Question

___________ closes the windpipe at the time of swallowing food.

Answer 1

Hint: The trachea, also called as the windpipe, is a cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and it is present in almost all air-breathing animals with lungs. The trachea extends from the larynx and branches into the two primary bronchi which enters the lung through hilum.

Complete answer:
The trachea begins to form in the second month of embryonic development, becoming longer and more fixed in its position over the time. It is epithelium lined with column-shaped cells that have hair-like extensions called cilia, with scattered goblet cells that produce protective mucins and help in throwing back the harmful particles and pathogens.

The epiglottis is a leaf-shaped flap in the throat that prevents food particles while eating from entering the windpipe and the lungs. It stays open during breathing, allowing air entry into the larynx. During swallowing, it closes to prevent aspiration of food into the lungs, forcing the swallowed liquids or food to go along the esophagus toward the stomach instead of entering in the respiratory path. It is thus the valve that diverts passage to either the trachea or the esophagus and prevents the harmful effects of aspiration.

The epiglottis has two surfaces present
• A forward-facing anterior surface
• A posterior surface facing the larynx

 The forward-facing surface is covered with several layers of thin cells called stratified squamous epithelium and is not covered with keratin, the same surface as the back of the tongue. The back surface is covered in a layer of columnar epithelial cells with cilia, similar to the rest of the respiratory tract. It also has mucous-secreting goblet cells present.

Note: When food or other objects travel down the respiratory tract rather than down the esophagus to the stomach due to some defect in epiglottis, this is called aspiration. This can lead to airway obstruction, inflammation of lung tissue, aspiration pneumonia and in the long term may lead to atelectasis and bronchiectasis.