Anatomy of the Thorax 3

Question 1

Label the diagram of the different muscles layers of the heart and pericardium

Answer 1

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Question 2

What is the pericardium?

Answer 2

• Pericardium is a fibro-serous sac that encloses the muscular heart and the roots of the great vessels including the aorta, the pulmonary trunk, pulmonary veins and the superior and inferior vena cava

Question 3

What are the two layers of the pericardium?

Answer 3

• The pericardium is made up of two main layers: a tough external layer known as the fibrous pericardium, and a thin, internal layer known as the serous pericardium (to overextend the orange metaphor, the outer peel could be thought of as the fibrous layer, with the inner white stuff being the serous layer).

Question 4

What are the functions of the pericardium?

Answer 4

• The pericardium has many physiological roles, the most important of which are detailed below:
• Fixes the heart in the mediastinum and limits its motion. Fixation of the heart is possible because the pericardium is attached to the diaphragm, the sternum, and the tunica adventitia (outer layer) of the great vessels
• Prevents overfilling of the heart. The relatively inextensible fibrous layer of the pericardium prevents the heart from increasing in size too rapidly, thus placing a physical limit on the potential size of the organ
• Lubrication. A thin film of fluid between the two layers of the serous pericardium reduces the friction generated by the heart as it moves within the thoracic cavity
• Protection from infection. The fibrous pericardium serves as a physical barrier between the muscular body of the heart and adjacent organs prone to infection, such as the lungs.

Question 5

What is the fibrous pericardium made off and what is its function?

Answer 5

• The fibrous pericardium is a strong fibrous layer, made of connective tissue that is generally non-distensible (not stretchy). This prevents overfilling of the heart.

Question 6

What does the build up of fluid around the heart cause?

Answer 6

• In clinical conditions of build up of fluid around the heart, the pressure caused by that is directed towards the heart itself because the fibrous pericardium cannot stretch much to accommodate any pathological build up of fluid around the heart.

Question 7

What is the fibrinous pericardium continuous with?

Answer 7

• The fibrous pericardium is a continuation of the central tendon of the diaphragm. It fuses with the outer coats of the blood vessels that pass through it such as the aorta and vena cava

Question 8

What ligament attaches the pericardium to the posterior surface?

Answer 8

Stern pericardial ligaments

Question 9

Where is the serious pericardium enclosed?

Answer 9

The serous pericardium is a membranous layer that is enclosed within the fibrous pericardium

Question 10

What does the serious pericardium line?

Answer 10

• It lines the internal surface of the fibrous pericardium and a layer that lines the heart, so we have parietal and visceral layers of pericardium

Question 11

What is the other word for visceral pericardium?

Answer 11

• The visceral layer that lines the outer layer of the heart is also called the epicardium

Question 12

What is the pericardial cavity and what is its function?

Answer 12

• The space between is called the pericardial cavity which contains pericardial fluid that acts as a lubricant, to minimise friction generated by the heart as it contracts

Question 13

What is a pericardial effusion?

Answer 13

• Build up of fluid around the heart might have serious consequences because of the organisation of the pericardium
• One case is called pericardial effusion
• Pericardial effusion is the passage of fluid from capillaries to (or accumulation of pus in) the pericardial cavity, between the visceral and parietal layers of serous pericardium.

Question 14

What problems does a pericardial effusion cause?

Answer 14

• The fibrous pericardium can cause problems when there is a build up of fluid. It cannot expand so pressure is directed towards the heart itself
• The heart consequently becomes compressed and ineffective
• Inflammation of the pericardium (pericarditis) usually causes sharp chest pain (commonly relieved by sitting forwards) – chest pain, affects cardiac output, secondary pericardial effusion

Question 15

What are the pericardial sinuses?

Answer 15

• Pericardial sinuses are formed as a result of the way the heart folds during embryonic development. In a developing foetus the heart begins as a tubular structure: an arterial and venous end. Different areas grow at different rates. Growth causes the heart to fold.
• Explains the reflections of pericardium around chambers and vessels

Question 16

Label the heart

Answer 16

On image

Question 17

Where is the transverse pericardial sinus located and what does it do?

