Anatomy and Development of the Heart III Flashcards
The most common cyanotic heart defect
Tetralogy of Fallot (TOF)
Caused by a malpositioning of the aorticopulmonary septum
-the cyanosis frequently appears sometime after birth
TOF
In TOF, the aorticopulmonary septum forms in a displaced fashion toward the
Pulmonary side of the truncus arteriosus and conus cordis
This displacement is toward the right side of circulation, which means it is called
Dextrapositioning
The pulmonary trunk is anatomically anterior and to the left of the
Ascending aorta
The dextrapositioning of the aorticopulmonary septum in TOF results in
- ) Pulmonary stenosis
- ) Overriding aorta
- ) Ventricular septal defect
The aorta is abnormally wide and overrides both ventricles
Overriding aorta
Secondary to the major structural defects seen in TOF, we also see
Right ventricular hypertrophy
Because of the pulmonary stenosis, the pressure in the right ventricle is elevated causing right ventricular blood to shunt through the VSD into the overriding aorta. This right to left shunt results in
Cyanosis
When the aorticopulmonary septum does not form, the truncus arteriosus does not become the
Ascending aorta and pulmonary trunk (Persistent Truncus Arteriosus)
In persisten truncus arteriosus, both ventricles empty their blood into the same artery, thus oxygenated and deoxygenated blood are mixed and we see
Cyanosis
Because the absent aorticopulmonary septum would have contributed to the membranous ventricular septum, persistent truncus arteriosus is accompanied by
VSD
This defect is the most common cause of cyanosis presenting immediately at birth
Transposition of the great arteries
In the transposition of the great arteries, the aorticopulmonary septum, which normally forms in a spiral shape is not
Spiraled
What affect does the lack of spiraling have on the positioning of the aorta and pulmonary trunk?
Their positions are reversed
i.e. right ventricle flows to aorta instead of pulmonary trunk
Septal defects are common and PDA is typically seen in infants with
Transposition
The region within the thoracic cavity between the two pleural spaces
Meiastinum
What are the following borders of the mediastinum?
- ) Superior
- ) Inferior
- ) Anterior
- ) Thoracic inlet
- ) Diaphragm
- ) Sternum
What are the following borders of the mediastinum?
- ) Posterior
- ) Lateral
- ) Vertebral column
2. ) Mediastinal Pleura
The mediastinum is arbitrarily divided into a superior and inferior region by an imaginary horizontal plane at the level of
T4
Where does this plane interset
- ) Posteriorly
- ) Anteriorly
- ) Bottom of T4 vertebra
2. ) Manubriosternal junction (sternal angle)
Within the mediastinum this plane is at the level of
the
Tracheal bifurcation
The region above this plane is the
Superior mediastinum
The region below this plane is divided into which three regions?
- ) Middle mediastinum
- ) Anterior mediastinum
- ) Posterior mediastinum
The fibrous pericardium and everything within it comprise the
Middle mediastinum
Between the pericardium and sternum is the
Anterior mediastinum
Between the pericardium and the vertebral column is the
Posterior mediastinum
The structures in the superior mediastinum may be considered in layers. From posterior to anterior the
5 layers are:
- ) Digestive layer
- ) Respiratory layer
- ) Arterial Layer
- ) Venous layer
- ) Glandular layer
The digestive layer is made up of the
Esophagus
The respiratory layer is made up of the
Trachea
Bifurcates at T4 and therefore does not descend below the superior mediastinum
Trachea
The arterial layer is made up of the
- ) aortic arch and its branches
- ) distal ascending aorta
- ) proximal descending aorta
What are the 3 branches of the aortic arch?
