Heart Anatomy and Development Lecture Notes

150 Q&A flashcards covering adult heart anatomy, coronary circulation, conduction system, cardiac cycle, and detailed heart development including fetal circulation and birth changes.

What are the four parts of the mediastinum?

The mediastinum is divided into anterior, middle, posterior, and superior sections to organize structures within the thoracic cavity.

Which mediastinal part contains the heart, great vessels, and pericardium?

The middle mediastinum centrally houses vital structures like the heart, the great vessels that enter and leave it, and the protective pericardium.

In the anterior mediastinum, what small space is located between the sternum and pericardium, and what does it contain?

The small space located between the sternum and pericardium is the anterior mediastinum, and it primarily contains the internal thoracic vessels.

Where is the parietal serous pericardium located?

The parietal serous pericardium is the inner lining of the fibrous pericardium, forming the outer layer of the serous pericardium.

What is the serous pericardium reflected onto the surface of the heart called?

The serous pericardium that is reflected onto the surface of the heart itself is called the visceral serous pericardium, also known as the epicardium.

What is the potential space between the serous and fibrous pericardium called?

The pericardial cavity is the potential space located between the parietal and visceral layers of the serous pericardium, containing a small amount of fluid to reduce friction.

Which heart chambers are the right and left atria?

The right and left atria are the two upper receiving chambers of the heart, collecting blood from the body (right atrium) and lungs (left atrium).

Which heart chambers are the right and left ventricles?

The right and left ventricles are the two lower pumping chambers of the heart, ejecting blood to the lungs (right ventricle) and the rest of the body (left ventricle).

What vessels return blood to the right atrium from below?

Blood returns to the right atrium from below and from the body via the inferior vena cava, superior vena cava, and from the heart itself via the coronary sinus.

What is the fossa ovalis?

The fossa ovalis is a shallow depression in the interatrial septum, representing the remnant of the foramen ovale, an embryonic opening that allowed blood to bypass the fetal lungs.

What is the right auricle?

The right auricle is a small, ear-shaped muscular appendage of the right atrium that slightly increases its capacity.

What muscle forms the rough anterior wall of the right atrium?

The pectinate muscles are parallel muscular ridges that form the rough anterior wall and auricle of the right atrium.

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

Blood passes from the right atrium to the right ventricle through the right atrioventricular valve, also known as the tricuspid valve, named for its three cusps.

What structures connect the tricuspid valve cusps to the ventricular wall?

The chordae tendineae are fibrous cords that connect the free edges of the tricuspid valve cusps to papillary muscles within the ventricular wall, preventing valve eversion during ventricular contraction.

What are the muscular ridges lining the interior of the right ventricle?

Trabeculae carneae are irregular muscular ridges and columns that line the interior surfaces of the right and left ventricles, contributing to myocardial strength and possibly preventing suction.

What is the moderator band (septomarginal trabecula) and what is its function?

The moderator band, also known as the septomarginal trabecula, is a muscular band in the right ventricle that extends from the interventricular septum to the anterior papillary muscle, carrying part of the right bundle branch of the AV conduction system.

Where does blood exit the right ventricle?

Blood exits the right ventricle through a smooth-walled cone-shaped region called the conus arteriosus, then passes through the pulmonary valve into the pulmonary trunk.

What prevents reflux from the right ventricle to the right atrium during systole?

During ventricular systole (contraction), the closure of the tricuspid valve, tethered by the chordae tendineae and papillary muscles, prevents the backflow (reflux) of blood from the right ventricle into the right atrium.

Which valve prevents reflux from the left atrium into the left ventricle?

The left atrioventricular (AV) valve, also known as the mitral valve (or bicuspid valve due to its two cusps), prevents the backflow (reflux) of blood from the left ventricle into the left atrium during ventricular systole.

Where do the left and right coronary arteries emerge from the aorta?

The left and right coronary arteries, which supply blood to the heart muscle, emerge from the aortic sinuses, which are small pockets located immediately above the cusps of the aortic valve.

Which groove houses the left anterior descending (LAD) artery?

