trachea beneath the submucosa: 16-20 c-shaped hyaline cartilages that keep the lumen permanently...
TRANSCRIPT
Trachea
• Beneath the submucosa: 16-20 C-shaped hyaline cartilages that keep the lumen permanently open
• Cartilages form an incomplete ring around the trachea
• Open on the posterior aspect where a thick layer of smooth muscle fibers (trachealis muscle) and fibroelastic ligament bridge the open ends of each cartilage
Lungs
• Pair of conical organs that occupy the greater part of the thoracic cavity– Right lung – 3 lobes– Left lung – 2 lobes
Pleura
• Double layer of fibrous tissue that envelopes the lungs– Parietal pleura– Visceral pleura– Pleural cavity
• Mesothelium (simple squamous epithelium)
Bronchial Tree• The branching pattern of the main
bronchi• Main bronchi
– Right main bronchus– Left main bronchus
• Secondary bronchi– Right – 3, Left – 2
• Tertiary bronchi– Right – 10, Left – 8
Bronchopulmonary Segment
• Each tertiary bronchus and the area of the lung that it supplies
• These segments each have their own artery (thus, each segment is supplied by a bronchus and an artery)
• Each bronchopulmonary segment is a discrete anatomical and functional unit.
Bronchi
• Extrapulmonary – main bronchi (before they enter lung substance)– Same structure as trachea, but smaller caliber
• Intrapulmonary – all bronchi within the lung substance– Same structure as extrapulmonary, with
exceptions
Intrapulmonary vs. Extrapulmonary BronchiExtrapulmonary Intrapulmonary
Hyaline cartilage
C-shaped Irregular platesBig bronchi: completely encircle the lumenSmaller bronchi: incomplete rings or isolated plates
Smooth muscle fibers
Present only in the area where cartilage is deficient
Occupy a recognizable layer between the mucous membrane and the cartilage plates
Intrapulmonary vs. Extrapulmonary BronchiExtrapulmonary Intrapulmonary
Mucous membrane
Thrown into folds
Epithelium Pseudostratified columnar
ShorterSmaller bronchi: ciliated columnar
Goblet cells Fewer
Bronchial Tree
• Bronchioles – 1 mm diameter, disappearance of cartilage– Terminal bronchioles – 0.5 mm diameter or less
• Respiratory bronchioles– Alveolar ducts
Bronchioles
• Smaller caliber than bronchi• Wall: no cartilage, gland, lymph nodes• Epithelium: respiratory epithelium but
diminishes in height and transforms to cuboidal as bronchial tree goes distally, no goblet cells
• Smaller bronchioles: Clara cells
Clara Cells
• Non-ciliated, columnar cells• Contain microvilli• Rounded apices• Contain dense secretory granules – protect
the bronchiolar lining, form a non-sticky layer that helps keep the bronchioles patent