Biology 104 Human Digestive System Anatomy

external nares or nostrils

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Digestive system Biology 104

external nares or nostrils.  The external nares lead to a chamber dorsal to the hard 

palate, called the nasal cavity.   


Air then passes from the nasal cavity to the nasopharynx, which is a chamber 

dorsal to the soft palate.   Only mammals have a hard palate, which separates the 

breathing and eating passageways.   This allows mammals to chew food and breathe at 

the same time. Only mammals truly chew their food and have teeth specialized for 

chewing.  After air enters the glottis, it proceeds through the larynx and trachea to the 




Path of Food 



The head and neck contain the mouth, oral cavity, and pharynx.   




Food enters the oral cavity through the mouth, which is bounded by the lips.  

The roof of the oral cavity is formed by a bony palate, the hard palate.  At the posterior 

end of the hard palate the bone ends and the roof of the mouth becomes soft, i.e. the soft 

palate. (The difference in texture is not notable on the models, but bone is modeled in the 

hard palate. )  The oral cavity is that part of the digestive tract from the lips to the end of 

the hard palate. 



Digestion begins in the oral cavity, as digestive enzymes such as amylases 

secreted in saliva, are mixed with the food during chewing.   Amylase catalyzes the 

breakdown of amylose, or starch, into simpler carbohydrates. 


The tongue pushes food from the oral cavity into the region ventral to the soft 

palate, which is called the oropharynx.  Projecting into the oropharynx is a flap, the 

epiglottis, which partially surrounds an opening at its base, called the glottis.  The glottis 

eventually leads to the lungs.  Note the two openings in the pharynx.  One goes to the 

trachea, which is always open due to its rings of cartilage, and the other opening is to the 



When food enters the oropharynx, a reflex makes the epiglottis fold back, closing 

the glottis and allowing food to slide into the esophagus.  Once in the esophagus, 

peristaltic contractions of the esophagus push the food to the stomach.  No digestion 

occurs in the esophagus.  It is just a passageway that connects the pharynx to the 



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