CV Lea Thoracic Cavity and Mediastinum Flashcards
(164 cards)
1
Q
Describe the vertebral components of the thorax
A
12 thoracic vertebrae
a. costal facets on bodies of articulation w/rib head
1. superior and inferior demifacets
2. atypical: TV1 and TV10-12 have single facet
b. costal facets on transverse processes for articulation w/right tubercle (TV1-100
2
Q
Describe the ribs of the thoracic wall
A
True ribs 1-7: attach directly to sternum
False ribs 8-10: attach to costal cartilage of rib above and form the infracostal margin
Floating ribs 11-12: not attached to sternum, anteriorly end in muscle
3
Q
Describe anatomical features of typical ribs
A
ribs 3-9
Head - proximal end; articulates w/adjacent vertebral bodies
Neck - between head and tubercle
Tubercle - at jxn of neck and body, articulates w/transverse process
Angle - anterolateral angulation of body just lateral to tubercle
Shaft - mid and distal portion of rib; inferior portion has a concave internal surface, the costal groove, which provides protection for intercostal VAN
Costal cartilage - provides increased elasticity for thoracic wall
4
Q
Describe anatomical features of atypical ribs
A
1st rib is broad, horizontal shaft with pronounced curvature. Head has single facet for TV1. Shaft contains 3 grooves for subclavian a and v and, scalene tubercle
2nd rib has serratus ant tuberosity superiorly
10th rib has single articular facet for TV10 body
11th and 12th ribs have single facet on head and absence of neck/tubercle
5
Q
What are clinical correlations of the rib
A
Rib fractures occur near angle where rib is weakest.
Middle ribs are most often broken.
Flail chest: results from multi broken ribs in 2 or more places and causes a loose segment of thoracic wall which moves paradoxically during resp
6
Q
Describe landmarks of the manubrium
A
Suprasternal notch (jugular) - anterior to TV2/3 intervertebral disc
Clavicular notch - for articulation w/clavicle
Lateral facets for articulation w/costal cartilage of ribs 1 & 2
Articulates w/body of sternum via manubriosternal joint/symphysis
Sternal angle or Angle of Louis is located at manubriosternal joint
7
Q
Describe the body of the sternum
A
Articulates w/ costal cartilages of ribs 2-7
8
Q
Describe the Xiphoid process
A
Cartilaginous but ossifies w/ age.
Lateral demi-facets for articulation w/costal cartilage of rib 7.
Articulates w/ body of sternum via xiphosternal joint/synchondrosis
Note the infrasternal angle
9
Q
What are the clinical correlations of the sternum
A
Sternal angle demarcates articulation of rib 2. A horizontal plane passed from sternal angle to disc between T4-T5 marks the boundary between superior and inferior mediastinum - THE TRANSVERSE THORACIC PLANE
10
Q
What are pectus excavatum and carinatum
A
anterior thoracic wall sunken-in and anterior wall protrusion “pigeon breast”, respectively.
These are congenital malformations of the sternum and ribs
11
Q
What are the borders of the Superior Thoracic Aperture
A
Ant: jugular notch
Lat: 1st rib
Post: 1st thoracic vertebra
12
Q
What is the clinical relevance of the Superior Thoracic Aperture
A
It extends obliquely from 1st thoracic vertebral anteroinferiorly to manubrium. The plural space extends superiorly into the neck.
Injury or surgery within this region may affect plural cavity and lungs i.e. pneumothorax
13
Q
What are the borders of the Inferior Thoracic Aperture
A
Ant: Xiphisternal joint
Lat: costal margin
Post: 12th thoracic vertebrae and 11th&12th ribs
14
Q
Why is the Inferior Thoracic Aperture clinically relevent
A
It extends obliquely from TV12 anterosuperiorly to xiphisternal joint. The plural space extends inferiorly to lie posterior to the abdominal region.
Injury or surgery to this region may affect plural cavity and lungs i.e. pneumothorax
15
Q
Describe the sternocostal joint
A
Articulates costal cartilages and sternum (7 pair)
Joint capsule supported by ant and post radiate ligaments.
1st sternocostal joint is a synchondrosis, permitting no movement (imptn in mechanics of respiration)
2nd-7th sternocostal joints are synovial plane
16
Q
Describe costochondral joints
A
Articulation between rib and costal cartilage.
Synchondroses - very little movement, frequently dislocated in minor trauma
17
Q
Describe the interchondral 8th-10th joints
A
Articulations between costal cartilages of ribs 8-10 w/costal cartilage above
18
Q
Describe costovertebral joints
A
Articulation between rib head w/vertebral bodies, intervertebral disc, and is synovial plane.
Ribs 2-9 artic w/adjacent vert bodies and intervertebral discs; an intra-articular lig extends from crest of the head to intervertebral disc limiting movement of this joint.
Ribs 1,10-12 artic only w/body of same # vertebrae
Radiate ligs support joint capsule
19
Q
Describe costotransverse joint
A
Articu between rib tubercle and vert transverse proc.
Synovial.
Ribs 11 & 12 do not have costotransverse joints
Support lig include: lateral, superior costotransverse lig, constotransverse lig
20
Q
What are the muscles of the thoracic wall
A
EXTERNAL INTERCOSTALS - fibers pass infero-medially.
1. Anteriorly, at costochondral joint, muscle replaced by external intercostal membrane.
INTERNAL INTERCOSTALS - fibers pass inferio-laterally
1. Posteriorly, at angel of rib, muscle replaced by internal intercostal membrane.
INNERMOST INTERCOSTALS -
1. discontinuous sheet of of muscle - transversus thoracis (sternocostalis) anteriorly, innermost intercostal laterally and subcostalis posteriorly.
Neurovascular bundle runs between 2nd and 3rd layers (internal and innermost intercostals)
21
Q
Describe the deep Thoracic Fascia
A
The Endothoracic Fascia is the CT lining entire surface of internal thoracic wall and superior diaphram.
It adheres parietal pleura to thoracic wall.
22
Q
Why is Endothoracic Fascia clinically relevent
A
Provides a cleavage plane between thoracic wall and pleura; important for surgeries requiring access to thoracic cavity
23
Q
Describe the “pump handle motion” of thoracic wall
A
Rotational movement at costotransverse joint causes elevation & depression of most distal (ant) portion of upper ribs.
