Welcome back to the Reid Anatomy Laboratory. You should still have your face shield from MS1, however, if you need a replacement face shield they are available at the statins near the lab entrance.

For a video on eyeglasses style face shield assembly...
                            ------- click here ------

Face shields must be worn whenever working with your donor for splash eye protection.

b) Place a strip of label tape on the front top.

c) Write your given or preferred name on the strip of tape with the marker pen.

d) Unclip the side rubber pins and insert one end of the shield to the glasses frame (clipping the pin in place holding the shield) then bend the shield around to the other side (clipping the pin back in place)

You will keep your face shield through all of your anatomy time, we suggest in your locker so it is available each day and for future classes.

If you lose, forget, or break your face shield there will be spares at PPE supply stations in the lab available in future sessions. 

At the end of the lab today, return the marker pen and any unused shields to the front supply station where the spare face shields are located.

During your medical career you will assemble many types of face shield and coverings, the ones we use are very common splash shields (impact shields have heavier polycarbonate).

If you find the eyeglasses style uncomfortable or difficult to fit, there are forehead foam styles available in the lab on request. However, we find the eyeglass style suffers less internal fogging during use than foam styles (i.e. less condensation formation).

PROCEDURE - Coronary Arteries

1. PRE-WORK (before lab) review the organization of the bony thoracic cage from your atlas or on an articulated skeleton in the lab.
    (Figure240a) (Figure201) (Netter187) (Netter192)

a) Sternum: Identify the jugular notch (suprasternal notch), manubrium, body of the sternum, and xiphoid process.

b) Rib cage: Identify the inferior edge of the rib cage, the costal margin, noting the anteroinferior slope of the ribs (i.e. they start higher in the back and curve around to the front). Also note the ribs make a sharp change in curvature (a rotation) at the lateral sides of the thoracic cage. This change in curvature is the costal angle (or angle of the rib).

c) 'Bare area': The bare area of the heart is the region directly posterior to the rib cage on the left between the left 4th and 6th costal cartilages. This is a region where the left lung is not present anterior to the heart allowing for needle access to the pericardia without risk of pneumothorax.

2. Locate the Patient Chart on the bookstand and review the key information on your patient; name, age, sex, cause of death.
    (Example Chart)

The Patient Chart serves as a record of the history and physical of your patient.

During the course you will be examining the anatomy of your patient in detail. This work may reveal prior surgeries or medical conditions the patient has.

If you determine they have had a past surgery or procedure add notes on what you have determined to that section on the Patient Chart.

Similarly, if you find an anatomic variant in your patient also add that detail to the anatomic variant section on the Patient Chart.

The Patient Record serves as a detail of the patient for the MS1 and MS2 teams who, in turn, add additional details found in the patient with each course.

3. Expose the donor thorax and remove the chest plate.

4. Remove the donor heart from the white bucket.

The heart has been soaking in a mix of wetting agent and water prepared by the MS1 class. This will have softened blood clots inside the heart making removal easier in steps below.

 5. Place the heart into the correct orientation in the thoracic cavity to review how it is positioned.
    (Netter216)

The heart sits at an angle such that the apex (tip) of the heart is pointed to the left anterolateral side of the thorax.

This results in the most anterior chamber of the heart being the right ventricle and the most posterior chamber being the left atrium.

The right atrium is to the right (forming most of the right heart border) and the left ventricle to the left (forming the left heart border).

6. Examine the transected ends of the aorta and superior vena cava on the heart or donor body and note the dramatic difference in wall thickness.

Arteries are thicker overall than veins. Of the three histological layers, the tunica intima, media, and adventitia, the most prominent layer in arteries is the tunica media while the dominant layer in veins is the tunica adventitia.

It is not uncommon for plaques and calcifications to occur in the aorta we individuals age. The presence of calcifications is a significant risk factor for developing aneurysms and/or overall cardiovascular mortality.

7. Examine the surface of the heart and observe the shiny layer of visceral pericardium which covers all the coronary vessels.
    (Netter216)

The visceral pericardium is a mesothelium, i.e. a single cell layer thick. It is common for adipose connective tissue to accumulate below this single cell mesothelium layer.

The amount of fatty tissue present around the heart will vary greatly between individuals. In general, older individuals will exhibit more fatty tissue that must be dissected to expose the coronary vessels.