Answer 17

• Transverse pericardial sinus located
o posterior to ascending aorta and pulmonary trunk
o Anterior to SVC
o Superior to left atrium
• Separates the hearts arterial outflow from venous inflow
• Can be used to identify and ligate arteries of the heart during CABG

Question 18

Label the great vessels and pulmonary trunk

Define great vessels

Answer 18

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Collective term used with reference to the large vessels that bring blood to and from the heart

Question 19

Where is the pulmonary artery in relation to the aortic orifice?

Where does it ascend in relation to the aorta?

What level does the pulmonary artery divide into the left and right pulmonary arteries?

What is found to the right and left?

Answer 19

• The pulmonary trunk arises slightly anterior to aortic orifice
• Ascends posteriorly and to the left, lying anterior and to left of ascending aorta
• Approx. T5-T6, opposite left border of sternum it divides into left and right
• Left: inferior to aortic arch
• Right: posterior to ascending aorta and SVC

Question 20

What is the ascending aorta found within?

Where does it originate?

Where does it enter the superior mediastinum?

Answer 20

• Ascending within pericardial sac
o Originates at aortic orifice (lower edge of CC3) and continues to CC2
o Enters superior mediastinum = arch

Question 21

Where does the aortic arch lie in relation to the sternum and trachea?

What level does it form the descending aorta?

Answer 21

• Arch lies behind manubrium sterni, in front of trachea
• Arches upwards and backwards
• Becomes continuous with descending aorta at level of sternal angle

Question 22

What are the aortic arch branches?

Answer 22

• Brachiocephalic trunk (divides into right subclavian and right common carotid
• Left common carotid
• Left subclavian

Question 23

What does the ligamentum arteriosum connect?

Answer 23

The ligamentum arteriosum connects the arch of the aorta with the pulmonary trunk, it is a remnant from fetal circulation. Blood passes through the ductus arteriosus in the fetus from the pulmonary trunk to bypass the lungs to go round the body

Duct then closes to form a ligamentum arteriosum

Patent ductus arteriosus can remain

Ligamentum arteriosum connects bifurcation of pulmonary trunk with aorta (fetal remnant of ductus arteriosus)

Question 24

What parts of the vena cava are in the pericardial sac

What level does the vena cava pass through the fibrous pericardium?

Answer 24

Inferior half within pericardial sac

Passes through fibrous pericardium at CC2 and enters right atrium

Question 25

What level does the inferior vena cava pass through the diaphragm?

Answer 25

Passes through diaphragm at T8 and enters fibrous pericardium

Short portion within the pericardial sec before entering right atrium

Question 26

Describe how the heart acts as a pump

Answer 26

• Functionally the heart consists of 2 pumps: right pumps blood: receives deoxygenated blood and sends to the lungs
• The left pump receives oxygenated blood from the lungs to the body
• Each pump consists of an atrium and a ventricle separated by a valve
• Anatomically 4 chambers of the heart
• Pulmonary circulatory system: between the heart and the lungs
• Systemic circulatory system: between the heart and the body

Question 27

Label the heart in-situ

Answer 27

On image

Question 28

Where does the right atrium:

1. lie?
2. receive blood from?

Where does the coronary sinus lie in relation to the IVC?

Answer 28

• This forms the right border of the heart
• It receives blood from the SVC and IVC and the coronary sinus (drains the walls of the heart)
• We can see how the SVC and IVC enter the right atrium
• The coronary sinus sits medial to the inferior vena cava

Question 29

What is the crista terminalis, musculii pectinati, fossa ovale and Atrioventricular orifice?

