Esophagus
- Development
- Week 4 - development begins when primitive foregut
forms
ventral tubular structure
- lateral grooves invaginate --> fuse to form trachea
(ventral) and esophagus (dorsal)
- incomplete fusion leads to TEF or laryngopharyngeal cleft
anomolies (1:3500 live births)
- Week 6-7 - epiglottis, aryepiglottic folds, false
vocal chords,
and laryngeal ventricles
- epiglottis seperates from the tongue at around 7wks
- final "proportionate" length reached by 7wks
- Week 8-10 - esophageal lumen re-established
- Week 16-20 - stratified squamous epithelium replaces
ciliated
columnar epithelium and Swallowing observed
- Anatomy
- Normal esophageal length
- Birth - 10cm (8-10)
- 1 year - 20cm (doubles from birth)
- Adult - 25cm (10in)
- upper border = caudal border of the cricoid cartilage and
lower
margin of cricopharyngeus muscle (~C6 level)
- Diameter = 2cm with 3 points of constriction
- Cervical constriction - pharyngoesophageal junction (cricopharyngeus muscle at
level of
cricoid cartilage) - Upper Esophageal Sphincter (UES)
normally ~15cm
from incisors
- Thoracic constriction - caused by arch of aorta (22.5cm
from incisors)
and left main bronchus (27.5cm
from
incisors)
- Diaphragmatic constriction - esophageal hiatus in
diaphragm.
Right crus of diaphragm and expanded circular smooth muscle
= Lower
Esophageal sphincter (LES) - at level of T10 approx 40cm
from incisors
- Distal termination (2-3cm below diaphragm)
- esophagus ends by entering the cardial orifice of the
stomach
left of the midline at the level of the T11 and the 7th
costal cartilage
- Z-line (zig-zag) demarcates the junction of the esophagus
and
the stomach
- Muscle
- Upper third - Striated
- Middle - mixed
- Lower third - smooth muscle
- Blood Supply
- Arterial
- Upper esophagus - superior and inferior thyroid arteries
- Middle esophagus - bronchial, R intercostal arteries,
desc
aorta
- Lower esophagus - off the celiac trunk (L inferior
phrenic,
L gastric, Splenic)
- Venous
- Upper - SVC
- Middle - azygous
- Distal -(portal) portal vein through L gastric vein,
(systemic) esophageal veins entering the azygos vein [Note: if potal veins back
up due to
liver dz, (portal HTN) submucosal veins can dialate due
to the
portosystemic anastamosis causing esophageal varices]
- Innervation
- Afferent
- Vagus - pain, temp, chem/osmotic stimuli
- Spinal nerve - mechanosensitive information /
nociceptors
- intraepithelial nerve endings mediate acid-induced
pain
- Calcitonin fene-rlated peptide and substance P mediate
visceral pain
- Efferent
- UES - cricopharyngeal muscle/Inferior pharyngeal
constrictor
- 3 major nerves:
- Vagus (X) - pharyngoesophageal, superior laryngeal,
recurrent laryngeal
- Vagus is motor innervation predominant but
provides
sensory innervation to the vocal cords to protect
the airway and eject
bolus if entering the airway
- Glossopharyngeal nerve
- sympathetic fibers from superior cervical ganglion
- Parasympathetic
- Nucleus ambiguus and dorsal motor nucleus of vagus
- innervation of esophageal muscles and glands
- Sympathetic
- cervical and thoracic chain (spinal nerve T1-T10)
- Regulates
- blood vessels
- sphincter contraction
- peristalsis
- glandular activity
- Physiology
- UES is normally
contracted except during sleep (UES and LES are contracted
between
swallows) - resting pressure is variable (range = 30-80 mm Hg)
- 17 +/- 7 mmHg @33wks
- 26 +/- 14 mmHg @ term
- 53 +/- 23 mmHg in adults
- UES increases in pressure due to:
- distention of esophagus
- acidic pH
- Average speed of esophageal peristalsis = 1cm/sec
- Average speed of food bolus through hypopharynx during
swallowing 10cm/sec
- LES resting pressure
=
20-30 mmHg (wylie reports 15-20)
- LES is tonically contracted except:
- Primary peristalsis
- Secondary peristalsis
- Transient LES relaxations (TLESR) caused by
- mechanoreceptors in the proximal stomach respond to
gastric distention and accomodation after a meal
- release of CCK from the duodenum when nutrients enter
- Development of LES pressures
- 18.1 mmHg @ Term (37+wks)
- Low LES pressure can be caused by:
- Drugs - theophylline, nitroglycerine, botulinum toxin
- inflammation
- displacement of LES into thoracic cavity(hiatal
hernia)
- smooth msucle disorder
- Increased LES pressure can be caused by:
- diplacement of LES into abdominal cavity
- external abdominal compression
- cholanergic agents (bethanechol), gastrin
- esophageal achalasia and diffuse esophageal spasm
- Glands in esophagus release mucous important for clearance
of
food and neutralizing and refluxed acid
- Histology
- GI tract contains 4 layers: Mucosa, Submucosa, Muscularis,
Serosa
- the Esophagus does not have a true serosal layer, but
rather
has adventitia
- Mucosa
- Esophageal squamous mucosa contains 3 layers:
- The esophagus is lined by stratified squamous
(non-keratinized) epithelium
- Columnar epithelium lines the distal end
- The Z-line represents the squamo-columnar junction.
