Anatomy and Physiology - Respiratory System

Respiratory System

Main functions

1. to conduct air into the lungs
2. to deliver oxygen via capillary membranes to the blood
3. to remove carbon dioxide
4. regulation of acid-base

Respiration can be divided into 3 parts:

1. Ventilation – movement of air from outside to inside the body and its distribution within the trachea-bronchial system to gas exchange units in the lungs
2. Perfusion – flow of blood through the lungs
3. Diffusion – transfer of gases across the alveolar-capillary membrane to the blood in the pulmonary capillaries

The nervous system controls the movement of the respiratory muscles and adjusts the rate of breathing so that it matches the need of the body during various activities. Poor air quality is the major cause of respiratory disease.

The Upper Airways

Main Functions

1. to conduct air to the lower airways
2. to protect the lower airway from foreign matter
3. to warm, filter and humidify inspired air

Upper Airways include the nose, nasal cavity, sinuses, pharynx, larynx, epiglottis and vocal chords

The Lower Airways

Main Functions

1. air conduction to the alveolar level of the lungs
2. mucociliary clearance
3. pulmonary surfactant production

Lower airways include nasal passages, trachea, bronchioles and respiratory units

Blood Supply of the Pulmonary System

Bronchial Circulation

• Arises from the thoracic aorta and the upper intercostal arteries and consists of a bronchial artery network
• Serving as a part of the systemic blood supply, these arteries nourish the trachea and bronchi to the level of the respiratory bronchioles, alveolar ducts or alveolar walls (tissues don’t participate in gas exchange)

Pulmonary Circulation

• Provides blood flow, called perfusion, to the alveolar-capillary membrane (low pressure)
• The entire output of the right ventricle is delivered into the lungs
• 20% of total blood stays in the pulmonary capillary bed