Bronchi and Lungs Pages 440-445

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Bronchi and Lungs

Pages 440-445

Formed by division of the trachea

Each bronchus enters the lung at the

(medial depression)

hilum

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

Occupy most of the thoracic cavity

Each lung is divided into lobes by fissures

Left lung—two lobes

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:

Pulmonary (visceral) pleura covers the lung surface

Parietal pleura lines the walls of the thoracic cavity

Pleural (serous) fluid

fills the area between layers

Allows gliding and decreases friction during breathing

Pleural space

lies between the layers

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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.

All have reinforcing

cartilage

in their walls

Exception are the smallest branches

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

The lungs are mostly air spaces; the rest is the

stroma

, mostly elastic connective tissue

Alveoli:

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

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