What is the food bolus?

The Cud. Alimentary bolus is the mass formed by the crushed food in the mouth by the effect of chewing and mixed with the saliva. The food bolus is swallowed voluntarily and goes down through the esophagus to the stomach.

In the stomachthe food bolus is mixed with pepsin and hydrochloric acid and transforms into chyme.

Bolus formation

Cud. Alimentary bolus
The food bolus is formed in the mouth and passes to the stomach through the esophagus.

When food enters the mouth, the chewing and the salivation They prepare food to be swallowed. Chewing, the main mechanism of mechanical digestion, breaks down food into smaller pieces that are easier to swallow.

This grinding also increases the surface of the food, thus facilitating the action of the digestive enzymes. As you chew, food mixes with saliva.

Saliva lubricates the ground mass so that it passes through the esophagus more easily and also contains enzymes that begin the digestion of carbohydrates in the mouth itself.

The mass made up of ground food mixed with saliva forms the Cud. Alimentary bolus.

Bolus swallowing

Once he lingual nerve perceives that the food bolus is ready to be swallowed, depending on its consistency, it is voluntarily pushed towards the throat with the tongue.

In the pharynx, sensory receptors activate the swallowing reflex and the epiglottis it moves to plug the trachea and prevent the food bolus from passing into the respiratory system. This epiglottis reflex is involuntary.

At the same time, the uvula (bell) rises to prevent food from passing into the nose, also in an involuntary reflex action. All these reflexes cause swallowing to stop chewing and breathing temporarily.

The movement of the food bolus in the pharynx exerts pressure that causes the opening of the upper esophageal sphincter (ESS) allowing the bolus to pass into the esophagus.

The EES closes once the bolus has entered the esophagus preventing digestive fluids from entering the mouth (esophageal reflux). Peristaltic movements of the smooth muscles (rhythmic movements in waves) occur in the esophagus push the food bolus into the stomach.

When the food bolus reaches the end of the esophagus, the lower esophageal sphincter (LES) so that the bolus can pass into the stomach. The LES closes after the passage of the bolus to prevent stomach acids and partially digested food from passing into the esophagus (gastroesophageal reflux).

Chyme formation

In the stomach, the food bolus mixes with pepsin and hydrochloric acid from gastric juices to form an acid paste of semi-solid consistency called chyme.

In the formation of chyme, the movements of the muscular walls of the stomach play an important role, so it has part of mechanical digestion and part of chemical digestion.

As the chyme forms, it passes from the stomach to the intestine, where the nutrients and water in the chyme are absorbed. The unabsorbed remainder forms faeces, which travels through the intestine until it is defecated through the anus.

Food bolus obstruction

In some situations, a obstruction of the passage of the alimentary bolus into the stomach.

The most common cause is a improper chewing but there are also some medical conditions that can favor this obstruction and cause difficulty in swallowing solid foods (dysphagia):

  • Schatzky's ring: also called lower esophageal ring, it is a congenital malformation consisting of a narrowing in the lower part of the esophagus.
  • esophageal stricture: narrowing of the esophagus due to gastroesophageal reflux continued over time. It is also known as peptic stricture.
  • Dysphagia is also more common in children, the elderly, and people who are mentally disabled or have suffered some type of brain injury.

Obstruction of the food bolus can cause chest pain, excessive salivation and a feeling of shock. Some situations of bolus obstruction may require emergency care, usually treated by endoscopy.

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