The document describes the anatomy and histology of the esophagus. It begins by outlining the objectives to describe the anatomy, including its extent, parts, relations, constrictions, blood supply, innervation, and lymphatics. It then describes the esophagus's length and path between the pharynx and stomach. The esophagus can be divided into cervical, thoracic, and abdominal parts. The document details the histological layers of the esophagus - mucosa, submucosa, muscularis propria, and adventitia/serosa - and notes important clinical implications like Barrett's esophagus.

1. ANATOMY AND
HISTOLOGY OF
THE
ESOPHAGUS
GIT 301
ANATOMY MBCHB YEAR 3

2. OBJECTIVES
• DESCRIBE THE ANATOMY: extent, length, parts,
relations, strictures, blood supply, innervation and
lymphatics.
• DESCRIBE HISTOLOGY OF THE ESOPHAGUS

3. The esophagus is a muscular tube around 25cm long
passing between the pharynx in the neck and the
stomach in the abdomen. It begins at the inferior
border of the cricoid cartilage, opposite vertebra CVI,
and ends at the cardiac opening of the stomach,
opposite vertebra TXI.
The esophagus descends on the anterior aspect of the
bodies of the vertebrae, generally in a midline position
as it moves through the thorax . As it approaches
the diaphragm, it moves anteriorly and to the left,
crossing from the right side of the thoracic aorta to
eventually assume a position anterior to it. It then
passes through the esophageal hiatus, an opening in
the muscular part of the diaphragm, at vertebral level
TX.
The esophagus can be divided into 3 parts
1. Cervical
2. Thoracic
3. Abdominal

4. Relations of the esophagus
Cervical part
Anteriorly: trachea and laryngeal
nerves
Laterally: lobes of the thyroid
gland
Posteriorly: vertebral column

5. Thoracic part
Anteriorly: trachea, left recurrent laryngeal
nerve, left principle bronchi, pericardium,
left atrium
Laterally: Right mediastinal pleura,
Terminal part of the azygos vein, Left
mediastinal pleura, Left, subclavian artery,
Aortic arch, Thoracic duct
Posteriorly: Bodies of the thoracic
vertebrae, Thoracic duct, Azygos vein, Right
posterior intercostal arteries, Descending
thoracic aorta (at the lower end)

6. Abdominal part
Anteriorly: left lobe of the liver.
Posteriorly: left crus of the diaphragm.

7. Esophageal constrictions
The esophagus is a flexible, muscular tube that can be compressed or narrowed by
surrounding structures at four locations
• the junction o f the esophagus with the pharynx in the neck
• in the superior mediastinum where the esophagus is crossed by the arch of the aorta
• in the posterior mediastinum where the esophagus is compressed by the left main bronchus
• in the posterior mediastinum at the esophageal hiatus in the diaphragm.
These constrictions have important clinical consequences. For example, a swallowed object is
most likely to lodge at a constricted area. An ingested corrosive substance would move more
slowly through a narrowed region, causing more damage at this site than elsewhere along the
esophagus . Also, constrictions present problems during the passage of instruments for
example an endoscope. The esophageal constrictions are also common sites for development
of esophageal carcinomas

9. Distance of constrictions from central incisors

10. Blood supply
The arterial supply and venous drainage of the
esophagus in the posterior mediastinum involve
many vessels. Esophageal arteries arise from the
thoracic aorta, bronchial arteries , and ascending
branches of the left gastric artery in the
abdomen. Venous drainage involves small vessels
returning to the azygos vein, hemi azygos vein,
and esophageal branches to the left gastric vein
in the abdomen.
Arterial supply
• Upper third by the inferior thyroid
artery.
• The middle third by the thoracic
aorta.
• The lower third by the left gastric
artery

11. Venous drainage
• The upper third drains in into the
inferior thyroid veins.
• The middle third into the azygos veins.
• The lower third into the left gastric vein,
which is a tributary of the portal vein.

