Thorax and Mediastinum Flashcards
0
Q
The spleen is on the _______.
A
Left
1
Q
The liver is on the _______.
A
Right
2
Q
What is the purpose of the thoracic inlet?
A
It is how the thoracic cavity communicates with the front of the neck. .
3
Q
What is the thoracic inlet bounded by?
A
The thoracic inlet is bounded by T1, the first pair of ribs, and the upper margin of the manubrium. The inlet slopes downward and is occupied on each side by the apices of the lungs and pleura and the neurovascular structures for the upper limbs. Centrally by the vessels for the head and neck and the trachea and esophagus
4
Q
What is the purpose of the thoracic outlet?
A
The thoracic cavity communicates with the abdomen via the thoracic outlet.
5
Q
What is the thoracic outlet bounded by?
A
It is closed by the diaphragm, bounded by T12, rib 12, the edges of the lower 6 ribs, and the xiphisternal joint
6
Q
What forms the costal margin?
A
Costal cartilages 7-10 join to form the costal margin
7
Q
What makes up the bony skeleton of the thoracic wall?
A
12 thoracic vertebrae, intervertebral discs, 12 pairs of ribs, and sternum
8
Q
What makes up the sternum?
A
- Manubrium: suprasternal notch, clavicular notches
- Body: 4 fused sternebrae
- Xiphoid process: descends into the infrasternal angle
- Intervening cartilaginous joints
9
Q
What is significant about the sternal angle (of Louis)?
A
It is readily palpable and is a reliable landmark for the 2nd costal cartilage (T4 and T5). Ribs and intercostal spaces are counted from here. Sternum is the site for bone marrow biopsy, and median sternotomy for cardiac surgery.
10
Q
What are the costal cartilages of ribs?
A
Of ribs 1-7 - articulate with the sternum (with their facets on the sternum). These are the true ribs
11
Q
What forms the costal margin?
A
Costal cartilages of ribs 8, 9, and 10 articulate anteriorly with the costal cartilages of the adjacent superior rib, to form the costal margin on each side.
12
Q
What are the free ribs?
A
Ribs 11 and 12 are free
13
Q
What are other components of ribs?
A
Head, neck, angle, costal cartilage. The tubercle of the rib is a posterior project at the junction of the neck and shaft. THe angle of the rib is where the rib turns sharply anteriorly
14
Q
What contains the neurovascular bundle of the ribs?
A
The subcostal groove on the shaft
15
Q
Describe the costovertebral joint:
A
It is synovial, the head of the rib articulates with the bodies of 2 adjacent vertebrae and the intervening intervertebral disc, and by the tubercle with the transverse process of the corresponding vertebra
16
Q
Describe the sternocostal joint:
A
It is synovial, between the costal cartilages 2-7 and the lateral margin of the sternum
17
Q
Describe the costochondral joint:
A
They are hyaline cartilaginous joints between ends of costal cartilages and ribs
18
Q
Describe the interchondral joints:
A
Synovial, between cartilages 7-10 at the costal margin
19
Q
Describe the manubriosternal joint:
A
Fibrocartilaginous
20
Q
Describe the xiphisternal joint:
A
Cartilaginous
21
Q
What is the purpose of the joints of the sternum and ribs?
A
They allow for movements of the ribs and sternum which increase the diameters of the thorax during inspiration. Disorders that limit mobility of these joints hamper respiration
22
Q
What is the purpose of costal cartilages? And what happens to them with age?
A
They add considerable resilience to the thoracic cage and protect the sternum and ribs from more frequent fracture. In old age, they may ossify and become radio-opaque (confusing in a chest x-ray).
23
Q
What are the intercostal spaces?
A
The 3 muscles between adjacent ribs that are innervated by intercostal nerves.
24
Describe the path and innervation of VPR (intercostal nerve):
It runs around the chest wall in the neurovascular plane and supplies the intercostal muscles, and the overlying skin by lateral and anterior cutaneous branches. It also supplies the parietal pleura. Nerves 7-11 leave their intercostal spaces and enter the anterior abdominal wall - thoracoabdominal nerves
25
What does the DPR (intercostal nerve) supply?