Cardiac muscle sometimes extends over parts of the coronary arteries and cardiac veins in structures called myocardial bridges. If present, these will also need to be dissected open to follow the major vessels.

8. Examine the anterior side of the heart and identify the left and right auricles.

The first step when identifying anything on the heart is to recognize which side of the heart you are viewing. The great vessels are useful landmarks, from left to right you should see the pulmonary trunk, aorta, and superior vena cava.

Each atrium has a small muscular pouch at the superior end called the auricle (also known as an atrial appendage). This looks like a small flap or protuberance from each atria near the aorta. The right atrium forms a right auricle, the left atrium forms a left auricle.

9. Examine the exterior surface for the coronary sulcus separating the atria and ventricles.
    (Netter216) (Netter218)

The coronary sulcus (often called the atrioventricular sulcus) separates the atria from the ventricles.

If the heart has significant fat buildup these sulci may be partially or completely obscured by that fat. When we remove the fatty tissue to follow coronary vessels the sulci will be more apparent.

The sulcus separating the left atrium and ventricle is called the left coronary sulcus and branches of the left coronary artery pass along the sulcus.

The sulcus separating the right atrium and ventricle is called the right coronary sulcus and branches of the right coronary artery pass along the sulcus.

10. Examine the exterior surface for the interventricular sulci separating the left and right ventricles.
    (Netter216) (Netter218)

The anterior interventricular sulcus separates the ventricles in front (anterior) and the posterior interventricular sulcus separates the ventricles behind (posterior). These demarcate the location of the interventricular septum (wall between the ventricles).

The apex of the heart is the most inferior point of the heart where the left and right ventricles terminate.

11. Look into the pulmonary artery and identify the cusps of the semilunar valves.
    (Netter226) (Photo2013)

Sometimes there are small blood clots that need to be picked or washed out of the vessel in the sink in order to see the cusps.

In the pulmonary artery, these are the anterior cusp, left cusp, and right cusp. The anterior cusp of the pulmonary artery is furthest away from the aorta.

Their names derive from where they were positioned developmentally, not from their position in the adult.

12. Look into the aorta and identify the cusps of the semilunar valves.
    (Netter226) (Photo2013)

Sometimes there are small blood clots that need to be picked or washed out of the vessel in the sink in order to see the cusps.

In the aorta, these are the posterior cusp, right cusp, and left cusp. The posterior cusp of the aorta and the anterior cusp of the pulmonary artery are furthest away from each other.

Examine the area of the aortic wall where the cusps of the valves attach. This region of the aorta is called the aortic root (sometimes called the aortic annulus, reflecting the crown like arrangement of the valves and wall). Sometimes there will be a noticeable dilation or widening of the aorta in the region of the valves.

Microscopically, this region of the aorta is thickened with fibrous connective tissue and continues into the heart past the valves to make strong attachments into the wall of the heart.

Examine the wall of the aorta just inside the semilunar valve cusp for the orifices (openings) of the coronary arteries.

The left coronary artery is located just superior to the left cusp, and the orifice to the right coronary artery located just superior to the right aortic cusp.

The coronary artery orifices will be the starting points for exposing the coronary arteries in the next section.

The vascular pattern described below is the most common, but be aware that there is considerable variability in secondary branches from the coronary vessels. Occasionally coronary arteries will exist as a doubled structure, with two vessels running in parallel rather than a single vessel.

13. Starting with the left coronary artery, insert a blunt probe from inside the aorta part way into the opening of the left coronary artery.

14. On the surface of the heart palpate and feel for the blunt probe between the left auricle and pulmonary trunk.
    (Figure226) (Netter222) (Photo2003) 

This is the initial portion of the left coronary artery and starting point for following the vessel.

15. Using blunt dissection clean any fatty tissue away from the vessel and expose to the first division of the vessel, which is often quite close to the aorta.
    (Figure226) (Netter222) (Photo2004)

The left coronary artery divides into the anterior interventricular branch and the circumflex branch.

16. Blunt dissect and follow the anterior interventricular branch all the way to the apex of the heart as it courses in the anterior interventricular sulcus.
    (Figure226) (Netter222) (Photo2005)

This branch is accompanied by the great cardiac vein that we will review below.

Clinicians will often refer to the anterior interventricular branch as the left anterior descending (LAD) artery. The anterior interventricular branch supplies the anterior surface of the heart. You may observe a variable sized diagonal branch and numerous small unnamed branches, but we won't dissect these specifically.

