Anatomy of Oesophagus

Dr.Neeraj Kumar BanoriaAstt. Professor

Deptt. Of SurgeryM.L.B.Medical College

Jhansi,(U.P.) ,INDIA

KEY POINTS

1. The adult human esophagus is an 18- to 25-cm long muscular tube that has cervical, thoracic, and abdominal parts.

2. The esophagus wall is composed of striated muscle in the upper part, smooth muscle in the lower part, and a mixture of the two in the middle.

3. The myenteric plexus is well developed in the smooth muscle, but is also present in the striated muscle part of the esophagus.

4. The function of the myenteric plexus in the striated esophagus is not well understood.

5. Esophagus develops from foregut and by week 10 is lined by ciliated epithelial cells.

6. Beginning at 4 months, the ciliated epithelium starts to be replaced by squamous epithelium. At either end of the esophagus the ciliated epithelium gives rise to esophageal glands.

7. The upper esophagus is derived from branchial arches 4, 5, and 6, but the derivation of the lower esophagus is not known.

8. The development of various elements of esophageal wall requires coordination of a variety of genes and mediators.

9. Esophageal peristalsis appears in the first trimester, and gastroesophageal reflux can be documented in the second trimester.

• Unlike the remainder of the GI tract, the esophageal tube has neither mesentery nor serosal coating .

Introduction • From mouth to stomach, the food conduit consists of

the oral cavity, pharynx, and esophagus.

• The esophagus serves as a dynamic tube, pushing food toward the stomach.

• Mucus produced by the esophageal mucosa provides lubrication and eases the passage of food.

• Active peristaltic contractions propel residual material from the esophagus into the stomach.

Anatomical DivisionThe esophagus is a midline structure lying on the

anterior surface of the spine. It descends through three compartments: the neck, the

chest, and the abdomen. This progression has led to its classic anatomic division

into cervical, thoracic, and abdominal segments.Two new subdivisionsOne is functional aspects and makes a distinction

between the esophageal body and the upper and lower sphincters.

The other is oncosurgery aspects and distinguishes between the proximal and the distal esophagus, with the tracheal bifurcation used as a partition.

Anatomic Division• Cervicalo Cervical begins at the lower end of pharynx (level of 6th

vertebra or lower border of cricoid cartilage) and extends to the thoracic inlet (suprasternal notch); 18 cm from incisors.

• Thoracico Upper thoracic: from thoracic inlet to level of tracheal

bifurcation; 18-23 cm.o Mid thoracic: from tracheal bifuraction midway to

gastroesophageal junction; 24-32 cm.o Lower thoracic: from midway between tracheal bifurcation and

gastroesophageal junction to GE junction, including abdominal esophagus; 32-40 cm.

• Abdominalo Considered part of lower thoracic esophagus; 32-40 cm.

Gross anatomy of esophagus• The oesophagus is a muscular tube, typically25 cm long, which

connects the pharynx to the stomach.• It begins in the neck, level with the lower border of the cricoid

cartilage and the 6th cervical vertebra.• Descends anterior to the vertebral column through the superior

and posterior mediastina.• Passes through the diaphragm, level with the 10th thoracic

vertebra. • Ends at the gastric cardiac orifice level with the 11th thoracic

vertebra.• Between swallows the esophagus is collapsed but the lumen can

distend to approximately 2 cm in the antero-posterior dimension and up to 3 cm laterally to accommodate a swallowed bolus.

Deviations of esophagus

A healthy esophagus has three minor deviations along its trajectory-

• The 1st inclines to the left as far as the root of the neck, gradually

returns to the median plane near the 5th thoracic vertebra.

• Hence surgical approaches to the esophagus are easier from the left

than from the right when performing intestinocervical esophageal

anastomoses after esophagectomy.

• The 2nd deviation is at the level of the 7th thoracic vertebra, where the

esophagus turns slightly to the right of the Spine, before it pierces

the diaphragm.

Deviations of esophagus cont.• it can also bend slightly to the right as it is pushed by the aorta before

bending to the left to reach the oesophageal hiatus(the 3rd

deviation).The terminal esophagus and the esophagogastric junction

are positioned slightly lateral to the xiphoid process of the sternum

and to the left of the spine

• At this point, the fundus and proximal part of the stomach extend

anterolateral to the body of the vertebra,as a result, the greater

curvature faces the posterior subdiaphragmatic space, and the

anterior gastric wall faces laterally.

• The oesophagus also bends in an anteroposterior plane to follow the

cervicothoracic curvatures of the vertebral column.