The kin and muscle of the posterior thoracic wall. A single thoracic spinal nerve supplies a segment of skin from the anterior midline to posterior midline on one side.
26
Clinical note: What will produce complete anesthesia within the middle of 3 intercostal spaces?
Although the distribution of the ventral rami is segmental, overlap of adjacent nerves is so great that section of 3 consecutive nerves is necessary to produce complete anesthesia. Irritation of intercostal nerves may give rise to pain referred to the front of the chest or abdomen. Must inject above and below the nerves b/c of the interaction.
27
Describe the fibers of the intercostal muscles:
External intercostal - medial and inferior (into the pocket)
Internal intercostal - lateral and superior
Innermost intercostal - more mixed fibers, do not need to ID
28
External intercostal muscles are used for:
Normal respiration, inspiration
29
Internal intercostal muscles are used for:
Forced expiration
30
Describe the path of the internal thoracic artery:
Arises from the 1st part of the subclavian a. and descends BEHIND the upper 6 costal cartilages immediately lateral to the sternum. It divides into superior epigastric and musculophrenic arteries.
31
What are the branches of the internal thoracic artery?
1. Anterior intercostal arteries
2. Pericardiophrenic a
3. Posterior intercostal arteries
32
Which artery accompanies the phrenic n?
Percardiophrenic a.
33
Describe the branches of the anterior intercostal a:
- Upper 6 from the internal thoracic a.
- Lower 5 from musculophrenic a.
- Anastomose with posterior intercostal a.
34
Describe the branches of the posterior intercostal a:
- Lower 9 from thoracic aorta
| - First 2 from superior intercostal a.
35
What does the posterior intercostal vein drain into on the right?
Azygos vein
36
What does the posterior intercostal vein drain into on the left?
Hemiazygos system
37
Where do anterior intercostal veins drain into?
The internal thoracic veins.
38
What is the significance of anastomose between the anterior intercostal, posterior intercostal, and superior and inferior epigastric arteries?
They provide an important collateral pathway in obstruction of the thoracic aorta, as in coarctation of the aorta.
39
What is the significance of the superior epigastric a?
It supplies muscle, pleura, breast, and sternum. It is important in open heart surgery, try to preserve.
40
What is the pleural cavity?
Potential space between the visceral and parietal pleura, contains a film of fluid that facilitates movement of lungs
41
Where is the parietal layer continuous with the visceral layer?
At the hilum of the lung. Here the pleura forms a cuff that surrounds the structures entering and leaving the lung in the root of the lung. The PULMONARY LIGAMENT is a loose extension of the cuff below the root of the lung which allows for the expansion of the pulmonary veins
42
What is the parietal pleura innervated by?
Intercostal and phrenic nerves. It is highly sensitive to pain.
43
Costal pleura lines:
The chest wall, separated from the intercostal muscles by the endothoracic fascia - a natural cleavage plane
44
The diaphragmatic pleura covers:
The diaphragm, except over the central tendon
45
The mediastinal pleura covers:
The mediastinum and extends from the sternum to the thoracic spine
46
Cupola covers:
The apex of the lung, it is strengthened by the suprapleural membrane (thickened endothoracic fascia) which is attached to the inner border of the 1st rib and the transverse process of C7.
47
Describe the visceral pleura:
- It closely invests the lung
- Supplied by bronchial arteries
- Autonomic innervation
- Insensitive except to stretching
48
Why is a penetrating injury in the supraclavicular region of the neck dangerous?
The cupola extends 2-3 cm above the level of the medial third of the clavicle so it could puncture the pleural cavity and the lung.
49
What lies behind the cupola on the neck of the 1st rib?
The sympathetic trunk and 1st thoracic nerve. Disease of the apex of the lung can infiltrate the cupola leading to paralysis of the intrinsic muscles of the hand and Horner's syndrome. Atrophy of hypothenar muscles
50
Are there lungs at the level of T8 and T9?
No, the parietal pleura extends lower than the lungs, this is where fluid accumulates in the costo-diaphragmatic recess
51
What is a pleural reflection?
Borders of the parietal pleura are formed at the continuity of the costal, medistinal, and diaphragmatic pleura
52
Where is the costomediastinal recess formed?
