PSIO120 Module 1 Revision: Respiratory System

Respiratory System Overview

• Facilitates gas exchange of O2 and CO2 between atmosphere, blood, and tissues.
• Contributes to homeostasis and pH adjustment of body fluids.
• Serves as an interface between external and internal environments.

Respiration Processes

• Involves respiratory and circulatory systems to supply O2 and dispose of CO2.
• Four main processes:
  • Pulmonary ventilation: movement of air in and out of lungs.
  • External respiration: gas exchange between lungs and blood.
  • Transport: movement of O2 and CO2 within blood.
  • Internal respiration: gas exchange between systemic blood vessels and tissues.

Structural Components of the Respiratory System

• Upper respiratory:
  • Nose, nasal cavity, paranasal sinuses, pharynx.
• Lower respiratory:
  • Larynx, trachea, bronchi and branches, lungs and alveoli.

Conducting Zone vs. Respiratory Zone

• Conducting zone: pathways to gas exchange sites (includes nose to terminal bronchioles).
• Respiratory zone: sites of gas exchange (includes respiratory bronchioles, alveolar ducts, sacs, and alveoli).
• Respiratory muscles, such as the diaphragm, assist in pressure control for breathing.

Functions of the Nose

• Two main regions: external nose and nasal cavity.
• Functions: provides airway, moistens and warms air, filters and cleans air, acts as a resonating chamber for speech, houses olfactory receptors.

Nasal Cavity Features

• Contains conchae (turbinates) that increase mucosal area and air turbulence.
• Meatuses improve surface area for warming and moistening air.
• Nasal mucosa filters and warms air during inhalation, reclaiming heat and moisture during exhalation.

Paranasal Sinuses

• Located in frontal, sphenoid, ethmoid, and maxillary bones.
• Lighten skull, warm/moisten air, and serve as resonating chambers.

Pharynx Structure

• Muscular tube connecting nasal cavity and mouth to larynx and esophagus.
• Divided into three regions: nasopharynx, oropharynx, and laryngopharynx.

Larynx Functions

• Connects to hyoid bone, continuous with trachea.
• Functions include providing a patent airway, routing air and food, and voice production.

Trachea Structure

• Windpipe extending from larynx into mediastinum.
• Made of four layers: mucosa, submucosa, hyaline cartilage (C-shaped rings), and adventitia.

Bronchi Structure

• A series of branching air passages known as the bronchial (respiratory) tree.
• Bifurcation of trachea forms left and right primary bronchi.

Conducting Zone Structures

• Lobar bronchus divides into segmental bronchi, which further divide.
• Terminal bronchioles are the smallest structures (<0.5 mm in diameter).

Respiratory Zone Features

• Composed of respiratory bronchioles, alveolar ducts, and alveolar sacs.
• Approximately 300 million alveoli constitute the main site for gas exchange.

Alveoli Characteristics

• Surrounded by elastic fibers with pores of Kohn for air pressure equalization.
• Contain macrophages for sterility, lysozymes, and antibodies (Ig-G).
• Types: Type I (95%) facilitate gas exchange; Type II (5%) produce surfactant.

Lung Structure

• Right lung consists of 3 lobes; left lung consists of 2 lobes.

Blood Supply to Lungs

• Pulmonary circulation involves low pressure, high volume.
• Pulmonary arteries deliver systemic venous blood; pulmonary veins carry oxygenated blood to the heart.

Pleurae Composition

• Thin, double-layered serous membrane with parietal pleura (thoracic wall) and visceral pleura (lung surface).
• Pleural fluid provides lubrication and surface tension.

Boyle's Law

• Describes inverse relationship between gas pressure and volume (P1V1 = P2V2).
• As chamber volume decreases, pressure increases proportionally, and vice-versa.

Lung Pressures

• Intrapulmonary (intra-alveolar) pressure fluctuates with breathing and equalizes with atmospheric pressure.
• Intrapleural pressure remains negative, ensuring lung expansion.