Flashcards in The Thorax - RR Deck (382):
What are the false ribs of the thorax?
8-12 --> 8,9,10 join cartilage immediately superior.
11,12 --> floating ribs, have free anterior end.
What are the main features of a typical rib? (3-9)
Head --> Articulates with body of corresponding vertebra and vertebra superior.
Tubercle --> Articulates with transverse process of corresponding vertebra.
Body or shaft --> Twisted about its long axis, turning sharply forward at ANGLE.
What ribs are seldom fractured?
1,2 --> protected by clavicle.
11,12 --> seldom fractured
What is the site of a typical rib fracture?
The angle - point of greatest curvature.
What does fracture of a well protected rib (like 1) suggest?
Severe chest trauma
What is important to keep in mind about rib fractures in children?
Thoracic and abdominal organ trauma may occur in children without rib fracture.
What is thoracotomy?
A segment of rib can be excised to gain access to the thoracic cavity by longitudinally splitting the periosteum.
Osteogenic cells of the periosteum regenerate bone to fill the defect.
What are the atypical ribs and what is their special feature?
Ribs 1 and 10-12 --> Articulate with only 1 vertebra each.
What is the cervical rib?
Elongated transverse process of C7, often attached to 1st thoracic rib by fibrous band.
What happens in thoracic outlet syndrome?
The subclavian artery or inferior trunk of the branchial plexus is stretched or compressed between the anterior and middle scalene muscles, often when the arm is hanging at the side.
What are the symptoms of thoracic outlet syndrome?
Numbness and tingling in the extremity --> simulates cervical disc problem.
What may be the cause of thoracic outlet syndrome?
1. Cervical rib
2. Hypertrophied scalene muscles
3. Anomalous fibrous band
What are the main parts of the sternum?
1. Jugular notch
5. Xiphoid process
Describe the manubrium.
Easily palpable jugular (suprasternal) notch on superior border at root of neck.
With what does the manubrium articulate?
1. With clavicle
2. 1st costal cartilage
3. Superior part of 2nd costal cartilage
4. Body of sternum
With what does the body of the sternum articulate?
2. 2-7 costal cartilages
3. Xiphoid process
What is important to remember about the body of the sternum?
Has marrow cavity --> used for bone marrow biopsy.
What may the xiphoid process be?
Bifid or perforated.
At what vertebral level can the xiphoid process palpated?
In infrasternal angle at T10 vertebral level.
What does the xiphisternal joint mark?
Inferior border of heart and superior border of liver.
What is the MC congenital defect of the thoracic wall?
What happens in pectus excavatum?
A caving in of the sternum and costal cartilages during development --> may impair cardiac and respiratory function.
When does pectus excavatum become apparent?
Usually during puberty.
What is pectus carinatum or pigeon chest?
A congenital protrusion of the sternum and costal cartilages that may occur alone or as part of syndrome --> sometimes impairing respiration and decreasing endurance.
What should we consider when we see a traumatic sternal fracture?
Evaluation for heart injury.
What does the sternal angle mark?
Level of 2nd costal cartilage --> useful in counting ribs.
Besides 2nd costal cartilage, what else does the sternal angle indicate?
1. Marks the bifurcation of the trachea
2. Beginning and end of the arch of the aorta
3. Division in superior/inferior mediastinum
What are the main joints of the thoracic wall?
2. Costovertebral joints of head of rib and costotransverse
What is the clinical image in paralysis of the intercostal muscles?
Intercostal tissues being sucked in during inspiration and ballooning out during expiration.
When do we insert the needle in order to block an intercostal nerve or to enter the pleural cavity?
Block an intercostal nerve --> Near the inferior border of the rib superior to the intercostal space.
To enter the pleural cavity --> Near the superior border of the rib inferior to the intercostal space.
What is the sequence of artery, vein, and nerve in the intercostal space?
VAN --> inside the costal groove.
What is the origin of the intercostal nerves and where are they located?
Anterior rami of first 11 spinal nerves in intercostal spaces --> lie between internal and innermost intercostal muscles.
Where is cardiac pain often referred to?
To the medial side of the left arm, because the T1 and T2 dermotomes continue there from the thoracic wall.
Communication of the intercostobrachial nerve (T2) with the medial brachial cutaneous nerve (C8, T1) is one pathway for referred pain.
Why is 1st intercostal nerve short?
Because most of anterior ramus of T1 joins anterior ramus of C8 to form lower trunk of brachial plexus.
What is the intercostobrachial nerve?
Lateral cutaneous branch of 2nd intercostal nerve (T2).
What is the subcostal nerve?
Anterior ramus of T12 spinal nerve and lies immediately below rib 12.
What are the thoracoabdominal nerves?
7-11th intercostal nerves --> leave intercostal space anteriorly to supply anterolateral abdominal wall.
What dermatome lies at the level of the nipple and what at the level of the umbilicus?
The T4 dermatome --> nipple
The T10 dermatome --> umbilicus
What are the intercostal blood vessels?
Include 11 pairs of posterior intercostal arteries and veins and one pair of subcostal arteries and veins.
What ribs does mammary gland overlie in young adult female?
Where is the nipple located in young adult females and males?
Over 4th intercostal space.
How is mammary gland supported?
By suspensory ligaments that attach to overlying skin.
What is the relationship of breast with pectoralis major?
Separated from deep fascia over pectoralis major (pectoral fascia) by retromammary space --> allows movement on chest wall.
How many lobes does the mammary gland have?
15-20 --> each drained by a single corresponding lactiferous duct that opens on nipple.
What is the lactiferous sinus?
Expansion for each lactiferous duct deep to nipple, serves as milk reservoir during lactation.
What is interesting to keep in mind about the mammary gland?
May extend into axilla as axillary tail.
What is the blood supply of the breast?
Mammary branches of:
1. Internal thoracic
3. Lateral thoracic arteries.
Veins are tributaries of internal thoracic, intercostal, and lateral thoracic veins.