Answer 29

You can also see distinct features of the right atrium such as:
The right auricle – ear like, conical muscular pouch overlapping the origin of the aorta
• The crista terminalis – runs from the SVC to the IVC on the internal surface of the right atrium, this is called crista terminalis, it marks the transition from the internal surface of the atrium between the anterior wall (formed from bundles of muscle fibres) and posterior (where the walls are smooth). It divides the atrium into the rough and smooth area
• The musculi pectinati – roughed bundles of muscle fibre that sit anterior to the crista terminalis. They line the internal surface of the auricle part of the atrium, well as rest of atrium is smooth
• Fossa ovale – an embryonic remnant, because during fetal development there is a link between the right and left atrium to bypass the lungs
• Atrioventricular orifice – blood moves from the right atrium into the right ventricle through the AV orifice

Question 30

Label the internal right atrium

Answer 30

On image

Question 31

Describe the anatomy of the right ventricle

Answer 31

• Blood entering from right atrium into the right ventricle moves in a horizontal and anterior direction. It passes the atrioventricular valve with 3 valves: tricuspid valve
• Outflow tract: pulmonary trunk
• Pulmonary trunk closed by pulmonary valve: 3 semilunar cusps

Anatomy of the right ventricle II
• The atrioventricular valve has 3 cusps that are attached muscular wall of the ventricle.
• The muscular wall of the ventricle has irregular structures called trabeculae carnae, some of these are specified into raised bumps called papillary muscles. These act as an attachment point for the cusps of our AV valve.
• When the ventricle contracts the papillary muscles will stop the cusps from turning inside out as the pressure rises in the ventricles, to prevent blood from flowing back up into the atrium.
• Chordae tendineae attach cusps to papillary muscles (part of ventricular wall).

Question 32

Describe the anatomy of the left atrium

Answer 32

• The left atrium has a smoothed wall structure, you can also see the Musculi pectinati that line the internal surface of the left auricle
• Forms most of base of heart
• Blood enters X4 pulmonary veins
• Anterior half is continuous with left auricle
o No equivalent to the crista terminalis
• Depression on interatrial septum is the valve of the foramen ovale
• Blood moves into left ventricle via atrioventricular orifice
• Guarded by the mitral valve – 2 cusps (bicuspid/mitral)
Anatomy of the left ventricle I
• Anterior to left atrium
• Wall x3 thicker than right ventricle
• Blood passes through AV orifice towards apex
• Guarded by the mitral valve

Question 33

Describe the anatomy of the left ventricle

Answer 33

• Blood flows into the ascending aorta and then into the arch
• Entrance into the aorta is guarded by a semi-lunar valve
• Blood flows into the aortic vestibule
• Guarded by the aortic valve
• Similar in structure to pulmonary valve
• As blood recoils after ventricular contraction, and fills the aortic sinuses formed by the cusps, it is forced into coronary arteries
• Sinuses is just a filling
• Origin of the aorta is the aortic sinuses

Question 34

What is the blood supply to the heart?

Where are they distributed?

Answer 34

• Supplied by coronary arteries
• Two: right and left
• Arise from aortic sinuses of the ascending aorta

• Coronary arteries and branches are then distributed over the surface in the sub-epicardial connective tissue

Question 35

Where does the right coronary artery arise from and describe its path

Answer 35

• Arises from the aorta and runs anteriorly forward between the pulmonary trunk and right auricle
• Descends almost vertically in the right atrioventricular groove
• An inferior border continues posteriorly to anastomose with left coronary artery
• Offers a marginal branch and a posterior interventricular branch. This supplies both surface of the right ventricle: anterior and posterior surface
• If an individual is right dominant it will also have the right coronary artery giving of the posterior interventricular branch

Question 36

Where does the left coronary artery arise from and describe its path

Answer 36

• Usually larger than right
• Arises from aortic sinus and passes anteriorly forward between the pulmonary trunk and left auricle
• Then enters atrio-ventricular groove and divides into anterior inter-ventricular branch (left anterior descending artery) and a circumflex branch. Also gives off a left marginal artery
• 20% of people the posterior interventricular artery comes of the left circumflex artery (left dominant) OR it comes of the right coronary artery

Question 37

What does the right coronary arteries supply?

What do the left coronary arteries supply?

