Flashcards in TBL17 - Esophagus Deck (10):
What does the esophageal mucosa consist of?
The esophageal mucosa consists of a richly vascular lamina propria covered by nonkeratinized stratified squamous epithelium
What does the nonkeratinized stratified squamous epithelium abruptly change to and where does this occur? Define the clinical relevance of the junction.
1) The nonkeratinized stratified squamous epithelium abruptly changes to simple columnar epithelium at the esophagogastric junction
2) An abrupt transition occurs in the epithelial lining at the esophagogastric junction. This serrated border, called the Z line, is clinically important, as it is the most common site of esophageal carcinoma
What is Barrett’s esophagus and what is the likelihood of its transformation into an adenocarcinoma?
1) In Barrett esophagus—metaplasia of the esophageal epithelium—columnar epithelium, similar to that of the stomach, replaces the usual stratified squamous epithelium
2) A response to esophagitis or injury, it can occur anywhere above the gastroesophageal junction
3) It may rarely lead to the more serious adenocarcinoma
4) Patients with persistent gastroesophageal reflux disease, in which acid reflux disrupts the esophageal mucosal barrier, are predisposed to metaplastic change in the esophageal epithelium
What is the most common cause of esophagitis and what conditions are typically associated with the causation?
1) Inflammation of the esophagus with damage to the epithelium is called esophagitis
2) Its most common cause is reflux of gastric contents into the lower esophagus, which impairs reparative capacity of esophageal mucosa
3) It often accompanies hiatal hernia or may occur with an incompetent lower esophageal sphincter
What is the muscularis mucosae and what does it do? Where is it present? What do periodic contractions of the muscularis mucosae do?
1) The muscularis mucosae, a longitudinal layer of smooth muscle, separates the mucosa and submucosa
2) The muscle layer is present along the entire GI tract
3) Periodic contractions of the muscularis mucosae creates folding of the mucosa to assist peristaltic propulsion of digested substances along the GI tract
What separates the muscularis mucosae and externa? What do secretory acini in this intermediate layer do?
1 )The submucosa separates the muscularis mucosae and muscularis externa
2) Secretory acini in the submucosa secrete mucus into ducts that open into the esophageal lumen to lubricate the apical surface of the lining epithelium
What does the muscularis externa consist of? Where is skeletal muscle present? Where is smooth muscle present?
1) The muscularis externa consists of inner circular and outer longitudinal muscle layers, composed of smooth and skeletal muscle fibers, respectively
2) Skeletal muscle is present in the outer layer in the proximal third of the esophagus
3) Smooth muscle composes both layers in the distal two-thirds
What is external to the muscularis externa and what does it consist of?
External to the muscularis externa, the adventitia consists of loose connective tissue without a covering mesothelium i.e., only the short abdominal portion of the esophagus is intraperitoneal and enclosed by visceral peritoneum
Why is esophageal adenocarcinoma associated with rapid tumor cell metastasis outside the esophageal boundaries?
1) There is a high metastatic potential of such tumors because they rapidly invade the esophageal wall, which has a relatively rich lymphatic drainage and an outer, ill-defined adventitia along most its length rather than a more circumscribed serosa
2) Whereas squamous cell carcinoma usually occurs in the mid-esophagus arising from stratified epithelium, adenocarcinoma most often occurs more distally and derives from glandular epithelium