Heart

What is another term for the pericardium?

Heart sac.

What type of covering does the pericardium have?

Fibroserous covering.

What fluid is found within the pericardial cavity?

Serous fluid.

What is the function of the serous fluid in the pericardial cavity?

To facilitate easy movement of the heart wall within the pericardial sac.

Name the two main layers of the serous pericardium.

Visceral layer and parietal layer.

What is another name for the visceral layer of the serous pericardium?

Epicardium.

Where is the visceral layer of the serous pericardium firmly attached?

To the heart wall.

What is the pericardial cavity?

The tiny space between the visceral and parietal layers of the serous pericardium, filled with serous fluid.

What can the heart accommodate a small degree of due to the pericardium?

Distension (rhythmic pulsation).

Under what conditions might the heart stretch?

Exercise and disease.

What is pericardiocentesis?

A medical procedure to remove an excess of fluid in the pericardial cavity.

Where is the heart located within the thorax?

Within the mediastinum.

Is the heart positioned symmetrically or asymmetrically in the thorax?

Asymmetrically.

Approximately what percentage of the heart lies to the left of the median plane?

About 60%.

Where is the base of the heart located?

Dorsally.

Where is the apex of the heart located?

Ventrally, close to the sternum.

Between which ribs does the projection of the heart on the chest wall generally extend in the dog?

Between the third and sixth ribs.

What is the general shape of the heart?

Conical.

What is the hilus of the heart considered to be?

The base of the heart, through which great vessels enter and exit.

Name the four compartments (chambers) of the heart.

Right atrium, right ventricle, left atrium, left ventricle.

Which side of the heart receives deoxygenated blood?

The right side (right atrium and right ventricle).

Where does the right ventricle pump blood to?

To the lungs via the pulmonary trunk.

Which side of the heart receives oxygenated blood?

The left side (left atrium and left ventricle).

Where does the left ventricle pump blood to?

To the rest of the body via the aorta.

What separates the atria from the ventricles?

A transverse, incomplete septum, indicated on the surface by the coronary groove.

What is the function of the atria?

To collect blood and ensure enough is present to fill each ventricle quickly.

What is the function of the ventricles?

To pump blood out of the heart.

Which ventricle typically has thicker walls?

The left ventricle.

Why does the left ventricle have thicker walls?

Because it pumps blood to the entire systemic circulation against higher pressure.

What is the blood supply to the heart called?

The coronary circulation.

From where do the coronary arteries originate?

From the aorta.

Specifically, where on the aorta do the coronary arteries arise?

From two of the three sinuses above the semilunar cusps at the root of the aorta.

Name the two main coronary arteries.

Left coronary artery and right coronary artery.

Which coronary artery is typically larger?

The left coronary artery.

What are the main branches of the left coronary artery?

Interventricular paraconal branch and circumflex branch.

What area of the heart does the interventricular paraconal branch supply?

The walls of the left ventricle and most of the interventricular septum.

Where does the circumflex branch of the left coronary artery run?

In the coronary groove towards the caudal aspect of the heart.

Where does the right coronary artery run?

Between the right auricle and the pulmonary trunk to the coronary groove.

What is the function of the heart valves?

To ensure a unidirectional flow of blood and prevent reflux.

Where are the atrioventricular valves located?

Between the atria and the ventricles.

Name the left atrioventricular valve.

Bicuspid or mitral valve.

Name the right atrioventricular valve.

Tricuspid valve.

Where are the semilunar valves located?

At the exit of the ventricles into the great arteries.

Name the semilunar valve at the exit of the right ventricle.

Pulmonary valve.

Name the semilunar valve at the exit of the left ventricle.

Aortic valve.

What is the heart's inherent rhythm controlled by?

The sinoatrial node (pacemaker).

Where is the sinoatrial node located?

Below the epicardium of the right atrial wall ventral to the cranial caval opening.

What is the next node in the heart's conducting system after the sinoatrial node?

The atrioventricular node.

Where is the atrioventricular node located?

Within the interatrial septum, cranial to the opening of the coronary sinus.

What structure arises from the atrioventricular node to conduct the impulse to the ventricles?

The atrioventricular bundle.

What are Purkinje fibers?

Modified cardiac muscle fibers that conduct impulses much more rapidly than those of the common sort.

What is the layer of the heart wall primarily composed of cardiac muscle?

Myocardium.

What is the thin, smooth inner lining of the heart chambers?

Endocardium.

What is the term for the contraction phase of the heart?

Systole.

What is the term for the relaxation phase of the heart?

Diastole.