Bc of inferior slope of distal portions of ribs, ant elevation causes increase in A-P diameter of thoracic wall.
Importance of 1sr rib fixation in mediating this motion.
24
Q
Describe “bucket handle motion” motion of thoracic wall
A
Gliding movement at post (costovertebral & costotransverse) joints causes elevation & depression of lateralmost portions of ribs.
Bc inferior slope of lateral portion of ribs, lateral elevation also causes an increase in transverse diameter of thoracic wall.
25
What increases the vertical diameter of the thoracic wall
Caused by contraction of the DIAPHRAGM
Inn by phrenic n (C3,4,5 keeps diaphragm alive).
Musculotendinous septum separating thoracic and abdominal cavities.
Primary muscle of respiration, especially quiet resp.
Flattens during contraction and increases intrathoracic volume.
During deep expiration the sup surface extends to 4th intercostal space
During forced inspiration diaphragm can move down 10 cm (2 vert bodies).
26
What are the additional muscles of resp that are located in the thoracic wall
```
Serratus post sup and inf (inspiration)
Levator costarum (insp)
external intercostal muscles (insp)
internal intercostal muscles (exp)
transverse thoracic muscles (exp)
```
27
What are other muscles that are included in forced resp
```
Sternocleidomastoid (insp)
scalene (insp)
serratus ant (insp)
pectoralis major and minor (insp)
quadratus lumborum (insp)
anterolateral abd wall muscles (exp)
```
28
Describe innervation of the thoracic wall by intercostal (11pair) and subcostal (1 pair) nerves
Ventral rami of 12 pair of thoracic spinal nn form 11 intercostal nn and 1 subcostal n which travel in costal groove along inferior margin of rib.
Provide inn to muscles of thoracic wall (except levator costarum) & skin of anterolateral thoracic and abd wall.
Provide preganglionic symp n cell processes from spinal cord to symp chain via 14 pair of white rami.
Provide postganglionic symp nerve cell processes to sweat glands, smm in arrector pili, and smm in blood vessels of thoracic & abd wall.
29
Describe the course of intercostal nerves
1st, travel w/in endothoracic fascia.
| Near rib angle, nerve pass between 2nd and 3rd muscle layers
30
What are the branches of intercostal nerves
Rami communicantes, muscular branches, collateral branches given off near angle of rib, course along sup border of rib.
Lateral perforating branch given off near midaxillary line, pierce lateral body wall and divide into ant & post cutaneous branches.
Ant perforating branches - given off near lateral border of sternum, pierce ant body wall and divide into medial and lateral cutaneous branches supplying sensory innervation to thoracic and abd walls
31
Describe atypical intercostal nerves
Ventral ramus T1 divides into large superior trunk which goes to brachial plexus and small inferior trunk (1st intercostal nerve). Intercostal nerve 1 typically has no cutaneous branch, and therefore, T1 dermatome is not represented on thoracic wall.
Lateral cutaneous branch of intercostal n 2 (often 3) forms intercostobrachial cut n, supplying skin & subcutaneous tissue of axilla & medial brachium.
Intercostal nerves 7-11 subcostal n continue anterolaterally as thoracoabdominal nn to supply skin & musculature of abd wall
32
What is the dermatome pattern of the thoracic wall
Nipple - T4 (males)
Xiphoid - T6
Umbilicus - T10 (key dermatome)
Note the C4 dermatome abuts the T2 dermatome anteriorly
33
Describe the vasculature of the thoracic wall via Anterior intercostal arteries (9 pair)
Originate from:
a. Internal thoracic artery (aka internal mammary a.)
1. Branch of subclavian artery.
2. Descends along internal surface of anterior thoracic wall, lateral to sternum.
3. Near 6th or 7th costal cartilage, divides into two terminal branches: musculophrenic and superior epigastric arteries.
4. Directly provides ant intercostals arteries 1-6.
b. Musculophrenic artery - Follows costal arch and provides anterior intercostal arteries to lower intercostal spaces.
34
Describe the courses and branches of anterior intercostal arteries
a. Typically, two anterior intercostal arteries supply each intercostal space.
b. Anastomose with the posterior intercostal arteries.
c. Perforating and muscular branches follow same pattern as nerves.
35
Describe vasculature of thoracic wall via Posterior intercostal aa (11 pair) and subcostal a (1 pair)
Originate from
a. Thoracic (descending) aorta – segmentally provides posterior intercostal arteries 3-11 and subcostal artery.
b. Costocervical trunk (branch of subclavian artery) – provides supreme (superior or highest) intercostal artery which supplies the posterior 1st and 2nd intercostal spaces.
36
Describe courses and branches of post intercostal arteries and subcostal a
a. Travel with and follow the same course and distribution of intercostal nerves.
b. Posterior branch (ramus) – given off near vertebral column; supplies skin, subcutaneous tissue, and intrinsic muscles of back, as well as the spinal cord and vertebral column. (same course and distribution as the doral ramus of a spinal nerve)
c. Collateral branch – given off near angle of the rib.
d. Lateral perforating (cutaneous) branch – given off near the MAL.
e. Anterior perforating (cutaneous) branch – given off in parasternal area.
37
Describe the intercostal veins
1. The 1st–3rd posterior intercostal veins unite to form the superior intercostal vein; drains directly into the azygos (right) or brachiocephalic vein (left).
2. Anterior intercostal veins drain to internal thoracic veins.
3. Posterior intercostal veins drain to the azygos system of veins
38
Describe the neurovascular bundle of intercostal space
“VAN” – orientation of neurovascular bundle within the intercostal space
-Collateral branches travel along superior border of lower rib
39
Why is the neurovascular bundle clinically important
a needle or chest tube inserted into the intercostal space needs to be inserted along the superior border of the rib in order to avoid the main neurovascular bundle.
40
Describe the parasternal nodes
1. Along the lateral border of the sternum.
2. Afferents: anterior thoracic wall, superior portion of the abdominal wall, superior surface of the liver, and the medial portions of the mammary gland.
3. Efferents: bronchomediastinal trunk.
41
Describe intercostal nodes
1. Located near the heads and necks of the ribs.
2. Afferents: posterolateral thoracic wall.
3. Efferents: thoracic duct or right lymphatic duct (1st – 6th spaces); also spread to abdomen and enter cisterna chyli directly (7th – 11th spaces).
