The Respiratory System
LUNGS – NORMAL STRUCTURE Anatomy Right lung: 375–550 g (avg. 450 g), 3 lobes (upper, middle, lower), 2 fissures ( narrow grooves, clefts) Left lung: 325–450 g (avg. 400 g), 2 lobes (upper, lower), 1 fissure . Middle lobe represented by lingula ( tongue-like projection of the superior lobe that overlaps the heart) Airway pathway: Trachea → Right/Left Main Bronchi → Segmental bronchi → Terminal bronchioles → Acinus (functional unit). Acinus structure: Respiratory bronchioles Alveolar ducts Alveolar sacs (alveoli) Airway Wall Composition Trachea/bronchi: Cartilage, smooth muscle, mucous glands . Bronchioles: Smooth muscle only ; no cartilage/mucous glands . Blood Supply Dual supply: Pulmonary arteries: Deoxygenated blood. Bronchial arteries: Oxygenated blood. 🧬 Histology Bronchi/Bronchioles: Lined by pseudostratified ciliated columnar epithelium with goblet cells (decrease toward bronchioles). Bronchioles: No goblet cells;...