Deglutition or Swallowing | Physiology

Summary

This video explains the process of digestion, focusing on the three stages of swallowing (digitation). It covers the voluntary oral stage, where food (bolus) moves from the mouth to the pharynx, followed by the involuntary pharyngeal stage, which directs the bolus into the esophagus. Finally, the esophageal stage is described, where the bolus moves into the stomach through coordinated peristalsis. The script emphasizes the intricate muscle movements and pressure changes that prevent food from entering the wrong passages, ensuring smooth progression through the digestive system.

Takeaways

• 😀 Digitation, also called swallowing, is the process by which food moves from the mouth into the stomach.
• 😀 Swallowing occurs in three stages: oral, pharyngeal, and esophageal.
• 😀 The oral stage is voluntary, involving the movement of the bolus from the mouth into the pharynx.
• 😀 During the oral stage, the bolus is placed on the posterior dorsal surface of the tongue and pushed into the pharynx by tongue movements and positive pressure.
• 😀 The pharyngeal stage is involuntary and ensures the bolus moves from the pharynx into the esophagus while preventing entry into the mouth, nasopharynx, and larynx.
• 😀 Protection mechanisms during swallowing include the soft palate blocking the nasopharynx, the epiglottis covering the larynx, and vocal cords approximating.
• 😀 Swallowing temporarily halts breathing, a phenomenon called swallowing apnea or digitation apnea.
• 😀 The esophageal stage is also involuntary, moving the bolus from the esophagus into the stomach using peristalsis, which is wave-like contraction of esophageal muscles.
• 😀 There are primary and secondary peristaltic waves: primary starts when the bolus enters the esophagus, while secondary occurs if the bolus gets stuck.
• 😀 Entry of food into the stomach is controlled by the lower esophageal sphincter, which relaxes to allow passage and then closes to prevent reflux.
• 😀 The oral stage is voluntary, but the pharyngeal and esophageal stages are involuntary, demonstrating a coordinated process between conscious and reflexive actions.

Q & A

What is the process of digestion also called?

The process of digestion is also called swallowing.

How many stages are there in the process of swallowing?

There are three stages in the process of swallowing: the oral stage, the pharyngeal stage, and the esophageal stage.

What happens in the oral stage of swallowing?

In the oral stage, the bolus (food mixed with saliva) moves from the oral cavity into the pharynx. This stage is voluntary.

What are the key movements involved in the oral stage?

The bolus is placed on the posterior dorsal surface of the tongue, then the anterior part of the tongue is retracted and depressed. Afterward, the posterior part of the tongue is elevated and retracted against the soft palate, pushing the bolus into the pharynx.

What is the role of the tongue during the oral stage?

The tongue helps by creating positive pressure in the oral cavity, which pushes the bolus into the pharynx. The retraction and elevation of the posterior part of the tongue against the soft palate also aid in this process.

What happens during the pharyngeal stage of swallowing?

During the pharyngeal stage, the bolus is pushed from the pharynx into the esophagus. This stage is involuntary and involves several coordinated movements to prevent the bolus from entering the wrong areas, such as the nasopharynx, oral cavity, or larynx.

How does the body prevent the bolus from entering the wrong passage during swallowing?

The body uses the position of the tongue against the soft palate, elevation of the soft palate, and backward movement of the epiglottis to prevent the bolus from entering the nasopharynx, oral cavity, or larynx.

What is 'swallowing apnea'?

'Swallowing apnea' refers to the temporary arrest of breathing during swallowing. This occurs as a protective mechanism to prevent food from entering the respiratory tract.

What happens in the esophageal stage of swallowing?

In the esophageal stage, the bolus moves from the esophagus into the stomach. This is also an involuntary stage, where peristaltic contractions help propel the bolus downward.

What is peristalsis, and how does it contribute to swallowing?

Peristalsis is the wave-like contraction and relaxation of muscles in the esophagus that helps propel the bolus from the esophagus into the stomach. It occurs in both primary and secondary phases, depending on whether the bolus has reached the stomach or remains stuck in the esophagus.