What is the innervation of the breast?
By intercostal nerves T2-T6.
Discuss the lymphatic drainage of the breast.
1. 75% of lymph passes to axillary lymph nodes but also
2. Lymph nodes near the clavicle
3. Lymph nodes draining upper abdominal wall
4. From medial quadrants --> parasternal nodes along internal thoracic artery or across midline to OPPOSITE breast.
During a radical mastectomy what nerves are especially vulnerable?
1. The long thoracic nerve --> lies on the superficial surface of serratus anterior muscle --> Paralysis of the serratus anterior --> prevents abduction of the arm above 90 degrees --> winged scapula.
2. The thoracodorsal also may be injured.
What is the costodiaphragmatic recess?
The lowest part of the pleural cavity and may accumulate abnormal pleural fluid.
What are the 2 main pleural recesses?
1. Costodiaphragmatic recess
2. Costomediastinal recess
What procedures may lead to open pneumothorax?
1. Posterior approach to the kidney near rib12.
2. Liver biopsy
3. Nerve block of the stellate ganglion
4. or branchial plexus at the root of the neck.
5. IV line insertion into the subclavian vein.
How is thoracentesis performed?
A needle or incision over a lower intercostal space in the midaxillary line penetrates:
2. Superficial fascia
3. Serratus anterior
4. Intercostal muscles
5. Endothoracic fascia
6. Parietal pleura
During thoracentesis, ,what nerve is prone to injure?
The long thoracic nerve.
Parietal or visceral pleura injury is painful?
Parietal due to SOMATIC afferent innervation.
Visceral pleura is not painful due to VISCERAL afferent innervation.
What pain on deep inspiration suggest pleural origin
Pain in the thorax, abdomen, or shoulder.
To what can shoulder pain be referred?
To pain from irritated diaphragmatic pleura.
Where can pain related to pneumonia or cancer of the lower lobe be referred to?
To the anterior abdominal wall.
What is the carina of the trachea?
A posterior process of last tracheal cartilage that internally marks bifurcation of trachea as seen with bronchoscope.
What does distorted carina often indicate?
Metastatic lung cancer.
Discuss the features of right main bronchus.
1. Crossed superiorly by arch of azygos vein --> passing to superior vena cava.
2. Aspirated objects will more likely enter wider, more vertical right main bronchus.
Discuss the anatomical location of left main bronchus.
Passes inferior to arch of aorta and anterior to esophagus.
What is the eparterial bronchus?
Another name for right upper lobe bronchus because it arises above level of pulmonary artery.
What structures divide within substance of each lung?
1. One main bronchus
2. One pulmonary artery
3. 2 Pulmonary veins
What are the 3 surfaces of the lung?
What is the root of the lung and what is the hilum?
Root --> structures passing between the lung and mediastinum.
Hilum --> Region where structures enter or leave the lung.
What is the pulmonary ligament?
Double-layered vertical fold of pleura extending inferiorly from hilum to base.
What are the possible neural complications of a pancoast tumor?
1. Involve the sympathetic chain and interrupt sympathetic innervation to the head --> Horner.
2. May also involve the inferior roots of the branchial plexus, producing upper-extremity symptoms.
What are the symptoms of Horner syndrome?
1. Ipsilateral anhidrosis
How is the right lung divided?
Into upper, middle, and lower lobes by oblique and horizontal fissures.
At what level is the horizontal fissure?
At level of the 4th rib and costal cartilage.
Is right lung shorter or longer than left?
Shorter due to higher right dome of diaphragm.
How many lobar and segmental bronchi does the right lung contain?
3 lobar (secondary) and 10 segmental (tertiary) bronchi.
How is left lung divided?
Into upper and lower lobes at oblique fissure.
What is the cardiac notch of the left lung?
A notch that lies over heart and pericardium anteriorly.
What is the lingula of the left lung?
Lingula forms inferior margin of cardiac notch and corresponds to middle lobe of the right lung.
How many lobar and how many segmental bronchi has the left lung?
2 Lobar and 8-10 segmental.
What is a bronchopulmonary segment?
Pyramidal regions of lung supplied by one segmental (tertiary) bronchus and its accompanying segmental branch of pulmonary artery.
Drained in part by intersegmental veins used as surgical landmarks.
How many bronchopulmonary segments are in the right lung and how many in the left?
10 in the right lung and 8-10 in the left depending on fusion of segments.
What is the clinical importance of the cardiac notch?
Allows a needle to enter the pericardium and heart through the left 5th intercostal space without damaging the lung and pleura.
What are basically the bronchopulmonary segments?
Independent functional and surgical units.
How does gravity moves foreign material to different bronchopulmonary segments of the right lung depending on the patient's position?
Standing/sitting patient --> Posterobasal segment is involved.
Supine --> Superior segment of the lower lobe.
Right-sided recumbent position --> Middle lobe or posterior segment of the right upper lobe.
--> Patient can be optimally positioned for postural drainage of an infected bronchopulmonary segment aided by percussion of the chest wall over the segment.
What is the clinical importance of intersegmental veins?
They are surgical landmarks for segmentectomies.
What attaches left pulmonary artery to aortic arch?
Ligamentum arteriosum - remnant of the fetal ductus arteriosus.
What is the course of the right pulmonary artery?
Crosses UNDER arch of aorta to reach hilum of right lung.
What is the role of bronchial arteries?
Supply oxygenated blood to bronchial tree and visceral pleura.
How may bronchial arteries are on the left, and how many on the right?
2 on the left --> descending aorta
1 on the right --> often branching from 3rd right posterior intercostal artery.
What is the relationship of bronchial veins with lung cancer?
Lung cancer may metastasize to the spinal cord and brain through venous system if cancer cells enter a bronchial vein and pass to azygos system --> vetrebral venous plexuses --> ascend to the dural venous sinuses in the cranial cavity.