- ) Brachiocephalic trunk
- ) Left common carotid artery
- ) Left subclavian artery
The venous layer is made up of the
SVC and its tributaries: the right and left brachiocephalic veins
Formed by the union of the internal jugular and subclavian veins
Brachiocephalic veins
Has a vertical course in line with the SVC
The right brachiocephalic vein
Has an oblique course downward and to the right across the midline
The left brachiocephalic vein
The glandular layer is made up of the
Thymus
Enters the superior mediastinum with the left common carotid artery
Left vagus nerve
The left vagus nerve passes anterior to the aortic arch and gives off the
Left recurrent laryngeal nerve
Passes under the aortic arch distal to the ligamentum arteriosum
Left recurrent laryngeal nerve
Enters the superior mediastinum after already having given off the right recurrent laryngeal nerve in the neck
Right vagus nerve
Passes under the right subclavian artery and courses upward to the larynx
-never in the mediastinum
Right recurrent laryngeal nerve
The descending aorta, thoracic duct, azygos vein, hemiazygous vein, esophagus, vagus nerves and sympathetic trunks are all located in the
Posterior mediastinum
Enters the posterior mediastinum to the left of the esophagus and gradually moves behind the esophagus as they descend
Descending aorta
In the inferior part of the posterior mediastinum, the aorta is posterior to the
Esophagus
Arises below the diaphragm as the cisterna chyli and ascends from the diaphragm in a vertical course slightly to the right of the midline
Thoracic Duct
The thoracic duct shifts to the left and continues its vertical ascent to the left of the midline at about the
T6 level
The thoracic duct drains into the junction of the
Left subclavian and internal jugular veins
The only significant structure in the anterior mediastinum is the
Inferior portion of the thymus
The diaphragm is composed of a
Muscular portion and a central tendon
Dome shaped and upon contraction of its muscular portion it descends
Diaphragm
The diaphragm is innervated by the
Phrenic nerve (C3-C5)
The lumbar portion of the diaphragm has which three region of origin?
- ) Lumbar origin
- ) Costal origin
- ) Sternal origin
The lumbar origin is comprised of three things, what are they?
- ) 2 crura
- ) Medial arcuate ligament
- ) Lateral arcuate ligament
A thickening of the deep fascia covering the anterior surface of the psoas major
Medial arcuate ligament
A thickening of the deep fascia covering the anterior
surface of the quadratus lumborum
Lateral arcuate ligament
Diaphragm muscle fibers that originate from the inner surfaces of the lower 6 ribs are said to be part of the
Costal origin
Muscle fibers of the diaphragm arising from the inner surface of the xyphoid process are part of the
Sternal origin
What are 4 aperatures in the diaphragm?
- ) Caval Hiatus (T8)
- ) Esophageal Hiatus (T10)
- ) Aortic Hiatus (T12)
- ) Sternocostal Hiatus (T10)
Transmits the IVC and some branches of the right phrenic nerve
-within the central tendon to the right of the midline
Caval Hiatus
Transmits the esophagus and the anterior and posterior vagus nerves
-within the muscle of the right crus to the left of the midline
Esophageal hiatus
The skeletal muscle of the right crus serves as a sphincter for the
Esophagus
Transmits the aorta, the azygos vein, and the thoracic duct
-behind the two crura in the midline
Aortic Hiatus
Transmits the superior epigastric vessels
-between the muscle of the sternal origin and the costal origin
Sternocostal Hiatuses
The sympathetic trunk, the thoracic splanchnic nerves, the hemiazygos vein and most branches of the phrenic nerves pass through the diaphragm without a specific
Hiatus
Any muscle that has one of its attachments on the ribs can assist with
Inspiration
Because the innervation to the diaphragm (motor and sensory) is primarily from C3-5, pain arising from the diaphragm (e.g. subphrenic abscess) is referred to these dermatomes in the
Shoulder region
What is an important landmark at T2?
Jugular notch
What is an important landmark at T3?
Base of scapular spine and top of aortic arch
What is an important landmark at T7?
Inferior angle of scapula
What is an important landmark at T8?
Caval Hiatus
What is an important landmark at T9?
Xyphoid process
What is an important landmark at T10?
Esophageal Hiatus
What is an important landmark at T12?
Aortic Hiatus
The Sternal angle, second costal cartilage, tracheal bifurcation, and upper end of the ascending aorta are located at
T4