Respiratory System

Overview of the Respiratory System

• The respiratory system goes beyond breathing; it plays a critical role in gas exchange, energy production, and maintaining homeostasis.

Functions of the Respiratory System

1. Gas Exchange: Provides a large surface area for gas exchange between air and blood.

2. Air Movement: Facilitates movement of air to and from the lungs.

3. Protection: Shields respiratory surfaces from dehydration, pathogens, and temperature changes.

4. Sound Production: Enables communication via speech and vocalization.

5. Olfactory Detection: Enables detection of odors through olfactory receptors located in the nasal cavity.

Anatomical Organization:

• Upper Respiratory System: Nose, nasal cavity, paranasal sinuses, pharynx.

• Lower Respiratory System: Larynx, trachea, bronchi, bronchioles, and alveoli.

  • Lower respiratory system includes structures involved in conducting air and gas exchange.

Respiratory Mucosa:

• Lines the conducting portion, changes along the tract.

• Contains mucous cells that trap debris and pathogens, forming the respiratory defense system.

Airway Conditioning:

• The conducting portion warms, humidifies, and filters incoming air to protect delicate lung tissues.

Structure of the Nose and Nasal Cavity:

• The nasal cavity is divided into two sections by the nasal septum, lined with hairs and mucus for filtration.

• Air turbulence helps with moisture and warmth of the air, enhancing olfactory reception.

Functions of the Pharynx:

• Shares digestive and respiratory roles.

• Divided into nasopharynx, oropharynx, and laryngopharynx, accommodating airflow and food passage.

Larynx:

• Connects pharynx to trachea; serves in sound production and protects against food entry during swallowing.

• Cartilage Structure: Major cartilages include thyroid (largest), cricoid (base), and epiglottis (covers glottis).

Trachea and Bronchial Tree:

• The trachea extends from the larynx and divides into bronchi.

• C-shaped cartilage rings provide structure and prevent collapse; smooth muscle controls airway diameter.

Alveoli and Gas Exchange:

• Alveoli are the primary site for gas exchange; structured for maximum surface area.

• Surfactant produced by type II alveolar cells prevents collapse by reducing surface tension.

• Gas exchange occurs at the blood-air barrier, with efficiency aided by thin membranes and large surface area.

Respiratory Volumes and Capacities:

• Tidal Volume: Volume of air moved during a normal breath (~500 mL).

• Inspiratory/Expiratory Reserve Volumes: Extra air that can be inhaled or exhaled (~3300 mL for males, ~1900 mL for females).

• Residual Volume: Air that remains post-exhalation (~1200 mL for males).

• Total Lung Capacity: Combination of all lung volumes, varies with age and sex.

Gas Transport:

• Oxygen is primarily transported bound to hemoglobin in red blood cells (O2 + Hb ⇌ HbO2).

• Carbon dioxide is transported in three main forms: bound to hemoglobin, as bicarbonate, and dissolved in plasma.

Regulation of Respiration:

• Involuntary centers in the medulla and pons control rhythm and depth of breathing.

• Voluntary control can override basic rhythms for functions like speech or breath-holding.

Age-related Changes:

• Lung elasticity decreases with age, reducing compliance and vital capacity.

• Aging individuals may show increased susceptibility to respiratory diseases (e.g., emphysema) due to environmental factors.

Integration with Other Systems:

• The respiratory system works closely with the cardiovascular system to maintain homeostasis, adjusting blood flow and respiratory rates as needed, particularly at high altitudes.