Anatomy and Physiology of the Esophagus

Question 1

4 layers of esophagus

Answer 1

• Mucosa
  
  • mucous membrane (non-keratinized squamous epithelium)
  • lamina propria
  • mucosa muscularis
• Submucosa
  
  • contains vascular, lymphatic, nerve plexus
• Muscularis propria
  
  • inner circular muscle layer
  • outher longitudianl muscle layer
• Adventitia
  
  • loose connective tissue
  • some vascular, lymphatic, nerve networks

Question 2

Esophagus does not have what histologic layer that is present throughout the rest of the GI tract

Answer 2

Serosa

Question 3

Properties of muscularis proria throughout esophagus

Answer 3

Transition in muscle fiber type:

• Striated muscle fibers (proximally)
• Smooth muscle fibers (distally)

Question 4

Longitudial muscle layer originates from what structure?

Answer 4

Posterior aspect of cricoid cartilage

• Two muscle bundles wrapping laterally and meeting on dorsal aspect of esophagus roughly 3 cm below cricoid

Question 5

V-shaped area of weakness on dorsal esophagus just distal to cricopharyngeus muscle (covered only by circular muscle layer of mulcularis propria)

Answer 5

Laimer’s triangle

• Due to presence of two muscle bundles wrapping laterally and meeting on dorsal aspect of esophagus roughly 3 cm below cricoid

Question 6

Area of esophageal weakness that is proximal to cricopharyngeus muscle

Answer 6

Killian’s triangle

Question 7

Inner cicular muscle layer of the muscularis propria is in continuity with what structure?

Answer 7

Inferior constrictor muscles

• Thicker than outer longitudial muscle layer of muscularis propria
• Transverse orientation in proximal and distal esophagus
  
  • Remaining fibers have oblique orientation to aid in peristalsis

Question 8

Blood supply to esophagus

Answer 8

Segmental Supply

• Cervical esophagus: Inferior thyroid artery
• Thoracic esophagus:
  
  • Bronchial arteries (1 right, 2 left)
  • Descending Aorta branches
• Abdominal esophagus:
  
  • Left gastric
  • Inferior phrenic arteries

Question 9

Venous drainage of esophagus

Answer 9

Segmental

• Cervical esophagus: inferior thyroid veins
• Thoracic esophagus:
  
  • Bronchial veins
  • Azygous vein
  • Hemiazygous vein
• Abdominal esophagus:
  
  • Coronary vein of the portal system
• Submucosal venous plexus of stomach and esophagus connected, permiting coronary-azygous vein portosystemic shunt seen in portal hypertension

Question 10

Lymphatic drainage of esophagus

Answer 10

Not Segmental

• Lymphatic networks (submucosa most extensive)
  
  • Drain into collecting trunks that pierce muscularis propria and drain to perisophageal regional lymph nodes and/or thoracic duct
• Esophageal Lymphatic Drainage Patterns:
  
  • Proximal esphagus: drains to deep cervical LN
  • Middle 1/3 esophagus: superior and posterior mediastinal LN
  • Distal 1/3 esophagus: gastric and/or celiac LN

Question 11

Majority of innervation of esophagus

Answer 11

Vagus nerve

• Directly (including recurrent laryngeal nerves)
• Indirectly (via its fibers)
• Includes motor, sensory, parasympathetic and sympathetic pathways

Question 12

Recurrent laryngeal nerve innervates what structures?

Answer 12

• Cricopharyngeus muscle
• Cervical esophagus
• Injury may lead to aspiration and dysmotility

Question 13

Innervation to mid and distal esophagus

Answer 13

• Mid esophagus: direct branches of vagus nerve
• Distal esophagus: anterior and posterior esophageal plexuses
  
  • Fibers of each plexus coverge to form left (anterior) and right (posterior) vagus nerves to stomach

Question 14

Intrinsic innervation of esophagus

Answer 14

Myoenteric (Auerbach’s) plexus

• Between outer (longitudinal) muscle fibers of muscularis propria and submucosal (Meissner’s plexus)

Question 15

Endoscopic points of esophageal narrowing and average measurements

Answer 15

• Upper esophageal sphincter (14-15cm)
• Crossing of left main bronchus and Aortic Arch (24-26 cm)
• Lower esophageal sphincter (36-40 cm)

Question 16

3 phases of swallowing

Answer 16

• Oral (voluntary)
• Pharyngeal
• Esophageal

Question 17

Purpose of esophageal phase of swallowing

Answer 17

Transport of volus through opened UES, down esphagus, and through opened LES

Question 18

Defintion of UES

Answer 18

High-pressure area ~ 2-3 cm in length that separates pharynx from esophagus

Question 19

Key muscle involved in UES function

Answer 19

Cricopharyngeaus

• At rest, UES tonically contracted (prevents reflux into pharynx and lung aspiration)

Question 20

Definition of LES

Answer 20

Physiologic and anatomic area of esophagus that prevents esophageal reflux by remaining tonically contracted.

Question 21

Characteristics of LES

Answer 21

• Relaxation occurs in response to peristalsis
• Transient relxation (5-30 sec) can lead to normal, brief periods of physiologic reflux

Question 22

GI hormones that can cause relaxation of LES

Answer 22

• Secretin
• Cholecystokinin (CCK)
• Glucogon
• Gastric inhibitory peptide (GIP)
• Vasoactive intestinal peptie (VIA)
• Neurotensin

Question 23

Extrinsic factos that can cause increased LES pressure

Answer 23

• Increased intra-abdominal pressure
• Contraction of diaphragm at level of crus during Valsalva maneuver

Question 24

GI hormone that increases LES tone

Answer 24

Gastrin

Question 25

Categories of esophageal contraction

Answer 25

• Primary waves:
  
  • normal peristaltic contractions triggered by voluntary swallowing
• Secondary waves:
  
  • peristaltic waves occuring in response to esophageal distention or irritation
  • carry out “housekeeping” function
• Tertiatry waves:
  
  • not coordinated; do not produce effective peristalsis
  • occur in normal patients
  • can occur spontaneously or in response to swallow
  • may be seen in dysmotility disorders

Question 26

Category of esophageal contraction:

Normal peristaltic contractions triggered by voluntary swallowing

Answer 26

Primary wave

Question 27

Category of esophageal contraction:

Peristaltic waves occuring in response to esophageal distention or irritation

Answer 27

Secondary wave

“Housekeeping” function

Question 28

Category of esphageal contraction:

Not coordinated contraction

May be seen in normal esophagus

May be present in dysmotility disorder

Answer 28

Tertiary wave