Respiratory System Trachea Notes Trachea magnified 1 Trachea

Respiratory System • Trachea Notes • Trachea- magnified- 1 • Trachea- magnified- 2 • Lung Notes Index

Notes Trachea Lumen Epithelium Lamina propria Submucosa Hyaline cartilage Adventitia Tracheal glands

Notes Trachea- magnified Lumen Epithelium Lamina propria Mucous & serous acini Submucosa Smooth muscle fibers Hyaline cartilage

Notes Trachea- magnified Lumen Goblet cells Pseudostratified ciliated columnar epithelium Lamina propria with blood vessels and connective tissue

Notes Lung Bronchiole Alveoli Hyaline cartilage Bronchus Smooth muscle Serous and mucous acini Pulmonary artery Alveolar duct

Trachea: Mucous membrane: It is lined by pseudostratified ciliated columnar epithelium with goblet cells resting on a basement membrane. Deep to the basement membrane is the lamina propria made up of areolar tissue with elastic fibres and lymphocytes. Submucosa: It is composed of a loose meshwork of connective tissue, containing large blood vessels and nerves. Mucous, serous and mixed types of glands also occur in this layer. Their ducts open on the free surface of the epithelium.

Hyaline cartilage: It is present outside the submucosa. Cartilage is covered by perichondrium on all sides, which separates it from the neighbouring structures. Cartilages are enclosed in an elastic fibrous membrane, which connects the cartilages to one another. Posterior wall of trachea is devoid of cartilage. Here outer longitudinal and inner circular layers of smooth muscles (trachialis muscle) are present within the fibrous membrane. Adventitia: It is the outer most layer with connective tissue, blood vessels and nerves.

Lung: A section through the lung shows the cut sections of • Bronchioles • Alveoli • Branches of pulmonary artery • Tributaries of pulmonary vein Bronchi: Mucosa: It is consisting of pseudostratified ciliated columnar epithelium. It is highly folded because of underlying smooth muscle fibers. Lamina propria: Contains connective tissue, smooth muscle fibers and mucous and serous glands. Hyaline cartilage: Is seen outside lamina propria and found in small pieces.

Bronchiole: Mucosa: It is made up of simple columnar cells with folds. Lamina propria: Contains some connective tissue and smooth muscle fibers, which are responsible for the folds of mucous membrane. Glands and cartilages are absent. Alveoli: Are lined by simple squamous cells. Between the alveoli there is very thin interalveolar septa with capillaries, elastic fibers and various types of cells like fibroblasts, mesenchymal cells, macrophages etc. The lining cells of alveoli are of 2 types.

Squamous (type 1) cells: There are simple squamous cells. They have prominent nuclei projecting into lumen. Secretory (type 2) cells: These are rounded cells that project into the lumen. The secretions of these cover the inner surface of the alveoli and act as a surfactant, which reduces the surface tension of the alveoli and prevents the collapse of alveoli during expiration. In addition there alveolar phagocytes (dust cells) seen bulging from the walls of alveoli into the lumen. Blood vessels: Cut sections of branches of pulmonary artery and tributaries of pulmonary veins are seen close to the bronchi. They are lined by simple squamous epithelium.