What is stroke volume?

The volume of blood ejected by the ventricle with each contraction.

What is cardiac output?

The product of stroke volume and heart rate.

What helps in the return of blood to the heart during diastole?

Ventilation and contraction of the diaphragm.

Closure of which valves produces the first heart sound (S1)?

Atrioventricular valves.

Closure of which valves produces the second heart sound (S2)?

Semilunar valves.

In which intercostal space is pericardiocentesis most safely performed in the bovine?

The 5th intercostal space of the left side.

What is the sternopericardial ligament?

A ligament that forms at the ventral apex of the pericardial sac and attaches to the sternum.

What is the approximate percentage of body weight that the heart typically constitutes?

About 0.75%.

Is the heart relatively larger in smaller or larger species?

Smaller species.

How does exercise affect the size of the heart?

It becomes larger (hypertrophied).

What is the coronary groove?

A groove on the surface of the heart that separates the atria from the ventricles.

What is the paraconal (left) interventricular groove?

A shallow groove that descends toward the apex on the cranial aspect of the heart.

What is the subsinuosal (right) interventricular groove?

A shallow groove that descends toward the apex on the caudal aspect of the heart.

What is the ligamentum arteriosum?

The fibrosed remnant of the ductus arteriosus.

Where does the ligamentum arteriosum attach?

Joins the pulmonary trunk on its right face.

What is the fossa ovalis?

A depression in the interatrial septum, a remnant of the foramen ovale in the fetus.

What are trabeculae carneae?

Myocardial ridges that project mainly from the outer wall of the ventricles.

What are papillary muscles?

Muscles within the ventricles that are connected to the cusps of the atrioventricular valves.

What are chordae tendineae?

Fibrous cords that connect the cusps of the atrioventricular valves to the papillary muscles.

What is the intervenous tubercle?

A ridge within the right atrium between the openings of the cranial and caudal vena cava.

Describe the reflection of the pericardium around the great vessels.

The visceral and parietal layers of the pericardium continue into each other at complex reflections.

How does the position of the heart in ruminants differ from the general description?

In ruminants, the heart extends between the 2nd to 5th intercostal spaces.

What is the clinical challenge posed by the position of the heart in larger animals?

Much of the heart is covered by the forelimb.

Describe the sternopericardiac ligament more specifically.

A thick external fibrous covering that blends with adventitia of the great vessels.

What is the significance of the cardiac notch of the lungs?

Allows the heart to be closer to the thoracic wall for auscultation.

How does the exit of the aorta compare to the pulmonary trunk?

The exit to the aorta takes a more central position.

What is the fibrous skeleton of the heart?

A framework of dense connective tissue that surrounds the heart valves.

Describe the arrangement of chordae tendineae and papillary muscles in relation to atrioventricular valves.

Chordae connect each cusp to papillary muscles.

What are ossa cordis, and in which species are they prominent?

Nodules of bone in the fibrous skeleton, prominent in bovines.

Explain the variation in the circumflex branch across different species.

Terminates differently in horse/pig vs carnivores/ruminants.

Describe the venous drainage of the heart.

Collection of deoxygenated blood via cardiac veins, mostly the great cardiac vein.

How does coronary blood flow differ during systole and diastole?

Greatest during diastole due to relaxation of the myocardium.

What is the clinical relevance of collateral circulation in coronary arteries?

Preformed anastomoses can provide alternative blood supply.

Explain the embryological development of the interventricular septum.

Fusion of muscular thickening with endocardial cushions.

How does the left atrium receive blood?

From the lungs via pulmonary veins.

Describe the structure of the trabecula septomarginalis in right ventricle.

Muscular band providing shortcut for electrical impulse.

How does autonomic innervation affect heart function?

Sympathetic increases rate while parasympathetic decreases rate.

What is the clinical significance of heart valve projections on the chest wall?

Guide for placing stethoscope for auscultation.

Explain why the heart is within the mediastinum.

It resides in the central thoracic compartment between pleural cavities.

How might pericardial effusion affect the heart's function?

Limits heart filling during diastole, can cause cardiac tamponade.

Describe blood supply to the atrial myocardium.

Distributed by branches of coronary arteries.

What are the implications of the heart's position relative to the diaphragm?

Proximity can lead to conditions affecting its function.

Explain the function of the ligament at the apex of the pericardial sac.

Stabilizes the heart within the thoracic cavity.

How does heart size change from newborn to adult?

Grows in proportion to overall body size.

Discuss the significance of the connective tissue layer of the parietal pericardium.

Provides structural integrity and stability to the heart.