The left anterior descending (LAD) artery, a major branch of the left coronary artery, is housed within the anterior interventricular groove (or sulcus), which separates the two ventricles on the anterior surface.

Which artery runs in the atrioventricular groove?

The left circumflex branch, typically originating from the left main coronary artery, runs in the atrioventricular groove (coronary sulcus), encircling the heart between the left atrium and left ventricle.

What is the posterior interventricular artery a branch of in many individuals?

In many individuals, the posterior interventricular artery, which supplies the posterior walls of both ventricles and the posterior part of the interventricular septum, is a branch of the right coronary artery.

What is the sinuatrial nodal artery?

The sinuatrial nodal artery is a specific branch, usually from the right coronary artery, that supplies blood to the sinuatrial (SA) node, the heart's natural pacemaker.

Which vein parallels the great cardiac artery?

The great cardiac vein parallels the great cardiac artery (often alongside the LAD artery) and drains blood from the anterior aspects of the ventricles and left atrium into the coronary sinus.

Which vein parallels the posterior interventricular artery?

The middle cardiac vein runs alongside the posterior interventricular artery, draining blood from the posterior parts of the ventricles into the coronary sinus.

Which vein parallels the right coronary artery?

The small cardiac vein typically parallels the right coronary artery, draining blood from the right atrium and right ventricle into the coronary sinus.

What is the clinical consequence of occlusion of a coronary artery?

Occlusion (blockage) of a coronary artery leads to ischemia, which is a lack of oxygen to the heart muscle, and can result in myocardial infarction (MI), commonly known as a heart attack, where heart tissue dies.

Where do cardiac veins drain before entering the right atrium?

Most cardiac veins drain into the coronary sinus, a large venous channel located in the posterior atrioventricular groove, which then empties directly into the right atrium.

What initiates the heartbeat in the conduction system?

The sinuatrial (SA) node, often called the pacemaker of the heart, is the specialized structure that initiates the electrical impulses for the heartbeat in the cardiac conduction system.

Where is the SA node located?

The SA node is located in the superior-lateral wall of the right atrium, near the junction where the superior vena cava (SVC) enters the atrium.

Where is the AV node located?

The atrioventricular (AV) node is located in the interatrial septum, close to the opening of the coronary sinus, and acts to relay and briefly delay electrical impulses from the atria to the ventricles.

Which structure conducts impulses from the AV node to the ventricles?

The AV bundle, also known as the bundle of His, conducts electrical impulses from the AV node through the fibrous skeleton of the heart to the ventricles via its right and left bundle branches.

Which autonomic structures modulate the cardiac conduction system?

The autonomic cardiac plexuses, which include branches from the vagus nerve (parasympathetic) and the sympathetic trunk, modulate the rate and force of contraction of the cardiac conduction system.

What are the two main phases of the cardiac cycle?

The two main phases of the cardiac cycle are diastole (relaxation and filling of the heart) and systole (contraction and ejection of blood from the heart).

During diastole, what happens to the valves?

During diastole, the aortic and pulmonary valves are closed to prevent backflow from the great arteries, while the atrioventricular (AV) valves (tricuspid and mitral) open to allow blood from the atria to fill the ventricles, often aided by atrial contraction.

During systole, what happens to the valves?

During systole, the atrioventricular (AV) valves (tricuspid and mitral) close to prevent backflow into the atria, while the aortic and pulmonary valves open to allow the ventricles to contract and eject blood into the aorta and pulmonary trunk.

What forms from the cardiogenic region in the lateral plate mesoderm by day 21?

By day 21 of embryonic development, the heart tube forms from the cardiogenic region within the lateral plate mesoderm, which will eventually give rise to all parts of the heart.

On which day does the heart begin to beat?

The embryonic heart begins to beat on approximately day 22 of development, marking the crucial initiation of circulatory function.

What are the incipient chambers of the heart tube?

The incipient (early) chambers of the heart tube are the sinus venosus, primitive common atrium, primitive ventricle, and bulbus cordis, which will undergo significant remodeling to form the adult heart.

What adult structures do the sinus venosus and coronary sinus become part of?

In adult anatomy, the sinus venosus primarily becomes part of the smooth wall of the right atrium (sinus venarum) and the coronary sinus, which drains most of the heart's venous blood.

