Question

Pseudostratified epithelium is found in (a) rectum (b) urinary bladder (c) wall of oesophagus (d) inner lining of bronchiole

Short answer

The pseudostratified epithelium is found in the inner lining of bronchiole (d).

Step-by-step solution

Identify the Characteristics of Pseudostratified Epithelium

Understand that pseudostratified epithelium appears to have multiple layers due to nuclei at different levels. However, each cell is attached to the basement membrane. This type of epithelium typically contains cilia and goblet cells and is involved in secretion or absorption.

Compare with Known Locations of Pseudostratified Epithelium

Recognize that pseudostratified epithelium is not found in the rectum (option a) or the esophagus (option c), as these areas are lined by other types of epithelium. The urinary bladder (option b) is lined by transitional epithelium, known for its ability to stretch. Pseudostratified epithelium is, however, found in the respiratory tract.

Conclude the Correct Option

Since the respiratory tract is lined with pseudostratified ciliated columnar epithelium, which facilitates movement of mucus, the inner lining of bronchiole (option d) is the correct answer. This is the only option where pseudostratified epithelium is found.

Key concepts

Epithelial Tissue

Understanding the body's surfaces and cavities involves studying epithelial tissue, one of the four primary types of tissues in animals. Its primary function is to protect, cover, and line organs, and it also plays roles in absorption, filtration, excretion, and sensory reception. Epithelial tissues adhere to one another forming tight, continuous sheets. They lack blood vessels and thus are dependent on the underlying connective tissue for nutrition and waste removal.

One unique type of epithelial tissue is the pseudostratified epithelium. Despite appearing as though it has multiple layers due to the nuclei's varied positions, each cell actually reaches the basement membrane maintaining just a single layer. This architecture makes it distinct from truly layered stratified epithelia. Pseudostratified epithelial cells may have cilia or be specialized as goblet cells that produce mucus—adaptations that emphasize their role in secretion and movement of substances over the epithelial surface.

Respiratory Tract Histology

If you delve into respiratory tract histology, you'll encounter the intricacies of how various cells are adapted to their functions. The respiratory tract is lined with distinct epithelia suited for the airway's progressive tasks from nasal cavity to alveoli. In the upper respiratory tract, such as in the inner lining of the bronchioles, pseudostratified ciliated columnar epithelium predominates.

Characterized by cilia and interspersed goblet cells, this epithelial type serves a vital role in the mucociliary escalator. This is a defense mechanism where pathogens and debris are trapped in mucus secreted by goblet cells and transported away from the lungs by the rhythmic beating of the cilia. Clearly identified in histological slides by their classic 'false-layered' appearance and motile cilia, they are crucial for maintaining cleanliness and protection in the respiratory tract.

Cell Biology

Cell biology is the study of cells' structure, function, and behavior, and is pivotal in understanding pseudostratified epithelium. Within this specialized epithelium, cells vary in height but all share contact with the basement membrane although not all reach the free surface. This epithelial form showcases the importance of cell organization and specialization in tissue function.

Cilia, the hair-like projections observed atop certain cell types like those in the pseudostratified epithelium of the respiratory tract, demonstrate how cellular structures are tailored to specific tasks. The beating of cilia propels mucus, showcasing the coordinated activity of cells towards the overall function of the epithelium. Additionally, goblet cells exemplify the specialization of cells within the epithelium, which are dedicated to mucus production, a key aspect of the epithelium’s protective function.