988 THE DIGESTIVE SYSTEM. 
by the palate in its growth backwards ; the part above the palate is represented in the adult 
by the lateral recess of the pharynx and the part below it by the sinus tonsillaris. From 
the lower and greater part of the sinus tonsillaris the tonsil is developed ; the upper part 
of the sinus persists, however, as the supratonsillar fossa. The tonsil at first is a smooth 
depression of the mucous membrane. About the fourth month of foetal life downgrowths 
of the epithelium take place, which are afterwards converted into the tonsillar crypts. 
Subsequently lymphoid cells accumulate around the downgrowths and form the lymphoid 
tissue, which constitutes the mass of the organ. 
The upper and anterior part of the naso-pharynx is derived from the stomatodeum, 
the remainder of the cavity from the foregut. 
THE G&SOPHAGUS. 
The esophagus or gullet is the portion of the digestive canal which intervenes 
between the pharynx above and the stomach below. With the exception of the 
pylorus, it is the narrowest, and at the same 
AX —Hyoid bone time one of the most muscular parts of the 
(Zax lo whole alimentary tube. 
— Thyroid cartilage It extends from the termination of the 
Gnenidreantilies pharynx, at the lower border of the cricoid 
=| re rae ; cartilage and opposite the sixth cervical 
C= i vertebra, to the cardiac orifice of the stomach, 
CE pave aia opposite the eleventh dorsal vertebra. Between 
mls these two points it traverses the lower part 
of the neck, the whole length of the thorax, 
yo uiciaten and, having pierced the diaphragm, it enters 
the abdomen, and immediately afterwards 
joins the stomach. In this course it does 
not adhere to the mesial plane of the body, 
Thoracic aorta but twice leaves it, and curves to the left. 
The first of these curvatures corresponds to 
the lower part of the neck and the upper part 
of the thorax, where the cesophagus projects 
Aperture in diaphragm beyond the left margin of the trachea to the 
extent of } or + inch (4 to6 mm.). It returns 
to the middle line about the level of the aortic 
arch. Lower down, behind the pericardium, 
it again passes to the left, and at the same 
time forwards, in order to reach the ceso- 
phageal opening in the diaphragm (which is 
placed in front and to the left of the aortic 
= 
—Left bronchus 
= 
a 
wens 
(sophagus 
Thoracie duct 
Dorsal vertebra xii. Paris 
Abdominal aorta~ By 
“7s. 
bi, ee opening),-and it maintains this direction 
wudnt aa ihe until the stomach is reached. . 
To In addition to the curvatures just described, 
~Duodenum it is also curved in the antero-posterior direc- 
tion, in correspondence with the form of the ver- 
tebral column upon which it, in great part, lies. 
In length it usually measures about ten 
inches (25 cm.). 
Its breadth, where the tube is widest, varies 
between half an inch (13 mm.) in the empty 
contracted condition and an inch or more 
(25 to 30 mm.) in the fully distended state. 
When seen in sections of the frozen body (Fig. 666), the cesophagus usually 
appears either as a flattened tube with a transverse slit-like cavity, or as an oval 
or rounded canal with a more or less stellate lumen. The former condition is 
more common in the neck, owing to the pressure of the trachea, and the latter 
in the thorax. 
When exposed in the ordinary post-mortem examination soon after death, 
Fig. 665.—D1IaGRAM TO SHOW THE COURSE 
OF THE CHSOPHAGUS. 
