1. RESPIRATORY SYSTEM

2. Lower respiratory tract It includes: A. Trachea, B. Lungs, C. Bronchi. It includes: A. Trachea, B. Lungs, C. Bronchi.

3. Respiratory tract

5. 1. Thyroid cartilage: Consist of 2 flat pieces of hyaline cartilage or laminae fused anteriorly forming laryngeal prominence. It is incomplete posteriorly forming two processes called superior & inferior cornu. Upper part of the cartilage is lined with stratified squamous epithelium & the lower part with ciliated columnar epithelium. 1. Thyroid cartilage: Consist of 2 flat pieces of hyaline cartilage or laminae fused anteriorly forming laryngeal prominence. It is incomplete posteriorly forming two processes called superior & inferior cornu. Upper part of the cartilage is lined with stratified squamous epithelium & the lower part with ciliated columnar epithelium.

6. 2. Cricoid cartilage:  It lies below thyroid cartilage & is also composed of hyaline cartilage.  It posteriorly articulates with the Arytenoid cartilages & with the inferior cornu of the thyroid cartilage.  It is lined with ciliated columnar epithelium. 2. Cricoid cartilage:  It lies below thyroid cartilage & is also composed of hyaline cartilage.  It posteriorly articulates with the Arytenoid cartilages & with the inferior cornu of the thyroid cartilage.  It is lined with ciliated columnar epithelium.

7. 3. Arytenoid cartilages:  These are 2 pyramid shaped hyaline cartilages.  They r situated on broad part of the cricoid cartilage forming part of posterior wall of the larynx.  They give attachments to vocal cords.  They are lined with ciliated columnar epithelium. 3. Arytenoid cartilages:  These are 2 pyramid shaped hyaline cartilages.  They r situated on broad part of the cricoid cartilage forming part of posterior wall of the larynx.  They give attachments to vocal cords.  They are lined with ciliated columnar epithelium.

8. 4. The epiglottis:  Leaf shaped fibroelastic cartilage  It is attached to the anterior inner surface of the thyroid cartilage.  It is covered with stratified squamous epithelium.  It closes the larynx during swallowing. 4. The epiglottis:  Leaf shaped fibroelastic cartilage  It is attached to the anterior inner surface of the thyroid cartilage.  It is covered with stratified squamous epithelium.  It closes the larynx during swallowing.

9. TRACHEA Structures associated with the trachea: Superiorly: the larynx. Inferiorly:the right & left bronchi. Anteriorly:Isthmus of Thyroid gland & the arch of the aorta & the sternum. Posteriorly:the esophagus separates the trachea from the vertebral column. Laterally:the lungs Structures associated with the trachea: Superiorly: the larynx. Inferiorly:the right & left bronchi. Anteriorly:Isthmus of Thyroid gland & the arch of the aorta & the sternum. Posteriorly:the esophagus separates the trachea from the vertebral column. Laterally:the lungs

10. STRUCTURE OF THE TRACHEA It is composed of 3 layers of tissues & held by between 16-20 incomplete rings of hyaline cartilage. Rings are incomplete posteriorly. Connective tissues & involuntary muscle join the cartilages & form the posterior wall which is in contact with the esophagus. It is composed of 3 layers of tissues & held by between 16-20 incomplete rings of hyaline cartilage. Rings are incomplete posteriorly. Connective tissues & involuntary muscle join the cartilages & form the posterior wall which is in contact with the esophagus.

11. Three layers of tissue: I. The outer layer: consists of fibrous & elastic tissue & encloses the cartilages. II. The middle layer:consists of bands of smooth muscles in a helical manner. There is some areolar tissue. III. The inner lining:consists of ciliated columnar epithelium, containing mucus secreting Goblet cells. Three layers of tissue: I. The outer layer: consists of fibrous & elastic tissue & encloses the cartilages. II. The middle layer:consists of bands of smooth muscles in a helical manner. There is some areolar tissue. III. The inner lining:consists of ciliated columnar epithelium, containing mucus secreting Goblet cells.

12. LUNGS There are 2 lungs, each lying on each side of the midline in the thoracic cavity. They have- o Apex, o Base, o Costal surface, o Medial surface- Hilum at 5 th, 6 th, 7 th thoracic vertebrae. The area between the lungs: Mediastinum. Lobes of the right & left Lungs.

13. PLEURA & PLEURAL CAVITY: Pleura consists of a closed sac of serous membrane which contains a small amount of serous fluid. Each lung is pushed into this sac so that 2 layers are formed: a. One adherent to the lungs -visceral b. Another adherent to the wall of the thoracic cavity-parietal PLEURA & PLEURAL CAVITY: Pleura consists of a closed sac of serous membrane which contains a small amount of serous fluid. Each lung is pushed into this sac so that 2 layers are formed: a. One adherent to the lungs -visceral b. Another adherent to the wall of the thoracic cavity-parietal

14. Inside the lungs.. Bronchi & bronchioles:  Two primary bronchi are formed when trachea divides at the level of 5 th thoracic vertebra.  The right bronchus: -wider, shorter & more vertical than the left one. - Approx 2.5 cm  The left bronchus: - About 5cm long - Narrower.

15. BRONCHIAL TREE The bronchi divide as follows: Bronchi bronchioles terminal bronchioles respiratory bronchioles alveolar ducts alveoli. The bronchi divide as follows: Bronchi bronchioles terminal bronchioles respiratory bronchioles alveolar ducts alveoli. s