42
Describe lateral diaphragmatic (phrenic) nodes
a. Located where phrenic nerves pierce diaphragm.
b. Afferents: central diaphragm, superior surface of liver.
c. Efferents: to parasternal and posterior mediastinal lymph nodes
43
Describe anterior diaphragmatic nodes
a. Located near the xiphoid process on the superior surface of diaphragm.
b. Afferents: anterior diaphragm; superior surface of the liver.
c. Efferents: drain to parasternal nodes.
44
Describe posterior diaphragmatic nodes
a. Located near the aortic hiatus.
b. Afferents: posterior portion of diaphragm.
c. Efferents: posterior mediastinal nodes
45
What are the divisions of the mediastinum
1. Superior Mediastinum
2. Inferior Mediastinum
a. Anterior mediastinum
b. Middle mediastinum
c. Posterior mediastinum
46
What are the boundaries of the Superior Mediastinum
1. Superior: superior thoracic aperture
2. Inferior: transverse plane passing from sternal angle to the disk between TV4-TV5, (transverse thoracic plane).
3. Anterior: manubrium
4. Posterior: anterior surface of vertebral bodies of TV1-TV4
47
Describe the thymus in the superior mediastinum
a. Located directly posterior to manubrium.
b. Primary lymphatic organ in infants, in adults mostly replaced with fatty tissue.
c. Vascular supply – internal thoracic and inferior thyroid vessels.
d. Lymphatic drainage – parasternal and tracheobronchial nodes.
e. Innervation is mainly from the vagus nerve and sympathetic trunk (vasomotor).
48
Describe the brachiocephalic veins in the superior mediastinum
a. Formed posterior to sternoclavicular joint from union of subclavian and internal jugular veins (called venous angle or jugulovenous angle).
b. Left brachiocephalic v. is longer than right and travels transversely across superior mediastinum; right brachiocephalic v. descends just right of manubrium.
49
Describe the superior vena cava in the superior mediastinum
a. Formed from the union of the left and right brachiocephalic veins.
b. Descends to the right of the sternum from the level of the first costal cartilage to the third costal cartilage (where it then enters the right atrium).
50
Describe the aortic arch and its main branches in the superior mediastinum
a. Begins at TV4/TV5 intervertebral space as a continuation of ascending aorta.
b. Arches posteriorly and to the left over the root of the left lung.
c. Ends posteriorly and to the left of midline at the TV4/TV5 intervertebral disc, becoming the descending (thoracic) aorta.
d. 3 main branches (65% of population)
1. Brachiocephalic trunk (artery)
2. Left common carotid artery
3. Left subclavian artery
e. Ligamentum arteriosum passes from the origin of the left pulmonary artery to the arch of the aorta; represents remnant of the fetal ductus arteriosus which shunted blood from the pulmonary trunk to aorta in order to bypass the fetal lungs.
51
What additional structures are located w/in the superior mediastinum
Trachea (see lung lecture for details).
Esophagus (see posterior mediastinum for details).
Thoracic duct (see posterior mediastinum for details).
Sympathetic trunk / sympathetic chain ganglia (see posterior mediastinum for details)
52
Describe the phrenic nerve w/in the superior mediastinum
a. Derived from spinal segments C3, C4, C5
b. Motor innervation to the thoracic diaphragm.
c. Sensory innervation to the diaphragm, mediastinal pleura, and pericardium.
d. Enters thorax from neck by passing anterior to the subclavian artery.
e. Pass anterior to the root of the lungs
53
Describe the Vagus N (CN X) w/in superior mediastinum
a. Enter the superior mediastinum along lateral border of common carotid arteries.
b. Pass posterior to the root of the lung.
c. Carry preganglionic parasympathetic nerve cell processes to thoracic autonomic plexuses.
d. Within superior mediastinum, the left vagus nerve gives off a left recurrent laryngeal nerve which loops underneath the arch of the aorta just lateral to the ligamentum arteriosum, then courses superiorly in the tracheo-esophageal groove to supply laryngeal muscles.
e. As the right and left vagus nerves approach the esophagus in the posterior mediastinum, the left vagus becomes the anterior vagal trunk and the right vagus becomes the posterior vagal trunk.
54
Discuss the clinical relevance of vagus nerve in the superior mediastinum
Due to its position in the superior mediastinum, aortic aneurysm, bronchogenic or esophageal cancer, and/or enlargement of mediastinal lymph nodes can impinge on the recurrent laryngeal nerve and cause hoarseness (due to loss of innervation to laryngeal muscles).
55
What are the boundaries of the anterior mediastinum
a. Superior: transverse thoracic plane
b. Inferior: diaphragm
c. Lateral: mediastinal parietal pleura
d. Anterior: sternum
e. Posterior: anterior surface of pericardium
56
What structures are associated w/anterior mediastinum
thymus, sternopericardial ligaments, fat, lymphatics, connective tissue.
57
What are the borders of the posterior mediastinum
1. Superior: transverse thoracic plane
2. Inferior: diaphragm
3. Lateral: mediastinal parietal pleura
4. Anterior: posterior surface of pericardium
5. Posterior: bodies of thoracic vertebrae TV5-TV12
58
Describe the esophagus w/in posterior mediastinum
a. Originates at the CV6 level as a continuation of the pharynx.
b. Travels through superior mediastinum posterior and slightly left of trachea.
c. Travels right along midline through the posterior mediastinum.
d. Exits thorax through the esophageal hiatus of the diaphragm at TV10.
e. Cervical, Thoracic and Diaphragmatic Constrictions – CV6 pharyngoesophageal, TV4-5 broncho-aortic, TV10 diaphragmatic.
f. Vascular supply – esophageal and bronchial arteries and veins.
g. Lymphatic drainage – posterior mediastinal lymph nodes
59
Describe the Esophageal autonomic plexus sympathetic innervation
i. Preganglionic nerve cell bodies at T2-T6 and processes enter sympathetic chain.
ii. Postganglionic nerve cell bodies in sympathetic chain ganglia.
Many of these nerve cell processes travel with the cardiopulmonary splanchnic nerves ; thus esophageal pain and pain from myocardial infact can present very similarly.