The sharp anterior border of the pleura is formed along the line where the costal and mediastinal pleura meet behind the sternum.
53
Where is the costodiaphragmatic recess formed?
The inferior border is the line of union of costal and diaphragmatic pleura.
54
The recesses are not occupied by the lung except during:
Deep INSPIRATION
55
Anteriorly, the lines of pleural reflection meet in the midline behind the sternum and pass vertically downward to the 6th costal cartilage. The inferior pleural edge then crosses the:
- 8th rib in the mid-clavicular line
- 10th rib in mid-axillary line
- 12th rib at the lateral border of the erector spinae
56
Where does the anterior pleural reflection deviate? ANd why?
At the 4-5th costal cartilage, it allows entry to the pericardial cavity without violating the pleural cavity
57
The inferior border of the lung crosses __________ than the pleura.
2 ribs higher
58
Why is the pleural space clinically important?
Usually the 2 pleural layers are in close opposition and the space between them is only a potential one. It may fill with air (pneumothorax), blood (hemothorax), or pus (emphysema). Fluid can be drained from the pleural cavity by inserting a needle thru an intercostal space at the upper border of the rib. The site for insertion is determined by localized the level of the fluid using xray, ultrasound, and percussion. Usually the needle is inserted below the upper level of the fluid in the midaxillary line or posteriorly.
59
Because the parietal pleura is innervated by intercostal nerves, inflammation of the pleura results in pain referred to the:
Cutaneous distribution of these nerves (to thoracic or abdominal walls).
60
Which part of the left lung is analogous to the middle lobe of the right lung?
The lingula
61
Relationships with the lungs - apex:
Projects upward into the neck for 2-3cm above the clavicle
62
Relationships with the lung - base:
Related to the diaphragm
63
Relationships with the lungs - costal surface:
Related to the ribs
64
Relationships with the lungs - mediastinal surface:
Related to the vertebral column and the mediastinum
65
What is the hilum?
Region on the mediastinal surface where structures in the root of the lung enter and leave the lung
66
What is the root of the lung formed by?
Structures entering and leaving the hilum, and that connect the lung to the trachea and heart. This includes the main bronchus, pulmonary vessels, bronchial vessels, nerves and lymphatics.
67
The root is enveloped by pleura that is prolonged inferiorly as the:
Pulmonary ligament
68
R side anterior to the root of the lung is:
Superior vena cava and phrenic nerve
69
R side posterior to the root of the lung is:
The vagus n
70
R side root of the lung, what arches over it?
Azygous vein arches over it
71
L side anterior to the root of the lung is the:
Phrenic n.
72
L side posterior to the root of the lung is the:
Vagus n.
73
L side root of the lung is inferior to:
Arch of the aorta
74
On the left side, describe the arrangement of veins, bronchi, and arteries:
At the entry into the lungs, the superior pulmonary veins are ventral, the bronchi are posterior (dorsal) and the pulmonary arteries are between them
75
How many lobes in the right lung?
3 - upper, middle, lower
76
How many lobes in the left lung?
2 - upper and lower
77
What divides the lung into upper and lower lobes?
The oblique fissure - surface marking of the oblique fissure: course of the 6th rib, or vertebral border of scapula with arm elevated
78
What separates the middle lobe from the upper lobe in the right lung?
Horizontal fissure (extends medially from the oblique fissure) Equivalent of the middle lobe is the lingula in the left lung
79
The trachea descends into the thorax anterior to the:
Esophagus
80
The trachea bifurcates into R and L mainstem bronchi at the level of the:
Sternal angle. Carina is a ridge on the inside at the bifurcation. It is formed by a posterior projection of the last tracheal cartilage
81
Main stem bronchi give off:
Lobar (secondary) bronchi from which the tertiary (segmental) bronchi arise. These aerate the bronchopulmonary segments.
82
How many bronchopulmonary segments in the right lung? Left lung?
R - 10, L - 8
83
How do the right main and left main bronchus differ?
The right main bronchus is wider, shorter, and more vertical than the left. This is important clinically - the greater width and more vertical course of the right main bronchus accounts for the greater tendency for foreign bodies and aspirated material to pass into the right bronchus and right lung.
