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The trachea is formed by a number of horseshoe-shaped rings, joined together vertically by overlying ligaments, and by the trachealis muscle at their ends. The epiglottis closes the opening to the larynx during swallowing. The trachea begins to form in the second month of embryo development, becoming longer and more fixed in its position over time.
The cells in the respiratory epithelium are of five main types: a) ciliated cells, b) goblet cells, c) brush cells, d) airway basal cells, and e) small granule cells (NDES) [6] Goblet cells become increasingly fewer further down the respiratory tree until they are absent in the terminal bronchioles; club cells take over their role to some extent here. [7]
The lower respiratory tract is also called the respiratory tree or tracheobronchial tree, to describe the branching structure of airways supplying air to the lungs, and includes the trachea, bronchi and bronchioles. [8] trachea. main bronchus (diameter approximately 1 – 1.4 cm in adults) [9] lobar bronchus (diameter approximately 1 cm)
Type I cells provide 95% of the surface area of each alveoli and are flat ("squamous"), and Type II cells generally cluster in the corners of the alveoli and have a cuboidal shape. [33] Despite this, cells occur in a roughly equal ratio of 1:1 or 6:4. [32] [33] Type I are squamous epithelial cells that make up the alveolar wall structure.
An X-ray of a human chest area, with some structures labeled. The contents of the thorax include the heart and lungs (and the thymus gland); the major and minor pectoral muscles, trapezius muscles, and neck muscle; and internal structures such as the diaphragm, the esophagus, the trachea, and a part of the sternum known as the xiphoid process.
There are three principal shapes of epithelial cell: squamous (scaly), columnar, and cuboidal. These can be arranged in a singular layer of cells as simple epithelium, either simple squamous, simple columnar, or simple cuboidal, or in layers of two or more cells deep as stratified (layered), or compound , either squamous, columnar or cuboidal.
trachea: Pseudostratified columnar, ciliated: respiratory epithelium: respiratory bronchi Pseudostratified columnar, ciliated respiratory terminal bronchioles Simple cuboidal, ciliated respiratory: respiratory bronchioles: Simple cuboidal, ciliated - respiratory alveoli Simple squamous sensory: cornea: Stratified squamous, non-keratinized ...
Hyaline cartilage is located in the trachea, nose, epiphyseal plate, sternum, and ribs. [2] Hyaline cartilage is covered externally by a fibrous membrane known as the perichondrium. [2] The primary cells of cartilage are chondrocytes, which are in a matrix of fibrous tissue, proteoglycans and glycosaminoglycans. [2] [3]