The connective tissue of the mucosa is loosely structured at the beginning of the larynx and in the laryngeal vestibule. However it is rigidly attached at the vocal fold edge. A multilayered nonkeratinizing squamous epithelium covers the mucosa of the laryngeal cavity and continues into the laryngeal vestibule. There, the cover changes to a ciliated multilayered stratified epithelium. A multilayered nonkeratinizing squamous epithelium interrupts the otherwise continuous respiratory epithelium at edge of of the vocal cord. Infraglottic cavity is situated under the vocal cords and is covered by a multilayered ciliated epithelium. This epithelium lines the entire lower airways all the way to the small bronchioles.
Trachea is covered by multilayered ciliated epithelium which contains goblet cells (secrete mucin). The epithelial layer is followed by lamina propria mucosae which contain collagen – and elastic fibers ands some glands and occasionally lymph follicles. Then there is a hyaline cartilage.
The interalviolar septum is the common wall between adjacent alveoli. The alveolar epithelium consists of two different cell types, the type 1 pneumocytes and type 2 pneumocytes which produce a surfactant. The septa contain elastic and collagenius fibers as well as apart from fibrocytes, leukocytes, macrophages, mast cells and nerve fibers. There also some capillaries.
ARTERIES AND VEINS
The walls of arteries and veins consists of three layers: the tunica intima, media and adventitia. There are two types of arteries: conducting arteries and peripheal arteries. Conducting arterial walls contain many elastic fibers and membranes. Peripheral arteries show a special abundance of smooth muscle cells. Tunica intima is made up of one layer of endothelial cells and is supported by an internal elastic lamina. Tunica media is made up of smooth muscle cells and elastic tissue. Tunica adventitia is mainly composed of collagen and is supported by external elastic lamina. Capillaries consist of pericytes and endothelial cells.
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