Gross
Landmark
- difficult to ascertain true junction
- Cardiac stomach mucosa is columnar
- Esophageal glands or squamous epithelium lined ducts
lets you know you are in the esophagus
- variablity of Z-line also due to metaplasia 2/2
Peptic
Dz, GERD, H.pylori
- lamina propria
- Loose aereolar connective tissue contains: blood
vessels,
nerves, inflammatory cells, and mucous-secreting glands
(lymphocytesm
plasma cells, occasional lymphoid follicles are present)
- projections of the lamina propria project into the
squamous epithelium at regualar intervals (creates an
irregualr lower
border)
- mucosal growth and integrity maintained partly by
epidermal growth factor (EGF)
- muscularis mucosae
- Identifiable at the level of the cricoid cartilage,
becomes thicker distally
- irregular proximally, forms continuous longitudinal
(ext)
and transverse (int) fibers
- Submucosa
- loose connective tissue with blood vessels, nerves,
submucosal ganglia, lymphatics, and submucosal glands
- Submucosal plexus (Meissner)
- developed by 13wks gestation
- extensive lymphatic plexus
- 2 types of submucoasal glands:
- superficial - neutral mucin
- deep - acidic mucin
- Muscularis
- Well developed circular and longitudinal muscle layers
- LES - extends 2cm above and 3cm below diaphragmatic hiatus
- Myenteric Plexus (Auerbach)
- lies between outer longitudinal muscle and inner
circular
muscle layers
- developed by 9wks gestation
- Adventitia
- no serosal layer
- external layer consists of loose connective tissue with
blood
vessels, lymph and nerves
- continuus with connective tissue of mediastinum
- elastic fibers at the GEJ connect the esophagus to the
diaphragm
- Motility
- Primary Peristalsis - swallowing
- Secondary peristalsis - triggered by stretch on esophageal
wall
- sphincters relaxation induced by swallowing, vomiting, and
release of gas
- Transient relaxation - can occur normally with gastric
distention (post prandial)
- 90% of GE reflux episodes due to Transient relaxations
- Esophageal Manometry
- Measuring the pressures within the esophagous at rest and
while swallowing
- Indications for testing:
- Non-obstructive dysphagia/odynophagia, Dx of achalasia,
nutcracker esophagus, and diffuse esophageal spasm
- Eval chest pain
- Accurate placement of esophageal pH probe (esp if
abnormal
anatomy)
- Evalaute medical therapy
- confirm dx of systemic dz associated with esophogeal
dysmotility
- LOS - Lower Oesophageal Sphincter
- Procedure:
- Manometry Catheter with at least 3 recording sites (5,
10,
15cm above LOS)
- Catheter is placed intranasally
- Standard protocol (3 maneuvers)
- pull through from stomach (assess LES resting pressure
and location)
- wet swallows with water to determine LES relaxation
- Assessment of peristalsis in esophageal body
- Hi-Res manometry - detailed segmental assessment
- 1 sensor / cm
- useful in Dx of subtle anomalies - vigorous achalasia,
LES pseudo-obstruction, etc...