Discuss the lymphatic drainage of the lung.
1. Superficial lymphatic plexus
2. Deep lymphatic plexus
3. Bronchopulmonary nodes
4. Tracheobronchial nodes
5. Right and left bronchomediastinal lymph trunks
What is the superficial lymphatic plexus?
Lies just beneath visceral pleura and drains toward hilum.
What is the course of deep lymphatic plexus and what does it include?
Follows bronchial tree to hilum and includes peribronchial pulmonarry nodes lying within the substance of lung.
What sites drain to bronchopulmonary nodes and where are these nodes located?
At root of lung --> receive drainage from both superficial and deep plexuses.
What sites drain to tracheobronchial nodes and where are these nodes located?
Located at tracheal bifurcation and receive lymph from bronchopulmonary nodes.
What sites drain to right/left bronchomediastinal lymph trunks and what is their course?
The tracheobronchial nodes.
Eventually reach a venous angle, either directly or through right lymphatic duct and thoracic duct, respectively.
What is interesting to keep in mind about the lymphatic drainage of the upper and lower lobe of the left lung?
Upper lobe --> Left bronchiomediastinal trunk
Lower lobe --> Right bronchomediastinal lymph trunk
What is the nerve supply of the lungs?
Pulmonary plexuses contain:
3. Visceral afferent fibers
Derived from the deep cardiac plexus.
What do the parasympathetic fibers produce in the lung?
Come from the vagus nerve --> bronchial constriction + mucus secretion.
Discuss the SNS innervation of the lung.
Post ganglionic fibers from UPPER 5 thoracic sympathetic ganglia --> Relax bronchial smooth muscle and constrict pulmonary vessels.
What is the role of the visceral afferent fibers from vagus nerves?
1. Sensitive to stretch and participate in reflex control of respiration.
2. End in bronchial mucosa and participate in cough reflex.
When does the laryngotracheal (respiratory) diverticulum form?
During week 4 in floor of the pharynx.
What separates developing larynx and trachea from pharynx and esophagus?
The tracheoesophageal septum
In what does esophageal atresia result?
What is the week of development of the lung buds at caudal end of laryngotracheal tube?
Week 5 --> growing into splanchnic mesoderm surrounding foregut to give rise to primary, secondary, and tertiary bronchi by week 6.
Why esophageal atresia leads to polyhydramnions?
Esophageal atresia prevents the fetus from shallowing and absorbing amniotic fluid in the small intestine.
What is a possible complication of tracheoesophageal fistula and esophageal atresia?
What may lead to an acquired tracheoesophageal fistula?
What are the 4 periods of the development of the lung?
3. Terminal sac
What weeks does the pseudoglandular period comprise?
What structures are formed during pseudoglandular period?
Conducting system as far as terminal bronchiole.
Is birth during pseudoglandular period compatible with life?
What weeks are comprised in the canalicular period?
What structures are formed during the canalicular period?
Terminal bronchioles give rise to respiratory bronchioles --> each of which divides into alveolar ducts and respiratory vasculature forms.
Is birth during canalicular period compatible with life?
Some infants may survive with intensive care --> Some terminal sacs (primitive alveoli) develop toward end of period.
What weeks are comprised during the terminal sac period?
Week 26 till birth
What happens during the terminal sac period?
More terminal sacs develop and pulmonary surfactant is produced by type II alveolar cells (pneumocytes).
What weeks are comprised in the alveolar period?
Week 32 of gestation through age of 8 years (when alveolar form and mature).
What do we give to prevent neonatal respiratory distress syndrome (hyaline membrane disease)?
What is the role of the serous fluid between the visceral and parietal pleura?
Links volume of lungs with movements of diaphragm and thoracic wall and facilitates respiration.
What is the target group of spontaneous pneumothorax?
Occurs in tall, slender male smokers under 40. (Also Marfan syndrome patients).
--> Air enters the pleural cavity because of rupture of a bleb on a diseased lung.
What is important to keep in mind about tension pneumothorax?
May fatally compromise cardiopulmonary function.
Where does mediastinum shifts in atelectasis and where in tension pneumothorax?
Atelectasis --> Towards affected lung.
Tension pneumothorax --> Away from affected lung.
What happens in fat embolism syndrome?
1-3 days following long bone fracture or orthopedic surgery -->
1. Acute respiratory failure
2. CNS dysfunction
What are the risks of thoracocentesis through lower intercostal space?
1. Injury to diaphragm and live on the right.
2. Injury to diaphragm and spleen on the left.
Where does the right dome of the diaphragm arch?
Superiorly to 5th rib.
Where does the left dome of the diaphragm arch?
To the 5th intercostal space.
What is the innervation of the diaphragm?
1. Motor and sensory innervation from phrenic nerves.
2. EXCEPT for peripheral part with sensory supply from LOWER INTERCOSTAL nerves.
What cord segments are responsible for the diaphragm innervation?
C3,4,5 --> phrenic nerve.
Which are the diaphragm openings?
1. Vena caval T8
2. Esophageal T10
3. Aortic T12
Do diaphragm movements affect aortic blood flow?
They don't affect aortic blood flow because aortic hiatus is posterior to the diaphragm.
What do we do for chronic intractable hiccups (sometimes)?
Crushing one phrenic nerve.
How do we see a paralyzed diaphragm on radiograph?
Paralyzed hemidiaphragm rises during inspiration (elevated by abdominal viscera).
From what structures is the diaphragm derived?
1. Septum transversum
2. Pleuroperitoneal membranes
3. Esophageal mesentery
4. Body wall mesoderm
Where does the septum transversum lie?
Lies in cervical region in week 4, adjacent to 3,4,5 CERVICAL SOMITES --> Account for innervation of diaphragm by phrenic nerve (C3,4,5).
What is the course of the septum transversum?
