ANATOMY OF ESOPHAGUS WITH PHYSIOLOGY OF DEGLUTITION

OESOPHAGUS

Susritha.k,dpt of ent;ASRAMS

TABLE OF CONTENTS1)DEVELOPMENT OF

- PHARYNX

- OESOPHAGUS & TRACHEA.

2)DEVELOPMENTAL ANAMOLIES.

3)ANATOMY OF OESOPHAGUS.

4)BLOOD SUPPLY

5)VENOUS & LYMPHATIC DRAINAGE.

6)NERVE SUPPLY.

7)PHYSIOLOGY OF DEGLUTION.

EMBRYOLOGY OF PHARYNX

Buccopharyngeal membraneseparates stomodeum from fore gut.

Cranio-caudally boundaries of foregut are:

Ventrallystomodeum.

developing heart.

septum transversum.

Dorsallynotochord.

dorsal aorta.

Splanchnic mesoderm

Segmentation &

differentiation

6 pairs of mesodermal

bars

Branchial arches.

b/w the archesbranchial clefts.

Corresponding endodermal groovespharyngeal pouches.

Each branchial arch extends to meet its fellow on the opposite side.

BRANCHIAL APPARATUS

Branchial arches

Branchial clefts

Pharyngeal pouches.

Development of pharynx.

DEVELOPMENT OF OESOPHAGUS

4th wk of IULrespiratory diverticulum appears at ventral wall of foregut.

Tracheo-oesophageal septumseparates resp.diverticulum fromdorsal part of foregut.

Thus results the formation of Oesophagus~dorsally

Respiratory primordium~ventrally.

At 1st osophagus is short but later elongates with the descent of heart & lungs.

DEVELOPMENT OF TRACHEA BRONCHI AND LUNGS.

During its separation from foregut,lung budgets converted into a tubetrachea

2 lateral out pouchingsbronchial buds.

AT THE BEGENNING OF 5TH WK EACH BUD ENLARGES TO FORM

Rt main bronchi

3 secondary bronchi.

Divide forming 10 teritiary bronchi.

Lt main bronchi

2 secondary bronchi.

Divide forming 8 teritiary bronchi.

DEVELOPMENT OF TRACHEA & BRONCHI

FORMATION OF SECONDARY BRONCHI

FIGURE SHOWING FORMATION OF TERTIARY BRONCHI

MATURATION OF LUNGS

CANALICULAR PERIOD TERMINAL SAC PERIOD

ALVEOLAR PERIOD

DEVELOPMENTAL ANAMOLIES

OESOPHAGEAL ATRESIA/TRACHEO-OESOPHAGEAL

FISTULA.

Spontaneous posterior deviation of oesophago tracheal septum.

Mechanical factor pushing dorsal wall of foregut anteriorly.

Most common common form

proximal part of oesophagus ends as blind sac

distal partconnected to trachea just above its bifurcation.

OESOPHAGEAL ATRESIA//TR.OS FISTULA

TRACHEOSCOPY SHOWING OESOPHAGEAL FISTULA.

RADIOGRAPHICAL FEATURES OF TRACHEO OESOPHAGEAL FISTULA

ANATOMY OF OESOPHAGUS

EXTENSION: lower border of cricoid at Vc6 levelpasses through diaphragm at V T10 levelends at V T11 near cardiac orifice.

LENGTH:25cms.

DIAMETRE:2.5-3cms.

Curvatures.

Midline infront of prevertebral fasia

Then inclines slightly to left.

(enters thoracic inlet)

again at T5 midline

at T7 again deviates to left

Passes infront of thoracic aorta.

CONSTRICTIONS

At cricopharyngeal sphincter15cms from incisors.

Where aortic arch crosses22-25cms from incisors.

Where it is crossed by left bronchus27-28cms from incisors.

Where it passes through diaphragm38-40cms from incisors.

Topographically, there are three distinct regions: cervical, thoracic, and abdominal.

CERVICAL OESOPHAGUS:

extends from the pharyngoesophageal junction to the suprasternal notch.

about 4 to 5 cm long.

At this level, the esophagus is bordered anteriorly by the trachea, posteriorly by the vertebral column, and laterally by the carotid sheaths and the thyroid gland.

THORACIC OESOPHAGUS:

Extends from the suprasternal notchdiaphragmatic hiatus.

Passes posterior to the trachea, the tracheal bifurcation, and the left main stem bronchus.

The esophagus lies posterior and to the right of the aortic arch at the T4 vertebral level.

From the level of T8 until the diaphragmatic hiatus the esophagus lies anteriorly to the aorta

ABDOMINAL OESOPHAGUS:

extends from the diaphragmatic hiatusorifice of the cardia of the stomach.

Forms a truncated cone, about 1 cm long.

Structurally, the esophageal wall is composed of four layers:

> innermost mucosa,

>submucosa,

>muscularis propria,

>adventitia.

Unlike the remainder of the GI tract, the esophagus has no serosa.

Lined by non keratinised stratifed squamous epithelium.

HISTOLOGY-OESOPHAGUS.

MUSCULATUREThe muscular coat consists

-external layerlongitudinal fibers

-internal layercircular fibers.

The longitudinal fibers are arranged proximally in three fasciculi.

-A ventral fasciculus

-two lateral fasciculi that are continuous with muscle

fibers of the pharynx.

LONGITUDINAL FIBRES: form a uniform layer that covers the outer surface of the esophagus.

CIRCULAR FIBRES: provides the sequential peristaltic contraction that propels food toward the stomach.

The circular fibers are continuous with the inferior constrictor muscle of the hypopharynx.