17. Follow the circumflex branch as it courses to the left in the left coronary sulcus to reach the posterior side of the heart.
    (Figure226) (Netter222) (Photo2006)

This branch is accompanied by the great cardiac vein that we will review below.

The circumflex branch of the left coronary artery continues to give rise to additional named and unnamed branches that supply the wall of the ventricle. We will not dissect those specifically.

18. Return to the aorta and insert a blunt probe into the opening of the right coronary artery. 

19. On the surface of the heart palpate for the probe and find the artery between the right auricle and ascending aorta.
    (Figure226) (Netter222)

This is the initial portion of the right coronary artery and starting point for following the vessel.

20. Use blunt dissection to follow the vessel to the first small branch, the sinoatrial nodal artery.
    (Figure226) (Netter222) (Photo2007)

The sinoatrial nodal artery arises very close to the origin of the right coronary artery, and ascends along the anterior wall of the atria to supply the sinoatrial node.

In approximately 25-30% of individuals the sinoatrial nodal artery will arise from the left coronary artery or circumflex branch.  If you cannot find the sinoatrial nodal artery, it may have arisen from the left passing posterior to the aorta.

21. Follow the right coronary artery as it courses within the right coronary sulcus.
    (Figure226) (Figure227) (Netter222)

Small veins, the anterior cardiac veins, pass superficially across the right coronary artery. The anterior cardiac veins bridge the atrioventricular sulcus between the right atrium and right ventricle. These veins drain directly into the right atrium.

This right coronary artery also gives rise to additional named and unnamed branches supplying the wall of the ventricle. We will not dissect those specifically.

22. Continue along the right coronary artery as it turns posteriorly around the right coronary sulcus.
    (Figure226) (Netter222) (Photo2009)

23. As the right coronary artery reaches the posterior interventricular sulcus the artery gives rise to the posterior interventricular branch.
    (Figure226) (Netter222) (Photo2009)

Approximately 70% of individuals have the posterior interventricular branch arising from the right coronary artery (a right dominant heart), 10% from the circumflex artery (a left dominant heart), and 20% have dual contributions arising from both. Heart dominance has no relation to left/right handedness.

Clinicians will often refer to the posterior interventricular branch as the posterior descending artery (PDA).

The posterior interventricular artery gives rise to the AV nodal artery which provides blood supply to the AV node. This vessel is small and heads into the myocardia towards the AV node making it hard to distinguish unambiguously.

24. Follow the posterior interventricular branch as it courses along the posterior interventricular sulcus to the apex of the heart.

The posterior interventricular branch is accompanied by the middle cardiac vein that we will dissect below.

PROCEDURE - Cardiac Veins

25. Examine the posterior surface of the heart for the coronary sinus.
    (Figure227) (Netter222) (Photo2011)

The coronary sinus is a dilated portion of the venous system approximately 2cm in length located in the coronary sulcus.

The coronary sinus opens directly into the right atrium (we will see that opening when we examine the interior chambers of the heart).

We will not dissect the cardiac veins specifically but they are listed below for review.

The great cardiac vein, which travels with the anterior interventricular branch then around to the posterior side of the heart, dilates in diameter becoming the coronary sinus. The exact point that the great cardiac vein becomes the coronary sinus is open to debate, but a working definition is the point where the oblique vein joins to the great cardiac vein at the left extreme of the coronary sinus. However, it is not always easy to find a distinct oblique vein as this is also a delicate venous vessel.

The middle cardiac vein accompanies the posterior interventricular artery within the posterior interventricular sulcus to join with coronary sinus. The middle cardiac vein normally joins the coronary sinus at the right extreme, but can join into the midpoint of the coronary sinus in some individuals.

The small cardiac vein accompanies the right marginal branch and joins into the right end of the coronary sinus. It is quite variable between individuals and can drain directly into the right atrium, cross to the middle cardiac vein, or even be absent in some people.

Many additional very small veins in the walls of the heart on the inside also drain directly into all four chambers, these are called thebesian veins. Since this 'dilutes' high oxygenation state blood, aortic outflow blood oxygen percent is ~98%.

PROCEDURE - Chambers of the Heart

26. To open a flap in the wall of the right atrium, use scissors to make a small opening starting in the right auricle.
    (Figure228)

27. Insert one blade of the scissors into the opening and make a series of cuts to open the anterior wall.

Make a short horizontal cut extending to the right (Figure228, cut 1).

