b. The lips, fleshy folds surrounding the opening of the mouth, are covered on
the outside by skin and on the inside by a mucous membrane. Cheeks, forming the
lateral boundaries of the mouth, are muscular structures covered on the outside by skin
and lined with squamous epithelium. The hard palate consists of portions of the two
maxillae bones and the two palatine bones. The soft palate is fashioned by muscle and
contains the uvula (the cone-shaped, fleshy mass of tissue hanging from the soft palate
above the back of the tongue). The tongue is a solid mass of skeletal muscle that
contains the sensations of taste. The teeth are the organs of mastication (the process
of chewing food). Refer to figure 1-1 for position of the mouth.
PHARYNX (THROAT)--PRIMARY ORGAN
a. The pharynx, more commonly called the throat, is a funnel-shaped tube which
starts at the internal nares and runs about five inches down the neck. It lies just behind
the nasal cavity and oral cavity and just in front of the cervical vertebrae. Skeletal
muscles make up the wall of the pharynx along with a mucous membrane.
Figure 1-2. The pharynx.
b. The pharynx has three anatomical divisions: The nasopharynx, the
oropharynx, and the laryngopharynx. This organ is a common passageway for both the
respiratory and digestive systems.
a. The esophagus is a muscular, collapsible tube which is about ten inches long.
It lies behind the trachea and extends from the pharynx to the stomach. See figure 1-1
for position of the esophagus.
b. The esophagus can be divided into thirds according to its composition. The
upper third of the esophagus is made up of striated (striped) muscle. The middle third
has striated and smooth muscle, and the lower third has smooth muscle.