They run transversely in cranial & caudal regions.

obliquelybody of the esophagus.

The internal muscular layer is thicker than the external muscular layer.

Below the diaphragm, the internal circular musclethickens ,constituting the intrinsic component of LES.

Muscular fibers in the cranial partred and consist chiefly striated muscle.

Intermediate partmixed.

Lower partcontains only smooth muscle.

RADIOLOGICAL VIEW OF OESOPHAGEAL MUCOSA.

Two high-pressure zones prevent the backflow of food:

the upper and lower oesophageal sphincter.

These functional zones are located at the upper and lower ends of the oesophagus.

UPPER OESOPHAGEAL SPHINCTER

Between pharynx and the cervical oesophagus.

Located at C5-C6 level.

The UES is a musculocartilaginous structure.

Composed of mainly three muscles: cricopharyngeus, thyropharyngeus,cranial cervical oesophagus.

The cricopharyngeus muscle is a striated muscle.

produces maximum tension in the A.P direction and less tension in lateral direction.

composed of a mixture of fast- and slow-twitch fibres.

This muscle forms the main component of UES.

KILLIANS TRIANGLE OR LAIMERS TRIANGLE.

Triangular area in the wall of pharynx b/w thyropharyngeus and cricopharyngeus muscles.

LOWER OESOPHAGEAL SPHINCTER

The lower esophageal sphincter is a high-pressure zone located where the esophagus merges with the stomach.

Mean pressure here is approx. 8mm Hg.

The LES is a functional unit composed of an intrinsic and an extrinsic component.

INTRINSICoesophageal muscle fibers and is under neurohormonal influence

EXTRINSICdiaphragm muscle.

The endoscopic localization of the LES is different from the manometric localization.

The endoscopic localizationdetermined by changes in the esophageal mucosal transition from nonstratified squamous esophageal epithelium to the gastric mucosa “Z-line”or B ring.

Functional location of LES is 3 cm distal to the Z-line.

LES-ENDOSCOPIC VIEW

Bulbous distension of distal oesophagusvestibule.

It corresponds to manometrically defined LES.

‘B’RING/Z-LINE

BLOOD SUPPLYThe rich arterial supply of the esophagus is segmental .

Branches of the inferior thyroid arteryUES and cervical esophagus.

Paired aortic esophageal arteries or terminal branches of bronchial arteriesthoracic esophagus.

The left gastric artery and a branch of the left phrenic arteryLES and the most distal segment of the esophagus.

VENOUS DRAINAGE

The venous supply is also segmental.

From the dense submucosal plexus the venous blood drains into the superior vena cava.

veins of proximal and distal esophagus azygous system.

Veins of mid oesophaguscollaterals of left gastric vein.

LYMPHATICS

The lymphatics from the proximal 1/3rd drain into the deep cervical LNs subsequently into the thoracic duct.

Middle 1/3rd into superior and posterior mediastinal nodes.

Distal 1/3rd gastric and celiac lymph nodes.

NERVE SUPPLY

Parasympathetic nerve supply (SENSORY,MOTOR,SECRETOMOTOR)

Upper ½rec.laryngeal nerve.

Lower ½oesophageal plexus formed by the 2 vagus plexus.

The sympathetic nerve supply(VASOMOTOR)

Upper ½by fibres from mid cervical ganglion.

Lower ½directly from upper four thoracic ganglia.

Esophageal sensory innervation

is carried by the vagus nerve

To the nodose ganglion

Through the thalamus

Terminates in the cortex.

The ganglia that lie between the longitudinal and the circular layersmyenteric or Auerbach's plexus.

That lie in the submucosa form the submucous or Meissner's plexus.

Auerbach's plexusregulates contraction of the outer muscle layers.

Meissner's plexusregulates secretion and the peristaltic contractions of the muscularis mucosae.

PHYSIOLOGY OF DEGLUTITION

DEFINITION:

Deglutition is the process of propulsion of bolus of food from oral cavity into stomach.

ORAL PHASE:

Voluntary ; under the control of cerebral cortex.

Food bolus~on a depression in middle of tongue.

Bolus held b/w tongue & ant.hard palate

Ant. to post. tongue movement(1 sec)

Movement of bolus into oropharynx.

ORAL PREPERATORY PHASE: processing of bolus to render it swallowable.

ORAL PROPULSIVE PHASE: propelling of food from oral cavity into oropharynx.

PHARYNGEAL PHASE:

Soft palate elevates closing the naso pharynx.

Sup.constrictor contracts ; tongue base drives the bolus posteriorly.

Respiration ceases.

Larynx elevates.

Epiglottis retroflexes & arytenoids adduct.

Bolus propulsion.

Cricopharyngeus & inf.constrictor relaxesfood into upper oesophagus.

UESrelaxes in pharyngeal phase;closesafter passage of food.

OESOPHAGEAL PHASE:(8-20SECS)

Comenses as soon as food passes cricopharyngeal sphincter.

Peristaltic wavein response to distension of wall by bolus.

Circular muscles contract behind & relax infront of bolus.

Followed by contraction of smooth muscle.

LES relaxes & bolus moves into oesophagus

Oesophageal phase

Swallow reflex: complex neurological event involving participation of

high cortical centres.

tract of nucleus solitarius & nucleusambiguous.

CNs 5,7,9,10 & 12.

PHASES OF DEGLUTITION

THEORY OF CONSTANT PROPORTION.

THEORY OF INTEGRAL FUNCTION.

THEORY OF NEGATIVE PRESSURE.

THEORY OF ORAL EXPULSION.

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THEORIES OF DEGLUTITION