Anatomy and Physiology of the Esophagus Flashcards
4 layers of esophagus
- 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
Esophagus does not have what histologic layer that is present throughout the rest of the GI tract
Serosa
Properties of muscularis proria throughout esophagus
Transition in muscle fiber type:
- Striated muscle fibers (proximally)
- Smooth muscle fibers (distally)
Longitudial muscle layer originates from what structure?
Posterior aspect of cricoid cartilage
- Two muscle bundles wrapping laterally and meeting on dorsal aspect of esophagus roughly 3 cm below cricoid
V-shaped area of weakness on dorsal esophagus just distal to cricopharyngeus muscle (covered only by circular muscle layer of mulcularis propria)
Laimer’s triangle
- Due to presence of two muscle bundles wrapping laterally and meeting on dorsal aspect of esophagus roughly 3 cm below cricoid
Area of esophageal weakness that is proximal to cricopharyngeus muscle
Killian’s triangle
Inner cicular muscle layer of the muscularis propria is in continuity with what structure?
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
Blood supply to esophagus
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
Venous drainage of esophagus
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
Lymphatic drainage of esophagus
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
Majority of innervation of esophagus
Vagus nerve
- Directly (including recurrent laryngeal nerves)
- Indirectly (via its fibers)
- Includes motor, sensory, parasympathetic and sympathetic pathways
Recurrent laryngeal nerve innervates what structures?
- Cricopharyngeus muscle
- Cervical esophagus
- Injury may lead to aspiration and dysmotility
Innervation to mid and distal esophagus
- 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
Intrinsic innervation of esophagus
Myoenteric (Auerbach’s) plexus
- Between outer (longitudinal) muscle fibers of muscularis propria and submucosal (Meissner’s plexus)
Endoscopic points of esophageal narrowing and average measurements
- Upper esophageal sphincter (14-15cm)
- Crossing of left main bronchus and Aortic Arch (24-26 cm)
- Lower esophageal sphincter (36-40 cm)
3 phases of swallowing
- Oral (voluntary)
- Pharyngeal
- Esophageal
Purpose of esophageal phase of swallowing
Transport of volus through opened UES, down esphagus, and through opened LES
Defintion of UES
High-pressure area ~ 2-3 cm in length that separates pharynx from esophagus
Key muscle involved in UES function
Cricopharyngeaus
- At rest, UES tonically contracted (prevents reflux into pharynx and lung aspiration)
Definition of LES
Physiologic and anatomic area of esophagus that prevents esophageal reflux by remaining tonically contracted.
Characteristics of LES
- Relaxation occurs in response to peristalsis
- Transient relxation (5-30 sec) can lead to normal, brief periods of physiologic reflux
GI hormones that can cause relaxation of LES
- Secretin
- Cholecystokinin (CCK)
- Glucogon
- Gastric inhibitory peptide (GIP)
- Vasoactive intestinal peptie (VIA)
- Neurotensin
Extrinsic factos that can cause increased LES pressure
- Increased intra-abdominal pressure
- Contraction of diaphragm at level of crus during Valsalva maneuver
GI hormone that increases LES tone
Gastrin
Categories of esophageal contraction
- 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
Category of esophageal contraction:
Normal peristaltic contractions triggered by voluntary swallowing
Primary wave
Category of esophageal contraction:
Peristaltic waves occuring in response to esophageal distention or irritation
Secondary wave
“Housekeeping” function
Category of esphageal contraction:
Not coordinated contraction
May be seen in normal esophagus
May be present in dysmotility disorder
Tertiary wave
