Respiratory System

Primary Purpose of the Respiratory System:

• Continuous absorption of oxygen (O) & excretion of carbon dioxide
• Filtering air to prevent allergens & microbes from reaching the lungs
• Transporting oxygenated blood to tissues
• Warming & humidifying inspired gas

Trachea Branch Point:

• Branches into two main stem bronchi at the "Carina"

Aspirated Objects:

• Most aspirated objects/fluids end up in the right main stem bronchus because:
• Right bronchus is larger & more in-line with the trachea

Left Lung Features:

• The left bronchus is shorter than the right
• Anatomical correspondence of the left lung to the right lung's middle lobe is the "Lingula"

Terminal Bronchioles Characteristics:

• Smallest purely conducting airways
• Average 3 to 4 mm in diameter
• Generally five divisions below segmental bronchi

Flow Type Beyond Terminal Bronchioles:

• Laminar flow

Mucosa Cell Types:

• Most common in larger airways: Pseudostratified ciliated columnar epithelium

Effects of Histamine Release:

• Causes bronchoconstriction (1)

Functions of Airway Mucus:

• Protects airways from water loss & toxic particles
• Traps inhaled contaminants

Ciliary Action:

• "Mucociliary escalator" - forward stroking of cilia

Classification of Airway:

• From nares to terminal bronchioles is called "Conducting airways"

Definition of Acinus:

• Comprises all structures distal to a terminal bronchiole
• Represents the functional unit of the lungs

Alveolar Cells:

• Type I cells cover over 90% of the alveolar-capillary membrane
• Type II cells secrete pulmonary surfactant

Surfactant Importance:

• Promotes lung stability

Phagocytic Cells in Lungs:

• Alveolar macrophages ingest foreign material

Collaterals for Ventilation:

• Canals of Lambert & Pores of Kohn

Thoracic Anatomy:

• Midclavicular line = anatomical landmark
• Thin serous membrane on thoracic wall: Parietal pleura

Sternum Parts:

• Upper portion: "Manubrium"

Diaphragm Movement:

• During tidal breathing: Pulled down 1 to 2 cm

Diaphragm Innervation:

• Nerves arise from spinal nerves C3 to C5

Accessory Muscles of Inspiration:

• External intercostals & scalene muscles elevate ribs

Pleural Fluid Function:

• Reduces friction

Chest Radiograph Observations:

• Costophrenic angle blunted mainly by excess fluids

Pulmonary Circulation:

• Delivers oxygenated blood to the heart (via left atrium)

Airway Opening in Unconscious Patient:

• Neck extension needed

Trachea Length:

• Approximately 10 to 12 cm in adults

Costal Pleura & Diaphragmatic Pleura Angle:

• Known as Costophrenic angle.