992 THE DIGESTIVE SYSTEM. 
membrane loosely to the muscular coat, and admits of the former being thrown into folds 
when empty. In this coat are contained the numerous racemose mucous elands which open 
into the cavity of the esophagus (Fig. 669). 
The mucous membrane is of a greyish pink colour, much paler than that of the 
pharynx, and of a firm and resistant texture. 
It is covered by a thick stratified, squamous 
epithelium, on the surface of which the open- 
ings of numerous glands are found. Below, — 
its junction with the gastric mucous membrane 
is indicated by a distinct, irregularly dentated 
or crenated line, which runs transversely round 
Inferior | the tube. In carefully preserved specimens the 
smooth mucous membrane of the casophagus 
above this line contrasts strongly with the 
Teper border of mammillated gastric mucous membrane below. 
cricoid cartilage Owing to the inelasticity of this coat, and 
the fact that it is but loosely connected to 
Tendinous band ¢he muscular coat by the submucosa, it is 
thrown into a series of longitudinal folds 
when the cesophagus is empty and contracted ; 
hence the stellate lumen often seen in sections 
Cireular fibres of the cullet. 
of esophagus a 
: Glands. — Numerous racemose mucous 
we, glands, large enough to be distinctly seen 
Longitudinal bands with the naked eye, are found in the sub- 
Te Ree DeeeLowER PAu” Or rin. Paannx sro wc One: They are pretty evenly distributed 
END nan UPPER PART or Tae (soraacus Over the, whole tube, yand) dosmatgea paca 
have been slit up from behind, and the mucous to be more numerous towards either end 
membrane removed to show the muscular fibres, (Coffey). In addition to these, other glands, 
The two longitudinal bands are seen coming resembling closely those of the cardiac end 
round to the front to be attached by a common i ‘ ; mi he i 
tendon to the upper border of the cricoid car- of the stomach, are found in the mucous 
tilage. See explanation of last figure. membrane of certain portions of the ceso- 
phagus. They are entirely confined to the 
mucosa, and do not extend beyond the muscularis mucosee. These glands are 
specially numerous at both the upper and lower ends of the tube (Coffey, Schafer). 
Vessels and Nerves. —Its arteries consist of 
numerous small branches derived, in the neck, 
from the inferior thyroid, in the thorax, from 
the bronchial arteries and thoracic aorta, and in 
Stratified 
squamous 
epithelium 
the abdomen, from the coronary artery of the 
stomach, and also from the left phrenic. 
The veins form a plexus on the exterior of 
the esophagus, from which branches pass, in the 
lower part of the tube, to the coronary, vein of 
the stomach, and, higher up, to the azygos, and 
thyroid veins. There is thus established on the 
lower part of the csophagus a free communica- 
tion between the portal and systemic veins. 
The lymphatics pass to the inferior set of deep 
cervical glands in the neck, and to the posterior 
mediastinal glands, many of which, of large size, 
are seen around the tube, in the thorax. 
The nerves are derived from the recurrent 
laryngeal, and from the cervical sympathetic in 
the neck, from the pneumogastrics and sym- 
pathetic in the thorax. 
DEVELOPMENT OF THE CESOPHAGUS. 
The oesophagus is developed from the 
portion of the foregut lying between the 
pharynx and the dilatation which represents 
the future stomach. At first, owing to the 
— Areolar coat 
Muscularis 
mucosee 
Submucosa 
with mucous 
glands 
Circular 
muscular 
fibres 
Longitudinal 
muscular 
fibres 
Fic. 669.—STRUCTURE OF THE CHSOPHAGUS, 
transverse section (after Horsley). 
flexure of the head on the trunk in the early embryo, it is relatively short, but, as the 
neck is developed, it gradually becomes elongated and cylindrical. 