1. Functions: vasoconstriction; decreased gland secretion.
60
Describe the Esophageal autonomic plexus parasympathetic innervation
a. Preganglionic nerve cell bodies in brainstem, processes travel with vagus nerve.
b. Vagus nerve provides numerous esophageal branches.
c. Postganglionic cell bodies in the wall of esophagus.
d. Functions: vasodilation; increased gland secretion; increased peristalsis
61
Describe the descending aorta w/in the posterior mediastinum
a. Continuation of the aortic arch at TV4/TV5 level.
b. Travels through the posterior mediastinum to the left of midline.
c. Exits thorax at TV12 through aortic hiatus of thoracic diaphragm.
62
What are the branches of the descending aorta w/in the posterior mediastinum
1. Posterior intercostal (9 pair) and subcostal arteries
2. Bronchial artery (usually 2 on left and 1 on right)
3. Esophageal artery (3-5 unpaired branches)
4. Pericardial and mediastinal arteries (unpaired)
5. Superior phrenic arteries (1 pair)
63
Describe the azygous system
a. Provides collateral circulation for venous blood between the IVC and SVC.
b. Azygos vein
1. Formed by union of right ascending lumbar and right subcostal veins.
2. Tributaries: right posterior intercostal veins, right esophageal, bronchial, mediastinal, pericardial, hemiazygos, and accessory hemiazygos veins.
3. Travels superiorly on the right side of the vertebral bodies, at TV4 it arches anteriorly over the root of right lung to enter the SVC.
4. Receives tributaries from the IVC.
64
Describe the Hemiazygos
1. Forms from union of left ascending lumbar and left subcostal veins.
2. Receives blood from the inferior 3 left posterior intercostal veins.
3. Travels superiorly through the posterior mediastinum to the left of midline; at TV9 crosses the midline and joins the azygos vein.
65
Describe the Accessory Hemiazygos
1. Begins at medial end of the 4th or 5th intercostal space and descends to TV8 where it cross the midline and joins the azygos vein.
2. Drains left posterior intercostal veins (4 - 8).
66
Describe the thoracic duct
Provides lymphatic drainage for ¾ of the body
a. Begins at LV2 level from a dilated sac called the cisterna chyli.
b. Enters thorax with aorta and ascends along midline; posterior to esophagus.
c. At TV5, crosses to the left of midline and travels in the superior mediastinum to the left of the esophagus. In the neck, the duct passes posterior to left common carotid artery and internal jugular vein to enter the venous angle.
d. In the thorax, the thoracic duct receives the left bronchomediastinal, left jugular, and left subclavian trunks before emptying into the venous angle.
(i. e. junction of left internal jugular and left subclavian veins)
67
Describe the thoracic splanchnic nerves
Headed for preaortic abdominal autonomic plexuses.
a. Composed of preganglionic sympathetic nerve cell processes.
b. Greater splanchnic nerve (T5-T9)
c. Lesser splanchnic nerve (T10-T11)
d. Least splanchnic (T12)
68
What is the tracheobronchial tree
multiple levels of airways branching from trachea to alveoli (18-22 divisions)
69
Describe the trachea
a. Starts at CV6 and runs through neck and superior mediastinum along midline.
b. Bifurcates into right and left primary (main) bronchi at the transverse thoracic plane.
c. Composed of C-shaped hyaline cartilage bars; filled in posteriorly with longitudinal smooth muscle called the trachealis.
d. Carina – last cartilage ring located at bifurcation of trachea; projects into lumen; identifiable on broncoscopy and on chest x-ray.
e. Vascular supply – bronchial, inferior thyroid vessels.
f. Lymphatic supply – paratracheal lymph nodes.
g. Innervation – recurrent laryngeal branches of vagus nerves.
70
Clinical importance of the trachea
Certain pathologies (bronchial carcinomas) cause the carina to be distorted, due to spread of metastatic cancer cells into tracheobronchial (carinal) lymph nodes.
71
Describe the bronchi
a. Left and right primary (main) bronchi.
b. Right bronchus is wider, shorter, and more vertically oriented than the left bronchus; thus foreign objects will typically lodge in the right bronchus.
c. Pass inferolaterally, within the root of the lung.
d. Within lung, primary bronchi give rise to secondary (lobar) bronchi; 3 on the right and 2 on the left.
e. Secondary bronchi further branch into tertiary (segmental) bronchi; 10 segments on the right and 8-10 segments on the left; supply bronchopulmonary segments.
72
What are the general features of the pleura
1. Thin serosal membranes (parietal and visceral) surrounding the lung.
2. Composed of simple squamous epithelial cells + thin layer of loose connective tissue.
3. Provide smooth surface for the lungs to move on during respiration.
4. Secrete serosal fluid (a watery secretion derived from the blood supply) which fills the pleural cavity and provides lubrication.
73
Describe the visceral pleura
1. Intimately adherent to all external surfaces of the lungs (including fissures).
2. Continuous with parietal pleura at the hilum of the lung.
74
Describe the parietal pleura
Lines internal surface of thoracic wall
75
Describe the surfaces of parietal pleura
a. Costal
b. Diaphragmatic
c. Mediastinal – lines mediastinal surfaces; continuous with the visceral pleural at the root of the lung; together with the visceral pleura forms the pulmonary ligament, an inferior extension of pleura which assists in maintaining position of lung in thoracic cavity.
d. Cervical – extends superiorly into the root of the neck reaching its apex slightly superior to the neck of the first rib; reinforced by the suprapleural membrane.
76
What are the lines of reflection of the parietal pleura
a. Vertebral – costal pleura becomes continuous with mediastinal pleura posteriorly.
b. Costal – costal pleura becomes continuous with diaphragmatic pleura inferiorly.
c. Sternal – costal pleura becomes continuous with mediastinal pleura anteriorly.
77
Describe pleuritis and pleurisy
If the pleura membranes become inflamed due to disease (pleuritis or pleurisy), they become rough and no longer slide easily over one another. Pleuritis can be very painful because the parietal pleura receives extensive sensory innervation from intercostal and phrenic nerves. Thus, pain is referred to the area of the thoracic wall or to the point of the shoulder via the phrenic nerve(C3,4,5). The visceral pleura sensory nerves travel with autonomic fibers of the bronchial vessels.
78
Why are the sternal reflections of the parietal pleura clinically relevent
The right sternal reflection passes inferiorly in the medial plane to the level of the 6th costal cartilage; the left sternal reflection passes inferiorly in medial plane to the level of the 4th costal cartilage and then turns laterally and inferiorly to the level of the 6th costal cartilage, creating a notch allowing a small part of the pericardium to be in direct contact with the anterior thoracic wall (bare area of the heart; important for pericardiocentesis).
