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Flashcards in Exam III: Thorax II Deck (40):


located in middle mediastinum
Pericardium is a tough fibrous sac that surrounds the heart
1. White tissue layer – fibrous pericardium – what you see if you remove chest plate – “fibrous like tissue bag”
2. Parietal layer
3. Pericardial cavity: filled with 25 mL of slick, serous fluid produced by mesothelial cells
Why do you need a lubricating fluid? Reduce friction so you can get a good heartbeat
4. Viscera layer of the pericardium – the layer that actually is on the heart itself. It comes up, wraps around, and becomes the parietal layer
Immediately underneath the visceral layer is the endocardium, the heart itself

Phrenic vessels supply blood to the pericardium Pericardium is innervated by the phrenic nerve
Any agitation of the pericardium will be received by the phrenic nerve, will manifest itself in C3,4,5 as pain (in neck)
Phrenic nerve –innervates diaphragm and pericardium


Landmarks of Pericardial Cavity

1. The transverse pericardial sinus – space formed in the pericardium where you could insert your fingers
Separates the arterial system from the venous system (arteries above; veins below)

2. Oblique pericardial sinus – if you put your finger in it, you can palpate the pulmonary trunk.


Cardiac Temponade

A build up of blood or other fluid in the pericardial sac putting pressure on the heart, which may prevent it from pumping effectively



Insertion of needle into pericardial cavity to draw off blood or pericardial fluid during cardiac temponade

The patient undergoing pericardiocentesis is positioned supine with the head elevated 30 to 60 degrees. This places the heart in proximity to the chest wall for easier insertion of the needle into the pericardial sac.

Anatomically, the procedure is carried under the xiphisternum up and to the left

Can also position needle through the 5th or 6th intercostal space at the left sternal border at the cardiac notch of the left lung or through the infrasternal angle


Clinical Findings Leading to Pericardiocentesis

Fibrous pericardium is a tough, fibrous tissue sack. Physiologically important for the “soft, squishy heart”
If fluid accumulates in the pericardial cavity, the “soft, squishy heart” will give first
Any kind of fluid build up will put pressure on the heart, compromising the heart – EKG finding, muffled heart sounds= medical emergency – need to do a pericardiocentesis
Stick a needle in patients chest, aim for cavity space. Aim for xiphoid sternal process


The Heart

Known as the point of maximal impulse – where heart beat feels the strongest

Surface name is what is against: anterior surface, base, left and right pulmonary surface, diaphragmatic surface
Great vessels are at the base of the heart, the other end is the apex


Heart Valves

Valves are tough piece of connective tissue
Fibrous dense connective rings – trigones – “heart’s skeleton” - the root of the valve
Fibrous rings also important for electrical insulation – atria and ventricle need to be electrically isolated to guarantee harmonious HB
AV bundle – only electrical connection between atria and ventricle; others than this exist in electrical isolation


Skeletal Structure of the Heart

Fibrous rings for tricuspid, bicuspid, aorta, and pulmonary valves


Right Atrium

First chamber of the heart
Fossa ovalis – in wall, which is an embryologic remnant of fossa ovale which allowed blood to go from left to right atria, bypassing lungs and closes after birth
Some people do not have a fuse, giving left to right communication, a left to right shunt resulting in blood mixing= bad
Blood gets returned in opening of coronary sinus
Crista terminalis – muscular ridge of a pseudochamber
Surface is rough through pectinate muscles – smooth muscles coming together would cause heart walls to stick together
Tricuspid valve – entrance to next chamber


Right Ventricle

Each leaflet is anchored through papillary muscle then trabeculae carnea muscles – the muscular connections of the valve to the myocardial wall
Have connections to IV septum and post myocardial wall – ischemic event or cardiac damage compromising wall – will compromise ability of wall to close – people who have had an MI could have a murmur
Wall damage causes valve not to close properly
Conus arteriosus –area of smooth wall that marks final part of LV – surrounds pulmonary valve which is right before pulmonary trunk
2 types of valves – pulmonary semilunar/cusp valves and leaflet valves (tricuspid)