Constrictions of esophagus• It is the narrowest part of the alimentary tract (except for the

vermiform appendix).

• Esophagus is constricted -1. at the beginning (15 cm from the incisor teeth), 2. where it is crossed by the aortic arch (22.5 cm from the incisor teeth), 3. where it is crossed by the left principal bronchus (27.5 cm from the incisors) and 4. as it passes through the diaphragm (40 cm from the incisors).

• These measurements are important clinically with regard to the

passage of instruments along the oesophagus.

Cross-section of esophagus at various level• Topographic anatomy of the esophagus shown from the cervical level (1)

to the esophagogastric junction (6).

• A transverse section through the mediastinum shows the esophagus and

its surrounding structures in a computed tomographic aspect.

• The close positional relationship among the esophagus, trachea, and

vertebrae and the fascial planes is displayed.

• The dark lines are the prevertebral and previsceral fascia (arrows); the

net-like pattern represents the respective areolar connective tissue.

Fig.1

Periesophageal Tissue, Compartments, and Fascial Planes

• Unlike the general structure of the digestive tract, the esophageal tube has neither mesentery nor serosal coating.

• Its position within the mediastinum and a complete envelope of loose connective tissue allow the esophagus extensive transverse and longitudinal mobility.

• Respiration may induce craniocaudal movement over a few millimeters, and swallows may result in excursion over as much as the height of one vertebral body.

• This mobility is also the reason why the esophagus may be subjected to easy blunt stripping from the mediastinum.

• Invasion by malignant tumor and fixation to the surroundings, however, strictly contraindicate the use of this technique.

• The connective tissues in which the esophagus and trachea are embedded are bounded by fascial planes, the pretracheal fascia anteriorly and the prevertebral fascia posteriorly.

• In the upper part of the chest, both fascias unite to form the

carotid sheath.

• The anterior and posterior spaces between these fascias form a communicating compartment between the neck and the chest.

• This communication provides a plane for rapid spread of infection through the mediastinum.

• The anterior space (previsceral or pretracheal space)- Infections spreading from anterior lesions of the esophagus may follow this route, but they are limited distally by the strong fibrous tissue of the pericardium.

• The posterior space(retrovisceral or prevertebral space)- extends from the base of the skull to the diaphragm. It is formed by the buccopharyngeal fascia spreading downward via a sheath that separates the esophageal tissue bed from the prevertebral fascia.

• Posterior space is clinically of greater importance than the anterior space. The reason is that most instrument perforations with subsequent outflow of esophageal contents occur above the narrowing of the cricopharyngeal sphincter in the posterior hypopharynx.

• At this level, as in the chest, there is no barrier for stoping spread of infection into the mediastinum.

• Rupture of the esophagus or leakage of an esophageal anastomosis may result in descending mediastinitis along these planes as well.

• Prompt diagnosis is vital for the patient because the prognosis for esophageal perforation depends on the rapidity with which treatment is initiated!

Anterior(a) & posterior (b) view

Anchoring of the esophagus“The esophagus is stabilized by bony, cartilaginous, and membranous structures”

As shown in figure Fig. 2

• The upper end of the esophagus obtains firm anchorage by the insertion of its

exterior longitudinal muscle into the cartilaginous structures of the hypopharynx

(posterior ridge of the cricoid cartilage) (1) via the cricoesophageal tendon (2).

• The circular muscle is stabilized by its continuity with the inferior laryngeal

constrictor muscles (1), which insert via the raphe to the sphenoid bone.

• Tiny membranes(170 μm in thickness and approximately 3 to 5 mm in length)

connect the esophagus with the trachea, bronchi, pleura, and prevertebral fascia

(3 and 4).

• Consisting of collagen and elastic fiber elements and occasional

interpositioned sparse muscle fibers, the membranes are stretchable to some

extent and accumulate around the tracheal bifurcation.

• The attachment at the lower end by the phrenoesophageal membrane & the

two diaphragmatic crura (5) is rather mobile, whereas the posterior gastric

ligaments,such as the gastrosplenic, phrenicolienal, and phrenicogastric

ligaments (6), and the lesser omentum (6) yield a tight adherence.

( LES, lower esophageal sphincter; UES, upper esophageal sphincter)

Fig. 2

Fig.3

Fig.3 description

• The posterior walls of the pharynx (4) and the esophagus (7 and 8) have been

cut open in the midline, as shown in a specimen (A) and half-schematically (B).

• The structures of the hypopharynx are exposed by retracting the overlying

incised tissue and removing the mucosa.