Now cut inferiorly and continue until just short of the inferior vena cava (Figure228, cut 2).

Then turn and cut horizontal again until just short of the atrioventricular sulcus (Figure228, cut 3).

28. Reflect the atrial anterior wall flap laterally, opening the right atrium. 

The chambers of the heart commonly have clotted blood inside. You may need to submerge the heart in one of the white buckets under your table.  Fill the bucket with water and submerge the heart to assist with removal of any large pieces of clotted blood and wash out residual small clots of blood.

29. Observe the inner surface of the anterior wall flap of the right atrium and identify.
    (Netter224) (Photo2014)

Pectinate muscles - these are horizontal ridges of muscle on the rough part of the wall.

Crista terminalis - which is a sharp crest of muscle along the junction of the smooth and rough parts of the wall. At its superior end near the entrance of the superior vena cava, invisible to the naked eye, is the location of the sinoatrial node.

30. Observe the inner surface of the posterior wall of the right atrium and identify.
    (Netter224) (Photo2015)

Opening of the superior vena cava - The superior vena cava to right atrium opening does not have any valves. Thus, during atrial contraction some backflow does occur.

Opening of the inferior vena cava - the inferior vena cava has a small valve located just to the left of the entrance of this vessel into the right atrium. The valve varies widely in size from a small ridge of tissue through to an elongated structure projecting several centimeters into the right atrial cavity

Opening of the coronary sinus - this opening has a small valve consisting of a semicircular fold of the lining membrane of the right atrium. The valve varies widely in size and can be completely absent.

Right atrioventricular (tricuspid) valve - This valve sits in the atrioventricular orifice and has anterior, posterior, and septal cusps.

Fossa ovalis - this is a circular opening that is normally sealed over in adults. It derives from the embryonic remnant of the foramen ovale.

An incomplete closure in the foramen ovale leaves a small channel in 10-25% of individuals, termed a patent foramen ovale. The small opening is usually asymptomatic and undiagnosed in most people.

The atrioventricular node lies in the inferior part of the septum between the septal leaflet of the tricuspid valve and the opening of the coronary sinus (Netter229). Like the sinoatrial node it cannot be seen macroscopically.

31. To open the right ventricle, examine the pulmonary trunk and identify the level of the valve. Make a series of cuts to open the wall.
    (Figure229)

Take care to cut only the ventricular wall, and not the atrioventricular valve, while making this cut. Having someone reflect the opening slightly and a third person shining light into the gap as it is being cut may help with accuracy of the cut through the wall.

Make a short horizontal cut in the anterior wall of the right ventricle immediately inferior to the pulmonary valves (Figure229, cut 1).

Insert scissors into the right end and make a second cut parallel to the atrioventricular sulcus (about 1cm from the sulcus) ending the cut at the inferior border of the heart (Figure229, cut 2).

From the left side of cut 1 make a third cut parallel to the interventricular sulcus about 2cm from the sulcus (Figure229, cut 3).

32. Reflect the ventricular wall flap inferiorly, opening the right ventricle.

The chambers of the heart commonly have clotted blood inside. The overnight soaking should have softened the clot such that you can remove any large pieces of blood clot with a probe.

While removing any clotted blood, take care not to damage the chordae tendineae strands that may be mixed amongst the blood clots.

When most of the clotted blood is gone, rinse out the atrium under a stream of cold water in a side sink to wash out residual small clots of blood.

33. Observe the chamber of the right ventricle and identify.
    (Netter224) (Photo2016)

Right atrioventricular (tricuspid) valve - This valve has three cusps, an anterior, a septal and a posterior cusp.

Chordae tendineae - These are string-like projections connecting to the cusps and arising from individual anterior and posterior papillary muscles, and from several small septal papillary muscles.

Papillary muscles - These arise from the walls of the ventricle and attach to the chordae tendineae. The anterior papillary muscle is the largest arising from the anterior wall. The septal papillary muscles is the smallest arising from the interventricular septum. The posterior papillary muscle is intermediate in size arising from the posterior side of the ventricle.

There can be multiple or bifurcated papillary muscles at each of those locations. The septal papillary muscle is the most common to have multiple small muscles.

Trabeculae carneae - These are a series of muscular ridges 'roughening' the wall of the right ventricle, the papillary muscles arise from these ridges.