79
Describe the significance of the cervical pleura to the parietal pleura
The extention of the cervical pleura into the root of the neck is clinically relevant as it may be punctured as a result of wounds in this region.
80
What are the inferior levels of the Parietal and Visceral Pleura Projections
Visceral Pleura Parietal Pleura
Midclavicular Line 6th rib 8th rib
Midaxillary Line 8th rib 10th rib
Scapular Line 10th rib 12th rib
81
What are the pleural recesses
a. Areas of pleural cavity which the lungs do not completely occupy during quiet respiration; two layers of parietal pleura come into contact with each other.
b. Costomediastinal – where mediastinal pleura contacts costal pleura anteriorly.
c. Costodiaphragmatic – where costal pleura contacts diaphragmatic pleura (around periphery of diaphragm).
d. The costodiaphragmatic recess can inadvertently be damaged during procedures or injuries in the abdomen.
82
Describe a pneumothorax
Pneumothorax results from puncture of the visceral or parietal pleura (from a broken rib, ice pick, emphysema etc) This allows air to enter the pleural cavity and this potential space becomes a real space. When the pleural cavity is compromised, the natural elasticity of lung causes it to collapse. Air (pneumothorax), blood (hemothorax), or fluid (hydrothorax; chylothorax) may accumulate in pleural recesses and must be aspirated to allow the lungs to reinflate once the pleura heals.
83
Describe a tension pneumothorax
Tension pneumothorax can have several causes (including trauma, emphysema, lung cancer, COPD etc). It is caused by a loss of integrity of the visceral or parietal pleura resulting in air entering the pleural space, however the air is unable to exit. Thus, a one-way valve is created. With each breath more air accumulates in the pleural space and intrathoracic pressure becomes high. The increased pressure will cause a shift in mediastinal contents to the contralateral side. This compromizes venous return through the superior and inferior venae cavae. Signs of tension pneumothorax include distended neck veins, muffled heart sounds and hypotension due to low cardiac output (Beck’s triad)
84
What are the surface projections of the right lung
1. Apex – extends to level of neck of first rib.
2. At midclavicular line, lung projects inferiorly to rib 6.
3. At midaxillary line, lung projects inferiorly to rib 8.
4. At scapular line, lung projects inferiorly to rib 10.
85
What are the surface projections of the left lung
a. Apex – extends to level of neck of first rib.
b. At midsternal line, lung projects inferiorly to rib 4, then turns inferolaterally to 6th rib at MCL. This sharp lateral turn creates the cardiac notch.
c. At midaxillary line, lung projects inferiorly to rib 8.
d. At scapular line, lung projects inferiorly to rib 10.
86
What is the hilum
the area where all structures enter and leave the lung. (on mediastinal surface of lung.)
87
Describe the lobes and fissures of the right lung
1. 2 fissures (oblique and horizontal) thus,
2. 3 lobes (superior, middle, inferior)
3. The horizontal fissure (of the right lung) follows the course of the 4th rib.
88
Describe the lobes and fissures of the left lung
1. 1 fissure (oblique) thus,
2. 2 lobes (superior, inferior)
3. Cardiac notch and Lingula
89
What are the oblique fissures
The oblique fissures (of right and left lungs) begin posteriorly at the level of the 4th rib. They pass anteroinferiorly, crossing the 4th and 5th intercostal spaces, to the 6th rib and costal cartilage anteriorly.
90
Describe the root of the lung
all the structures that enter or leave the lungs
1. Pulmonary artery
2. Pulmonary veins (superior and inferior)
3. Primary bronchi (right superior lobar bronchus may branch within root of lung)
4. Bronchial arteries and veins (typically 1 on right and 2 on left)
5. Pulmonary plexus of nerves
6. Lymphatic vessels and lymph nodes
91
What are bronchopulmonary segments
1. Smallest functional unit of the lung.
2. Area supplied by 1 tertiary bronchus and associated branch of pulmonary artery.
3. Separated from adjacent segments by connective tissue septa.
4. Pulmonary veins run between bronchopulmonary segments (i.e. intersegmentally)
92
What are the clinical correlations of the bronchopulmonary segments
Diseases of the lung (tumors, abscesses) often localize to a bronchopulmonary segment. These segments can be surgically resected without altering function of other segments.
a. Pneumonectomy = surgical removal of one lung
b. Lobectomy = surgical removal of one lobe of the lung
c. Segmentectomy = surgical removal of a bronchopulmonary segment
93
Describe the pulmonary arteries
1. Carry poorly-oxygenated blood from right ventricle to lungs.
2. Originate from the pulmonary trunk (artery) at the sternal angle.
3. Branch and course with the bronchial airways.
4. Supply distal portions of the tracheobronchial tree (small bronchioles and alveoli) and visceral pleura.
94
Describe the pulmonary veins
1. Superior and inferior veins.
2. Return oxygenated blood to the left atrium.
3. Originate from capillary beds around alveoli and course intersegmentally. (within the intersegmental connective tissue.)
95
What is a pulmonary embolism
results when a blood clot (usually from the lower extremities) enters a pulmonary artery or one of its branches and blocks blood flow to a portion of the lung. This is a life-threatening condition due to decreases in blood oxygenation and obstruction of pulmonary blood flow. Large emboli (blocking the main pulmonary artery) result in acute respiratory distress and often lead to death in a matter of seconds to minutes. Smaller emboli result in pulmonary infarction.
96
Describe systemic circulation
a. Bronchial arteries
1. Originate from thoracic aorta.
2. Typically two on the left and one on the right; the right often originates from 3rd right posterior intercostal artery.
3. Courses with the bronchial tree.
4. Supply trachea and bronchii.
b. Bronchial veins – course with bronchial arteries; terminate in azygos veins.
97
Describe lymphatic drainage of the lungs
1. Pulmonary nodes – within substance of lung; along bronchial tree.
2. Bronchopulmonary nodes – at hilum of lung.
3. Tracheobronchial nodes – at tracheal bifuration.
Note: lymph from the left inferior lobe drains to right tracheobronchial nodes.
Note: lymphatic drainage of the parietal pleura is to the thoracic wall (mainly intercostal, but also parasternal, diaphragmatic, axillary lymph nodes).
