An Ultrastructural and Histological Study of the Epithelium of the Respiratory Tract in the Neonatal and Adult Goat

Kahwa, Charles K. B (1992) An Ultrastructural and Histological Study of the Epithelium of the Respiratory Tract in the Neonatal and Adult Goat. PhD thesis, University of Glasgow.

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Abstract

The objectives of undertaking this study were firstly to characterise the normal surface features of the epithelial lining of the entire respiratory tract of the adult goat by the use of the scanning electron microscope (SEM). Secondly, to further characterise, by the transmission electron microscope (TEM), the epithelial cell population of the distal airways (terminal bronchioles, respiratory bronchioles) and alveolar membrane. Thirdly, to investigate, also by the use of the scanning electron microscope, the development of the respiratory tract epithelium in the neonatal kid. Fourthly, to provide a histological and histochemical picture of the epithelial lining of the respiratory tract. And finally to assess the use SEM in the study of clinical material, with the view of using it as another tool in diagnostic procedures. It was apparent that information on the gross anatomy of the respiratory tract of the goat was scarce and scattered in many different sources. Thus Chapter 1 was introduced to provide a brief account of the gross anatomy of the caprine respiratory system. Chapter 2 details the materials, general procedures and methods used in the the whole study. Details of the preparation of different buffers and fixatives are also provided. In Chapter 3, the histology of the epithelial lining of the respiratory tract was defined, together with the histochemistry of the respiratory tract mucosubstances. 17 clinically normal animals were used in the study. Samples were taken from 18 preselected sites along the entire lining epithelium. Histological sections were stained with H&E and AB/ PAS, the latter used for the histochemical study of the mucosubstances. A stratified squamous type of epithelium lined the nasal vestibule, rostral region of alar and basal folds, caudal region of the nasopharynx, laryngeal surface of the epiglottis, cranial surface of the vocal fold and infraglottic cavity. An intermediate type of epithelium, itself grading from stratified cuboidal to low columnar, was seen to occupy the transitional zone between the nonciliated and ciliated regions of the rostral nasal mucosa, nasopharynx, vocal fold and infraglottic cavity. A typical respiratory epithelium ( a pseudostratified ciliated columnar epithelium) lined the nasal concha and most of the conducting airways. The bronchioles, proximal to the terminal bronchioles were lined by a respiratory epithelium. Distal to the terminal bronchioles were lined by a simple columnar epithelium which changed into a simple cuboidal in the respiratory bronchioles. It was established that the majority of the individual surface mucus-producing cells were acidic in character. The submucosal glands produced mucosubstances of varying nature and differing proportions of acidic, neutral and mixed glycoproteins. In the bronchioles, surface mucus-producing cells were only seen proximal to the terminal bronchioles, where they produces almost equal amounts of both acidic and mixed mucosubstances. Chapter 4 detailed the surface characteristics of the lining epithelium of the respiratory tract of the adult goat. Surface characteristics of squamous, nonciliated microvillous, mucus-producing, Clara, alveolar Type I and alveolar Type II cells were described. Two types of mucus-producing cells were distinguished on the basis of their luminal surface characteristics. It was established that the nasal vestibule, and rostral regions of the alar and basal folds were lined by squamous cells which gradually gave way to an intermediate epithelium, characterised by nonciliated microvillous cells with bulging luminal surfaces presenting a "cobblestone" appearance. This type of epithelium gradually changed into a ciliated epithelium in the caudal regions of the alar and basal folds. The latter type of epithelium was also seen to line the ventral, middle and nasal conchae. The intermediate epithelium described in the rostral regions of the nasal cavity was also observed on the nasopharynx, vocal fold and infraglottic cavity, situated between a ciliated epithelium and a nonciliated squamous epithelium. The trachea, bronchi and bronchioles were lined by a ciliated epithelium. The degree of ciliation was observed to decrease with decreasing airway diameter, whilst the numbers of nonciliated microvillous cells increased. At the level of the terminal bronchioles, Clara cells, characterised by their apical protuberances and the presence of short, stubby surface microvilli, were in the majority, with ciliated cells presenting poorly developed cilia. Mucus-producing cells were not identified at this level with SEM. Respiratory bronchioles were seen to be present and well developed. Alveolar pores and alveolar macrophages were both rarely observed. Chapter 5 was undertaken to further characterise, by means of TEM, the cell population of the distal airways and alveolar membrane. Five cell types were identified, namely, ciliated, Clara, alveolar Type I and Type II and mucus-producing cells, the latter being only occasionally observed. Essentially all cell types observed presented cytological characteristics similar to those observed in other mammalian species. Having established the normal surface morphology of the epithelial lining of the respiratory tract of the adult goat. (Abstract shortened by ProQuest.).

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: M D Purton
Keywords: Veterinary science, Histology, Morphology
Date of Award: 1992
Depositing User: Enlighten Team
Unique ID: glathesis:1992-75409
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Nov 2019 20:13
Last Modified: 19 Nov 2019 20:13
URI: http://theses.gla.ac.uk/id/eprint/75409

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