What does the primitive common atrium become?

The primitive common atrium undergoes septation to form the definitive right and left atria of the adult heart.

What does the bulbus cordis contribute to in development?

During heart development, the bulbus cordis contributes to the formation of the outflow tracts of both ventricles, specifically the conus arteriosus of the right ventricle and the aortic vestibule of the left ventricle.

What is the septum primum?

The septum primum is a crescent-shaped septum that grows from the roof of the primitive common atrium towards the endocardial cushions, initially creating an opening called the ostium primum.

What is ostium primum?

Ostium primum is the initial opening or communication between the right and left atria, located inferiorly, before the septum primum eventually fuses with the endocardial cushions to close it.

What forms ostium secundum?

Ostium secundum is a new opening formed in the superior part of the septum primum through programmed cell death (apoptosis) as the ostium primum closes, ensuring continued blood flow between the atria.

What forms septum secundum?

Septum secundum is a second, crescent-shaped septum that grows from the atrial roof to the right of the septum primum, overlapping the ostium secundum and forming the basis for the foramen ovale.

What is the foramen ovale and when is it completed?

The foramen ovale is an oblique opening between the right and left atria, formed by the overlapping of septum primum (as a flap valve) and septum secundum; it is completed around day 46 of development and allows right-to-left shunting of blood in the fetus.

What valve acts as a flap to prevent backflow through the foramen ovale?

The septum primum acts as a flap valve for the foramen ovale, ensuring that blood flows only from the right atrium to the left atrium and preventing backflow or reflux during fetal life.

What are endocardial cushions important for?

Endocardial cushions are critical mesenchymal swellings that grow within the atrioventricular canal, playing a vital role in atrioventricular septation (dividing the common AV canal) and the formation of the meticulously structured AV valves.

When do endocardial cushions begin to grow into the primitive AV canal?

Endocardial cushions commence their growth into the primitive atrioventricular (AV) canal primarily around day 30 of embryonic development.

When do dorsal and ventral cushions meet to divide the AV canal?

The dorsal and ventral endocardial cushions meet centrally within the primitive AV canal to divide it into separate right and left atrioventricular orifices around day 33.

When are the AV valves formed?

The atrioventricular (AV) valves, namely the tricuspid and mitral valves, are formed approximately on day 90 of embryonic development, arising from the endocardial cushions and surrounding ventricular myocardium.

When does muscular ventricular septum begin to grow?

The muscular ventricular septum, which forms the thick, inferior portion of the interventricular septum, begins to grow from the floor of the primitive ventricle around day 28–30.

What forms the interventricular foramen?

The superior margin of the growing muscular ventricular septum forms the interventricular foramen, which is initially a large, temporary opening between the developing right and left ventricles.

When is the interventricular foramen closed, and by what structures?

The interventricular foramen is normally closed by day 60; by the fusion of tissue derived from the endocardial cushions and the descending conotruncal ridges, which collectively form the membranous part of the interventricular septum.

What are conotruncal ridges?

Conotruncal ridges are helical ridges that form on the walls of the proximal bulbus cordis and truncus arteriosus; these ridges spiral towards each other to separate the developing outflow tracts into distinct pulmonary and aortic channels.

What is the result of the spiral of the conotruncal ridges?

The spiral arrangement and fusion of the conotruncal ridges result in the division of the single ventricular outflow tract into two separate, spiraling channels: the ascending aorta and the pulmonary trunk.

What closes the ventricular outflow tract to form the membranous IV septum?

The inferior portion of the conotruncal septum (formed from the fused conotruncal ridges) descends to close the superior part of the interventricular foramen, thus completing the membranous interventricular septum.

Why do disruptions in 4th–7th week heart development often cause multiple defects?

Disruptions during the 4th–7th week of heart development frequently cause multiple cardiac defects because many critical developmental steps, such as septation and great vessel formation, occur simultaneously during this overlapping timeframe.

What carries oxygenated blood from the placenta to the fetus?

The umbilical vein carries oxygenated blood and nutrients directly from the placenta to the fetus, bypassing the fetal lungs.