84
When does the right main bronchus give off the upper lobe bronchus?
BEFORE reaching the lung. After entering the lung, it gives off the secondary bronchus to the middle lobe and continues as the lower lobe bronchus
85
The left main bronchus divides into:
The upper lobe and lower lobe bronchus
86
What can be visualized using bronchoscopy?
The interior of the trachea, the main lobar bronchi, and the commencement of the first segmental divisions
87
Describe the bronchopulmonary segments:
- Anatomical, surgical, and functional units of the lung
- Each segmental bronchus enters the bronchopulmonary segment
- A segment is pyramidal in shape, with apex toward the lung root, and surrounded by CT
- Has a segmental artery, bronchus, lymphatics, and autonomic nerves
- Segmental pulmonary vein lies between segments, but branches are found within bronchopulmonary segment
- Can be removed surgically
88
What is the blood supply of the lungs?
Bronchial arteries, pulmonary arteries, and pulmonary veins
89
What do the bronchial arteries supply?
From the thoracic aorta, supply the visceral pleura, bronchi, and CT
90
Deoxygenated blood from the right ventricle is carried to the lungs by:
The pulmonary arteries
91
Oxygenated blood returns to the left atrium via:
2 pulmonary veins
92
Where do the pulmonary arteries arise?
At the bifurcation of the pulmonary trunk within the concavity of the aortic arch
93
How does the right pulmonary artery run?
Horizontally to the right behind the ascending aorta and the SVC.
94
How does the left pulmonary artery run?
Passes anterior to the descending aorta
95
How do the pulmonary veins run?
Two veins, superior and inferior, leave each lung and enter the left atrium. They are intersegmental, carry oxygenated blood to the left atrium.
96
What is the nervous supply to the lungs?
From the vagus and sympathetic nerves, which form plexuses in the root of the lung
97
What is the role of the vagus n. in supplying the lungs?
Constrictor to the bronchial m, secretory to mucous glands
98
What is the role of the sympathetic nerves in innervation of the lungs?
Dilate the bronchi (relax the muscle) and reduce secretion
99
Clinical note: Sympathomimetic drugs and parasympathetic antagonists are used in the treatment of _____ and _____. What do they do?
Asthma and COPD - dry up secretion
100
How does the lymphatic drainage work?
Goes to bronchopulmonary lymph nodes in the hilum of the lung, and then to tracheobronchial nodes, then to the thoracic duct (L) or right lymphatic duct
101
What happens during inspiration?
The movements of the chest wall and diaphragm result in an increase in all diameters of the thorax - vertical, anteroposterior, and transverse. The vertical diameter is increased by the contraction and descent of the diaphragm
102
Inspiration also brings about an increase in:
Negative pleural pressure and expansion of the lung tissue. Air flows into the lungs. In expiration, the relaxation of the respiratory muscles and the elastic recoil of the lung reduce thoracic copacity and forces air out of the lungs
103
What is expiration aided by?
Contraction of abdominal muscles which act through the viscera, forcing the diaphragm upward
104
Describe the "pump-handle" movement:
Elevation of ribs 2-7 by the intercostal m. increases the anteroposterior diameter because the body of the sternum moves forward as these ribs are raised. This movement is facilitated by the hinge movement at the manubriosternal joint. If this joint is ankylosed, thoracic expansion is virtually lost and only diaphragmatic respiration is possible.
105
Describe the "bucket-handle" movement:
Elevation of the lower ribs increases the transverse diameter
106
What happens in deep and forced inspiration?
Additional muscles play a role: scalenes, SCM, serratus anterior, and pec minor. This increases the capacity of the thorax. Similarly, in deep expiration, forced contraction of the abdominal muscles aids in expiration
107
The area between pleural sacs, extends from the ________ to the diaphragm.
Thoracic inlet
108
What separates the superior from the inferior mediastinum?
A line drawn between the sternal angle and disc, between T4 and T5.
109
Inferior mediastinum is divided into:
1. Middle mediastinum
2. Anterior mediastinum
3. Posterior mediastinum
110
What is contained within the middle mediastinum?
