Provides for gas exchange -- intake of oxygen and elimination of carbon dioxide
Respiration
Process of gas exchange
Basic steps of Respiration
1. Pulmonary ventilation or breathing
2. External respiration
3. Internal respiration
Pulmonary ventilation or breathing
Mechanical flow of air into and out of the lungs
External respiration
Exchange of gases between the air spaces of the lungs and the blood in the pulmonary capillaries. Pulmonary blood gains oxygen and loses carbon dioxide
Internal respiration
Exchange of gases between blood and systemic capillaries and tissue cells
Upper respiratory system
Nose
Pharynx
Associated structures
Lower respiratory system
Larynx
Trachea
Bronchi
Lungs
Nose (external portion)
Supporting framework of bone and hyaline cartilage covered with muscle and skin and lined by mucous membrane
Large cavity in the anterior aspect of the skull that lies inferior to the nasal bone and superior to the mouth, it also includes muscle and mucous membrane
Internal nares (choanae)
Nasal cavity
Nasal septum (divides nasal cavity)
Vestibule
Meatuses
Pharynx
Funnel shaped tube about 13 cm (5 inches) long, divided into 3 anatomical regions: Nasopharynx, Oropharynx, Laryngopharynx
Larynx
Voice box, short passageway that connects laryngopharynx with trachea, lies in the middle of neck anterior to the 4th through 6th vertebra
Trachea
Wind pipe, tubular passageway for air that is about 12 cm long and 2.5cm in diameter
Bronchi
At the level of 5th thoracic vertebra the trachea divides into right and left primary bronchi, the point where trachea divides is called the CARINA
Lungs
Paired cone shaped organs lying in the thoracic cavity
Two layers of serous membrane or pleural membrane enclose and protect each lung: Parietal pleura (superficial layer), Visceral pleura (deep layer)
Pleural cavity between the 2 layers contains lubricating fluid
Alveolus
Cup shaped outpouching lined by simple squamous epithelium
2 types of alveolar epithelial cells: Type 1 (main site of gas exchange, simple squamous), Type 2 (septal cells, rounded or cuboidal with microvilli, secrete alveolar fluid, keeps normal moisture of air)
Pulmonary Ventilation
Also known as "breathing", process by which gases are exchanged between the atmosphere and lung alveoli
Inspiration
Breathing in, inhalation, just before each inspiration the air pressure in the lungs is equal to the pressure of the atmosphere, for air to flow in the lungs the pressure inside the alveoli must become lower than the environment - achieved by increasing the volume of the lung
Muscles of Inspiration
Sternocleidomastoid
Scalenes
External intercostals
Diaphragm
Expiration
Breathing out, exhalation, the pressure of the lungs is greater than the pressure of the atmosphere, passive process with no muscular contractions, results from elastic recoil of chest wall and lungs
Elastic recoil
2 inwardly directed forces: recoil of elastic fibers stretched during inspiration, inward pull of surface tension due to the film of alveolar fluid