Respiratory System: Anatomy and Functions

• The respiratory system is responsible for gas exchange, taking in oxygen, and expelling carbon dioxide
• It includes the upper respiratory tract (nose, pharynx, larynx) and the lower respiratory tract (trachea, bronchi, lungs)

Functions of the Respiratory System

• Gas exchange facilitates the exchange of oxygen and carbon dioxide between the air and the blood
• Ventilation moves air into and out of the lungs
• Protection filters inspired air to remove pathogens and irritants
• Sound production enables speech and other vocalizations
• Olfaction contributes to the sense of smell
• Regulation of blood pH influences blood acidity by controlling carbon dioxide levels

Upper Respiratory Tract

• Consists of the nose, nasal cavity, pharynx, and larynx
• The nose filters, warms, and humidifies incoming air
• The pharynx (throat) is a passageway for both air and food
• The larynx (voice box) contains the vocal cords and is essential for sound production

Lower Respiratory Tract

• Comprises the trachea, bronchi, bronchioles, and alveoli within the lungs
• The trachea (windpipe) carries air to the lungs, dividing into the left and right bronchi
• Bronchi branch into smaller bronchioles, which lead to alveoli
• Alveoli are tiny air sacs where gas exchange occurs with the blood

Lungs

• The primary organs of respiration, located in the thoracic cavity
• The right lung has three lobes, while the left lung has two lobes
• The pleural membrane surrounds each lung, providing lubrication and protection

Mechanics of Breathing

• Inhalation (inspiration) involves contraction of the diaphragm and external intercostal muscles, increasing the volume of the thoracic cavity
• This increase in volume decreases pressure, causing air to flow into the lungs
• Exhalation (expiration) is usually passive, as muscles relax and the thoracic cavity returns to its original volume, increasing pressure and forcing air out
• Forced exhalation involves contraction of abdominal and internal intercostal muscles

Gas Exchange

• Occurs in the alveoli of the lungs
• Oxygen diffuses from the alveoli into the blood, while carbon dioxide diffuses from the blood into the alveoli
• The large surface area of the alveoli and the thinness of the respiratory membrane facilitate efficient gas exchange
• Partial pressure gradients drive the movement of oxygen and carbon dioxide

Regulation of Breathing

• Controlled by the respiratory centers in the brainstem (medulla oblongata and pons)
• Chemoreceptors in the brain and blood vessels detect changes in carbon dioxide, oxygen, and pH levels, influencing breathing rate and depth
• Voluntary control of breathing is possible through the cerebral cortex, but the autonomic system usually regulates breathing

Respiratory Volumes and Capacities

• Tidal volume: The amount of air inhaled or exhaled during normal breathing
• Inspiratory reserve volume: The additional amount of air that can be inhaled after a normal inhalation
• Expiratory reserve volume: The additional amount of air that can be exhaled after a normal exhalation
• Residual volume: The amount of air remaining in the lungs after a maximal exhalation
• Vital capacity: The total amount of air that can be exhaled after a maximal inhalation (tidal volume + inspiratory reserve volume + expiratory reserve volume)
• Total lung capacity: The total volume of air the lungs can hold (vital capacity + residual volume)

Common Respiratory Diseases

• Asthma: Chronic inflammatory disease causing airway constriction and breathing difficulty
• Chronic obstructive pulmonary disease (COPD): Progressive lung disease including emphysema and chronic bronchitis, characterized by airflow obstruction
• Pneumonia: Infection of the lungs causing inflammation and fluid accumulation
• Lung cancer: Uncontrolled growth of abnormal cells in the lungs
• Cystic fibrosis: Genetic disorder causing mucus buildup in the lungs and other organs
• Tuberculosis: Infectious disease caused by bacteria, primarily affecting the lungs

Aging and the Respiratory System

• Lung tissue loses elasticity, decreasing lung capacity
• Respiratory muscle strength diminishes
• Alveoli become less efficient at gas exchange
• Increased susceptibility to respiratory infections

Overview of the respiratory system, including its primary functions such as gas exchange and ventilation. Covers the components of the upper and lower respiratory tracts. Focuses on the roles of the nose, pharynx, and larynx.