Left Atrium and Ventricle

Atrium: has 2 openings for pulmonary veins
Can see other side of the fossa ovale
Mitral valve/bicuspid valve

Ventricle: papillary muscle roots valve to wall
Can see next aortic semilunar/cusp valve –blood will then enter systemic circulation


Pump Flow

Heart is 2 pumps in 1 – pulmonary and systemic circulation
Right = pulmonary; left = systemic
2 different pumps; 2 different pressure – Right side = lower pressure; Left side = high pressure
Abnormalities in walls (holes) will give a left to right shunt (blood will go from left side to right side – left is under higher pressure) - causes right sided cardiac hypertrophy



Chest x-ray usually ordered to examine lung fields and cardiac size
Quick and dirty – compare the diameter of the cardiac silhouette to the overall diameter of the thoracic cage Looking for a ratio of .5 or less, if greater, indicates pathology
Look for presence of costodiaphragmatic recesses – should not be occluded or obliterated (indicates pleural effusion – liquid residue in pleural cavity)
Breast tissue makes it look more radioopaque
Identify arch of aorta, pulmonary trunk, apex of heart, LV, RV, and RA
Any trauma to chest – RV most susceptible
Called a P.A. film – X-ray comes from back so we do not artificially magnify the heart
Also want a sagittal film – can see vertebral column, some of cardiac silhouette, and costodiaphragmatic recess


Electrical Properties of the Heart

Heart has its own pacemaker – the SA node (sinoatrial node) located in the RA – sets heart’s rate and rhythm Generates AP, sent out as wave across atrium causing depolarization causing atria to contract

On floor of RA is AV node – generates AP for ventricles Travels through single bundle fiber – the Bundle of His which will divide into a left bundle and right bundle
Will project down to apex of heart, the travel up and around the myocardium
Left will travel back to the base of the heart, right will take a side trip through the septal modulator bands, adds at tiny, tiny electrical delay
This allows the left to start the depolarization slightly before the right – allows heart to engage in a twisting motion so as much blood as possible is released into the circulation



EKG is demonstrating depolarization/repolarization
P – atrial depolarization (atrial contraction)
QRS – ventricular depolarization
T – ventricular repolarization

Elongated QRS – conduction delay
QRS – rabbit ears/twin peaks – bundle branch block (1 side contracting before the other) = specifically left bundle branch block
Atria and ventricles beating on their own = complete heart block
MI = elevated ST – “tombstones”
Depressed ST = cardiac ischemia


Heart Sounds

Sound 1 = lub; closing of AV valves (tricuspid and bicuspid)
Sound 2 = dub; closing of aortic and pulmonary valves


Auscultation of the Heart

Need to listen to all 4 valves
Tricuspid – 5th intercostal space parasternally (directly adjacent to sternum) – listening to valve “beyond” the valve - checking for murmurs
Aortic valve – 2nd intercostal space, parasternally
Pulmonary valve -2nd intercostal space, left side
Mitral valve – 5th intercostal space midclavicularl line – the apex of the heart


Coronary Vasculature

Heart deals with all of the blood of body, but does not meet metabolic demands of heart – role of coronary vasculature
Semilunar valves are cusp valves – on the aortic valve have little holes, the opening and origin of coronary arteries
Every time the valve closes, blood will fill up cusps and forcefeeding R + L coronary arteries
Most variable vasculature in body
Coronary artery starts at base of aorta, wraps behind pulmonary trunk
Left coronary area will bifurcate - anterior interventricular artery to apex of heart and circumflex goes to the backside of the heart
Left coronary artery has other names – left mainstream vessel, and the widow maker – if it is occluded obliterate perfusion to the entire anterior surface of the heart and the posterior surface of the heart – results in massive MI
Right coronary artery supplies the sinu-atrial branch, gives a marginal branch, then wraps around backside of the heart and provides posterior interventricular artery


Coronary Vasculature: Right and Left Dominant

Some people will be right dominant – left coronary artery - LAD, circumflex = “normal”