98
Describe the superficial (subpleural plexus) lymphatic system
a. Drains visceral pleura and most of lung parenchyma.
b. Drain to bronchopulmonary nodes → superior and inferior tracheobronchial nodes → bronchomediastinal trunk.
c. The bronchomediastinal trunk drains to the thoracic duct on the left and to the right lymphatic duct on the right.
99
Describe the deep pulmonary plexus
a. Drains larger bronchioles and bronchi.
| b. Drain to pulmonary nodes → bronchopulmonary nodes → tracheobronchial nodes → bronchomediastinal trunk
100
Describe lung innervation
1. The lungs receive both parasympathetic and sympathetic innervation.
2. These nerves distribute to the lungs via the anterior and posterior pulmonary plexuses located along the primary bronchi. These plexuses are a continuation of the deep cardiac plexus.
Note: Innervation of the parietal pleural is via nerves supplying the thoracic wall including intercostal and phrenic nerves. Thus, pain is referred to the area of the thoracic wall supplied by the intercostal nerve or to the root of the neck/shoulder via phrenic nerve.
101
Describe sympathetic innervation of the lungs
a. Preganglionic nerve cell bodies are located in T2-T6 segments of the spinal cord, processes enter sympathetic chain.
b. Postganglionic nerve cell bodies located in upper thoracic and cervical
portions of the sympathetic chain ganglia.
c. Postganglionic nerve cell processes form cardiac branches which are called cardiopulmonary splanchnic nerves. (c.f. Most other “splanchnic’’ nerves are preganglionic.) The thoracic cardiopulmonary splanchnic nerves are the primary sympathetic supply to the lungs.
d. Efferent: vasoconstriction; bronchodilation; inhibit gland secretion.
e. Afferent: acute pain.
102
Describe the parasympathetic innervation of the lungs
a. Preganglionic nerve cell bodies in the brain stem, processes travel with the vagus nerve.
b. In the thorax, the vagus gives off thoracic cardiac parasympathetic branches.
c. Postganglionic nerve cell bodies are in the wall of the airways.
d. Efferent: vasodilation; bronchoconstriction; gland secretion.
103
Describe the surface projections of the heart
A. Superior border: 2nd left costal cartilage to 3rd right costal cartilage.
B. Right border: 3rd right costal cartilage to 6th right costal cartilage.
C. Inferior border: 6th right costal cartilage to left 5th intercostal space at MCL (apex).
D. Left border: left 5th intercostal space (MCL) to 2nd left costal cartilage
104
What is the pericardium
A closed fibroserous sac surrounding the heart and origins of great vessels
105
Describe the fibrous pericardium
1. Tough external layer composed of dense connective.
2. Anchors heart and prevents overfilling.
3. The fibrous pericardium is attached:
a. anteriorly to the sternum via sternopericardial ligaments.
b. posteriorly to the fascia of the esophagus.
c. Inferiorly to the central tendon of diaphragm via pericardiacophrenic ligaments.
d. Superiorly with the adventitia (outer connective tissue layer) of the great vessels
106
What is the serous pericardium
1. Thin serosal membranes (visceral and parietal layers)
| 2. A closed sac that provides smooth, frictionless surfaces for the heart to move in during contraction.
107
Describe the Parietal pericardium
a. Composed of simple squamous epithelial cells + thin layer of loose connective tissue
b. Adherant to inner surface of fibrous pericardium
108
Describe the Visceral Pericardium
a. Composed of simple squamous epithelial cells + thin layer of loose connective tissue
b. Lines heart surfaces; continuous with parietal pericardium at great vessels.
c. Forms outer layer of the heart and is called the epicardium.
109
What is the pericardial sac
1. Potential space between parietal and visceral pericardium; contains only a minimal amount of lubricating serous fluid.
110
What is Cardiac tamponade
If the pericardial space is filled with fluid (due to trauma, inflammation) the heart cannot fill to capacity due to the surrounding fluid and the inflexibility of the fibrous pericardium. This condition can be lethal as filling of the heart is reduced. The maximum capacity of pericardial sac is approximately 300 cc.
111
What is a pericardiocentesis
A procedure which removes excess pericardial fluid. Typically, a needle is inserted through the bare area of the heart (left of sternum; 5th or 6th intercostal space) to avoid pleural cavity.
112
Describe the Pericardial sinuses
Separate the arterial and venous ends of the embryonic tubular heart
a. Transverse Pericardial Sinus
1. Anterior border: aorta and pulmonary trunk.
2. Posterior border: SVC and pulmonary veins.
b. Oblique Pericardial Sinus
1. Pocket-like, cul-de-sac posterior to the heart.
2. Bounded by the pulmonary veins and IVC.
113
Why is the Transverse Pericardial Sinus clinically important
Because it allows surgeons to pass a surgical clamp around the major arteries and veins and insert tubes allowing blood to be diverted to a cardiac bypass pump during coronary artery surgery.
114
What is the vascular supply to the Pericardium
1. Pericardiacophrenic arteries (from internal thoracic artery)
2. Pericardiacophrenic veins → internal thoracic veins.
115
Describe the innervation of the Pericardium
1. Phrenic nerve provides sensory innervation to fibrous and parietal pericardium.
2. Visceral pericardium is supplied by the cardiac plexus (see below).
3. CLINICAL CORRELATION: Pain from the pericardium is typically referred to the shoulder/neck region (dermatomes supplied by the phrenic nerves; C3,4,5).
116
Describe pericarditis
If the serous pericardial membranes become inflamed (pericarditis), they become rough and no longer slide easily over one another. Pericarditis can be very painful due to the presence of pain fibers in the fibrous and parietal pericardium (There are no pain fibers in visceral pericardium).
117
Describe the orientation of the heart
1. Due to rotation during development, the left portion of the heart lies posterior and the right anterior.
2. The heart resembles a tipped-over cone. The apex is directed inferiorly and to the left while the base is directed posteriorly.
118
Describe the Great Vessels and Path of Blood Flow for the heart
1. SVC and IVC (enter right atrium); return poorly oxygenated blood.
2. Pulmonary trunk (artery) (exits right ventricle); carries de-oxygenated blood from heart to lungs; divides into right and left pulmonary arteries. (i.e. pulmonary circulation)
3. Pulmonary veins (enter left atrium); superior and inferior veins from left and right lungs carry oxygenated blood from the lungs to the heart.
