middle mediastinum and heart

What is the flow of blood from the body to the lungs?

Body → Superior vena cava / Inferior vena cava / Coronary sinus → Right atrium → Tricuspid valve → Right ventricle → Pulmonary valve → Pulmonary trunk → Pulmonary arteries → Lungs

What is the flow of blood from the lungs to the body?

Lungs → Pulmonary veins → Left atrium → Mitral (bicuspid) valve → Left ventricle → Aortic valve → Aorta → Body

Which vessels empty directly into the right atrium?

svc

ivc

coronary sinus

Which vessels empty into the left atrium?

Pulmonary veins (typically four)

Through which valve does blood pass from the right atrium to the right ventricle?

Tricuspid valve (right AV valve)

Through which valve does blood pass from the left atrium to the left ventricle?

Mitral valve (bicuspid valve, left AV valve)

Through which valve does blood leave the right ventricle?

Pulmonary valve

Through which valve does blood leave the left ventricle?

Aortic valve

What is the complete pathway of blood through the heart?

Body
→ Superior vena cava / Inferior vena cava / Coronary sinus
→ Right atrium
→ Tricuspid valve
→ Right ventricle
→ Pulmonary valve
→ Pulmonary trunk
→ Pulmonary arteries
→ Lungs
→ Pulmonary veins
→ Left atrium
→ Mitral (bicuspid) valve
→ Left ventricle
→ Aortic valve
→ Aorta
→ Body

Which chambers receive blood?

RA and LA

Which chambers pump blood?

RV and LV

What are the atrioventricular (AV) valves?

The AV valves are the valves located between the atria and ventricles:

• Tricuspid valve (right AV valve)

• Mitral (bicuspid) valve (left AV valve)

What valve is located between the right atrium and right ventricle?

Tricuspid valve

What valve is located between the left atrium and left ventricle?

Mitral valve (also called the bicuspid valve)

How many cusps does the tricuspid valve have?

3 cusps

What are the cusps of the tricuspid valve?

anterior,posterior, septal

How many cusps does the mitral valve have?

2

What are the cusps of the mitral valve?

anterior and posterior

During ventricular diastole, are the AV valves open or closed?

open

• The ventricles are relaxed and filling with blood.

• Blood flows from the atria into the ventricles.

During ventricular systole, are the AV valves open or closed?

closed.

• The ventricles are contracting.

• Closing the AV valves prevents blood from flowing backward into the atria.

What are the semilunar valves?

• Pulmonary valve

• Aortic valve

They are located at the exits of the ventricles and prevent backflow into the ventricles.

Which semilunar valve is located between the right ventricle and pulmonary trunk?

Pulmonary valve

Which semilunar valve is located between the left ventricle and aorta?

Aortic valve

What are the cusps of the pulmonary valve?

Right cusp

Left cusp
Anterior cusp

What are the cusps of the aortic valve?

Right cusp
Left cusp
Posterior cusp

Which aortic cusps contain the openings of the coronary arteries?

Right aortic cusp

Left aortic cusp

Which aortic cusp is called the non-coronary cusp?

Posterior cusp

What are the aortic sinuses (sinuses of Valsalva)?

The aortic sinuses are pocket-like dilations of the ascending aorta located just superior to the cusps of the aortic valve. They are formed by the valve cusps.

• Right aortic sinus

• Left aortic sinus

• Posterior (non-coronary) aortic sinus

During ventricular systole, are the semilunar valves open or closed?

open

• The ventricles are contracting.

• Blood is being ejected into the pulmonary trunk and aorta.

During ventricular diastole, are the semilunar valves open or closed?

closed

• The ventricles are relaxing.

• The valves prevent blood from flowing back into the ventricles.

What is the fibrous cardiac skeleton?

The fibrous cardiac skeleton is a framework of dense connective tissue located between the atria and ventricles.

How many fibrous rings (anuli) form the fibrous cardiac skeleton?

4

One ring surrounds each valve opening:

• Tricuspid valve

• Mitral valve

• Pulmonary valve

• Aortic valve

What structures do the fibrous rings surround?

The openings of the four heart valves.

What are the fibrous trigones?

The right and left fibrous trigones are connective tissue structures that connect the fibrous rings together.

