PubMed Google Scholar. A scanning electron microscopic study. Lab Invest — Google Scholar. Kawamata S, Fujita H Fine structural aspects of the development and aging of the tracheal epithelium of mice. Arch Histol Jpn — Rhodin JAG Ultrastructure and function of the human tracheal mucosa. Am Rev Respir Dis — Stockinger L Ultrastruktur und Histophysiologie des Respirationstraktes. Mikroskopie — Radivoj V. It is involuntary.
Peristalsis push food along the gastrointestinal tract The CO2 therefore diffuses into the blood cells and oxygen into the tissues. The blood full of CO2 returns to the lungs where it enters the capillaries in th The respiratory system consists of the nose, pharynx, larynx, trachea, bronchi, and lungs.
Respiration starts when oxygen enters either the passageways of th The lungs get oxygen through alveoli. The air is transported though the The air travels down your windpipe and into your lungs. After passing through you The Upper Respiratory Tract The human respiratory system involves complex organization of structural and defense mechanisms for the inhalation and exhalat What is the significance of the fact that the human trachea is reinforced with cartilage rings; Of the fact that the rings are incomplete posteriorly?
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Sign in Don't have an account? Set the Language Close. Flashcards » Lab 9 Quiz Study. Add to Folders Close. Please sign in to add to folders. Upgrade to Cram Premium Close. Upgrade Cancel. Although the olfactory receptors have the appearance of columnar epithelial cells, they are essentially nerve cells.
Each olfactory receptor cell carries at its apical end a peculiar knob or "olfactory vesicle" from which sprout several long but non-motile cilia see the Elektronenmikroskopischer Atlas im Internet , reichkolben , for EM images of this structure.
Each olfactory cell also has an axon which extends from the basal end of the cell to the olfactory bulb of the brain. The many axons from olfactory receptors pass through the medial portion of the ethmoid bone that is called the cribriform plate "cribriform" means "like a sieve," i. The olfactory mucosa is lubricated by Bowman's glands named after William Bowman , b.
Olfactory epithelial cells are quite wonderful, even beyond their utterly bizarre shape that displays elements of both epithelial and neural form. The cell that does all these things, firing off urgent messages into the deepest parts of the brain, switching on one strange unaccountable memory after another, is itself a proper brain cell, a certified neuron belonging to the brain but miles away out in the open air, nosing around the world.
How it manages to make sense of what it senses, discriminating between jasmine and anything else non-jasine with infallibility, is one of the deep secrets of neurobiology. This would be wonder enough, but there is more. This population of brain cells, unlike any other neurons of the vertebrate central nervous system, turns itself over every few weeks; cells wear out, die, and are replaced by brand-new cells rewired to the same deep centers miles back in the brain, sensing and remembering the same wonderful smells.
If and when we reach an understanding of these cells and their functions, including the moods and whims under their governance, we will know a lot more about the mind than we do now, a world away.
Tonsils are localized lymphoid specializations located in the mucosa of the pharynx as well as the tongue and palate. Each tonsil consists of an epithelial crypt an invaginated pocket surrounded by dense clusters of lymph nodules. Lymph nodules also called lymphoid follicles are sites where lymphocytes congregate. At the center of each lymph nodule is a "germinal center" where the lymphocytes proliferate.
Pharyngeal tonsils also called "adenoids" provide sites where immune surveillance cells lymphocytes can encounter foreign antigens which are entering the body through inspired air. Pharyngeal tonsils resemble those of the palate palatine tonsils , thumbnail to right , but with ciliated, pseudostratified columnar epithelium rather than stratified squamous epithelium lining the surface and crypts.
Conducting system. This pseudostratified respiratory epithelium consists primarily of columnar ciliated cells. Ciliary beating sweeps mucus and the dust it carries up the bronchi and trachea toward the pharynx, where it can be swallowed. Further down the tree, the columnar epithelium of trachea and bronchi transitions to simple cuboidal epithelium of bronchioles. The height of this epithelium decreases as one descends bronchiolar branches toward gas-exchange regions.
Lung alveoli , in contrast, are lined by very thin simple squamous epithelium. Electron micrographs of cilia may be seen at WebPath and at Elektronenmikroskopischer Atlas im Internet. A ciliated epithelium is also characteristic the female reproductive tract. Scattered among the ciliated cells are occasional mucus-secreting goblet cells.
Mucus moistens the epithelial surface so the ciliated cells can function and adheres to inhaled particles so dust and bacteria are caught before they are carried all the way into alveoli. For recent research on the properties of respiratory mucous in relation to ciliary function, see B. The name "goblet" refers to the cell's shape, narrow at the base and bulging apically.
The apical end of each goblet cell is occupied by a large mass of mucus, which compresses adjacent cells thus conferring the characteristic "goblet" shape and displaces the nucleus toward the basal end of the cell. Mucus-secreting cells of similar shape, also called "goblet cells," may be found in the gastrointestinal tract.
Basal cells those whose nuclei lie low in the epithelium, near the basement membrane are believed to be the source of replacement ciliated and goblet cells. In our slide set, ciliated respiratory epithelium is best represented by slides of the trachea or "trachea and esophagus". The trachea is the "trunk" of the branching tree of passageways leading into the lungs. Its major histological specializations include skeletal reinforcement in the form of incomplete i. For details of the ciliated, pseudostratified epithelium of the trachea, see above.
The distinction between bronchi and bronchioles is somewhat arbitrary, but in general bronchi have cartilagenous reinforcement and a columnar epithelial lining, while bronchioles lack cartilage and have a simple cuboidal lining.
Besides ciliated and mucus-secreting cells, bronchiolar epithelium may include club cells bronchiolar exocrine cells whose role is uncertain but which seem to have some specialized synthetic and secretory function.
Historical note: Older textbooks refer to bronchiolar exocrine cells as "Clara cells," a name which recognizes researcher Max Clara who worked on bodies of prisoners executed by the Nazi regime prior to WWII. Because of this tainted history, the alternative term "club cells" has been adopted by several journals and societies.
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