions of Mastication (chewing)?
All of the above
What is the role of salivary amylase in digestion?
It begins carbohydrate digestion
Which stage of swallowing involves muscle contractions to prevent food from entering the nasal cavities, trachea, and esophagus?
Pharyngeal stage
What initiates the cycle of biting, swallowing, and chewing again?
Chewing reflex and stretch reflex
Which teeth are primarily used for cutting food?
Incisors
Where is the swallowing reflex controlled?
Lower pons and medulla
What are peristaltic waves involved in during swallowing?
Moving food through the esophagus
Which cranial nerves are involved in transmitting motor impulses to the pharynx and upper esophagus during the swallowing process?
5th, 9th, 10th, and 12th
What initiates secondary peristalsis in the esophagus?
When primary peristalsis fails to move the food bolus to the stomach
Which nerves innervate the striated muscles of the upper third of the esophagus?
Vagus and glossopharyngeal nerves
What is the function of the upper esophageal sphincter (UES)?
Prevents food and air from entering the esophagus from the mouth
What controls the lower esophageal sphincter (LES)?
Vagus nerve
Study Notes
- The pharyngeal stage of swallowing is initiated by sensory impulses from the mouth received by the nucleus tractus solitarius (NTS) via the trigeminal and glossopharyngeal nerves, specifically at the most sensitive areas around the pharyngeal opening including the tonsillar pillars.
- This sensory input triggers the swallowing center in the medulla and lower portion of the pons to automatically initiate the swallowing process, which includes motor impulses transmitted to the pharynx and upper esophagus via the 5th, 9th, 10th, and 12th cranial nerves and superior cervical nerves.
- During the pharyngeal stage, the swallowing center inhibits the respiratory center to prevent respiration, allowing the food bolus to pass through the pharynx and upper esophagus without entering the trachea.
- The esophageal stage of swallowing begins after the pharyngeal stage and is primarily controlled by the swallowing reflex but also the enteric nervous system (ENS) when the vagus nerve is severed.
- During the esophageal stage, the esophagus serves as a conduit to move food from the pharynx to the stomach. The esophagus has striated muscles innervated by the vagus and glossopharyngeal nerves in the upper third and smooth muscles controlled by the vagus in the lower two thirds.
- The esophagus exhibits primary and secondary peristalsis. Primary peristalsis is a continuation of the wave that begins in the pharynx and moves food to the stomach in 8-10 seconds. Secondary peristalsis is initiated when primary peristalsis fails to move the food bolus to the stomach.
- Esophageal secretions, including mucus, lubricate the esophagus and protect it against acidic juices of the stomach.
- The esophagus is guarded by two sphincters: the upper esophageal sphincter (UES) and the lower esophageal sphincter (LES). The UES is a voluntary muscle that prevents food and air from entering the esophagus from the mouth. The LES is a circular muscle that guards the entrance into the esophagus from the stomach. It is formed of skeletal muscle but is not under voluntary control.
Test your knowledge of the pharyngeal stage of swallowing with this quiz. Learn about the nervous initiation and sensory impulses involved in this crucial stage of swallowing.
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