Histology of Trachea, Bronchial tree & Bronchus

Histology of Respiratory System

                                    Histology of  Trachea

The trachea is lined with typical respiratory epithelium. A variety of migratory cells are also found in the epithelium includes lymphocytes,leukocytes and mast cell.

               

The proprio sub-mucosa consists of loose connective tissue and different cells such as fibrocytes,lymphocytes,globular leukocytes and mast cells.Tubulo-acinar sero-mucous glands are present in the proprio sub-mucosa.

The most feature of trachea is hyaline cartilage which occurs as roughly “ C “ or U shaped separate pieces. The dorsal free end of cartilages are bridges by tracheal muscle. In most species,the muscle attach to the perichondrium of internal sides of cartilage. The external perichondrium is surrounded by loose connective tissue of adventitia.

                                                       Bronchial tree

The trachea divides into two primary bronchi that enter the large of hilum.After entering the lungs,the primary bronchi give twise to three secondary bronchi in right lung and in left lung,each of which supply the pulmonary lobe.These lober bronchi  divide repeatedly,giving rise to smaller bronchi,whose terminal branches

         

            

are called bronchi.Each bronchiole branches to form 5-7 terminal bronchioles. Each terminal bronchole  sub-devides into two or more respiratory bronchioles that serve as region of transition between conducting and respiratory portion.                                                                                                                                                                                        

                                                          Bronchus

The histological appearance of bronchus generally similar to the trachea,except that the various layers  squamous linner. Bronchi are lined by respiratory epithelium which includes ciliated columnar cell,goblet cell,basal cell and brush cell. Proximodistally,the composition of epithelium changes,goblet cells and basal cells decrease. At the same time,the epithelial height and the thickness of proprio-submucosa progressively decrease.

The proprio-submucosa is loose connective tissue contain sero-mucous gland. The hyaline cartilage is the form of irregular plates,and the smooth muscle bundles are presented either between or an the luminal side of the plates,large amount of cartilage decrease proximodistally,whereas the smooth muscle becomes relatively more abundant. The adventitia consists of loose connective tissue.