1. Eighth lecture

3. 4- Epiglottis The epiglottis is the flap of cartilage lying behind the tongue and in front of the entrance to the larynx. 5- The uvula IIs a fleshy piece of muscle, tissue and mucous membrane that hangs down from the palate. IIt is the part that moves upward when we say "Ah!".

4. 6- The Trachea  It is a tube 2 cm diameter and 10 cm in long.  It is kept open by incomplete rings of cartilage the deficiency on the posterior surface being filled in with fibrous and mascular tissue. The wall of trachea consists of: 1- Mucosa is formed of: (A)Epithelium. (B) Corium (Lamina Propria) 2- Submucosa 3- Fibro-Cartilagenous coat

5. 7- Bronchi It is composed of: 1- Extra-pulmonary bronchi 2- Intra-pulmonary bronchi: a- Bronchioles b- Terminal Bronchioles c- Respiratory Bronchioles

6. 8- The Alveoli, Alveolar Sacs and Alveolar Ducts Alveolar Ducts : Long branching passages arise from respiratory bronchioles. Alveolar Sacs : Is a group of alveoli which open into a common central space (the atrium). The alveoli : are the minute "air spaces" which open into the alveolar ducts, and to a lesser extent into the respiratory bronchioles.

7. The Alveolar Phagocytes: They are phagocytic cells present free inside the lung alveoli. e.g. 1- Dust Cells. 2- Heart Failure Cells. Types of alveolar epithelial cells: 1.Type I: Pneumocytes: flat squamous cells, constitute the major of the alveolar lining cells (95%). 2.Type II: pneumocytes: cuboidal cells represent 5% of the alveolar lining cells.

8. 9-THE LUNGS  The lungs are paired organs in the chest that perform respiration.  In human, there are two lungs each one is present at one side in the thoracic cavity.  The right lung has 3 lobes an 2 fissures,  While the left has two lobes and one fissures.

10. Adaptation of lungs to their function Filtration action of the respiratory passages. Secretion of mucus by mucosa of air passages. It acts as a trap for foreign particles and bacteria. Cough reflex. Sneezing reflex. Moistening of dry air and buffering of hot or cold air.

11. Peristaltic movement of bronchioles driving foreign particles to larger passages. Movement of cilia of respiratory mucosa drives mucus with its trapped particles to the pharynx where it is coughed or expelled. The tonsils have a protective function against bacteria. The presence of a thin layer of fluid between the parietal and visceral layers of pleura acts as a lubricant. Adaptation of lungs to their function

12. 10-The pleura It is a thin double- layered protective serous membrane:- 1.The parietal pleura 2.The visceral pleura

13. 10-The pleura The parietal pleura: Consists of a fibro-elastic membrane, lined on the inside by simple squamous epithelium. The visceral pleura: Consists of a fibro-elastic membrane which invests the lung, and is continuous with its inter-lobular septa. It is lined on the outside by simple squamous epithelium. The visceral & parietal layers of the pleura are separated by a thin film of fluid to lubricate the sliding movement of the visceral over parietal.

14. The blood supply of the lungs:  Blood flows to the lungs via branches of the pulmonary artery.  A network of capillaries encloses each alveolus.  It is between the capillaries and the alveoli that gas exchange occurs.  Blood returns to the heart in venules and veins which will give rise to the pulmonary veins.