Respiratory System

Overview of the Respiratory System

  • Definition: The respiratory system comprises the organs and structures that allow breathing. It includes the lungs, nose, mouth, and airways that connect these organs.

  • Function: Main roles include bringing oxygen into the body during inhalation and removing carbon dioxide during exhalation.

Components of the Respiratory System

Major Organs and Structures

  • Lungs: Vital organs for gas exchange.

  • Heart: Circulates blood to transport oxygen and carbon dioxide.

  • Diaphragm: A muscle critical for breathing.

  • Blood vessels: Support circulation of blood.

  • Nasal and Oral Cavities: Structures for air entry.

  • Trachea: Windpipe that conducts air into the bronchi.

  • Larynx: Voice box, involved in sound production.

  • Pharynx: Throat, passage for food and air.

Anatomical Parts of the Respiratory System

  • Upper Respiratory Tract:

    • Nasal Cavity: Airway entry, filtered by hairs, contains conchae and sinuses.

    • Pharynx: Divided into Nasopharynx, Oropharynx, and Laryngopharynx, serving both respiratory and digestive functions.

    • Larynx: Houses vocal cords and serves as a passage for air.

  • Lower Respiratory Tract:

    • Trachea: Connects larynx to bronchi.

    • Bronchi: Right and Left primary bronchi leading to each lung.

    • Bronchioles: Smaller airways within lungs that lead to alveoli.

    • Alveoli: Primary site for gas exchange.

Function of the Respiratory System

Gas Exchange

  • Mechanism: Gaseous exchange primarily occurs in alveoli where oxygen enters the blood, and carbon dioxide is expelled.

  • External Respiration: Involves the exchange of gases between the lungs and capillaries.

  • Internal Respiration: Involves gas exchange at the tissue level between blood and body cells.

  • Conducting Zone: Filters, warms, and moistens air as it travels to the lungs.

  • Respiratory Zone: Site of gas exchange within lung tissue, particularly the alveoli.

Structural Anatomy

Nose and Nasal Cavity

  • External and Internal Portions:

    • External: Supported by bone and cartilage, covered with skin.

    • Internal: Lined with mucous membranes. Contain cilia for filtering air.

Sinuses

  • Paranasal Sinuses: Cavities within surrounding bones: Frontal, Sphenoid, Ethmoid, and Maxillary sinuses.

Pharynx

  • Components: Nasopharynx, Oropharynx, Laryngopharynx, each serving different functions in passage of air and food.

  • Function: Serves as a passageway for food and air; houses tonsils for immune defense.

Larynx

  • Composition: Composed of cartilage (Thyroid, Cricoid, Epiglottis, Arytenoid) and ligaments.

    • Vocal Cords: Produce sound by vibrating as air is expelled.

Trachea

  • Characteristics: Flexible tube, lined with ciliated epithelium and reinforced with C-shaped cartilage rings to maintain patent airway.

Breathing Mechanics

Inhalation (Inspiration)

  • Active Process: Diaphragm and external intercostals contract, increasing thoracic cavity volume and decreasing pressure to allow air inflow.

  • Muscles Involved: Diaphragm (75% of air input) and external intercostals (25%).

Exhalation (Expiration)

  • Passive During Rest: Muscles relax, and the elasticity of lung tissue aids in expelling air.

  • Active During Forceful Breathing: Internal intercostal muscles and abdominal muscles assist in pushing air out.

Mechanics of Breathing

Breathing Control

  • Medulla Oblongata: Houses the respiratory center regulating breathing rate and depth.

  • Dorsal Respiratory Group (DRG): Activates diaphragm; Ventral Respiratory Group (VRG) controls rhythmic breathing.

Airflow Factors

  • Pressure Gradient: Airflows from high to low pressure.

  • Other Influential Factors: Lung compliance, airway resistance, and surface tension of alveolar fluid.

Pulmonary Volumes and Capacities

  • Tidal Volume (TV): Air volume per breath (approx. 500 mL).

  • Minute Ventilation (MV): Total air inhaled/exhaled per minute (TV x breathing rate).

Gas Exchange Facilitators

  • Partial Pressure Differences: Drive the diffusion of gases; oxygen enters where pressure is higher in alveoli vs. blood.

  • Diffusion: Facilitated by surface area and membrane thickness, influenced by solubility and molecular weight of gases.