2- PharynxThe pharynx is the part of the digestive system of many animals immediately behind the mouth and in front of the esophagus

The human pharynx is divided into three sections: 1. the nasopharynx2. the oropharynx3. the laryngopharynx

3- The LarynxBecause of its location, the larynx has threeimportant functions: 1- Control of the airflow during breathing. 2- Protection of the airway. 3- Production of sound for speech.

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4- Epiglottis

The epiglottis is the flap of cartilage lying behind the Tongue and in front of the entrance to the larynx .

5- The uvulaIs a fleshy piece of muscle, tissue and mucous membrane that hangs down from the palate.It is the part that moves upward when we say, "Ah!".

6- The TracheaIt is a tube 2 cm diameter and 10 cm in long.It is kept open by incomplete rings of cartilage the deficiency onthe posterior surface being filled in with fibrous and mascular tissue.

The wall of trachea consists of:1- Mucosa: it is formed of(A) Epithelium (B) Corium (Lamina Propria)2- Submucosa3- Fibro-Cartilagenous coat

7- Bronchi

It is composed of:1- Extra-pulmonary bronchi2- Intra-pulmonary bronchi: a- Bronchioles b- Terminal Bronchioles c- Respiratory Bronchioles

8- The Alveoli, Alveolar Sacs and Alveolar Ducts

•Alveolar Ducts : Long branching passages arise from respiratory bronchioles.•Alveolar Sac : 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 alesser extent into the respiratory bronchioles.

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.