What shunts oxygenated blood through the liver to the IVC in the fetus?

The ductus venosus is a fetal shunt that allows a significant portion of the oxygenated blood from the umbilical vein to bypass the liver's sinusoids and flow directly into the inferior vena cava (IVC).

Where does the oxygenated blood mix in the fetal liver and IVC?

In fetal circulation, oxygenated blood from the placenta mixes with deoxygenated blood in the liver (via hepatic portal vein) and within the inferior vena cava (IVC) as it receives blood from both the ductus venosus and fetal lower body.

Where does blood in the right atrium go after entering from the IVC and SVC in the fetus?

After entering the right atrium from the IVC and SVC in the fetus, most of the oxygenated blood is shunted directly through the foramen ovale to the left atrium, bypassing the non-functional fetal lungs.

From the left atrium, where does blood go next in fetal circulation?

From the left atrium in fetal circulation, blood proceeds into the left ventricle, which then pumps it into the ascending aorta to supply the head, arms, and descending aorta.

Where does deoxygenated blood returning from the head and arms via the SVC go?

Deoxygenated blood returning from the head and arms via the superior vena cava (SVC) enters the right atrium, then mostly passes into the right ventricle and subsequently into the pulmonary trunk.

What is the role of the ductus arteriosus in fetal circulation?

The ductus arteriosus is a crucial fetal shunting vessel that diverts blood from the pulmonary trunk (which would normally go to the lungs) directly into the descending aorta, again bypassing the fetal lungs.

Where does descending aorta blood go in the fetus?

In the fetus, blood from the descending aorta supplies the gut and lower extremities, with a significant amount branching off into the two umbilical arteries to return deoxygenated blood and waste products to the placenta.

What becomes of the umbilical vein after birth?

After birth, the umbilical vein collapses and fibroses, forming the ligamentum teres hepatis, which fixes the liver to the anterior abdominal wall.

What becomes of the ductus venosus after birth?

After birth, the ductus venosus functionally closes shortly after the umbilical cord is clamped and eventually fibroses to form the ligamentum venosum in the adult liver.

What happens to the foramen ovale after birth?

After birth, with the first breaths, pulmonary vascular resistance drops, increasing blood flow to the lungs and pressure in the left atrium, causing the septum primum to press against the septum secundum, functionally closing the foramen ovale and eventually forming the fossa ovalis.

What happens to the ductus arteriosus after birth?

After birth, with increased systemic vascular resistance and decreased prostaglandins, the ductus arteriosus constricts and eventually fibroses to become the ligamentum arteriosum, a fibrous band connecting the aorta and pulmonary artery.

What happens to the umbilical arteries after birth?

After birth, the umbilical arteries rapidly constrict and then completely obliterate, forming the medial umbilical ligaments (or folds) in the adult.

Patent foramen ovale refers to what type of defect?

A patent foramen ovale (PFO) refers to a small opening that persists in the interatrial septum at the site of the former foramen ovale, allowing a communication between the atria; it is generally considered an atrial septal defect when the opening is larger than probe-size.

What is Patent Ductus Arteriosus (PDA)?

Patent Ductus Arteriosus (PDA) is a congenital heart defect where the ductus arteriosus fails to close after birth, allowing oxygenated blood from the higher-pressure aorta to flow into the lower-pressure pulmonary trunk, leading to increased pulmonary blood flow.

What major neonatal hemodynamic change occurs after birth?

After birth, a major hemodynamic change is a significant drop in pulmonary vascular resistance due to the expansion of the lungs and the increased oxygen tension, facilitating blood flow to the lungs.

What happens to the umbilical vein after birth?

After birth, the umbilical vein collapses and undergoes fibrosis to form the ligamentum teres, a round ligament in the adult liver.

What becomes of the ductus venosus in the adult?

In the adult, the ductus venosus, a fetal shunt, becomes the ligamentum venosum, a fibrous cord found in the fissure for the ligamentum venosum on the inferior surface of the liver.

What becomes the fossa ovalis in the adult?

In the adult, the fossa ovalis is formed by the functional and anatomical closure of the foramen ovale, which was an opening between the atria in the fetal heart.