Left coronary artery casts off SA nodal artery
Circumflex becomes posterior artery
Both the SA and posterior interventricular are to the left - anatomic minority


Coronary Venous Drainage

Anterior interventricular vein =great cardiac vein (runs parallel to anterior interventricular artery)
Wraps around back, where we have a middle cardiac vein and a right marginal vein
All veins converge on the coronary sinus

Backside of the heart – note the coronary sinus
Great cardiac vein comes from the front
Coronary sinus is the last stop of all the oxygenated blood used by the heart – directly empties into RA


Cardiac Innervation

Sympathetic for heart = T1-T4
Will ascend to cervical ganglion, synapse, and then postganglionic fibers will come back down to chest in cardiac plexus
Parasympathetic innervation comes from the vagus nerve (X)

Ligamentum arteriosum – fibrous connective tissue running from aorta to pulmonary trunk- embryologic structure carried through to adulthood
In embryologic development – no need for functioning lungs - provides a portal for anything in the pulmonary trunk to enter systemic supply and avoid lungs
In adulthood, only a fibrous connective band is left
May not obliterate – allows for another area of left to right shunting
Consequences of overloading pulmonary circulation? Pulmonary edema and pulmonary hypertension


Cardiac Plexus

Autonomic division of the peripheral nervous system is directly responsible for heart rate, force of contractions, and cardiac output
Branches from parasympathetic and sympathetic systems contribute to the formation of the cardiac plexus consisting of the superficial and deep cardiac plexus between the aortic arch and tracheal bifurcation


Referred Pain

Results from “brain confusion”
MI manifests as crushing chest pain to arm
Brain constantly receives info form somatic T1-4
GVAs and GSAs located in the dorsal root ganglion – myocardial event sensed by GVAs
Brain not used to receiving info of cardiac crisis, brain initially interprets as somatic T1-T4 pain



Mediastinum developed into several compartments
Middle mediastinum – heart
Sternal angle – forms a depression – will be between vertebrae IV and V; above that line is the superior mediastinum and below is inferior mediastinum
Superior Mediastinum: Most concerned w/the great vessels – aortic arch -> brachiocephalic trunk -> right common carotid and right subclavian
Anterior mediastinum – in front of pericardium
Posterior mediastinum- behind pericardium



More important in children, atrophies with age
Spans superior mediastinum up to neck, also found in anterior compartment
Responsible for T cell maturation – important for immune function
Born in bone marrow, go to thymus for self maturation – self recognizing T cells are destroyed


Super Vena Cava and Brachiocephalic Veins

Contents of the Superior Mediastinum:
1. Retrosternal Great Veins
2. Left Brachiocephalic: formed by union of left internal jugular and subclavian veins
3. Right Brachiocephalic- formed by union of right internal jugular and subclavian veins
4. Superior Vena Cava: formed by the union of the right and left brachiocephalic


Aortic Arch

Contents of the Superior Mediastinum:
1. Intermediate Structures
2. Aortic arch and great branches:
A. Right brachiocephalic artery that divides into the right common carotid and right subclavian
B. Left common carotid artery
C. Left subclavian artery
** Ligamentum arteriosum – obliterated ductus arteriosus
** Arch – site of most aortic aneurysms


Thoracic Aorta

Location: TV 4 – TV 12

Gives rise to the following arteries :
Superior phrenic


Azygos Venous System

Function: drains the body wall and highly variable system of veins

Major Veins in the System: Azygos (right side) and Hemiazygos and accessory azygous (left side)

Located in the posterior mediastinum


Azygos Vein

Formed by: right ascending lumbar vein and right subcostal vein

Right superior intercostal vein (junction of intercostal veins 1,2,3, and 4 on right side)

Azygos dumps into inferior vena cava


Hemiazygos and Accessory Hemiazygos Veins

Formed by: left lumbar vein and left subcostal vein
Crosses to right side ~ TIX (behind: aorta, esophagus, and thoracic duct) and then enters the azygos

Accessory Hemiazygos
Crosses to right ~ VIII (crosses of over to azygos or connects with the hemiazygos)

