Respiratory System Lecture Flashcards

Overview of the Respiratory System

• The respiratory system is vital for life, facilitating gas exchange and cellular metabolism.

• Three key processes: Pulmonary gas exchange (blood and lungs), Tissue gas exchange (blood and cells), and Cellular respiration (cells consume O2 and produce CO2).

Anatomy of the Respiratory System

Major Structures:

• External Nose: Main entry point for air.

• Nasal Cavity: Cleans, warms, and humidifies inhaled air.

• Pharynx: Shared pathway for air and food.

• Larynx: Voice box; keeps airway open (patent).

• Trachea: Conducting tube to lungs.

• Bronchi: Branch from trachea to lungs.

• Lungs: Contain alveoli for gas exchange.

Functions of the Respiratory System

Primary Functions:

1. Pulmonary Ventilation: Movement of air in/out of lungs.

2. Gas Exchange: Includes:

   • External Pulmonary gas exchange: gas exchange between alveoli and blood.

   • Internal Pulmonary gas exchange: gas exchange between blood and body tissues.

3. Gas Transport: Movement of gases within the blood.

4. Tissue Gas Exchange: Oxygen delivery to cells and CO2 removal.

Additional Functions:

• Regulation of blood pH via CO2 levels.

• Production of chemical mediators such as ACE.

• Voice production through airflow over vocal cords.

• Olfaction: sense of smell facilitated by inhalation.

• Protection against pathogens in the respiratory tract.

Structure and Histology of the Respiratory Tract

Upper Respiratory Tract:

• Nasal Cavity: Extends from nostrils (nares) to choanae; includes the vestibule, hard palate, and nasal septum.

• Conchae: Enhance air cleaning and humidification.

Pharynx Regions:

1. Nasopharynx: Lined with pseudostratified epithelium; houses Eustachian tubes.

2. Oropharynx: Lined with moist stratified squamous epithelium; contains palatine and lingual tonsils.

3. Laryngopharynx: From epiglottis to esophagus, also lined with stratified squamous epithelium.

Larynx:

• Primary function is maintaining an open airway and facilitating sound production.

• Contains 9 cartilages: Thyroid, Cricoid, Epiglottis (unpaired); Arytenoid, Corniculate, Cuneiform (paired).

• The vocal folds are critical for sound production.

Lower Respiratory Tract:

Trachea and Bronchi:

• Trachea: Conducts air towards the lungs, lined with ciliated epithelium and supported by C-shaped cartilage rings.

• Bronchi: Divides into left and right main bronchi; further divides into lobar (secondary) bronchi.

Alveoli and Gas Exchange

Alveolar Structure:

• 300 million alveoli in lungs providing vast surface area for gas exchange.

• Two types of cells: Type I pneumocytes for gas exchange and Type II pneumocytes produce surfactant which prevents alveolar collapse.

Respiratory Membrane:

• Composed of the alveolar epithelium, capillary endothelium, and interstitial space.

• Facilitates diffusion of O2 and CO2 between air and blood.

Mechanics of Breathing

Muscles of Pulmonary Ventilation:

• Inspiration: Diaphragm contracts, external intercostals assist in lung expansion.

• Expiration: Typically passive; diaphragm and intercostal muscles relax, leading to lung recoil.

Changes in Thoracic Volume:

• During inspiration, thoracic volume increases and pleural pressure decreases, causing air to flow into the lungs.

• During expiration, decreased thoracic volume increases intra-alveolar pressure, expelling air.

Gas Laws

• Boyle's Law: P = k/V (pressure inversely proportional to volume).

• Dalton’s Law: Total pressure is the sum of individual gas partial pressures.

Measurement of Lung Function

• Spirometry: Measures tidal volume (TV), inspiratory reserve volume (IRV), expiratory reserve volume (ERV), and residual volume (RV).

• Pulmonary Capacities: Combinations of volumes, including inspiratory capacity (IC), functional residual capacity (FRC), vital capacity (VC), and total lung capacity (TLC).

Gas Exchange Physiology

Oxygen Transport:

• %98.5 transported via hemoglobin; %1.5 dissolved in plasma.

Carbon Dioxide Transport:

• %7 dissolved in plasma, %23 bound to hemoglobin, %70 as bicarbonate ions (HCO3-).

Factors Affecting Gas Exchange:

1. Partial pressure gradients:

   • O2 from higher (alveoli) to lower (blood).

   • CO2 from higher (cells) to lower (alveoli).

2. Membrane Thickness: Increased thickness decreases diffusion rate.

3. Surface Area: Decreased surface area reduces diffusion rate.

Conclusion

• Understanding the respiratory system's structure and function is vital for recognizing how we breathe, transport oxygen and carbon dioxide, and maintain homeostasis in bodily functions.