Pages 440-445

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Formed by division of the trachea
Each bronchus enters the lung at the
(medial depression)
then subdivide into smaller and smaller branches
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Trachea
Right main
(primary) bronchus
Right lung
Nasal cavity
Nostril
Larynx
Oral cavity
Pharynx
Left main
(primary) bronchus
Left lung
Diaphragm

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Occupy most of the thoracic cavity
Each lung is divided into lobes by fissures

Left lung—two lobes
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Right lung—three lobes
Connective tissue lines the fissures
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•
Serous membrane (“serosa”) covers the outer surface of the lungs; 2-layer membrane:
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–
Pulmonary (visceral) pleura covers the lung surface
Parietal pleura lines the walls of the thoracic cavity
•
•
fills the area between layers
–
Allows gliding and decreases friction during breathing
lies between the layers
© 2015 Pearson Education, Inc.

Intercostal muscle
Rib
Parietal pleura
Pleural cavity
Visceral pleura
Trachea
Thymus
Lung
Apex of lung
Right superior lobe
Horizontal fissure
Right middle lobe
Oblique fissure
Right inferior lobe
Heart
(in pericardial cavity of mediastinum)
Diaphragm
Base of lung
Left superior lobe
Oblique fissure
Left inferior lobe
(a) Anterior view.
The lungs flank mediastinal structures laterally.

Right lung
Parietal pleura
Vertebra
Posterior
Esophagus
(in posterior mediastinum)
Root of lung at hilum
•
•
•
Left main bronchus
Left pulmonary artery
Left pulmonary vein
Visceral pleura
Pleural cavity
Left lung
Thoracic wall
Pulmonary trunk
Pericardial membranes
Heart (in mediastinum)
Anterior mediastinum
Sternum
Anterior
(b) Transverse section through the thorax, viewed from above.

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
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All have reinforcing
in their walls
Exception are the smallest branches
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Hierarchy of branches:
Bronchi


Primary (largest)
Secondary

Tertiary
Bronchioles
Terminal bronchioles (smallest)
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Alveolar duct
Terminal bronchiole
Respiratory bronchioles
(a) Diagrammatic view of respiratory bronchioles, alveolar ducts, and alveoli
This is the only site of gas exchange
Alveoli
Alveolar duct
Alveolar sac

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The lungs are mostly air spaces; the rest is the
, mostly elastic connective tissue
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Alveoli:
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Inner walls lined with a squamous epithelial layer
Pulmonary capillaries cover external surfaces
Respiratory membrane (air-blood barrier) one side is air, and the other side is flowing blood
Formed by alveolar and capillary walls

Alveolar pores connect neighboring air sacs
© 2015 Pearson Education, Inc.