• In the center lies the cricoesophageal tendon (6), which attaches the

longitudinal muscle layerof the esophagus (8) to the cricoid cartilage (2).

• The terminal branches of the left laryngeal recurrent nerve (9) are dissected

and are seen lateral to the cricoesophageal tendon.

1= Thyroid cartilage.

CERVICAL OESOPHAGUS• The cervical oesophagus is posterior to the trachea and attached to

it by loose connective tissue.

• The recurrent laryngeal nerves ascend on each side in or near the tracheo-oesophageal groove.

• Posteriorly are the vertebral column, longus colli and prevertebral layer of deep cervical fascia.

• Laterally on each side are the common carotid arteries and posterior part of the thyroid gland.

• In the lower neck, where the oesophagus deviates to the left, it is closer to the left carotid sheath and thyroid gland than it is on the right.

• The thoracic duct ascends for a short distance along its left side.

• The left border of esophagus extends beyond the trachea so that the oesophagus is more easily exposed via left sided cervical incision.

• Malignant tumors are known to spread from the trachea to the esophagusand vice

versa. Clinically, such spread results in an “acquired fistula.” • It appears that the lack of interposed connective tissue between the two organs

predisposes to this unlucky event.

• A tracheoesophageal fistula after either an instrumental perforation, esophagectomy, or chemotherapy and irradiation in this inherently weak area is a catastrophic problem for both the patient and physician.

Transverse section through the neck and upper part of the chest of a human autopsy specimen viewed from a

cranial aspect.

1, Esophagus; 2, trachea; 3, pleura; 6, thyroid gland; and 8, vessels.

The histologic section shows theesophagus still in the midline posterior

position (A), whereas on the more distal level of the macroscopic cut surface (B), the esophagus has shifted toward the left.

Note-the intimate local relationship between the esophagus and the trachea.

Phrenoesophageal membrane (PEM)• The muscular portion of the diaphragm is inserted on the lumbar vertebrae, the

ribs, and the sternum.

• The central membranous portion is frequently larger and the left crus of the diaphragm may consist of membranous tissue rather than a significant muscular mass.

• The subdiaphragmatic and endothoracic aponeuroses blend at the central margin of the diaphragm to constitute the phrenoesophageal membrane (PEM), also known as Laimer's ligament or Allison's membrane.

• Intraoperatively, the PEM can be recognized by its well-defined lower edge and its slightly yellow color, even in the presence of severe periesophagitis.

• The PEM is composed of elastic and collagenous fiber elements, which guarantee

sufficient pliability.

• Because of its origin from a fascia, the PEM in general is relatively strong.

• PEM splits into two sheets.

• One sheet extends 2 to 4 cm upward through the hiatus, where its fibers traverse the esophageal musculature to insert on the submucosa.

• The other sheet passes down across the cardia up to the level of the gastric fundus, where it blends into the gastric serosa, the gastrohepatic ligament, and the dorsal gastric mesentery.

• Although there are sparse attachments via elastic cords in the pattern shown in 3rd figure, the PEM is clearly some distance away and separated by loose connective tissue and fat accumulation from the musculature of the gastroesophageal junction.

• This structural arrangement allows the terminal esophagus and the junction to move in relation to the diaphragm and to “slip through the hiatus like in a tendon sheath.”

• With advancing age, the elastic fibers are replaced by inelastic collagenous tissue, and the adhesion of the PEM to the lower portion of the esophagus loosens,which leads to loss of pliability.

• Disruption of the anchoring structures of the cardia and the proximal part of the stomach in conjunction with a wide hiatus may result in herniation of the gastroesophageal junction and the cardia, or even parts of the stomach, into the mediastinum.

• Abnormal anchoring of the PEM in youth and pathologic accumulation of adipose tissue in the separating connective tissue space between the PEM and the cardia musculature are thought to contribute to the development of a hiatal hernia.

Diaphragm and esophageal hiatus viewed from the abdominal aspect.

The phrenoesophageal membrane (PEM). The lower component of the PEM inserts on the gastric fundus.

On the left, the diaphragm is held up with forceps. Diaphragmatic decussating fibers (long arrow) and a submembranous inlay of adipose

tissue (short arrow) are seen. The PEM wraps the esophagogastric junction with a wide membranous collar.

Diagram of the tissue organization and supporting structures at the esophagogastric junction.

The esophagus is opened alongside the greater and lesser curvatures. The luminal aspect is displayed from the left side.

The fiber elements that attach the phrenoesophageal membrane to the muscle wall of the terminal esophagus are

shown.

