PLEURA AND LUNGS
I. GENERALITIES - THORACIC CAVITY
A. Three spaces inside the bony thorax
1. right pleural space
2. left pleural space(completely separate from right)
3. mediastinal space
B. Thoracic mediastinum - is defined as the space between the two pleural sacs
1. Superior mediastinum - superior to the horizontal plane of the sternal angle
2. Inferior mediastinum - below plane of sternal angle. Subdivided into;
a. middle mediastinum - area within and adjacent to the pericardium
b. anterior mediastinum - between the pericardium and the body of the sternum
c. posterior mediastinum - between the pericardium and vertebral bodies
II. PLEURA
A. Forms a closed cavity on each side
1. Outer wall, called parietal pleura is adherent to the thoracic wall, diaphragm and mediastinal structures
2. Inner wall, called visceral pleura, is adherent to outer surface of the lung
3. Each layer of pleura has a mesothelial and connective tissue component. The connective tissue (CT) of the parietal pleura fuses with the endothoracic fascia on the deep surface of the intercostal muscles. The CT of the visceral layer fuses with the CT of the lung
4. Function: the space is filled with serous fluid which lubricates, allowing the lung to move without friction and cohesion keeps lung in contact with thoracic wall
B. Parietal pleura - shaped like a domed, half cone
1. Cervical pleura - superior to level of the 1st ribs
2. Costal pleura - related to the deep surface of the ribs
3. Diaphragmatic pleura - related to the superior surface of the diaphragm
4. Mediastinal pleura - related to lateral aspects of structures in the mediastinum
5. Reflections - areas where one pleural surface is continuous with another
6. Recesses - potential spaces where the lung and its visceral pleura do not fill the parietal pleural surfaces meeting at a reflection
a. Costodiaphragmatic recess
b. Costomediastinal recess
7. Surface projections of the parietal pleura
C. Surface projections of the pleura
Right Left
Sternoclavicular joint Cross cross
Rib 2 meet at midline meet at midline
Rib 4 continues near midline deviates to left
Rib 6 deviates to right
Rib 8 midclavicular line midclavicular line
Rib 10 midaxillary line midaxillary line
Rib 12 neck of rib neck of rib
1. Pleura can extend beyond the limits of the bony thorax
a. Superior to 1st rib
b. Inferior to neck of 12th rib
c. Inferior to the angle between the 7th rib and the xiphoid process on the right side
2. Pulmonary ligament - the thickened connection of the parietal and visceral pleura, inferior to the root of the lung and ending in a free lower edge
3. Suprapleural membrane (Sibson’s fascia )- dome-like sheet of connective tissue (C T) attached to transverse process of C7 and R1 - helps support the cervical pleura
D. Visceral pleura - simply follows surface of the lung. Its form and surface projections can be considered as that of the lung - continuous with the parietal pleura at the root of the lung
E. Blood supply
1. Parietal pleura - can be considered the same as the somatic wall
a. posterior intercostal vessels
b. internal thoracic vessels
i. anterior intercostal branches
ii. anterior mediastinal branches
2. Visceral pleura - considered similar to the lung
a. bronchial aa.
b. pulmonary vessels
F. Innervation
1. Parietal pleura - similar to body wall
a. intercostal nn. - most areas including external diaphragmatic pleura
b. phrenic nn. - mediastinal and central diaphragmatic pleura
c. nerves contain sensory fibers for touch, pressure, pain etc.
d. some sympathetic fibers reach the parietal layer
2. Visceral pleura - similar to lung
a. no sensory endings for pain etc.
b. branches of pulmonary plexus
G. Lymphatics
1. Parietal pleura - drain adjacent body wall, diaphragm and mediastinum
2. Visceral pleura - drain with lungs
III. LUNGS
A. Shape and size
1. Conical shape with mediastinal side flattened
2. Left lung is "taller" than the right
3. Right lung is "broader" than the left
4. Apex - superior, rounded end
5. Base - flattened, inferior end
6. Surfaces
a. costal
b. diaphragmatic
c. mediastinal - has cardiac notch on left
d. vertebral
e. cervical
7. Dark coloration depends on amounts of accumulated dust, carbon particles, etc.
B. Root of the lung (hilum--T5-7) - contains structures passing between the mediastinum and the lung - specific relationships vary on the two sides
