HISTOLOGY

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Lung

Trachea:- •Trachea is lined by a ciliated pseudodtratified columnar with goblet cells.

•A and lie below the epithelium,but are not clearly demarcated from one another.

•Glands,mostly mixed,occur in deeper layers of lamina propria and within the submucosa.

•Rings of which are incomplete dorsally,support the tracheal wall.

•A layer of ,the is located dorsally in the trachea. •It is positioned internal to the gap in the tracheal cartilages in the horse,pig and ruminants. It lies external to the gap in cat and dog.

•An adventitia of connective tissue completes the wall of trachea.

3.Elastic fiber 15.sub-mucosa 11.Pseudostratified epithelium 12.Serous glands 17-trachealis muscle

5.Hyaline Cartilage

9.Perichondrium (C.T. that envelops cartilage where it is not at a joint)

10.Pseudosrtatified epithelium 12.Trachealis muscle 4.Goblet Cells

6.Lamina Propria Bronchus •The trachea bifurcates into two primary bronchi, which enter the and then branch several times to give rise to smaller secondary and tertiary bronchi.

• Bronchi differ from the trachea in having plates rather than rings of cartilage, and in having a layer of smooth muscle between the lamina propria and submucosa. 4 – Elastic band 6- Hyaline cartilage 7-lamina propria 9-mixed gland 10-muscularis 11-pseudostratified epithelium •Bronchioles are smaller branches of the bronchi, and are distinguished from them by the absence of cartilage and glands.

Terminal bronchioles :- •No cartilage but smooth muscle. •Clara cells present . •smallest conducting bronchioles consist of a simple cuboidal (or perhaps “low columnar”) epithelium of mostly exocrine cells, a few ciliated cells, and NO goblet cells, and are called terminal bronchioles .

Respiratory Bronchioles: You might see short, transitional regions of bronchioles which have alveoli in their walls. These bronchioles with alveoli in their walls are called respiratory bronchioles. Terminal bronchiole Respiratory Bronchiole

1- alveolus 2-bronchiole 6- Hyaline cartilage 11-pseudostratified epithelium 12-serous gland 1- alveolus 2- bronchiole 3-columnar epithelium ciliated 8-Lymphatic Nodule 10-muscularis 12-serous gland

3.Alveolus 9.Resp. Bronchiole

5.Cuboidal epithelium 10. Smooth muscle

7.Macrophage Lung

• Bronchus and bronchioles are present • and alveoli- Simple squamous epithelium •Macrophages or Dust cells (Heart failure cells) •Inter alveolar septa & Supportive tissue

References

Available on request.