The middle mediastinum and heart week 2 Flashcards Preview

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Flashcards in The middle mediastinum and heart week 2 Deck (32)
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What is angina? What are the two types?

Angina is a type of cp experienced when the heart does not recieve enough oxygen due to a paritally blocked coronary artery. 

stable angina: predictable (occurs with exertion), short in duration, treatable with rest and meds

unstable angina: occurs even at rest, unpredictable, lasts longer than stable angina, may not be relieved with rest or meds and can be a sign of MI


What is myocardial infarction?

Heart attack. occurs when blood flow to heart from a coronary artery is completely blocked. Lack of blood flow (ischemia) can cause damage or destruction of hear muscle tissue. 


What is angiplasty?

Procedure used to treat arteries that are occluded by threading a guide wire to the site of the diseased vessel and inflating a balloon to open the vessel by "squeezing" the plaque against the walls. Sometimes during this procedure, stents (small mesh wire tubes) are placed to help keep the artery open. 


What is the mediastinum? What are its boundaries?

The mediastinum is a broad central partition that spearates the two pleural cavities. It extends in an anterior-posterior direction from the sternum to the thoracic vertebral bodies and from a superior-inferior direction from the superior thoracic aperture to the diaphragm.


How and into what parts are the mediastinum divided?

The mediastinum is divided into superior and inferior portions by an imaginary line extending from btwn the manubrium and body of the sternum to the intervertebral disc btwn T4 and T5. 

The inferior mediastinum is further separated into anterior, middle, and posterior parts by the heart. 


What structures exist at the level of the sternal angle?


Rib (2nd, costal cartilage)

Arch of aorta

Trachea (biforcation)

Pulmonary trunk (biforcation)

Larygngeal recurrent nerve and ligamentum arteriosum

Azygos vein draining into the superior vena cava

Nerves (cardiac plexus)

Thoracic duct draining into left subclavian vein (does so a little above the sternal angle)


Where is the anterior mediastinum? What structures exist in the anterior mediastinum?

The anterior mediastinum is posterior the sternum and anterior to the pericardial sac. 

Contents of anterior mediastinum:

  • Thymus: immune organ. involutes with age
  • branches of the internal thoracic vessels
  • connective tissue
  • lymph nodes
  • sternopericardial ligaments


Where is the middle mediastinum located? What are its contents?

It is centrally located: Its contents are:

  • The pericardium
  • heart
  • phrenic nerves
  • pericardiophrenic artery and vein
  • origin of great vessels
    • ascending aorta
    • pulmonary arteries
    • pulmonary veins
    • superior vena cava 
    • inferior vena cava


The phrenic nerve innervates both the pericardium and diaphragm as well as the parietal pleura. What kind of fibers does the phrenic nerve give to each?

The phrenic nerve provides general somatic efferent innervation to the diaphragm.

The phrenic nerve provides general visceral afferent innervation to the parietal pleura and the pericardium. Reason for pain experienced with pleurisy and pericarditis. 


The pericardium is a sac that surrounds what structures? What are its components?

surrounds the hear and roots of the great vessels. composed of fibrous and serous components. 


What is the fibrous pericardium composed of? What is it attached to? What nerve and blood vessels pass over the fibrous pericardium?

It is composed of tough connective tissue. The fibrous pericardium is attached to the diaphragm at its base (not heart, just fibrous pericardium) and is continuous with the adventitia of the great vessels at its apex. The phrenic nerve courses over (and innervates) the fibrous pericardium as well as the pericardiophrenic vessels (see slide 9 of course notes)


What are the layers of the serous pericardium? Where are they located in relation fibrous pericardium and heart? What is the name of the space that exists btwn these two layers and what is in this space?

There is a parietal and visceral layer. The parietal layer lines the inner surface of the fibrous pericardium. The visceral layer is adherent to the heart and forms its outer covering (epicardium). Both layers of the serous pericardium are continuous at the roots of the great vessels. The pericardial cavity exists btwn these layers and contains a small amount of fluid. 


What are the pericardial sinuses and what are they created by? Why are they significant?

The areas of continuity between the two layers of serous pericardium around the great vessels create reflections of the serous pericardium.

transverse pericardial sinus: separates the aorta and pulmonary artery from the superior vena cava

oblique pericardial sinus: formed by reflections of the serous pericardium onto the pulmonary veins

This helps to identify vessels, important during surgery. 


Identify the indicated structures of the external heart. 


What border(s) of the heart does the right atrium form? What vessels does it receive blood from and where does blood leave? describe the anatomy of the right atrium.

The right atrium forms the right heart border (right margin, right pulmonary surface). It gives small contributions to the base of the heart and the anterior surface of the heart. It recieves blood from the inferior vena cava, superior vena cava, and the cornary sinus. 