1. Bronchi - most dorsal structures
2. Pulmonary arteries - between bronchi and vv.
3. Pulmonary veins - most ventral structures
4. Bronchial arteries - branches of aorta or right intercostal aa.
5. Branches of pulmonary plexus - autonomic nn.
6. Lymphatics and nodes
7. On left, aa. is highest; on right, eparterial bronchus is higher
C. Lobes and fissures
1. Oblique fissure on both right and left lungs
2. Transverse (horizontal) fissure on right lung only
3. Right lobes
a. superior
b. middle
c. inferior
4. Left lobes
a. superior - includes lingular portion of superior lobe
b. inferior
D. Surface projections of the lung
Right Left
Sternoclavicular joint Cross Cross
Rib 2 meet at midline meet at midline
Rib 4 continues near midline deviates to the left
Rib 6 midclavicular line midclavicular line
Rib 8 midaxillary line midaxillary line
Rib 10 edge of vertebral column edge of vertebral column
Oblique fissure - base of scapular spine, Rib 5 (midaxillary), to bony end of Rib 6
Horizontal fissure - Rib 5 (posterior axillary line), follows Rib 4 to sternum
E. Pulmonary tree (bronchial tree)
1. Trachea
a. specific relations discussed in neck or in superior mediastinum
b. D-shaped structure, cartilage with C T between
c. Bifurcates at level of sternal angle (lower in inspiration)
d. Carina - cartilage at the bifurcation - forms internal landmark, lowest extent of cough reflex
e. Trachea located near midline - shifted slightly to right by aortic arch
2. Main bronchi (primary bronchi)
a. Pass from tracheal bifurcation to root of lung
b. Right bronchus
i. shorter, straighter, larger, more direct line with trachea
ii. because of its angle, inhaled objects favor right side
iii. divides into superior, middle and inferior lobe bronchi
iv. superior lobe bronchus is "eparterial bronchus"
c. Left bronchus
i. smaller, longer
ii. divides into superior and inferior lobar bronchi
3. Segmental bronchi - next order of branching to BPS
4. Segmental bronchi > bronchioles > terminal bronchioles > respiratory bronchioles > alveolar ducts > alveolar sacs > alveoli
5. Blood supply of bronchi
a. Bronchial aa. - supply lower trachea and bronchi and nearby esophagus (may anastomose with pulmonary aa)
i. left bronchial aa. - arises from aorta (usually two)
ii. right bronchial aa. - arises from 1st right aortic intercostal to ICS 3
b. Bronchial veins - drain larger bronchi into azygous system
F. Pulmonary arteries
1. right is longer than left
2. branches follow bronchial tree
G. Pulmonary veins
1. develop intersegmentally - do not follow bronchial tree
2. form lobar pulmonary veins
a. middle and superior lobar veins unite on right side
b. two pulmonary veins from each lung drain to heart
H. Bronchopulmonary segments
1. Definition: a segmental bronchus, its associated aa., vv., and lung tissue
2. Contains
a. segmental bronchus
b. bronchiole aa
c. pulmonary aa
d. intersegmental pulmonary vv.
3. Right lung
a. superior lobe - apical, posterior, anterior segments
b. middle lobe - lateral and medial segments
c. inferior lobe - superior, anterior basal, posterior basal, medial basal, and lateral basal segments
4. Left lung
a. superior lobe
i. superior division - similar to right except for a fused apicoposterior segment
ii. lingular division - superior and inferior segments
b. inferior lobe - similar to right except fused anteriomedial segment can exist
I. Innervation of lungs
1. Anterior and posterior pulmonary plexus located at root of lungs
2. Continuous with cardiac and esophageal plexuses
3. Contain
a. postganglionic sympathetic fibers (T1-4 original levels) as direct visceral branches of the trunk
b. vagal parasympathetic fibers
c. afferent fibers from both sympathetic and vagal sources
4. Parasympathetic fibers for bronchial constriction and secretions
5. Sympathetic fibers for bronchial dilation and vasoconstriction
6. Afferent fibers for stretch, cough reflex, "pain"
7. Pulmonary aa - baroreceptors
8. Pulmonary vv. - chemoreceptors
J. Lymphatics
1. Plexi
a. Superficial - deep to visceral pleura
b. Deep - next to arteries and divisions of bronchial tree
2. Nodes
a. Pulmonary - associated with intrapulmonary bronchi
b. Bronchopulmonary - near hilus
c. Tracheobronchial - near tracheal bifurcation
d. Bronchomediastinal - along trachea
i. afferent - anterior mediastinal and retrosternal vessels
ii. efferent - to thoracic duct, right lymphatic duct or confluence
3. Lower left lung drains to right tracheobronchial nodes