THORACIC OESOPHAGUS• In chest,esophagus runs through the superior & posterior mediastinum.• It is little towards left in the superior mediastinum between the trachea and the vertebral

column. {fig.1(2),(3)}

• It passes behind and to the right of the aortic arch to descend in the posterior mediastinum along the right side of the descending thoracic aorta. {fig.1(2)}

• Below, as it inclines left, it crosses anterior to the aorta and enters the abdomen through the diaphragm at the level of the 10th thoracic vertebra. {fig.1(4)}

• Anteriorly,from above downwards, the trachea, right pulmonary artery, left main bronchus, pericardium (separating it from the left atrium) and the diaphragm are situated . {fig.1(3),(4),(5) & Anterior(a) & posterior (b) view }

• The vertebral column, longus colli, right posterior intercostal arteries, thoracic duct, azygos vein and the terminal parts of the hemiazygos and accessory hemiazygos veins,

and, near the diaphragm, the aorta are posterior. {fig.1(3),(4),(5) & Anterior(a) & posterior (b) view }

•

• A long recess of the right pleural sac lies between the oesophagus (in front) and the azygos vein

and vertebral column (behind) in the posterior mediastinum.perforation of the oesophagus at

this point may produce aright-sided pleural effusion.

• In the superior mediastinum, the terminal part of the aortic arch, the left subclavian artery,

thoracic duct, the left pleura and the recurrent laryngeal nerve are left lateral relations.

• In the posterior mediastinum, the oesophagus is related to the descending thoracic aorta and

left pleura. The right pleura, and the azygos vein as it arches forwards above the right main

bronchus to join the superior vena cava, are right lateral relations.

• When performing transthoracic esophagectomy, surgical access for safe removal of the

esophagus is preferably through the right side of the chest, and the azygos vein must usually be

divided before the esophagus can be dissected free.

.

•Below the pulmonary roots, the vagus nerves descend in contact with the oesophagus, the right mainly behind and the left in front; the vagi subsequently unite to form a plexus around the oesophagus.

•Low in the posterior mediastinum, the thoracic duct is behind and to the right of the oesophagus;, crossing to the left of the oesophagus from 7th to 5th thoracic vertebra and then ascendes up along its left border.

•Lower down the esophagus takes a curve to the left behind the pericardial sac & passes completely to the left of the midline toward the oesophageal hitus crossing anterior to the arota.

•Perforation of the lower 1/3rd of the oesophagus are therefore more likely to result in left-sided pleural effusion.

• On the right of the oesophagus, just above the diaphragm, a small serous infracardiac bursa may occur; it represents the detached apex of the right pneumatoenteric recess.

The position and relationships of the azygos vein, the thoracic duct, and the vagus nerve are shown from a right

lateral aspect.

ABDOMINAL OESOPHAGUS

• The abdominal oesophagus is 1–2.5 cm in length, and is slightly broader at the

cardiac orifice than the diaphragmatic aperture.

• It lies to the left of the midline and enters the abdomen through the

oesophageal aperture (formed by the two diaphragmatic crura) opposite the

level of the 10th thoracic vertebra.

• It runs obliquely to the left and slightly posteriorly, and ends at the gastro-

oesophageal junction/cardiac orifice of the stomach.

• Left lobe of the liver posteriorly to it, which it grooves slightly.

• Left crus of diaphgram, the left inferior phrenic vessels and the left greater

splanchnic nerve anterior to it,

• Its surface is covered in a thin layer of connective tissue and visceral

peritoneum which contains the anterior and posterior vagi as well as the

oesophageal branches of the left gastric vessels.

• The anterior vagus may be single or composed of multiple trunks, and is

closely related to the outer fibres of the longitudinal muscle coat of the

oesophagus.

• The posterior vagus is usually a single trunk and is less closely applied to the

oesophageal muscle within the loose connective tissue, which makes its

identification during surgery somewhat easier.

• Abdominal oesophagus is effectively tethered to the diaphragm by connective tissue,the phreno-oesophageal ligament. This is formed of two thickened bands of elastin-rich connective tissue-

i. superior phreno-oesophgeal ligament(On the thoracic side of the diaphragm)- is similarly formed from an extension of the subpleural endothoracic fascia. It is denser than its inferior counterpart with more elastin present and is tethered much more firmly through the muscle fibres of the oesophageal wall into the submucosal tissues. It may well act to restore lower oesophageal position after the movement engendered by the peristalsis of swallowing.

ii. Inferior phreno-oesophageal ligament (on abdominal side of diaphgram)-an extension of the transversalis fascia extending beneath the parietal peritoneum as it is reflected from the diaphragm onto the abdominal oesophagus. The fibres are only loosely attached to the adventitial tissues and a variable amount of fat often lies beneath it, between the oesophageal wall and the crural sling. This oesophageal fat pad tends to act to tether the oesophagus to the fibres of the crura but tends to regress with age.