What becomes the ligamentum arteriosum in the adult?

In the adult, the ductus arteriosus, a fetal shunt connecting the pulmonary artery to the aorta, becomes the ligamentum arteriosum, a fibrous cord.

What structure becomes the umbilical ligaments in the adult?

In the adult, the umbilical arteries, which carried deoxygenated blood from the fetus to the placenta, become the medial umbilical ligaments (or folds) in the anterior abdominal wall.

What is the role of the endocardial cushions in heart development?

Beyond their role in septation, endocardial cushions contribute directly to the formation and proper development of the atrioventricular (AV) valves (mitral and tricuspid), ensuring their competence.

When do conotruncal ridges begin to form?

Conotruncal ridges, which are crucial for outflow tract septation, begin to form around day 35 of embryonic development.

When do the conotruncal ridges complete the division of the ventricular outflow tract?

The conotruncal ridges complete the division of the ventricular outflow tract into the aorta and pulmonary artery around day 60 of embryonic development.

What is the fetal counterpart to the left atrium’s smooth wall?

The smooth wall of the adult left atrium is derived from the incorporation of the embryonic pulmonary veins into the primitive atrium, making the incorporated veins its 'fetal counterpart' in terms of origin. The rough-walled left auricle is derived from the primitive left atrium.

Which chamber forms the apex of the heart?

The left ventricle, due to its shape and orientation, forms the apex (the inferior pointed portion) of the heart.

Which valve guards the left AV orifice?

The mitral (left AV) valve, a bicuspid valve, guards the left atrioventricular orifice, controlling blood flow from the left atrium to the left ventricle.

Which valve guards the right AV orifice?

The tricuspid (right AV) valve, a three-cusped valve, guards the right atrioventricular orifice, regulating blood flow from the right atrium to the right ventricle.

How many cusps does the aortic valve have?

The aortic valve typically has three cusps (semilunar leaflets) that open to allow blood into the aorta and close to prevent backflow into the left ventricle.

How many cusps does the pulmonary valve have?

The pulmonary valve also typically has three cusps (semilunar leaflets) that open to allow blood into the pulmonary trunk and close to prevent backflow into the right ventricle.

What is the original receptacle for blood that becomes the right atrium and coronary sinus?

The sinus venosus, an embryonic venous chamber, is the original receptacle for blood in the developing heart and ultimately contributes to the smooth part of the right atrium (sinus venarum) and the coronary sinus in the adult.

Which chamber forms the base of the heart?

While both the right and left atria contribute to the base of the heart (the posterior surface), the left atrium forms the majority of this posterior aspect.

What vessel drains most of the heart muscle into the right atrium?

The coronary sinus is the principal vessel that drains most of the deoxygenated blood from the heart muscle into the right atrium.

Which artery is the principal supplier of the SA node?

The sinuatrial nodal artery, which typically branches off the right coronary artery, is the principal supplier of blood to the SA node, the heart's natural pacemaker.

What is the role of the moderator band in the right ventricle?

The moderator band (septomarginal trabecula) in the right ventricle serves as a shortcut for the right bundle branch of the AV conduction system, carrying impulses to the anterior papillary muscle to coordinate ventricular contraction.

Where is the epicardium located?

The epicardium is the visceral layer of the serous pericardium, tightly adhering to the outer surface of the heart muscle (myocardium).

What structures anchor the mitral and tricuspid valves to the ventricular walls?

The chordae tendineae are fibrous cords that connect the cusps of the mitral and tricuspid valves to the papillary muscles, which are muscular projections from the ventricular walls; together, they anchor the valves and prevent their eversion during ventricular contraction.

Which chamber forms the diaphragmatic surface of the heart?

The left ventricle forms the majority of the diaphragmatic surface (inferior surface) of the heart, which rests upon the diaphragm.

Which chamber forms the left border of the heart?

The left ventricle forms the left border (or obtuse margin) of the heart, extending from the left atrium to the cardiac apex.

Where does blood exit the left ventricle?

Blood exits the left ventricle by passing through the aortic valve into the ascending aorta, which then distributes oxygenated blood to the entire systemic circulation.