Rings = circles around valves

Trigones = bridges connecting the rings

What is the mitral-aortic intervalvular fibrosa?

The connective tissue segment located between the mitral valve ring and the aortic valve ring.

What is the function of the fibrous cardiac skeleton?

Provides attachment for cardiac muscle fibers.

Provides attachment for valve cusps.

Helps maintain the structural integrity of the heart.

How does the fibrous cardiac skeleton affect electrical conduction?

It electrically insulates the atria from the ventricles.

This prevents electrical impulses from spreading directly from atrial muscle to ventricular muscle.

What is the only normal electrical connection between the atria and ventricles?

The AV bundle (Bundle of His).

Why is the SA node called the pacemaker of the heart?

The SA (sinoatrial) node is called the pacemaker because it initiates the heartbeat and normally has the fastest rate of spontaneous depolarization in the heart.

Where is the atrioventricular (AV) node located?

In the posteroinferior region of the interatrial septum, near the opening of the coronary sinus.

• SA node = top of right atrium

• AV node = bottom of right atrium/interatrial septum

What is the pathway of electrical conduction through the heart?

SA node
→ AV node
→ AV bundle (Bundle of His)
→ Right and Left bundle branches
→ Purkinje fibers
→ Ventricular myocardium

What is the AV bundle (Bundle of His)?

A bundle of specialized conducting fibers that carries impulses from the AV node into the ventricles.

Why is the AV bundle clinically important?

It is the only normal electrical connection between the atria and ventricles.

• The fibrous cardiac skeleton electrically insulates the atria from the ventricles.

• Therefore, impulses must pass through the AV bundle to reach the ventricles.

Where are the right and left bundle branches located?

In the interventricular septum, where they descend toward the apex of the heart.

What are Purkinje fibers?

Specialized conducting fibers that rapidly distribute electrical impulses throughout the ventricular myocardium.

Where are Purkinje fibers located?

In the subendocardial layer of the ventricular walls (just deep to the endocardium).

Which cranial nerve provides parasympathetic innervation to the heart and lungs?

Vagus nerve (CN X)

What is the effect of parasympathetic stimulation on heart rate

Decreases heart rate

What effect does parasympathetic stimulation have on coronary vessels?

Coronary vasoconstriction

What effect does parasympathetic stimulation have on the bronchial tree?

Bronchoconstriction

What nerves provide sympathetic innervation to thoracic viscera?

Cardiopulmonary splanchnic nerves

What effect does sympathetic stimulation have on heart rate?

Increases heart rate

What effect does sympathetic stimulation have on coronary vessels?

Coronary vasodilation

Into which chamber does the coronary sinus drain?

RA

Which cardiac veins drain into the coronary sinus?

great cardiac vein, middle cardiac vein, small cardiac vein

Which cardiac veins drain directly into the right atrium?

Anterior cardiac veins

What is right coronary dominance?

Right coronary dominance means the posterior interventricular artery (PDA) arises from the right coronary artery (RCA).

What percentage of people have right dominance?

75%

What is left coronary dominance?

Left coronary dominance means the posterior interventricular artery (PDA) arises from the circumflex artery, a branch of the left coronary artery.

What percentage of people have left dominance?

15%

What is codominance?

Codominance means the posterior interventricular artery receives contributions from both the right and left coronary circulations

What is a myocardial infarction (MI)?

A myocardial infarction (heart attack) is death (necrosis) of cardiac muscle due to prolonged ischemia.

What causes an MI?

Sudden occlusion (blockage) of a coronary artery, usually due to a ruptured atherosclerotic plaque and thrombus formation.

Which coronary artery is most commonly occluded in an MI?

LAD (Left Anterior Descending artery), also called the anterior interventricular artery.

Why is cardiac pain referred to the left chest and upper limb?

Cardiac pain fibers enter the spinal cord at the same levels as somatic sensory fibers from the left chest and upper limb, so the brain misinterprets the source of the pain.

This is called referred pain.

Which spinal cord levels receive cardiac pain afferents?

t1-t4

What vessels are commonly used for coronary artery bypass grafting

Great saphenous vein

✅ Internal thoracic (internal mammary) artery