•Anteriorly, the subperitoneal connective tissue is particularly dense and blends with

both the outer layer of the oesophageal wall and the apex of the crural fibres of the

diaphragm.

•On the posterior aspect the peritoneal reflection is extremely short since the crura

lie steeply angled, and the posterior oesophageal wall has a much shorter ‘effective

length' than the anterior.

•This short reflection of peritoneum is sometimes referred to as the

gastrophrenic ligament and, via the peritoneum over the oesophagus

continues directly onto the posterior surface of the stomach.

•It covers the oesophageal branches of the left gastric vessels and the coeliac

branches of the posterior vagus and can thus be said to form an extremely

short, wide mesentery to the abdominal oesophagus.

•In all but the thinnest individuals a pad of adipose tissue is found beneath the

peritoneum covering the anterior surface of the lower abdominal oesophagus

and the adjacent gastric wall.

•It is a useful surgical marker for the external location of the gastro-

oesophageal junction.

Oesphagus sphincters

• There is an anatomical sphincter at the upper end & physiological sphincter at the lower end of the oesophagus. 2 types—

1. CRICOPHARYNGEUS OR Inferior constrictor of the pharynx

2. Oesophagogastric junction sphincter

1.CRICOPHARYNGEUS OR Inferior constrictor of the pharynx

• This muscle consist of 2 parts—• A lower transver part(cricopharyngeus) • an upper oblique portion(thyropharyngeus) The lower transver fiber arise from cricoid cartilage &

pass horizontally backward round the pharynx to be inserted into median raphae at the back of this tube.Its function is to prevent regurgitation of the esophageal content into the pharynx.

The upper oblique fibers arises from the cricoid & thyroid cartilage & encircle the hypopharynx,ending in median raphae.

• In act of swallowing,the upper(oblique) part of this muscle propel the content downward & lower (transver) part relaxes to allow the content to pass into the oesophagus.

• Incordination of this action,with failure of the cricopharyngeous to relax will result to increased pressure in the pharynx & production of a pharyngeal diverticulam.

• A cricopharyngeal myotomy is performed in condition associated with incordination of muscle relaxation(i.e pharyngeal diverticulam).

• Intraluminal pressure recording demonstrate a high pressure zone 2-4 cm.

2.The oesophagogastric junction• Normally gastric contents regurgitate into the oesophagus because

of the mechanism at the cardia preventing this.• Median arcuate ligament does not directly contribute to the

competence of the oesophagogastric junction but is of surgical importance in the region.it is a tough fibrous 1-3 mm wide condensation of medial fibrous borders of the 2 crura of diaphgram.

• It is usually at level just proximal to the origin of celiac artery.• The ligament is used as the main anchoring site for Hill-anti reflux

operation.• The origin of Phrenic vessel lies just proximal to celiac vessels &

should be carefully avoided when the ligament is dissected.• Median arcuate ligament may be absent or very attenuated.

Arterial supply• Unusual ! Arterial supply derived from vessels feeding mainly other organs – thyroid, trachea & stomach.

(“Shared vasculature”)

• Cervical Oesophagus: Right & Left superior & inferior thyroid arteries.

• Thoracic Oesophagus: Up to tracheal bifurcation Right & Left inferior thyroid Artery

direct supply from aorta (tracheo-bronchial tree)• Abdominal Oesophagus: 11 branches off Left gastric artery

and Branches of splenic artery posteriorly.

• All the major arterial vessels divide into minute branches at some distance from the esophageal wall,and it appears that such small esophageal tributaries, when torn from the esophagus, have the benefit of contractile periesophageal hemostasis.

• The minute extraesophageal branches enter the esophageal wall, pass through the tunica muscularis, and give off branches to the muscle before they form the wide vascular plexus within the submucosa and mucosa.

• The clear continuity of the vessels and the rich anastomosing intramural vascularity explain why a mobilized esophagus retains an excellent blood supply over a long distance.

• On the other hand, the extremely small caliber of the nutritional vessels also explains leaks after esophagointestinal anastomosis in the event of mechanical damage to the microvascular circulation.

Extravisceral sources of arterial blood supply to the esophagus, intramural anastomoses (dotted line), and topographic relationship of the azygos vein to the esophagus and tracheal bifurcation. The arrows indicate the direction of flow.