Left Superior intercostal vein: intervertebral veins 1,2, and 3; empties directly to the left brachiocephalic veins

Vena cava – on the right; aorta – on the left


Thoracic Duct

Originates from cisterna chyli (abdominal cavity)
Begins at ~ L2 and ascends on right side in the thoracic cavity
Crosses to the left side ~ T5 and continues until it continues to the superior mediastinum into the neck
Empties into the venous angle = left jugular trunk and left subclavian trunk

Cisterna chyli – the largest, grossly visible part of lymphatic system – all lymph return from lower half of body will go here – these plus thoracic duct are the only grossly visible compartments of lymphatic system you will see

Thoracic duct returns at junction


Superior Mediastinum

1. Thoracic Duct:
Passes though the superior mediastinum
Posterior to the arch of the aorta and initial portions of the left subclavian artery
Between the esophagus and left mediastinal part of the parietal pleura
Empties it contents at the union of the left internal jugular and subclavian veins (left venous angle)

2. Arch of aorta, brachiocephalic trunk, jugular, thoracic duct enters into the venous system


Abormalities: Coarctation

1. Coarctation (constriction) of the aorta – aorta narrows- vascular supply to limbs has already branched off, will have unequal pulses/BP in extremities (higher in upper than lower)

2. Coarctation will result in surrounding eventual changes - greater than average flow of blood through subclavians, which give rise to internal thoracic, which give supply to internal intercostals – results in increasing in pressure – blood vessels will become bigger – “macroni sized internal thoracic arteries will become bigger, as well as internal intercostals, which will supply blood into aorta” – roundabout fill into aorta


Nerves of the Superior Mediastinum: Intermediate Structures

Intermediate Structures:
Nerves: vagus nerves, phrenic nerves, sympathetic branches

Vagus= wanderer, sends off a collateral known as the left recurrent branch/the left laryngeal at high risk for injury during surgery – if damaged, will affect laryngeal tone – patient’s voice will change – landmark = ligamentum arteriosum

Have cardiac nerves coming from the sympathetic trunk
All come into the superficial cardiac plexus which innervates the myocardium


Nerves of the Superior Mediastinum: Prevertebral Structures

Prevertebral Structures:
Nerves: Vagus nerves dividing into the right recurrent laryngeal nerve


Sympathetic Trunks

Sympathetic Trunk and Derivatives

Sympathetic Innervation: T1 to L2

Greater Splanchnic – T5 - 9
Lesser Splanchnic – T10 - 11
Least Splanchnic – T12

Located in posterior mediastinum


Esophagus: General Information, Blood Supply, Venous Drainage, and Lymphatic Drainage

Location: traverses both superior and posterior mediastinum; muscular tube connecting mouth to stomach
Compressed by three structures: aortic arch, left main bronchus, and diaphragm
Relations of the esophagus and the descending aorta

Blood Supply: esophageal arteries from the thoracic aorta and the left gastric artery

Venous Drainage: azygos, hemiazygos, and esophageal veins leading to the left gastric vein (abdomen)

Lymphatic Drainage: posterior mediastinal nodes and left gastric nodes


Esophagus Abnormalities

Esophagus crossed at TV8 – passes into abdomen and stomach
Tight relationship between the trachea, esophagus, and aortic arch - congenital abnormality – may have a double arched aorta – constricts esophagus and makes it difficult to swallow
Esophageal disorders put trachea and aorta at risk
Common sites where things can get stuck in the esophagus: junction of esophagus with pharynx, where esophagus is crossed by aortic arch, where esophagus is compressed by left main bronchus, and at the esophageal hiatus
Hiatal hernia – common presentation – incessant heartburn, get full really quick cardiac sphincter getting pushed up into thoracic cavity


Esophagus Innervation

Esophageal plexus: right and left vagus nerves (goes to form the anterior and posterior vagal trunks), sympathetic trunks, and splanchinic nerves

Vagus nerve and sympathetics make esophageal plexus– sympathetics suppress peristaltic motion, but parasympathetic increases peristalsis