- Deglutition
- Swallowing requires the coordination of 30 muscles
- swallowing difficulties in 13% gen population, 26% preterm
infants, 90% children with neuro d/o
- swallowing develops ~ 11 wks gestation
- swallow volumes
- 2-6 mL/day @ 16wks
- 13-16 mL/day @ 20wks
- 500 mL/day @ full term
- sucking ~18-20 wks
- coordination of suck and swallow ~32-34wks
- POLYHYDRAMNIOS suggests
structural/anatomical abnormalities
- 3 stages: (Wylie book says 4)
- Oral (voluntary) (1. preparatory phase and 2.
transport phase)
- bolus is changed in size/shape (volume), pH, temp,
consistency (texture)
- moved to posterior of oral cavity
- Pharyngeal
- 3 most important functions
- facilitate safe deglutition and esophageal transport
of
enteric contents
- volume clearance with swallowing or emesis
- protect the airway
- protection of larynx
- vocal cord closure (laryngeal adductor reflex)
- esophagoglottal closure reflex (EGCR)
- retrograde refluxate overwhelms the UES and distends
esophagus, the EGCR abruptly closes vocal cords
- pharyngoglottal closure reflex (PGCR)
- injection of small amounts of water in pharynx of
neonates/infants causes vocal cord closure
- stage lasts about 1 sec
- bolus causes reflex stimulation and elevation of soft
palate and uvula (pharyngeal tube) which closes the
nasopharynx,
the epiglottis covers the larynx/trachea
- Velopharyngeal closure by levator veli palatini muscles
(elevate soft palate aka velum to divert food from the
nasopharynx)
- relaxation of the Upper esophageal sphincter and reflex
constriction (peristalsis) in the posterior pharyngeal
constrictors
allows passage of the bolus into the esophagus
- Esophageal
- Peristaltic waves propagate the bolus through the
esophagus
to the LES
- 3-4 cm/s
- transit time depends on age, bolus, texture (adult times
=
8-13s)
- Neurologic concerns
- Enteric Nervous System (ENS) develops around 12wks
gestation
- originate from neural crest but remain undifferentiated
until later in fetal development (external influences in
fetal
environment?)
- sonsory feedback can modify deglutition
- swallowing can be evoked by CN IX (glossopharyngeal),
superior laryngeal, and recurrent laryngeal nerves of CN X
(Vagus)
- regulated by medulla and pons
- Parasympathetic pathways control
- striated muscle via CN X activating lower motor neurons
in
the nucleus ambiguous
- Smooth muscle via CN X fibers in the dorsal motor
nucleus
- Neurotranmitters
- Exitatory (more concentrated proximally in esophagus)
- choline
acetyltransferase
(chAT)
- Supstance P
- Inhibitory (relaxation) (more concentrated distally in
esophagus)
- Nonadrenergic noncholinergic (NANC)
- Neuronal Nitric
oxide
synthase (nNOS or NO)
- Vasoactive
intestinal
peptide (VIP)
- intermediate in enhacing nNOS synthesis
- Period of refraction
- esophageal peristalsis is followed by period of
refractoriness
- contraction in response to swallow lasts 8-10 sec
- multiple swallows during the refractory period will
produce
a full peristaltic wave after the refractory period and
the last
swallow - known as deglutative
inhibition
- Disordered deglutition can be caused by:
- Prematurity
- Nasopharyngeal disorders
- choanal atresia
- nasal/sinus infection
- tumor
- septal defect
- Oropharyngeal disorders
- cleft lip/palate
- craniofacial syndromes
- Laryngeal disorders
- stenosis
- webs
- clefts
- paralysis
- laryngomalacia
- Congenital defects
- laryngotracheopharyngeal cleft
- tracheoesophageal fistula
- esophageal atresia
- esophageal web and stricture
- vascular anomalies (double aortic arch or right aortic
arch)
- Trauma to upper airway, oropharynx
- Neurological defects
- hypoxia
- microcephaly
- cortical atrophy
- CNS infection
- Arnold chiari malformation
- dysautonomia
- sensory integration or processing disorders
- CNS injury
- Neuromuscular diseases
- myotonic muscular dystrophy
- myasthenia gravis
- poliomyelitis
- muscular disorders - achalasia
References:
- Tortora, Gerard J.
Principles
of Anatomy and Physiology. 15th ed. Hoboken, NJ: J. Wiley,
2009. Print.
- Moore, Keith L.,, Arthur F.
Dalley, II, and Keith L Moore. Clinically Oriented Anatomy.
Fifth
edition. Baltimore: Wolters Kluwer Health, 2009. Print.
- Kleinman RE, Goulet O,
Mieli-Vergani G, et al, eds. Pediatric Gastrointestinal
Disease:
Pathophysiology, Diagnosis, and Management. 5th ed. Hamilton,
Ontario:
BC Decker; 2008.
- The NASPGHAN fellows
concise
review of pediatric gastroenterology, hepatology, and
nutrition. 1st
edition (2011)
- Wyllie, Robert & Hyams,
J.S.. (2011). Pediatric Gastrointestinal and Liver Disease.
10.1016/C2009-0-53242-4. (Accessed online Feb 2020)