Arterial cast showing the vascular supply to the middle and lower portions of the esophagus. Note that the esophageal branch derives from the bronchial artery. During esophageal resection, it should be ligated close to the esophageal wall so that the blood supply of the left main bronchus is not jeopardized.

Venous Drainage• Butler classified the esophageal veins into intrinsic and extrinsic veins,

referring to intraesophageal and extraesophageal wall veins.

1.Intraparietal Veins and Plexuses• The intraesophageal veins include a subepithelial plexus in the lamina

propria mucosa that receives blood from the adjacent capillaries.

• Aharinejad et al. described two small veins that usually accompany the arteries in the lamina submucosa, pierce the muscular wall of the esophagus together with the perforating arteries, and then form the extramural veins at the surface of the esophagus.

• No valves were found within the esophageal venous circulatory system.

• Two clearly delineated venous plexuses are present beneath the mucosa of the hypopharynx.

• One plexus lies on the dorsal aspect of the inferior constrictor muscle, and the other is in the midline posterior to the cricoid cartilage,this is exactly at the level of the pharyngoesophageal junction.

• The plexuses were located within an extremely thin submucosa; both were 2 to 3 cm broad and 4 cm long. The veins were up to 4 mm thick and of mostly longitudinal orientation, similar to Figure.

• The plexuses receive blood from the mucosa of the laryngopharynx and esophagus and drain into the thyroid and jugular veins.

• Considered to account for the postcricoid impression on the esophagus, they may be involved in the “globus sensation” in patients with venous stasis and tissue swelling.

• It is tempting to postulate that the plexuses also contribute to some extent to the competence and action of the UES.

The hypopharyngeal-endoesophageal venous plexuses, which are located just underneath the mucosa

• A specialized venous arrangement is present at the terminal esophagus (Figure below). It has been suggested that these venous anastomoses possibly constitute a communication between the azygos and the portal systems.

• The intermediate “palisade zone” (Figure below)is thought to act as a high-resistance watershed between both systems that provides bidirectional flow. Anastomoses between the systemic and the portal systems are found in the submucosa and lamina propria of the lower end of the esophagus and may enlarge in patients with portal venous obstruction to form varices.

Radiograph of the venous circulation at the esophagogastric junction and the esophagus after injection with barium gelatin. This example shows the various zones of different venous architecture, such as the gastric zone (GZ), the palisade zone (PZ), the perforating zone (PFZ), and the truncal zone (TZ), as well as the irregular polygonal network of the proper gastric veins.

2.Extraparietal Veins• The extrinsic veins drain into the locally corresponding large vessels: the inferior

and superior thyroid veins,the azygos and hemiazygos veins, and the gastric and splenic veins.

• One point of surgical interest is that because of the proximity to the hilum of the lung and its lymph nodes, the azygos vein is one of the initial structures to become involved by extramural spread of tumors of the midesophagus.

• In this situation, the azygos vein may easily be injured during esophageal resection. In particular, during blunt pull through stripping, injury to this vein is a high-risk factor for fatal hemorrhage.

• Collateral circulation between the azygos vein and the hemiazygos vein is well known. However, the hemiazygos, the accessoryhemiazygos, and the superior intercostal trunks may also form a vessel that does not connect with the azygos vein.

• The hemiazygos vein, if not ligated out, can be a source of severe bleeding when the esophagus is resected through a right thoracotomy.

Summry of venous drainage• Intra-oesophageal (Intrinsic) Drainage

– Longitudinally arranged in Submucosa – Distal end – portal anastamoses

• Extra-oesophageal (Extrinsic) Drainage into locally corresponding veins – Inf. thyroid (into innominate vein),– Azygos, hemiazygos – L gastric & splenic

Lymphatic Drainage• In the proximal third of the esophagus, lymphatics drain

into the deep cervical lymph nodes,

• In the middle third, drainage is into the superior and posterior mediastinal nodes (paratracheal, tracheobronchial,carinal, juxtaesophageal, and intra-aorticoesophageal lymph nodes).

• The distal-third lymphatics follow the left gastric artery to the superior gastric, pericardiac,inferior diaphragmatic lymph nodes and celiac lymph nodes .

Special features about lymphatic system of Esoph.• Lymph capillaries may commence in the tissue spaces of the mucosa

and then unite to form blind endothelial sacculations or channels.

• These initial lymphatics appear to originate exclusively in the region between the mucosa and the submucosa and form a network of collecting channels within the submucosa that run parallel to the organ axis.

