Respiratory 2009 - 1 Respiratory 2009 The respiratory...

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1 Respiratory 2009 The respiratory system takes in air, modifies and filters the air, and then transports the air to the respiratory part of the lung where oxygen and carbon dioxide can diffuse in and out of the blood. Traditionally, the respiratory system is divided into a conducting part and a respiratory part. To these, the ventilation mechanism is added. 1. Conducting part: nasal cavities, nasal pharynx, oral pharynx, larynx, trachea, bronchi, bronchiole, and terminal bronchioles. 2. Respiratory part: respiratory bronchioles, alveolar ducts, alveoli. This is where the action is: exchange of O 2 and CO 2. 3. Ventilation mechanism consists of thoracic cage, intercostals muscles, diaphragm, and the elastic and collagen fibers of the lung. Respiratory Epithelium : Most of the conducting portion of the respiratory tract is covered with ciliated pseudostratified columnar epithelium with many goblet cells. The ciliated columnar cells are the most abundant. Each of these cells has a least 300 cilia on its apical surface. Inside the cell membrane the cilia are attached to a basal body (centrioles). As you would expect, the basal body is surrounded by many mitochondria as it takes energy (ATP) to move the cilia. (Again note the polarity that is characteristic of many epithelial cells). The goblet cells are the next most frequent cells. They secrete mucus, a glycoprotein. In addition to these cells, there are three other cell types: basal cells, the short cells that are on the basement membrane but do not extend to the luminal surface; brush cells which are columnar cells with extensive microvilli on the apical surface and sensory nerve endings on their basal surface; and finally, small granule cells ( part of the diffuse neuroendocrine system) that secrete hormones. The basal cells (stem cells) can differentiate into the other cell types. Nose 1. The vestibule (nares) has keratinized stratified squamous epithelium, sebaceous glands, and hair (vibrissae). 2. In the fossae (nasal cavities), there is gradual loss of keratin and transition to ciliated pseudostratified columnar with goblet cells. The lateral part of the fossae has three boney projections, the superior , middle and inferior conchae . The epithelium of the superior conchae is specialized as olfactory epithelium. Beneath the epithelium lies the CT, again referred to as lamina propria. There are mucous and serous glands in this lamina and
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2 more importantly, large venous plexuses with very thin walls which serve to warm or cool the air that flows across them. Theses venous plexuses are call cavernous sinusoids or swell bodies. 3. Olfactory epithelium on superior conchae is modified pseudostratified. It is taller than regular respiratory epithelium and there are usually more than the two or three layers of nuclei that we associate with when thinking about pseudostratified epithelium. There are no goblet cells in olfactory epithelium. Bipolar neurons are present in the olfactory epithelium. These are tall columnar cells but very narrow at their apical end. There is a
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Respiratory 2009 - 1 Respiratory 2009 The respiratory...

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