The heart within the pericardium
111
What is contained within the anterior mediastinum?
Areolar tissue anterior to the heart and behind the body of the sternum, also has the thymus gland
112
What is contained within the posterior mediastinum?
Behind the heart, contains the thoracic aorta, esophagus, thoracic duct, nerves, lymphatics, and blood vessels.
113
Which mediastina are in contact with the superior mediastinum?
Anterior and posterior mediastina are in direct continuity with the superior mediastinum, their separation from it is descriptive, not anatomical.
114
Where is the plane between the superior and inferior mediastinum located?
Passes thru the bifurcation of the trachea, the concavity of the arch of the aorta, and just above the bifurcation of the pulmonary trunk.
115
Where does the superior mediastinum lie?
Behind the manubrium and in front of T1-T4
116
What are the principle contents of the superior mediastinum? (6)
1. Arch of the aorta and roots of its branches
2. Brachiocephalic veins and SVC
3. Vagus and phrenic nn, left recurrent laryngeal n, and sympathetic trunks
4. Trachea and esophagus
5. Thoracic duct
6. Thymus gland
117
The brachiocephalic veins and thymus are located _______ to the arteries.
Anterior
118
Superior mediastinum: Branches of arch of aorta:
The ascending aorta arches backward and to the left reaching its summit midway up the manubrium. Branches into: brachiocephalic trunk, left common carotid artery, left subclavian a.
119
Superior mediastinum: Relationship of brachiocephalic veins:
Internal jugular and subclavian veins join to form the brachiocephalic veins. The left brachiocephalic v. crosses to the right behind the manubrium and joins the R. brachiocephalic v, to form the SVC
120
Superior mediastinum: Pathway of vagus n:
The RIGHT vagus n. crosses anterior to the 1st part of the subclavian a. It descends on the right side of the trachea and then posterior to the root of the lung where it contributes to the pulmonary plexus. The right RECURRENT LARYNGEAL n. loops posterior to the subclavian a.
The LEFT vagus n. descends anterior to the arch of the aorta and then posterior to the root of the lung. It also contributes to the pulmonary plexus. The left RECURRENT LARYNGEAL n. loops posteriorly on the left side of the ligamentum arteriosum and ascends in the trachea-esophageal groove.
121
Superior mediastinum: Pathway of the phrenic nerves (3,4,5):
- R phrenic descends on the lateral surface of the SVC
- L phrenic crosses the arch of the aorta
- Both nerves descend anterior to the roots of the lungs between the fibrous pericardium and the mediastinal pleura
122
WHat is the phrenic n. accompanied by?
The pericardiophrenic vessels
123
What does the phrenic n. innervate?
Diaphragm, sensory to the pericardium and the diaphragmatic pleura
124
What are the contents of the posterior mediastinum?
- Thoracic aorta
- Esophagus and vagal plexuses
- Thoracic duct
- Azygous venous system
- Sympathetic trunks
- Lymph nodes
125
Posterior mediastinum - Describe the pathway of the thoracic aorta:
It starts where the arch of the aorta ends, at T4. At first to the left of the midline, it gradually slants right and leaves the thorax in the midline at T12, passing behind the diaphragm.
126
What are the parietal branches of the thoracic aorta?
- 9 pairs of posterior intercostal aa.
- Subcostal aa.
- Superior phrenic to diaphragm
127
WHat are the visceral branches of the thoracic aorta?
- Bronchial aa, 2 on left, 1 on right
| - To esophagus and mediastinum
128
How does the esophagus extend?
From the cricoid cartilage (C6) to cardiac orifice of the stomach (T10).
129
Which mediastina is the esophagus in?
Traverses the superior and posterior mediastinum. Superiorly, it descends on the anterior surface of the thoracic vertebra to the right of the thoracic aorta, and behind the left atrium. Inferiorly, it curves markedly to the left crossing in front of the aorta and enters the abdomen via the esophageal hiatus of the diaphragm at T10.
130
What is anterior to the esophagus?
Left main bronchus, left main atrium, and diaphragm (in sequence)
131
What is posterior to the esophagus?