4. Ascending aorta (exits left ventricle); transports oxygenated blood to the body (i.e. systemic circulation)
119
What are the external sulci of the heart
1. Atrioventricular sulcus (coronary sulcus)
| 2. Interventricular sulci (anterior and posterior)
120
Describe the apex of the heart
a. Directed inferiorly and to the left.
b. Composed entirely of left ventricle.
c. Lies posterior to the left fifth intercostal space (MCL).
121
Describe the base of the heart
a. Formed by left atrium
| b. Directed posteriorly
122
Describe the surfaces of the heart
a. Anterior (sternocostal); 2/3 right ventricle, 1/3 left ventricle.
b. Right; right atrium.
c. Left; left ventricle + auricular appendage
d. Diaphragmatic (in the anatomical position, the heart rests on its diaphragmatic surface); 2/3 left ventricle, 1/3 right ventricle.
123
Describe the borders of the heart
a. Right ; right atrium
b. Inferior ; 2/3 right ventricle, 1/3 left ventricle
c. Left ; left ventricle + auricular appendage
124
What is the function of the heart's fibrous skeleton
a. Provide structural support for heart valves; maintaining patency and preventing distention during heart contraction.
b. Provide attachment sites for the cardiac muscle and for the valve leaflets.
c. Insulates against impulse conduction from atria to ventricles; prevents aberrant spread of impulses.
d. Provides tunnel for passage of the A/V Bundle (of His)
125
What are the components of the fibrous skeleton
1. Fibrous rings (anulus fibrosis) – around the orifices of the 4 heart valves.
2. Fibrous trigones - connections between the fibrous rings.
a. Left fibrous trigone forms a link between aortic and mitral valves.
b. Right fibrous trigone forms a link between aortic, mitral, and tricuspid valves.
3. Membranous portions of interventricular and atrioventricular septa
126
Trace the flow of blood through the heart
1. Deoxygenated blood enters the right atrium through the SVC and IVC.
2. Blood passes through the tricuspid valve to enter right ventricle.
3. Blood exits right ventricle via pulmonary valve and pulmonary trunk – to lungs.
4. Oxygenated blood enters left atrium through pulmonary veins (two left, two right).
5. Blood passes through the bicuspid (mitral) valve to enter left ventricle.
6. Blood is pumped from the left ventricle to the systemic circulation through the aorta.
127
What is the sinus venarum of the right atrium
a. Smooth and thin-walled; derived embrologically from the sinus venosus.
b. Forms the entrances of the IVC, SVC, and coronary veins.
128
What is the auricle of the right atrium
a. Small, ear-like pouch extending anteriorly over the root of the aorta.
b. Represents the embryonic atrium.
c. Wall is lined with pectinate muscles.
129
What is the Crista terminalis of the right atrium
a. Dividing line between sinus venarum and embryonic atrium (auricle).
b. The crista terminalis is demarcated externally by the sulcus terminalis.
130
What is the Fossa ovalis
a. Oval depression in interatrial septa representing the embryonic foramen ovale.
b. Embryologically, the foramen ovale allowed deoxygenated blood returning from body to be shunted directly to the left atrium to bypass the fetal lungs.
131
What is the right atrioventricular orific
a. Opening between right atrium and right ventricle with tricuspid valve.
b. Surrounded by a fibrous ring to maintain shape and patency.
132
Describe the SA and AV nodes
a. SA node is located in the sub-epicardium of the right atrium near the junction of the sulcus terminalis and the SVC.
b. AV node is located in the sub-endocardium of the right atrium, near the opening of coronary sinus.
133
What is the Trabeculae carnae of the right ventricle
a. Muscular ridges of the ventricular wall.
b. Moderator band (septomarginal) – a specialized trabecular muscle passing from the interventricular septum to the anterior papillary muscle.
134
What is the Conus arteriosus
smooth-walled portion of right ventricle chamber leading to pulmonary artery.
135
Describe the right atrioventricular (tricuspid) valve
a. Located posterior to the sternum at the 4th or 5th intercostal space.
b. 3 cusps (anterior; posterior; and septal) attach to fibrous ring.
c. Chordae tendineae connect the valve cusps to the papillary muscles.
d. Papillary muscles attach valve cusps to ventricle wall. When papillary muscle contract they pull the valve leaflets centrally and close the AV orifice. This also prevents the valves from everting into right atrium during ventricular contraction.
136
What are the septa of the right ventricle
1. Membranous interventricular septum – very short, thin walled portion of the IV septum.
2. Muscular interventricular septum – much larger thick, muscular portion of the IV septum
137
Describe the pulmonary (semilunar) valve
a. Located posterior to the sternum at the level of the 3rd costal cartilage.
b. 3 cusps (anterior, left, right) attach to fibrous ring.
c. Free edge of the cusp is thickened to form the nodule and lunule.
d. Pulmonary trunk surrounding each cusp is dilated, forming pulmonary sinuses.
e. When ventricle relaxes, blood in pulmonary trunk reverses its flow. The sinuses fill with blood and the cusps close.
138
Describe the left atrium
1. During development, the proximal portion of the pulmonary vein becomes incorporated into the adult left atrium, forming the larger, smooth-walled posterior portion of the chamber.
2. Receives the 2 superior and 2 inferior pulmonary veins.
3. The auricle represents the embryonic atrium and is lined with pectinate muscles.
4. Interatrial and atrioventricular septa.
5. The valve of the foramen ovale is located in interatrial septa opposite fossa ovalis.
6. Left AV orifice
a. Opening between left atrium and left ventricle with bicuspid (mitral) valve.
b. Surrounded by a fibrous ring.
139
Describe the left ventricle
1. Trabeculae carneae muscles are finer, but more abundant than in the right ventricle.
2. Aortic vestibule: smooth walled portion of the left ventricle leading to the aorta.
140
Describe the Left atrioventricular (bicuspid;mitral) valve
a. Located posterior to the sternum at the 4th costal cartilage.
b. 2 cusps (anterior; posterior) attach to fibrous ring.
c. Chordae tendineae, papillary muscles (see tricuspid valve for action)
141
Describe the aortic (semilunar) valve
a. Located posterior to the sternum at the level of the 3rd intercostal space.
b. 3 cusps (posterior, left, right) attach to fibrous ring.
c. Within the left and right cusps are openings for left and right coronary arteries.