• Eventually, the plexuses give off branches that pass the muscle layers and empty into the collecting subadventitial and surface trunks.

• In contrast to the esophageal veins, all these channels possess valves.

• The concept that lymph flows in the submucosal channels more readily longitudinally than through the few transverse connections in the muscle and that only finally does lymph flow through the subadventitial lymphatics and small ducts into the mediastinal lymph nodes is supported by the clinical observation that initial tumor spread follows the longitudinal axis of the esophagus within the submucosa rather than extending in a circular manner.

• A paucity of lymphatics within the lamina mucosa and the abundance of submucosal lymphatic channels may explain why intramural cancer spreads predominantly within this layer.

• Unappreciated malignant mucosal lesions may be accompanied by extensive tumor spread underneath an intact mucosa, and tumor cells may follow the lymphatic channels for a considerable distance before they pass the muscular coat to empty into the lymph nodes.

• A tumor-free margin at the resection line,as confirmed from the anatomic point of view, does not guarantee radical tumor removal. This may be consistent with the relatively high postoperative recurrence rate at the resection line, including satellite tumors and metastases in the submucosa far distant from the primary tumor,even if the margins at the resection line were previously tumor-free.

• From clinical observations in cancer patients, one may deduct that lymph from above the carina flows in a cranial direction into the thoracic duct or subclavian lymph trunks whereas lymph from below the carina flows mainly toward the cisterna chyli via the lower mediastinal, left gastric, and celiac lymph nodes.

• Flow may, however, change under pathologic conditions. When lymph vessels become blocked and dilated because of tumor invasion, the valves become incompetent and the flow reverses.

• This explains the retrograde and unexpected spread of some

malignant tumors but limits the value of establishing pathways of normal flow.

Knowledge of the direction of lymph flow and the position of major lymph nodes is essential for understanding the potential spread of an esophageal malignancy

PREVIOUS FIGURE SHOWS—• Lymph from areas above the tracheal bifurcation drains mostly

toward the neck, and that below the tracheal bifurcation flows preferentially toward the celiac axis.

• Lymph flow at the bifurcation appears to be bidirectional.

• The dimensions of the lymph nodes are out of scale.

• In the normal, nonmalignant condition,esophageal and mediastinal lymph nodes are difficult to discern because of their small diameter of only 3 to 7 mm.

• Lymph nodes that drain the lung are usually bigger and can be

easily visualized by their carbon particle content.

Thoracic Duct• The thoracic duct begins at the proximal end of the cisterna chyli, at the level of the 12 th

thoracic vertebra,and passes up through the diaphragm via the aortic foramen.

• It then ascends through the posterior mediastinum, between the aorta on its left and the azygos vein on its right aspect, and continues left dorsal to the esophagus .

• At the level of the 5th thoracic vertebra and just above the arch of the azygos vein, the thoracic duct inclines to the left to become left side positioned with regard to the esophagus and spine.

• Then it ascends lateroposteriorly parallel to the trachea and esophagus to convey the lymph into the bloodstream and terminates at the confluence between the left subclavian and jugular veins.

• There are, however, numerous anatomic variations.

• The close local relationship of the delicate thoracic duct to the esophagus and trachea accounts for the occasional injury causing chylothorax during esophagectomy and cervical anastomosis.

Innervation

• Parasympathetic – Vagus – motor to muscular coats & secretomotor to glands

• Sympathetic – From cervical & thoracic sympathetic chain – Contraction of sphincters, wall relaxation, peristalsis

• Intramural – Combination of all innervation form plexuses & ganglia – In muscular layers (myenteric or Auerbach’s plexus) – In submucosa (Meissner plexus)

• The ganglia of Auerbach's plexus arescattered throughout the entire esophagus and have a variable number of cells.

• However, the concentrationof ganglion cells is greatest in the terminal esophagus and at the gastroesophageal junction.

Esophageal tissues

Wall structure at the esophagogastric junction. The tunica muscularis is composed of both a longitudinal (2a) and a circular layer (2b). a, muscularis mucosae; b, lamina propria; c, epithelium; G1, esophageal glands; G2, gastric glands; Ly,lymph vessels; N1, myenteric plexus; N2, submucous nerve plexus.

• The mucosa is thick. At the gastro-oesophageal junction, a jagged boundary line separates the greyish-pink, smooth, oesophageal mucosa from the reddish-pink gastric mucosa, which is covered by minute bulges and depressions. The tissues forming the thoracic oesophageal wall, from lumen outwards, are the mucosa (consisting of epithelium, lamina propria and muscularis mucosae), submucosa, muscularis externa and adventitia—

A.Mucosa(Tunica Mucosa)--The mucous layer is composed of three components: the muscularis mucosae, the tunica propria, and the inner lining of nonkeratinizing stratified squamous epithelium.