Descends into thoracic region between developing heart and liver due to differential growth.
To what structures does the septum transversum give rise?
To central tendon and to myoblasts that migrate into pleuroperitoneal membranes and esophageal mesentery.
What are the pleuroperitoneal membranes?
Mesodermal tissue of posterior body wall that closes pericardioperitoneal canals by fusing with septum transversum and dorsal mesentery of esophagus.
How is intraembryonic body cavity divided?
3. Peritoneal cavities
By pleuropericardial and pleuroperitoneal membranes.
What part of the diaphragm is formed by the esophageal mesentery?
Middle of the diaphragm posteriorly.
--> Invaded by myoblasts that give rise to crura of diaphragm.
What part of the diaphragm is formed by body wall mesoderm?
Peripheral part of diaphragm as a result of excavation by developing lungs and pleural cavities.
What is the MC congenital malformation of the diaphragm?
A congenital diaphragmatic hernia.
How does congenital diaphragmatic hernia result?
Developmental failure of the pleuroperitoneal membrane in week 6, usually posterolaterally on the left side (foramen of Bochdalek).
What is the complication of congenital diaphragmatic hernia?
Fatal pulmonary hypoplasia --> Abdominal viscera herniate into the thorax and compress the thoracic viscera.
What is the central tendon of the diaphragm?
Receives insertions of sternal, costal, and lumbar parts --> Cloverleaf-shaped central aponeurotic part.
Where does the median arcuate ligament attach?
Unites crura across midline anterior to aorta.
Where does the mediaL arcuate ligament attach?
Body to transverse process of L1 --> Arches over psoas major.
Where does the lateral arcuate ligament attach?
Transverse process of L1 to rib12 --> Arches over quadratus lumborum.
Where does the right crus of the diaphragm attach?
Bodies of L1-L3 --> Larger and longer than left crus.
Where does the left crus attach?
Bodies of L1-L2
At what vertebral level is the vena cava hiatus?
T8 --> Through central tendon --> Transmits inferior vena cava and right phrenic nerve.
At what vertebral level is the esophageal hiatus?
T10 --> Through right crus.
What passes through the esophageal hiatus?
2. Vagal trunks
3. Esophageal branches of left gastric vessels
At what vertebral level is the aortic hiatus?
T12 --> Between crura behind median arcuate ligament --> Posterior to diaphragm so movements don't affect aortic flow.
What passes through the aortic hiatus?
2. Thoracic duct
3. Maybe azygos vein
What is the mediastinum?
Median partition of tissue lying between paired pleural sacs that contains all thoracic organs EXCEPT lungs..
How is mediastinum divided?
B. Inferior :
How is mediastinum divided in superior and inferior?
Horizontal plane at the sternal angle till T5.
What are the boundaries of anterior mediastinum?
Body of sternum to pericardium.
What are the contents of anterior mediastinum?
Lymph nodes and loose connective tissue --> May contain much of thymus in children.
What are the boundaries of middle mediastinum?
Mostly enclosed within pericardial sac.
What are the contents of middle mediastinum?
1. Pericardium and heart
2. Roots of great vessels
3. Primary bronchi
4. Phrenic nerves
5. Arch of azygos vein
What are the boundaries of posterior mediastinum?
Pericardium and sloping posterior surface of diaphragm to bodies T5-T12.
What are the contents of posterior mediastinum?
1. Descending thoracic aorta
2. Esophagus + esophageal plexus
3. Thoracic duct
4. Azygos + hemiazygos veins
What are the contents of superior mediastinum?
1. Remnants of thymus
2. Right + Left brachiocephalic veins uniting to form superior vena cava.
3. Arch of aorta and its branches
6. Thoracic duct
7. Phrenic and vagus nerves
Why is a goiter prevented from expanding superiorly?
Due to the insertions of the sternothyroid muscles.
--> Only inferior extend (retrosternal goiter).
--> Possibly compressing trachea and causing dyspnea, or esophagus/SVC.
What is important to remember in resecting a parathyroid adenoma?
The inferior parathyroid glands may be found in the superior mediastinum because they migrate with the thymus during development.
What may result in fatal mediastinitis?
Spread of neck infection.
What must be examined if a tracheostomy in a child is to be performed?
Because a child's neck is relatively short, the LEFT brachiocephalic vein may be superior to the jugular notch, where it is at risk during a tracheostomy.
Give an overview of the pericardium.
1. Sac that encloses the heart, proximal segments of the great arteries and terminal segments of the great veins.
2. Consists of outer fibrous layer and inner serous sac.
What is the fibrous pericardium and with what is it fused inferiorly?
1. Tough, indistensible, fibrous external layer.
2. Fused inferiorly with central tendon of diaphragm.
Describe the pericardial cavity.
Potential space normally empty except for a small amount of lubricating fluid that allows heart to move freely as it beats.
What are the 2 pericardial sinuses?
1. Oblique pericardial sinus
2. Transverse pericardial sinus
How are the pericardial sinuses formed?
By reflection of visceral layer of serous pericardium onto parietal layer at roots of great vessels entering and leaving the heart.
What is the oblique pericardial sinus and how is it formed?
A blind pocket dorsal to left atrium --> formed by pericardial reflections surrounding pulmonary veins and venae cavae.
What is the transverse pericardial sinus?
Passageway between right and left sides of pericardial cavity:
ANTERIOR to SVC
POSTERIOR to ascending aorta + pulmonary trunk
SUPERIOR to pulmonary veins and left atrium
Is transverse pericardial sinus clinically important?
YES -Critical to cardiothoracic surgeon who must identify and clamp great vessels.
What is the Tx of cardiac tamponade?
How is pericardiocentesis performed?
Using a needle introduced in the left infrasternal angle OR
in the 5th intercostal space near the sternum.
What makes the intercostal approach in pericardiocentesis possible?
It is possible because of the cardiac notch of the left lung and a corresponding pleural notch.