Answer 37

• The branches of the right coronary artery are supplying the right atrium, the right ventricle and a part of the anterior intraventricular septum
• Some of the right coronary artery supplies the left ventricle (diaphragmatic surface) and also some of the posterior wall of the left ventricle
• The left coronary artery is supplying the left atrium, most of the left ventricle, the posterior intraventricular septum as well.

On image

Question 38

Where does the blood supply to the SAN and AVN come from?

Answer 38

• Blockage of a vessel to the conduction system will have an effect on electrical signalling in the heart

Question 39

What is right dominant?

What does the Posterior IV artery supply in right dominant people?

What is left dominant?

What is the SAN and AVN supplied by?

Define Co-dominant

Answer 39

• Several commonly occurring variations
• The most common presentation is of a RIGHT DOMINANT artery
o Posterior IV branch
o Supplies large portion of posterior wall of left ventricle
• Variation of a LEFT DOMINANT branch
o Posterior IV arises form the circumflex
• Additional variation in relation to SA and AV nodes
o Normally supplied by RCA
o Sometimes vessels from circumflex of LCA
• CO-DOMINANT – branches from the left and right coronary artery supply the posterior intraventricular area.
• Indicator of left ventricular strength: Left dominance associated with worst prognosis if there is a blockage of the left posterior intraventricular branch

Question 40

What is the coronary sinus?

What does it receive blood from?

Answer 40

• The coronary sinus drains the blood from the heart and sits on the posterior surface of the heart
• Coronary sinus receives 4 major tributaries – the great, middle, small and posterior cardiac veins

Question 41

What do the anterior cardiac veins drain?

Answer 41

• Anterior cardiac veins are very small, draining only the anterior portion of the right ventricle

Question 42

What tributaries does the coronary sinus receive?

Answer 42

Great, middle, small and posterior cardiac veins

Question 43

What is another name for the great cardiac vein and where does it run and drain?

Answer 43

• Also called the anterior intraventricular vein, it runs in the anterior intraventricular groove along with the anterior intraventricular artery
• Largest tributary of the coronary sinus that originates at the heart, curves onto the posterior surface of the heart into the coronary sinus
• Gradually enlarges to form the coronary sinus

Question 44

Locate the small cardiac vein and describe function

Answer 44

• Also located on the anterior surface of the heart and runs along the groove between the right atrium and the right ventricle
• Empties into the coronary sinus on the posterior surface of the heart

Question 45

Locate the middle cardiac vein and describe function

Answer 45

• Also known as the posterior interventricular vein
• Begins at the apex of the heart and ascends in the posterior interventricular groove to empty into the coronary sinus

Also known as the posterior interventricular vein

Question 46

Where is the posterior cardiac vein located?

Answer 46

Located on the posterior surface of the left ventricle

It lies to the left of the middle cardiac vein and empties into the coronary sinus

Question 47

Locate the Anterior and smallest Cardiac Vein

Where do they pass and enter?

Answer 47

 Anterior cardiac veins
 Small; arise on anterior surface of right ventricle
 Cross coronary sulcus and enter anterior wall of right atrium
 Smallest cardiac veins (aka thebesian)
 Valve-less
 Drain directly into cardiac chambers; numerous in right atrium and ventricle

Question 48

What does an occlusion in the LAD/ anterior interventricular artery cause?

Answer 48

• LAD is most commonly occluded of the coronary arteries – main supply to the interventricular septum and the bundle branches of the conducting system so will have an infarction of the conduction system
• Right coronary artery branches that supply the SA and AV node, blockage can lead to conduction system abnormalities

Question 49

Compare an angina to a MI

Answer 49

Angina
• Ischaemia but falls short of necrosis
• Stable: predictable; after exercise of exertion; pain eases after rest
• Unstable: more severe; can happen during resting

MI
• Complete block of an artery due to embolus
• Usually result of atherosclerosis
• Progressive blockage of a coronary artery can encourage collateral branching which can help in the event of an M.I.

Question 50

Which arteries are normally taken for a graft?

Where is the new vessel positioned?

Answer 50

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