Thoracic duct, parts of hemiazygous v, right posterior intercostal a, and aorta near diaphragm
132
Esophageal blood supply comes from:
Inferior thyroid a, thoracic aorta, and left gastric a.
133
Esophageal venous drainage is into:
The inferior thyroid vv., the azygous system, and the left gastric vv. This is a site of portal-system circulatory anastomoses
134
What is the esophagus innervated by?
Esophageal plexus of the vagus n supplies the m. and glands, increasing peristalsis and secretion. After passing behind the root of the lungs, the vagus n divides into branches that form the ANTERIOR and POSTERIOR ESOPHAGEAL PLEXUSES. Just above the diaphragm the fibers of the plexus converge to form anterior and posterior vagal trunks. Each trunk contains fibers from both nerves
135
The anterior plexus is mainly from the ____ vagus.
Left
136
The posterior plexus is mainly from the _______ vagus.
RIght
137
Where are the 3 narrowest parts of the esophagus?
1. Beginning of the esophagus, upper esophageal sphincter, due to cricopharyngeus
2. Where it is crossed by the left main bronchus
3. At its termination
* *These are sites where swallowed foreign bodies are most likely to become impacted
138
Why is the anastomoses between the azygous (systemic) and left gastric (portal) veins of clinical importance?
In portal hypertension, the esophageal veins distend and may rupture, leading to hemorrhage.
139
Posterior mediastinum - Describe the pathway of the thoracic duct:
Thoracic duct begins at the upper end of the CYSTERNA CHILI, a lymphatic sac, which lies between the abdominal aorta and the right crus of the diaphragm. THe thoracic duct then passes upward thru the aortic opening into the posterior mediastinum. It ascends BEHIND the esophagus to T5, where it crosses to the left and then enters the root of the neck. The duct passes laterally behind the left carotid sheath and enters the beginning of the L. brachiocephalic vein.
140
What does the thoracic duct drain?
The lymph of the whole body except that from the right side of head and neck, right upper limb, and right thorax
141
What is the azygous system of veins?
Includes the azygous to the R and the hemiazygous and accessory hemiazygous to the L. Pattern on the L side is highly variable
142
Describe the course of the azygous vein:
Begins in the abdomen by the union of the right subcostal v. + the ascending lumbar v.
Ascends posterior to the esophagus and anterior to the posterior intercostal aa, and arches forward over the root of the R lung to empty in the SVC.
143
What drains into the azygous v?
From posterior intercostal vv.
144
How is the hemiazygous v. formed?
Formed by the union of the L subcostal v. and ascending lumbar v.
145
What does the hemiazygous v. receive?
Lower posterior intercostal veins and crosses anterior to the body of T8 to enter the azygous vein.
146
What does the accessory hemiazygous v. receive?
Receives UPPER intercostal vv and enters hemiazygous v. or crosses to enter the azygous v.
147
What is the location of the thoracic sympathetic trunks?
Located on the necks of the ribs, anterior to the intercostal vessels and nerves. It is the most LATERALLY placed structure in the posterior mediastinum.
The 12 ganglia are connected to spinal nerves via the white and gray communicating rami
148
What forms the stellate ganglion (of the thoracic sympathetic trunk)?
The 1st thoracic ganglion is often fused with the inferior cervical ganglion to form the stellate ganglion.
Branches:
- Postganglionic sympathetic fibers to body wall, join each thoracic spinal nerve
- Postgang fibers from ganglia T1-5, to thoracic viscera: heart, lungs, and esophagus
- Pregang fibers from T5-T12 form the SPLANCHNIC nerves which pierce the crura of the diaphragm and pass to the celiac and renal ganglia from which postgang fibers arise for the abdominal viscera
- Greater splanchnic (from ganglia): T5-10
- Lesser splanchnic (from lower thoracic ganglia)
- Least splanchnic, from T12 ganglion
They course medial to the sympathetic trunks on the bodies of the thoracic vertebrae
149
Where are the lymph nodes of the thorax located?
Along the internal thoracic a, in the posterior mediastinum, on the diaphragm, and in relation to the trachea and aortic arch. THERE ARE LOTS!
150
Where is lymphatic drainage to?
L - to the thoracic duct
| R - to the right lymphatic duct