What are the risks of the 2 approaches of pericardiocentesis?
1. Approaching through the infrasternal angle --> risks damage to the diaphragm and liver.
2. Approaching through the 5th intercostal space --> risks internal thoracic and coronary arteries + the parietal pleura
What has cardiac tamponade in common with tension pneumothorax?
Both cause distended neck veins and hypotension.
How can pericarditis be differentiated from MI?
Friction rub is present and pain is affected by positioning.
What are the 3 components of the heart wall?
1. Outer epicardium
2. Middle myocardium
3. Inner endocardium
What are the components of the heart skeleton?
Consists of annuli fibrosi --> 4 firmly connected, fibrous connectivee tissue rings.
What is the role of the heart skeleton?
1. Provides rigid attachment for myocardial fiber bundles and for pulmonary, aortic, and AV valves.
2. Separates and electrically insulates myocardial fibers of atria from those of ventricles.
What is the base of the heart?
The posterior aspect and is largely formed by left atrium.
What is the apex of the heart?
Blunt inferolateral projection formed by left ventricle.
What part of the heart forms largely the diaphragmatic surface?
The left ventricle.
What parts of the heart form largely the sternocostal surface of the heart?
Right ventricle along with smaller parts of right atrium and left ventricle.
What forms the right border of the heart?
2. Right atrium
What forms the left border of the heart?
Mainly by left ventricle with small contribution from left auricle.
What separates the atria from the ventricles?
What heart chamber is most likely to be injured by an anterior chest wound or blunt trauma?
The right ventricle.
What is the radiological left border of cardiovascular shadow?
The arch of the aorta, the pulmonary trunk, the left auricle, and left ventricle.
Where does the apex beat lie?
To the left of the sternum in the 5th intercostal space.
What is the sinus venarum of right atrium?
Smooth-walled part derived from incorporation of right horn of sinus venosus.
To what does the right auricle corresponds and what does it contain?
Corresponds to part of primitive atrium of embryonic heart --> contains pectinate muscles.
What is the crista terminalis of the right atrium?
Separates sinus venarum from rough-walled part - superior end marks location of SA node.
What does the fossa ovalis mark?
It marks the site of foramen ovale through which blood passes from right atrium to left atrium before birth.
What is the role of the valve of the IVC in right atrium?
In embryonic heart --> directs blood from inferior vena cava through foramen ovale into left atrium.
What are the 2 parts of the left atrium?
A smooth-walled part and a rough-walled part (auricle).
From what is left atrium's smooth walled part derived?
From incorporation of pulmonary veins.
From what is rough-walled part of the left atrium derived and what does it contain?
From embryonic atrium --> contains pectinate muscles.
What are the 3 common structures of left and right ventricle?
1. Papillary muscles
2. Trabeculae carneae
3. Chordae tendineae
What are the papillary muscles in right and in left ventricle?
RV --> Anterior + Posterior + Septal
LV --> Anterior + Posterior according to location of their bases
What are the chordae tendineae?
Fibrous strands connecting papillary muscles to cusps of AV valves?
What is the conus arteriosus (infundibulum) of the right ventricle?
Smooth-walled outflow tract to pulmonary trunk --> separated from ventricle proper by supraventricular crest.
What is the septomarginal trabecula (moderator band)?
Trabecula carnea that carries fibers of right bundle branch to anterior papillary muscle.
What is the aortic vestibule of the LV?
Smooth-walled outflow tract.
What is the ventricle proper of the LV?
Wall two to three times thicker than that of RV.
What are the 3 cusps of the tricuspid valve?
Anterior + Posterior + Septal
What are the cusps of the mitral valve?
Anterior + Posterior
What are the cusps and the sinuses of the pulmonary valve?
Right + Left + Anterior semilunar cusps and pulmonary sinuses named according to their fetal position.
What are the cusps of the aortic valve?
Right + Left + Posterior semilunar cusps and aortic sinuses named according to their fetal position.
What structures are related to left and right aortic sinuses?
The orifices of left and right coronary arteries, respectively.
What is the role of the conducting system of the heart?
Sequences atrial + ventricular contractions --> Atria contract together, followed by ventricles contracting together from APEX towards BASE.
What are the cells of the conducting system of the heart?
Specialized cardiac muscle cells.
What is the EXACT location of the SA node?
Lies in right atrial wall at superior end of crista terminalis near SVC.
What artery supplies the SA node?
The SA nodal artery, usually brach of RCA.
What is the exact location of the AV node?
Located in interatrial septum near opening of coronary sinus in right atrium.
What is the blood supply of the AV node?
Supplied by atrioventricular nodal artery, usually brach of RCA.
Describe the AV bundle.
Begins at atrioventricular node and divides in muscular interventricular septum into left and right bundle branches --> which comprise subendocardial Purkinje fibers in ventricular wall.
What is the ONLY connection between myocardium of atria and ventricles?
The AV bundle when it descends through fibrous cardiac skeleton to reach membranous interventricular septum.
What is the blood supply of the AV bundle?
Mainly by anterior interventricular branch of the LCA (left anterior descending artery).
What is the role of the septomarginal trabecula of RV in the conducting system of the heart?
Carries fibers of right bundle branch.
When is blood flow through coronary arteries the greatest?
During diastole while myocardium is relaxed and aortic valve is closed.
Mention the 3 major variations in arterial blood supply of the heart.
1. Right dominant distribution -->MC.
2. Left dominant distribution.
3. Balanced distribution.
What characterizes the right dominant distribution?
Posterior interventricular artery arising from RCA.
What characterizes left dominant distribution?
The circumflex branch of LCA gives off posterior interventricular artery.
What characterizes balanced distribution?
Both right and left coronary arteries supply posterior interventricular arteries.
What 3 blood vessels are used as grafts for a blocked coronary artery?
