Related Experiment Video
Updated: Aug 11, 2026

Two-step Approach to Explore Early- and Late-stages of Organ Formation in the Avian Model: The Thymus and Parathyroid Glands Organogenesis Paradigm
Published on: June 17, 2018
The development of the epithelium and its innervation in the avian extra-pulmonary respiratory tract
Abstract:
The development of the epithelium and its innervation was investigated with the electron microscope in the larynx and trachea of embryo domestic fowls between the 10th and 21st days of incubation. From days 10 to 16 the airways were lined by undifferentiated cells which on day 15 or 16 became arranged in two distinct layers. Differentiation of the epithelial cells commenced on day 17, so that at hatching on day 21 fully differentiated ciliated cells, goblet cells, non-ciliated columnar cells, granular cells and basal cells were arranged into a simple or pseudostratified columnar epithelium. Comparisons are made with the differentiation of the respiratory epithelium in other vertebrates. Intra-epithelial axons were first seen on day 15 and increased rapidly in number. The varicose axon profiles contained both granular and agranular vesicles. The axons lay close to most types of epithelial cell, and some approached near to the surface of the epithelium. A synaptic complex, possibly efferent, involving a granular epithelial cell is described.
Related Concept Videos
Epithelial Tissues and Their Functions
Epithelial tissues provide the body's first line of protection from physical, chemical, and...
Classification of Epithelial Tissues: Overview
Based on the number of cell layers,...
Classification of Epithelial Tissues: Simple Epithelium
Because of the thinness of the cells, simple squamous epithelium is present where the rapid passage of chemical compounds is observed. For example, the endothelium that lines the capillaries and vessels...
Classification of Epithelial Tissues: Stratified Epithelium
The Bronchial Tree
The trachea, commonly known as the windpipe, is a tube that connects the larynx (voice box) to the bronchi. At a point called the carina, it bifurcates into two primary bronchi. The right primary bronchus is wider, shorter, and more vertical than the left primary...
Anatomy of Respiratory System II: Lower Respiratory Tract
The Larynx
It is located between the pharynx and the trachea, acts as a passageway for air, and hosts several critical structures, such as the epiglottis, vocal cords, and glottis. The epiglottis acts as a gateway, guiding food to the...