The interior of the RA is divided into two continuous parts by a smooth muscular ridge called the crista terminalis. Posterior to the crista terminalis is a smooth walled portion of the atrium while anterior to it the walls are covered by ridges called pecinate muscles. The fossa ovalis marks location of foramen ovale. 


Identify the parts of the right atrium. 


What borders does the right ventricle form? How does blood enter the right ventricle and where does it exit? Through what valve? Describe the anantomy of the right AV valve and the right ventricle. 

The right ventricle mainly forms the anterior surface of the heart. It gives a small contribution to the diaphragmatic surface. Blood enters the right ventricle through the right AV orifice. During ventricular contraction, this orifice is closed by the tricupsid valve. Each of the the 3 cusps of this valve are attached at their base to the fibrous ring of the right AV orifice. The free margins of the cusps are attached to chordae tendineae which arise from papillary muscles. Papillary muscles contract when the ventricles do to prevent eversion of the tricuspid valve but they do not close the valve!!! High pressure in the RV compared to RA causes the valve to close. There is an anterior, posterior, and septal cusp attached to the same named papillary muscles. The anterior papillary muscle is the largest and is right in front. The trabeculae carnae is the rough walled portion of the RV and is where papillary muscles extend from. The septomarginal trabecula, or moderator band, extends from the ventricular septum to the papillary muscles. Carries impulses from the AV node during ventricular systole and coordinates contraction of the anterior papillary muscle. The outflow tract of the right ventricle is the conus arteriosus (infundibulm). At its apex the opening into the pulmonary trunk is closed by the pulmonary valve. 


Identify the portions of the right ventricle. 


What borders does the left atrium form? How does blood enter the left atrium? Describe the anantomy of the left atrium.

The left atrium forms most of the base or the posterior surface of the heart. It makes small contributions to the anterior surface and the left pulmonary surface/left margin. A small part of the left auricle forms the obtuse margin of the heart. 

Oxygenated blood enters the left atrium from the pulmonary veins. Similar to the right atrium, the posterior portion of the atrium is smooth walled and the anterior portion contains pectinate muscle. However, there is no crista terminalis in the left atrium separating these 2 layers of muscle. The valve of the foramen ovale is a thin area or depression in the interartrial septum that prevented backflow of blood from the left to right atrium during development. 


Identifty the parts of the left atrium. 


What borders of the heart does the left ventricle form? Where does it recieve blood from and where does blood exit? Describe the anatomy of the left AV valve and the left ventricle. 

The left ventricle forms the diaphragmatic surface of the heart, the apex, the obtuse margin, and the left pulmonary surface/left margin. 

Blood enters the left atrioventricular orifice that is covered by the mitral valve. Blood exits via an outflow tract called the aortic vestibule. The left venticle possess trabeculae carnae (form ventricular wall) where the papillary muscles originate similarly to the right ventricle. Two papillary muscles (anterior and posterior) connect via chordae tendineae to the two cusps of the mitral valve. 


Identify the portions of the left ventricle. 


Idenitify the parts of the 4 valves of the heart. Make note of the relationship btwn the pulmonary artery and aorta. Which one sits anterior to the other?

Pulmonary valve is anterior to the aorta. Easy to remember cusps bc it has a right left, and anterior cusp while aorta has a right, left, and potsterior cusp. 


How do the pulmonary and aortic semilunar valves close? What is special about the aortic valve?

For both the pulmonary and aortic valves, each cusp forms a pocket-like sinus. After ventricular contraction, the recoil of blood fills the sinuses and forces the cusps closed preventing backflow of blood. The aortic valve is special because the coronary arteries have origins from the right and left cusps of the acending aorta. As blood recoils following ventricular contraction (ventricular diastole) and fills the aortic sinuses, blood is forced into the right and left coronary arteries. 


Identify the vasculature of the anterior heart. 


The ____ _____ _____ turns into the coronary sinus when it turns at the obtuse margin of the heart.

great cardiac vein


Identify the vasculature of the posterior heart. 


How do you begin counting ribs?

Palpate the jugular notch and move inferiorly along the manubrium until a notch is palpated. This is the sternal angle and the costal cartilages of the 2nd ribs are lateral to the sternal angle. The ribs can be counted down from there. 


Where is the right heart margin? Left heart margin? Where is the stethoscope placed to assess heart sounds?

Right heart margin: extends from 3rd-6th costal cartilage

Left heart margin: extends laterally from the 2nd intercostal space to the apex of the heart which lies in the 5th intercostal space at the midclavicular line. 


Note the rships of structures in this pic. Remember that the subclavian veins lie posterior (deep) to the clavicle and the subclavian arteries are deep to the veins.