1. Internal thoracic artery
2. Radial artery
3. Major saphenous vein
What 3 categories of patients may have silent myocardial ischemia?
3. Heart transplant patients
What are the branches of the RCA?
1. Artery to SA node
2. Artery to AV node
3. Right marginal
4. Posterior interventricular (posterior descending)
What area of the heart is supplied by RCA?
3. Posterior 1/3 of interventricular septum
4. SA/AV node
What are the main branches of the LCA?
1. Anterior interventricular (left anterior descending)
3. Left marginal
4. Posterior ventricular
What areas of the heart are supplied by LCA?
3. Anterior 2/3 of interventricular septum
4. Part of right ventricle
5. Obtuse margin of left ventricle
6. Posterior part of LV
Where does the coronary sinus drain the cardiac veins?
What is the largest cardiac vein?
The coronary sinus.
Of what vein is the coronary sinus a direct continuation?
Of the great cardiac vein.
What is the EXACT location of the coronary sinus?
Lies in posterior part of coronary sulcus and opens into RA.
What veins does coronary sinus receive?
Except anterior and smallest as tributaries.
What is the course of the great cardiac vein?
Ascends beside the anterior interventricular artery.
What is the course of the middle cardiac vein?
Ascends alongside the posterior interventricular artery.
What is the course of the small cardiac vein?
Runs along acute margin of RV --> Paralleling right marginal artery.
What surface of the heart is drained by posterior vein of the LV?
Diaphragmatic surface of the LV.
Of what is oblique vein of LA a remnant?
Of embryonic left sinus horn.
What area of the heart is drained by anterior cardiac veins and where?
Sternocostal surface of RV directly into RA.
What happens with the smallest cardiac veins?
Arise in walls of heart and open directly into chambers.
Where does the nerve supply of the heart originate?
Largely in cervical area --> Attesting to original location of cardiogenic area at cranial end of embryonic germ disc.
From where does the SNS innervation of the heart derive?
Mostly from cardiac branches of cervical sympathetic ganglia with some thoracic cardiac nerves.
From where does the PNS innervation of the heart derive?
From cervical and thoracic cardiac branches of vagus nerves.
What is the course of the visceral afferent fibers of the heart?
WHEN travel with SYMPATHETIC fibers --> Pass through cervical cardiac nerves and down cervical sympathetic trunk to cell bodies in posterior root ganglia of upper thoracic spinal nerves.
For what do visceral afferent fibers account?
For referred pain from heart.
When is cardiac pain referred?
When visceral afferent fibers from the heart enter the same spinal cord segment as somatic afferent fibers from involved dermotomes (T1-T5).
Besides the usual spots (substernal, left pectoral, left shoulder, and medial side of the left arm), where else may cardiac pain referred to?
3. Right upper extremity
because of the heart's early development in cardiogenic and neck regions.
What is the role of visceral afferent fibers that travel with PARASYMPATHETIC fibers?
Provide sensory input for important cardiac reflexes.
When and where does development of the heart begin?
In splanchnic mesoderm of cardiogenic area at end of week 3.
What is the initial process for the heart development?
Fusion of two endocardial tubes into a single heart tube that bends on itself forming U-shaped bulboventricular loop that includes one atrium + one ventricle.
How is partitioning of atrioventricular canal accomplished?
By growth of endocardial cushions in dorsal and ventral walls of atrioventricular canal and their fusion.
What is the result of partitioning of atrioventricular canal?
Divides common canal into right and left atrioventricular canals.
What is the septum primum?
Crescent-shaped membrane that grows into atrium from posterosuperior wall to fuse with endocardial cushions of AV canal.
What is the ostium primum?
Opening between primitive atria that is gradually closed by growth of septum primum.
What is the ostium secundum?
Opening created by programmed cell death in septum primum, providing new R-->L shunt between atria.
What is the septum secundum?
Second crescent-shaped membrane that grows from roof of atrium along right side of septum primum.
Does septum secundum completely partition atrial cavity?
No --> It stops growth and does NOT completely partition atrial cavity.
What is the foramen ovale?
Opening at inferior margin of septum secundum resulting from its failure to fuse with endocardial cushions of atrioventricular canal (septum intermedium).
Along with ostium secundum, what does foramen ovale allow?
What percentage of the population has probe patent foramen ovale?
25% but it is clinically insignificant.
Where does ASD occur usually?
In area of foramen ovale and is relatively common.
When does muscular interventricular septum formation begin and when does it end?
Begins as muscular ridge in week 4 with increase in height due to expansion of the ventricles on each side but stops in week 7 --> leaving septum incomplete.
How is membranous interventricular septum formed?
By fusion of truncoconal ridges with muscular interventricular septum + extension from endocardial cushion.
When is the partitioning of the ventricles complete?
By week 8.
What is the MC congenital heart defect what does it usually involve?
VSD and usually involves membranous interventricular septum.
What is the mechanism of VSD?
Failure of truncoconal ridges and endocardial cushion to fuse with muscular interventricular septum.
How is partitioning of the conus cordis and truncus arteriosus accomplished?
By fusion of paired truncoconal ridges to form aorticopulmonary septum.
How is the partitioning of conus cordis and truncus arteriosus take place?
In SPIRAL --> ensuring that aorta and pulmonary trunk twist around each other in a helix.
How does persistent truncus arteriosus result?
From complete failure in development of truncoconal ridges + related membranous interventricular septum.
What is the main complication of persistent truncus arteriosus?
Allow blood from BOTH ventricles to leave the heart through a COMMON vessel with partially oxygenated blood passing both to lungs and systemic circulation.
With what syndrome is persistent truncus arteriosus sometimes associated?
With DiGeorge syndrome (absent parathyroid gland and thymus).
How does transposition of the great arteries result?
From failure of truncoconal ridges to spiral as they partition outflow tract.
Mention 3 congenital heart defects that result in EARLY cyanosis.