Septomarginal trabecula (moderator band) - This muscle ridge crosses from the interventricular septum to the base of the anterior papillary muscle conveying within it the right branch of the bundle of His.

The specialized conducting elements of the heart are only present in ventricles and include the bundle of His (left and right atrioventricular bundles) which lead to a network of Purkinje fibers emanating from the apex region of the heart. None of the conducting elements are visible with the naked eye.

Pulmonary valve (Photo2017) - Observe the inside of the pulmonary valve noting the three semilunar cusps, anterior, right, and left cusps.

CLINICAL EXERCISE - Pulmonary Artery Catheter

34. In cases where detailed monitoring of cardiac function is warranted, a catheter is inserted into the pulmonary arteries via the heart.  

In this clinical exercise, you will track a simulated catheter along the pathway from an accessible vein through to the pulmonary arteries. For the steps to take:
                                 ------ click here ------

35. To open the left ventricle, turn the heart to view down into the aorta observing the cusps of the aortic valve.
    (Netter226)

36. Insert one blade of your scissors between the left and right semilunar cusps and make a long cut in the anterior wall of the left ventricle all the way to the apex of the heart approximately 2cm to the left of the anterior interventricular sulcus.
    (Figure231, cut 1)

37. Spread open the left ventricle  and moisten the inside with wetting agent so that you can remove any large pieces of clotted blood from the ventricle with a probe.

38. Observe the chamber of the left ventricle and identify.
    (Netter225) (Photo2019)

The left atrioventricular (bicuspid or mitral) valve - The left atrioventricular (mitral) valve has only anterior and posterior valve leaflets. Each is attached by chordae tendineae to the anterior and the posterior papillary muscles.

Chordae tendineae - These string-like projections connect the cusps of the mitral valve to individual papillary muscles. Follow them from the cusps down to these muscles

Papillary muscles (anterior and posterior) - These arise from the walls of the ventricle and attach to the chordae tendineae. Note that the chordae tendineae of each papillary muscle attaches to both mitral valve cusps.

These muscles are often called the anterolateral and posteromedial papillary muscles as they are not in a perfect anterior-posterior orientation.

Trabeculae carneae - These are a series of muscular ridges 'roughening' the wall of the left ventricle.

Interventricular septum - The interventricular septum is thin and membranous superiorly, but thick and muscular inferiorly. Insert fingers into the left and right ventricles and palpate feeling for the thickness of the septum in different regions (Netter228).

The atrioventricular node cannot be seen macroscopically, but if you introduce your right index finger into the left ventricle and your left index finger into the right atrium and press them together. The AV node lies between your fingers (Netter229).

39. When your heart dissections are complete, moisten and place the heart in the biohazard bag with the lungs (in the organ container) and place that heart/lung biohazard back into the translucent organ container to keep with your donor.

a) Empty the fluid from white bucket into one of the side sinks and rinse the bucket if needed.

b) Place white bucket left under your table with the lid off so that it can dry.

As the bags may leak, always keep bagged organs inside the translucent airtight organ box below the table.  Do not place the bags on the floor or on chairs.

CHECKLIST

Soft Structures

Heart
    Left and right atria
    Left and right ventricles
    Left and right coronary sulci
    Anterior and posterior interventricular sulcus
    Right auricle
    Left auricle
    Apex of the heart

Valves
    Aortic semilunar valves
        Posterior, left, and right cusps
    Pulmonary artery semilunar valves
        Anterior, left and right cusps

 Right and left coronary artery openings

Coronary arteries   
    Right coronary artery
        Sinoatrial nodal artery
        Posterior interventricular artery
    Left coronary artery
        Circumflex artery
        Anterior interventricular artery

Coronary veins
    Coronary sinus

Right atrium
    Pectinate muscles
    Crista terminalis
    Opening of the superior vena cava
    Opening of the inferior vena cava
    Opening of the coronary sinus
    Right atrioventricular (tricuspid) valve
    Fossa ovalis

Right ventricle
    Chordae tendineae
    Papillary muscles (anterior, posterior and septal)
    Trabeculae carneae
    Septomarginal trabecula (moderator band)
    Right atrioventricular (tricuspid) valve cusps
        Anterior, posterior, and septal

Left ventricle
    Left atrioventricular (mitral) valve cusps
        Anterior and posterior
    Chordae tendineae
    Papillary muscles (anterior and posterior)
    Trabeculae carneae
    Interventricular septum
        Muscular and membranous