1. Muscularis mucosae-- is composed mainly of longitudinal smooth muscle. This forms the long mucosal folds that run in the longitudinal axis of the tube and shapes the small transverse ripple folds at the cardia.All these folds disappear on distention of the esophageal lumen.

At the pharyngeal end of the oesophagus it may be absent or represented only by sparse, scattered bundles;below this it becomes progressively thicker. The longitudinal orientation of its cells changes to a more plexiform arrangement near the gastro-oesophageal junction.

2. Lamina propria(tunica propria)--contains areolar connective tissue, blood vessels, and lymph channels derived from the lower level of the mucosa.It contains scattered groups of lymphoid follicles (mucosaassociated lymphoid tissue), which are especially prominent near the gastro-oesophageal junction.

3. Epithelium--non-keratinized, stratified squamous epithelium, continuous with that of the oropharynx.quite thick (300–500 μm). At the base of the epithelium there is a basal lamina, to which epithelial cells are attached by hemidesmosomes.

Langerhans cells--Langerhans cells are present in the oesophageal epithelium. They are immature dendritic cells and resemble those found in the epidermis. They perform similar antigen-processing and antigen-presenting roles, which are important in immunostimulation of naive T cells and mucosal defence.

B. Submucosa--The submucosa loosely connects the mucosa and the muscularis externa. It contains larger blood vessels, nerves and mucous glands. Its elastic fibres are important in the reclosure of the oesophageal lumen after peristaltic dilatation

Oesophageal glands--Oesophageal glands are small tubuloacinar glands lying in the submucosa, each group sending a single long duct through the intervening layers of the gut wall to the surface. They are composed mostly of mucous cells, although they also contain serous cells that secrete lysozyme.

C. Muscularis externa• The muscularis externa is up to 300 μm thick, and consists of the outer

longitudinal and inner circular layers typical of the intestine. The longitudinal layer is generally thicker than the circular layer.

• The longitudinal fibres form a continuous coat around almost the entire length of the oesophagus, except that, posterosuperiorly, 3–4 cm below the cricoid cartilage, they diverge as two fascicles that ascend obliquely to the anterior aspect of the oesophagus.

• Here, they pass deep to the lower border of the inferior constrictor, and end in a tendon that is attached to the upper part of the ridge on the back of the cricoid lamina.

• The V–shaped space(Laimer's triangle) between these fascicles is filled by the circular muscle fibres of the oesophagus, which are thinly covered below by some decussating longitudinal fibres and above by the overlapping inferior constrictor.

Schematic drawing of the structures at the pharyngoesophageal junction seen from the posterior aspect. The location of Killian's and Laimer's triangles is indicated; Zenker's diverticula develop cranial to the cricopharyngeal muscle, and the upper esophageal sphincter is located caudal to the V-shaped area of Killian.

Muscle Types: Striated Versus Smooth

• striated musculature in the pharynx and particularly in the cricopharyngeal muscle, which is the upper esophageal sphincter muscle (UES).

• The first sparse smooth muscle fascicles appear 2 to 3 mm caudal to the UES.

• Farther caudally, progressively more and more smooth muscle bundles replace the striated muscle in both the external and internal layers.

• The transition between both types is neither abrupt nor confined to individual muscle bundles and lacks any distinct anatomic border.

• Caudal to the tracheal bifurcation, no striated muscle elements are seen any more.

• With regard to sphincter function, it might be of interest to be aware that the muscle type of the UES differs completely from that of the LES!

The diagram shows the distribution of striated and smooth muscle in adult esophagus

Development of the oesophagus • At a very early period

the stomach is separated from pharynx by a mere constriction from primitive pharynx. This constriction is future esophagus.

• Previous to this elongation the trachea and oesophagus form a single structure.

• This becomes divided into two by the in growth of two lateral septa, which fuse giving rise to trachea in front and oesophagus behind.

• At this stage the oesophagus becomes converted into a solid rod of cells, losing its tubular nature.

• This eventually becomes canalised to form a tube.

Common Congenital Tracheo-esophageal anomalies

• Oesophago-tracheal fistula – Commonest type – Newborn has violent fits of

vomiting & coughing on swallowing

– Polyhydraminos • Partial Obstruction of

Oesophaugs– Stricture – Atresia– newborn salivates excessively,

becomes cyanotic and vomits