12. Lymphatic drainage
• The upper third is drained into the deep
cervical nodes.
• The middle third is drained into the
superior and inferior mediastinal nodes
(para-esophageal nodes)
• The lower third is drained in the celiac
lymph nodes in the abdomen.

13. Innervation
Innervation of the esophagus, in general, is complex. Esophageal branches arise
from the vagus nerves and sympathetic trunks. Striated muscle fibers in the
superior portion of the esophagus originate from the branchial arches and are
innervated by branchial efferents from the vagus nerves. Smooth muscle fibers are
innervated by components of the parasympathetic part of the autonomic division of
the peripheral nervous system, visceral efferents from the vagus nerves. These are
preganglionic fibers that synapse in the myenteric and submucosal plexuses of the
enteric nervous system in the esophageal wall. Sensory innervation of the
esophagus involves visceral afferent fibers originating in the vagus nerves,
sympathetic trunks, and splanchnic nerves. The visceral afferents from the vagus
nerves are involved in relaying information back to the central nervous system
about normal physiological processes and reflex activities. They are not involved in
the relay of pain recognition. The visceral afferents that pass through the
sympathetic trunks and the splanchnic nerves are the primary participants in
detection of esophageal pain and transmission of this information to various levels
of the central nervous system.

14. Esophageal plexus
After passing posteriorly to the root of the lungs, the right
and left vagus nerves approach the esophagus. As they
reach the esophagus, each nerve divides into several
branches that spread over this structure, forming the
esophageal plexus. There is some mixing of fibers from the
two vagus nerves as the plexus continues inferiorly on the
esophagus toward the diaphragm. Just above the
diaphragm, fibers of the plexus converge to form two
trunks:
• the anterior vagal trunk on the anterior surface of the
esophagus, mainly from fibers originally in the left vagus
nerve;
• the posterior vagal trunk on the posterior surface of
the esophagus, mainly from fibers originally in the right
vagus nerve.

15. Histology of the
esophagus
Although different parts of the GIT
may appear to have very different
structures and functions, the wall still
maintains 4 main layers throughout:
the mucosa submucosa, muscularis
propria, and either an outer serosa or
adventi

17. Mucosa
The mucosa of the esophagus consists of 3 main
layers: the epithelium, lamina propria and
muscularis mucosa
The thick epithelium layer lines the lumen of the
esophagus and consist of stratified squamous non-
keratinized cells.
The lamina propria is a much thinner layer of
dense irregular connective tissue. It provides a
supporting function to the epithelium.
The muscularis mucosa is the outermost layer of
the mucosa and is comprised of a double layer
smooth muscle

18. Submucosa
It is highly vascular and contains
loose connective tissue. It
contains esophageal glands, that
secrete mucus to help ease the
passage of food
Muscularis externa
This layer in the top third
contains skeletal muscle, in the
middle third it is a mixture of
smooth and skeletal muscle, and
in the bottom third it is entirely
smooth muscle

19. Muscularis externa cont’d
The lower esophageal sphincter or LES for short is
actually not an anatomical sphincter, which means
histologically, there is no well defined thickening or
muscle that controls the LES. Instead the LES is
considered a physiological or functional sphincter
But when the sphincter is not functioning properly, it
can lead to gastric acid reflux into the lower
esophagus. Over time, prolonged exposure to gastric
acid can cause transition of the normal stratified
squamous cells of the lower esophagus into mucus
secreting epithelium
This condition is called Barrett esophagus and is a
form of metaplasia, it also predisposes to esophageal
adenocarcinoma

20. Adventitia
The adventitia is the outer layer of fibrous connective tissue surrounding the
esophagus
To some degree, its role is complementary to that of the serosa, which also provides a
layer of tissue surrounding an organ.
In the abdomen, whether an organ is covered in adventitia or serosa depends upon
whether it is intraperitoneal or retroperitoneal
• Intraperitoneal organs are covered in serosa ( mesothelium)
• Retroperitoneal organs are covered in adventitia (loose connective tissue)