1. Persistent truncus arteriosus
2. Trasposition of the great arteries
3. Tetralogy of Fallot
With what must transposition of the great arteries be accompanied to be compatible with life?
By VSD or ASD or a PDA.
How is tetralogy of Fallot caused?
By unequal partitioning of outflow tract by truncoconal ridges.
What are the four defects of tetralogy of Fallot?
1. Pulmonary stenosis
3. Overriding aorta
What do we see on an X-ray in tetralogy of Fallot?
A boot shaped heart due to RVH.
How many aortic arches usually develop?
6 pairs, one for each pair of pharyngeal arches.
Are all the aortic arches present simultaneously and can anyone be absent?
Not all present simultaneously --> The 5th pair may be absent
What are the derivatives of the 3rd aortic arch?
Proximal part forms common carotid artery.
Distal part forms internal carotid artery.
What are the derivatives of the 4th aortic arch?
Right arch forms proximal part of the subclavian artery.
Left arch forms part of the arch of the aorta
What are the derivatives of the 5th aortic arch?
What are the derivatives of the 6th aortic arch?
Right arch --> proximal part of right pulmonary artery.
Left arch --> proximal part of left pulmonary artery.
How does PDA result?
From failure of ductus arteriosus to close after birth, alone or in combination with other cardiac defects.
What is the main complication of PDA?
Will cause blood flow from aorta to pulmonary artery because of considerable difference in pressure between the 2 vessels --> May cause obstructive pulmonary vascular disease because of incr. blood flow.
What are the 2 types of coarctation of the aorta?
1. Preductal (occurs with PDA)
With what condition is preductal coarctation associated?
What does postductal coarctation require for survival?
Development of extensive collateral circulation in postductal coarctation to deliver blood into descending aorta.
What does preductal coarctation require?
Early surgery for survival.
What characteristic radiographic image is sometimes seen in coarctation of the aorta?
Rib notching from enlarged intercostal arteries.
What is the EXACT course of the ascending aorta?
Begins within pericardial sac at aortic valve and ascends behind sternum to end in arch of aorta at level of sternal angle.
What are the 2 only branches of the ascending aorta?
LCA and RCA.
What is the EXACT course of the aortic arch?
Lies within superior mediastinum in front of trachea, arching over right pulmonary artery and left main bronchus.
To what does the aortic arch give rise?
2. Left common carotid
3. Left subclavian arteries
that ascend in relation to trachea.
To what other artery may aortic arch give rise?
To thyroid ima artery.
What is the course of the thyroid ima artery and is there any clinical importance?
Ascends in midline of neck --> where it may be damaged during thyroid surgery or tracheotomy.
Is arch of the aorta prone to aneurysms, and if yes, how are they revealed?
Yes - May be revealed by pulsatile sewlling at jugular notch or hoarseness.
What are the important branches of the descending thoracic aorta?
1. Lower 9 pairs of posterior intercostal arteries and subcostal arteries.
2. 2 or more bronchial arteries
3. 2 to 5 esophageal arteries
From where does the supreme (superior) intercostal artery arise?
From costocervical trunk of subclavian artery.
What does the supreme (superior) intercostal artery supply?
The first two posterior intercostal arteries.
What is the course of the internal thoracic artery?
Arises in root of neck and descends vetrically just lateral to sternum.
What are the main branches of internal thoracic artery?
1. Anterior intercostal arteries to first five or six intercostal spaces.
2. Musculophrenic artery --> terminal branch to the diaphragm and 7th to 9th intercostal spaces.
3. Superior epigastric artery.
What is the course of the superior epigastric artery?
Terminal branch descending in the rectus sheath to supply abdominal wall and anastomose with inferior epigastric artery.
Where does the right brachiocephalic vein begin?
In union of right internal jugular and subclavian veins.
What does the right brachiocephalic vein receive?
Right internal thoracic vein + right supreme intercostal vein as tributaries.
Where does the left brachiocephalic vein begin?
In union of left internal jugular + subclavian arteries (left venous angle).
What is the course of the left brachiocephalic vein?
Descends obliquely to right behind manubrium.
What does the left brachiocephalic vein receive?
1. Left internal thoracic vein
2. Left supreme
3. Superior intercostal veins
4. Inferior thyroid veins
How is superior vena cava formed?
By the union of left and right brachiocephalic veins.
Where EXACTLY does superior vena cava enter the right atrium?
Behind 3rd right costal cartilage.
What does the SVC receive before it enters the pericardial sac?
Arch of azygos vein.
How can a left SVC result?
From persistence of the left anterior and common cardinal veins + degeneration of the right anterior and common cardinal veins.
Where does the left SVC drain?
Into the RA via coronary sinus.
How is the inferior vena cava formed?
By union of common ileac veins.
What is the course of the IVC?
Passes through diaphragm at level of T8 and pierces pericardial sac to end in RA.
How does left brachiocephalic vein develop?
From anastomosis between anterior cardinal veins.
From where is the proximal part of the IVC derived?
From proximal part of right vitelline vein.
From where is SVC derived?
From right anterior and common cardinal veins.
What is the role of the azygos system of veins?
Drains most blood from posterior thoracic wall.
What are the components of the azygos system?
Variable longitudinal veins lying across thoracic vertebral bodies.
If either SVC or IVC is obstructed, what does azygos system of veins form?
Caval-Caval anastomosis between the two.
With what important plexus does azygos system of veins communicate?
With vertebral venous plexus.
What referred pain do the phrenic nerves transmit?
From pericardium, mediastinal pleura, and pleural and peritoneal coverings of central diaphragm to base of neck + shoulder.
What is the course of the phrenic nerves?
Descends through middle mediastinum between fibrous pericardium and mediastinal pleura.
What is the course of the right vagus nerve?
Descends on right side of trachea --> posterior to root of right lung --> onto posterior esophagus --> contributing to esophageal plexus.