142
What is the importance of heart valve auscultation
1. Valve insufficiency (regurgitation) is the failure of any of the heart valves to close completely.Valve stenosis is narrowing of the valvular orifice.
2. This anomaly can be detected upon auscultation as a heart murmur
143
What are the important sites for ausultation
Pulmonary 2nd ICS; left of sternum
Aortic 2nd ICS; right of the sternum
Tricuspid 4th ICS left of the sternum
Bicuspid(mitral) 5th ICS; left MCL
144
What is the origin of the right coronary artery
a. The RCA originates from the right aortic sinus within the right cusp of aortic valve.
b. The vessels of the heart travel within the loose connective tissue of the epicardium.
145
What are the branches of the RCA
a. Sinuatrial node branch to SA node (60% from RCA; 40% from LCA)
b. Right marginal branch which travels along the inferior border of heart to apex.
c. Posterior interventricular artery which courses along the posterior interventricular sulcus to the apex of the heart. Gives rise to the atrioventricular node branch (80% from RCA; 20% from LCA).
146
What does the RCA supply
a. Right atrium, including the SA and AV nodes.
b. Most of the right ventricle.
c. Some of the diaphragmatic portion of the left ventricle.
d. Posterior 1/3 of the interventricular septum.
147
What is the origin of the left coronary artery
left aortic sinus; within the left cusp of the aortic valve
148
What are the branches of the LCA
a. Anterior interventricular branch courses within anterior interventricular sulcus.
b. Circumflex artery courses within coronary sulcus; gives off a left marginal artery.
149
What does the LCA supply
a. The left atrium
b. Most of the left ventricle
c. Some of the anterior portion of the right ventricle
d. The anterior 2/3 of the interventricular septum
150
What are variations in the arterial supply to the heart
1. Dominance is determined by which artery provides posterior interventricular branch.
a. Right dominance (67%)
b. Left dominance (15%)
c. Codominance (18%)
2. Some people have only 1 coronary artery; others have accessory artery (4%).
151
How does coronary artery disease occur
Coronary artery disease results from reduced blood flow to the heart, which can lead to a myocardial infarction (MI). If blood flow is suddenly occluded (for example, by an embolus), damage or death of the heart muscle occurs. If the occlusion occurs slowly (as in the case of the atherosclerotic process), collateral circulation within the heart may develop and may prevent a MI.
152
What is angina
Ischemia (reduced blood flow) to the heart which is sub-MI threshold produces angina. Angina results in chest pain, tightness of the chest and pain which radiates to the shoulder and inner arm region (mainly the left inner arm).
153
Describe the venous drainage of the heart
The coronary sinus receives most of the venous drainage of the heart; this vein travels within the posterior left coronary sulcus and opens into the right atrium.
154
What are the tributaries of the coronary sinus
1. Great cardiac vein (parallels the anterior interventricular artery).
2. Middle cardiac vein (parallels the posterior interventricular artery).
3. Small cardiac vein (parallels the right marginal artery).
155
What are smaller veins that enter the chambers of the heart
1. Anterior cardiac veins; drain the anterior surface of the right ventricle.
2. Venae cordis minimae; small veins originating in the myocardium drain directly into each chamber.
156
Describe the lymphatic drainage of the heart
A. Most lymph drains to the subepicardial lymphatic plexus.
B. Lymphatic vessels following RCA terminate in anterior mediastinal lymph nodes → left bronchomediastinal trunk.
C. Lymphatic vessels following LCA terminate in inferior tracheobronchial nodes → right bronchomediastinal trunk.
157
Describe the SA node
1. Located in right atrium near the SVC orifice (at crista terminalis).
2. Pacemaker – sets the heart rate between 60-100 beats/minute.
3. From SA node, impulses spread throughout left and right atrium to AV node.
158
Describe the AV node
1. Located in inferior portion of atrial septum; near the opening of the coronary sinus.
2. Once impulses reach AV node, there is a slight pause (in the order of milliseconds) before the impulses spread to the ventricles. This pause, which is maintained by the fibrous skeleton, allows time for atria to fully empty before the ventricles contract.
159
Describe AV conducting bundle ("Bundle of His")
1. Continuation of the AV node through the membranous interventricular septum.
2. After passing through the membranous portion of the interventricular septum, the AV bundle splits into left and right bundle branches.
3. Right bundle branch sends fibers through septomarginal band to anterior papillary muscle.
4. Contraction of ventricles begins at the apex and spreads superiorly.
160
Describe the cardiac plexus
1. Postganglionic sympathetic and preganglionic parasympathetic nerve cell processes to the muscles and nodal tissues of the heart.
2. Distributes via coronary arteries,
3. Superficial plexus (located inferior to aortic arch).
4. Deep plexus (located posterior to arch of aorta; anterior to tracheal bifurcation).
161
What are the sympathetic nerve to the heart
1. Preganglionic nerve cell bodies located in T1-T4 segments of spinal cord; their processes enter sympathetic chain.
2. Postganglionic nerve cell bodies located in upper thoracic and cervical sympathetic chain ganglia.
3. Postganglionic nerve cell processes from the sympathetic ganglia form cardiac branches which are called cardiopulmonary splanchnic nerves.
a. Superior cervical sympathetic cardiac nerve
b. Middle cervical sympathetic cardiac nerve
c. Inferior cervical sympathetic cardiac nerve
d. Thoracic cervical sympathetic cardiac nerves
162
What is the function of the sympathetic nerves to the heart
a. Increase heart rate.
b. Dilate coronary vessels to increase blood flow to the heart.
c. Also carry visceral afferents (acute pain fibers) to upper thoracic spinal segments. ( nerve cell bodies are located in dorsal root ganglia)
163
What are the parasympathetic nerves to the heart
1. Preganglionic nerve cell bodies located in the brain stem and processes travel with the vagus nerve.
2. In the neck, the vagus gives off cervical cardiac parasympathetic branches (superior and inferior) and in the thorax, thoracic cardiac parasympathetic branches.
3. Postganglionic nerve cell bodies are found within the wall of the heart (especially around the SA and AV node).
164
What is the function of parasympathetic innervation of the heart
a. Decrease heart rate
b. Constrict coronary vessels
c. Also may carry visceral afferents (stretch receptors; mainly in right atria)
