Animal Physiology what are the 2 stages of swallowing and wh

Animal Physiology

what are the 2 stages of swallowing and what happens during each stage?

Solution

Swallowing is the process in the human or animal body that makes something pass from the mouth to the pharynx, and into the esophagus, while shutting the epiglottis. The portion of food, drink or other material that will move through the neck is called a bolus.

There are 2 stages of swallowing-

1. Oral phase

2. Pharyngeal phase

Oral phase-

1) Moistening- The food is moistened by saliva from the salivary glands.

2) Mastication- Food is mechanically broken down by the action of teeth.

3) Trough formation- A trough is then formed at the back of the tongue by the intrinsic muscles (XII)

4) Movement of the bolus posteriorly-

At the end of the oral phase, the food bolus has been formed and is ready to be propelled posteriorly into the pharynx. In order of the anterior to posterior transit of the bolus, orbicularis oris contracts and adducts the lips to form a tight seal of the oral cavity. Next, the superior longitudinal muscle elevates the apex of the tongue to make contact with the hard palate and the bolus is propelled to the posterior portion of the oral cavity. Once the bolus reaches the palatoglossal arch of the oropharynx, the pharyngeal phase, which is reflex and involuntary, begins.

Pharyngeal phase

When this phase begins, the other activities such as chewing, breathing, coughing and vomiting are concomitantly inhibited.

5) Closure of the nasopharynx

6) Pharynx prepares to receive the bolus

7) Opening of the auditory tube

8) Closure of the oropharynx

9) Laryngeal closure

10) Hyoid elevation

11) Bolus transits pharynx