What is the course of the left vagus nerve?
Descends across left side of aortic arch --> posterior to root of left lung ---> onto anterior esophagus --> esophageal plexus.
What are the main branches of vagus in thorax?
1. To cardiac + pulmonary + esophageal plexuses.
2. Left recurrent laryngeal nerve.
What is the course of the left recurrent laryngeal nerve?
Curves below arch of aorta to left of ligamentum arteriosum --> ascends between trachea and esophagus.
What may perisistent hoarseness indicate?
An intrathoracic left laryngeal nerve lesion.
With what visceral fibers is pain from thoracic viscera carried? (only)
Pain from thoracic viscera is carried only in visceral afferent nerve fibers accompanying sympathetic fibers.
How is stellate (cervicothoracic) ganglion formed?
The 1st thoracic sympathetic ganglion is often fused with inferior cervical ganglion to form cervicothoracic (stellate) ganglion.
How are visceral branches from upper 5 thoracic sympathetic ganglia distributed?
Through aortic, pulmonary, and esophageal plexuses.
What are basically the thoracic splanchnic nerves?
Visceral branches from T5-T12 sympathetic ganglia to abdominal organs.
What fibers do the thoracic splanchnic nerves contain?
Preganglionic sympathetic fibers, which pass through their respective paravertebral ganglia to synapse in abdominal prevertebral ganglia.
Where are the bodies of the thoracic splanchnic nerves?
T5-T12 posterior root ganglia --> general visceral afferent nerve fibers.
Mention the 5 main autonomic plexuses of the thorax.
1. Superficial cardiac
2. Deep cardiac
What is the location of the superficial cardiac plexus?
Below the arch of the aorta.
With what plexuses does superficial cardiac plexus communicate?
1. Deep cardiac plexus
2. Coronary plexus
What is the location of the deep cardiac plexus?
Below the arch of the aorta and bifurcation of the trachea.
What is the location of the coronary plexus?
Along coronary arteries.
What is the role of the coronary plexus?
Provides innervation to heart.
What is the location of the pulmonary plexus?
Divided into anterior and posterior plexuses at roots of lungs.
What is the role of the pulmonary plexus?
Constitutes innervation of the lungs.
What is the location of the esophageal plexus?
Anterior and posterior surfaces of esophagus.
What does the esophageal plexus form at lower end of esophagus?
Anterior and posterior vagal trunks.
What is the main difference between paravertebral and prevertebral ganglia?
Paravertebral ganglia --> sympathetic chain ganglia.
Prevertebral ganglia --> ganglia at major branches of abdominal aorta.
From what ganglia does greater splanchnic nerve arise?
From what ganglia does lesser splanchnic nerve arise?
From what ganglia does LEAST splanchnic nerve arise?
What are the two structures responsible for the lymphatic drainage of the thorax?
1. Bronchomediastinal lymph trunk
2. Thoracic duct
What is the location of the bronchomediastinal lymph trunk?
Formed in superior mediastinum.
What are the afferents of the bronchomediastinal lymph trunk?
3. Tracheobronchial nodes
What are the efferents of the bronchomediastinal lymph trunk?
Thoracic duct or subclavian vein on left side.
Right lymphatic duct or subclavian vein on right side.
What is the location of the thoracic duct?
Begins at cisterna chyli --> ascends through aortic hiatus --> posterior and superior mediastina to end in root of neck.
What are the afferents of thoracic duct?
1. Body below respiratory diaphragm
2. Lower right and all left posterior intercostal nodes
3. Left jugular subclavian + bronchomediastinal lymph trunks
What are the efferents of thoracic duct?
Union of left internal jugular and subclavian veins --> left venous angle.
What may result from a thoracic duct injury in the thorax?
What is the curved path of the esophagus?
Starts left of midline --> pushed right by aortic arch --> inclines back toward left near diaphragm.
What are the 4 thoracic esophageal constrictions?
1. Origin at cricopharyngeus part of inferior pharyngeal constrictor.
2. Point where esophagus is crossed by arch of aorta and left main bronchus.
3. Point behind left atrium when left atrium is enlarged.
4. Point where esophagus passes through diaphragm (esophageal hiatus at T10).
What is clinically important about esophageal constrictions?
Are likely sites for shallowed foreign bodies to lodge and for strictures to develop after shallowing corrosive fluids.
What is to the right of the esophagus in superior mediastinum?
Only terminal part of the azygos vein --> easing surgical approach to mideasophagus from right.
What is anterior to the esophagus in posterior mediastinum?
Left main bronchus + pericardium + LA.
What is left above and posterior below the esophagus in posterior mediastinum?
Descending thoracic aorta.
What is the blood supply of the esophagus?
UPPER 1/3 --> Inferior thyroid.
MIDDLE 1/3 --> Esophageal branches of the aorta.
LOWER 1/3 --> Left gastric and inferior phrenic.
What is the venous drainage of the esophagus?
UPPER 1/3 --> Inferior thyroid vein.
MIDDLE 1/3 --> Azygos vein.
LOWER 1/3 --> Left gastric vein.
What innervates the upper esophagus?
Voluntary muscle --> recurrent laryngeal nerves.
What innervated middle and lower esophagus?
The esophageal plexus.
What is the lymphatic drainage of the esophagus?
UPPER --> Deep cervical nodes of the neck.
MIDDLE --> Posterior mediastinal nodes.
LOWER --> Left gastric nodes of the abdomen (through the esophageal hiatus).
What does the multiple lymphatic drainage of the esophagus tell us?
Esophageal cancer may metastasize in multiple directions.
Bilobed lymphoid organ lying behind sternum in superior mediastinum.
What is the blood supply of the thymus?
1. Internal thoracic
2. Inferior thyroid
What is the venous drainage of the thymus?
Largely by left brachiocephalic.
What nerves are in danger in thymectomy?
The phrenic nerves.