Question

The mucosal lining of the oesophagus of mammals is made up of
A. Simple columnar epithelium
B. Squamous epithelium
C. Stratified cuboidal epithelium
D. Stratified columnar epithelium

Answer 1

Hint: The oesophagus or oesophagus also known as the food pipe or gullet, is an organ in vertebrates through which food passes, aided by peristaltic contractions, from the pharynx to the stomach.

Complete answer:
The mucosa is the inner lining of the oesophagus.
It is made up of a thin layer of squamous cells (called the epithelium) a layer of connective tissue (called the lamina propria).
1. The oesophagus is a fibromuscular tube, about 25 cm (10 in) long in adults, which travels behind the trachea and heart. It passes through the diaphragm and empties into the uppermost region of the stomach. During swallowing, the epiglottis tilts backward to prevent food from going down the larynx.
2. The wall of the esophagus from the lumen outwards consists of mucosa, submucosa (connective tissue), layers of muscle fibers between layers of fibrous tissue, and an outer layer of connective tissue.
3. The mucosa is a stratified squamous epithelium of around three layers of squamous cells, which contrasts with the single layer of columnar cells of the stomach.
4. The transition between these two types of epithelium is visible as a zig-zag line.
It has two muscular rings or sphincters in its wall, one at the top and one at the bottom.
5. The lower sphincter helps to prevent the reflux of acidic stomach content.
6. The oesophagus has a rich blood supply and venous drainage. Its smooth muscle is innervated by involuntary nerves and in addition voluntary nerves that are carried in the vagus nerve to innervate its striated muscle.

So, the correct answer is “Option B”.

Note: In fish, the oesophagus is often lined with columnar epithelium.
In amphibians, sharks, and rays, the esophageal epithelium is ciliated, helping to wash food along, in addition to the action of muscular peristalsis.