60. Oesophagus - Histology Flashcards
(26 cards)
What does “histology” mean?
Histology is the study of the microscopic structure of tissues — looking at how cells, fibers, and layers are organized under the microscope.
How many main layers does the oesophagus wall have?
The oesophagus wall has four main layers:
Mucosa (innermost)
Submucosa
Muscularis externa (muscle layer)
Adventitia (outer layer)
What is the function of the mucosa in the oesophagus?
The mucosa is the innermost layer. It protects the oesophagus lining from damage by rough or hard food. It includes:
Epithelium: protective surface cells.
Lamina propria: connective tissue with small vessels and immune cells.
Muscularis mucosae: thin smooth muscle helping the mucosa move slightly.
What type of epithelium lines the oesophagus?
Non-keratinized stratified squamous epithelium.
This means multiple layers of flat cells, without a hard keratin surface, making it good at resisting mechanical stress but not resistant to acid.
What is the submucosa and what does it contain?
The submucosa is a connective tissue layer under the mucosa.
It contains:
Elastic fibers (for stretch and flexibility)
Blood vessels and lymphatic vessels
Mucous glands (oesophageal glands) that secrete mucus to lubricate the food passage
Submucosal (Meissner’s) nerve plexus that controls gland secretion and blood flow.
What is the muscularis externa, and what is its role?
It’s the thick muscle layer responsible for peristalsis (wave-like muscle contractions that push food down).
It has two sub-layers:
Inner circular muscle layer (squeezes the tube)
Outer longitudinal muscle layer (shortens the tube)
It also contains the myenteric (Auerbach’s) nerve plexus between these layers, which controls muscle movement.
What types of muscle are found in the oesophagus muscularis externa?
Upper third: skeletal (voluntary) muscle.
Middle third: mixed skeletal and smooth muscle.
Lower third: smooth (involuntary) muscle.
This unique combination lets swallowing start voluntarily but continue automatically.
What is the adventitia in the oesophagus?
The adventitia is the outermost connective tissue layer.
It holds the oesophagus in place, attaching it to nearby structures (like the trachea or spine).
In contrast to much of the digestive tract, the oesophagus does not have a serosa (smooth membrane) over most of its length.
Why are oesophageal mucous glands important?
They produce mucus that covers the inside surface, making it slippery so that food can pass smoothly and not damage the lining.
What happens at the gastroesophageal junction (lower end of the oesophagus)?
The epithelium abruptly changes from stratified squamous epithelium (oesophagus) to simple columnar epithelium (stomach lining), which can handle acid.
This area is important because acid reflux can damage the oesophageal side, sometimes leading to Barrett’s esophagus.
What is Barrett’s esophagus?
A condition where, due to long-term acid exposure, the oesophageal squamous epithelium changes (metaplasia) into a columnar epithelium more like the stomach’s — increasing cancer risk.
Which epithelium lines the oesophageal mucosa?
Non-keratinized stratified squamous epithelium — it protects against mechanical injury but is not acid-resistant.
What is the lamina propria in the oesophagus?
A layer of loose connective tissue under the epithelium, containing blood vessels, lymphatics, and immune cells.
What is the muscularis mucosae?
A thin layer of smooth muscle at the bottom of the mucosa that allows slight movement of the mucosal layer.
What does the submucosa contain in the oesophagus?
Dense connective tissue with elastic fibers, blood vessels, lymphatics, mucous glands (oesophageal glands), and the Meissner’s (submucosal) nerve plexus.
What type of glands are present in the oesophageal submucosa?
Mucous glands that secrete mucus to lubricate and protect the inner lining.
What are the two muscle layers in the oesophageal muscularis externa?
Inner circular muscle layer
Outer longitudinal muscle layer
What nerve plexus is located between the two muscle layers of the muscularis externa?
The myenteric (Auerbach’s) plexus, which coordinates muscle contractions.
What types of muscle are found in the oesophagus muscularis externa along its length?
Upper third: skeletal (voluntary) muscle
Middle third: mixed skeletal and smooth muscle
Lower third: smooth (involuntary) muscle
What is the adventitia in the oesophagus?
The outermost connective tissue layer that anchors the oesophagus to surrounding structures; unlike serosa, it is not covered by peritoneum.
Why does the oesophagus have non-keratinized epithelium instead of keratinized?
Because it needs to stay moist for food passage; keratin would make it dry and rigid.
Where is lymphatic tissue found in the oesophagus wall?
Mainly in the lamina propria and submucosa, helping with local immune defense.
How is the mucosa adapted for oesophageal function?
It has thick stratified squamous epithelium for protection and mucous secretion for lubrication, but no absorption structures.
Does the oesophagus mucosa have villi or crypts?
No — it has a flat surface without villi or crypts, since it is not designed for absorption.
