So you have chewed your food into a bolus – what next?
The pharynx (throat), a funnel shaped tube connected to the back of the mouth, receives the bolus and is responsible for passing it onto the oesophagus.
When we swallow various mechanisms come in to play! Food is squeezed into the pharynx by the pressure of the tongue moving upwards and backward against the roof of the mouth (soft palate) which in turn pulls upwards to close off the nasal cavities – so we do not have food coming out of our noses!! The sides of the pharynx move inwards forming a slit through which food must pass. The vocal cords in the larynx close as it is pulled upwards and forwards by the neck muscles and ligaments causing a flap of elastic cartilage, called the epiglottis, to fold over and block it. This flap sits at the end of the point of the pharynx where it splits into the larynx, which leads to the trachea and the lungs, and the oesophagus, which leads to the stomach. This whole process lasts about 2-6 seconds so it does not interrupt breathing!!! If food or liquid get into the larynx accidentally it stimulates a strong cough reflex to expel the substance in order to protect the lungs.
The act of swallowing starts off something called peristalsis which begins in the pharynx and carries on all the way through to the rectum. Peristalsis is the successive waves of involuntary muscular contraction passing along the length of the whole intestinal tract, causing the onward movement of any food bolus. This peristaltic action allows the food to pass from the mouth to the stomach in 8 – 10 seconds, slowing down once it reaches the stomach and gets even slower further along the rest of the intestinal tract.
Nurse Niki Medlock