B2 W3 - The Heart and the Mediastinum (Parts 1&2) Flashcards
What is the mediastinum?
The mediastinum is the broad central region of the thoracic cavity that separates the two laterally placed pleural cavities where the lungs sit.
What is a notable feature of the lungs in relation to the mediastinum?
The lungs take on any shape that is left over after the heart fills the mediastinum, leaving impressionable imprints on the lung surfaces from mediastinal structures.
Give some examples of structures that can leave impressions on the lungs.
The heartAortaSuperior vena cava (SVC)Azygous vein
Where is the mediastinum located?
The mediastinum is located between the lungs, extending from the sternum anteriorly to the vertebral bodies posteriorly.
What are the superior and inferior boundaries of the mediastinum?
Superiorly, the mediastinum starts at the superior thoracic apertureInferiorly it extends to the diaphragm.
Is the mediastinum visible on an X-ray?
YesThe mediastinum can be seen on an X-ray as a shadow that dilates inferiorly due to the presence of the heart.
What is the silhouette sign?
The silhouette sign refers to the normal shape of the mediastinum on an X-ray.A loss of this sign suggests a pathology in the heart or lungs.
What key structures can be identified on an X-ray of the mediastinum?
The aortic arch, also called the aortic knob or knuckle, and the pulmonary trunk can be seen on an X-ray of the mediastinum.
What is the hilum of the lung, and where is it located in relation to the mediastinum on an X-ray?
The hilum of the lung is where arteries, veins, lymphatic nerves, and the tracheobronchial tree enter and exit the lungs. It can be seen along the mediastinal border on an X-ray.
What features on a chest radiograph indicate whether the image was taken during inspiration or expiration?
On an inspiration X-ray, the lung field appears large, the diaphragm is flat, and the costodiaphragmatic space is well opened.
What is the costodiaphragmatic space?
The costodiaphragmatic space is a recess where the lungs extend down inferiorly during inspiration.
What anatomical landmark divides the mediastinum into superior and inferior regions?
The sternal plane, a horizontal line drawn at the level of the sternal angle, divides the mediastinum into superior and inferior regions.
Where is the sternal angle located?
The sternal angle is the ridge formed where the manubrium of the sternum meets the body of the sternum.
What vertebral level corresponds to the sternal plane?
The sternal plane intersects posteriorly with the T4/T5 intervertebral disc.
How is the inferior mediastinum further subdivided?
The inferior mediastinum is divided into three parts: anterior, middle, and posterior.
What structure defines the subdivisions of the inferior mediastinum?
The heart, located in the middle mediastinum, defines the three areas of the inferior mediastinum.
Why is the sternal angle important for rib counting?
The sternal angle marks the articulation of the second rib’s costal cartilage, serving as a starting point for counting ribs.
Describe the steps involved in rib counting using the sternal angle as a landmark.
First, locate the suprasternal notch, then palpate down the sternum to the sternal angle. Move immediately laterally to find the second rib’s costal cartilage, then count ribs up or down.
Can the divisions of the mediastinum be identified on a lateral radiograph?
YesThe divisions of the mediastinum, including the superior, anterior, middle, and posterior regions, can be identified on a lateral radiograph.
What does the lateral view of the mediastinum reveal about the anterior mediastinum?
The lateral radiograph demonstrates that the anterior mediastinum is a narrow space.
What is the costodiaphragmatic recess, and where is it located in relation to the mediastinum?
The costodiaphragmatic recess is part of the posterior mediastinum where the lungs extend down inferiorly.
What is the clinical significance of the costodiaphragmatic recess?
Potential site for fluid accumulation (blood, pus, interstitial fluid), leading to a pleural effusion.
What can be used to identify the mediastinal regions on a lateral radiograph?
The same landmarks used to define the mediastinal divisions, such as the sternal angle and T4/T5 intervertebral disc, can be used to identify the regions on a lateral radiograph.
What does identifying the mediastinal regions on a lateral radiograph allow you to do?
Identifying these regions allows you to determine the location of dense opacities or structures, which can help in identifying potential pathologies.
How does appreciating the spaces within the mediastinum on a lateral radiograph help in understanding pleural effusions?
Viewing the mediastinum laterally helps you to see spaces like the costodiaphragmatic recess, where various fluids can collect and result in a pleural effusion.
What types of fluids can collect in the costodiaphragmatic recess?
Fluids such as blood, pus, or interstitial fluid can collect in this space.
How do the vagus and phrenic nerves course through the superior mediastinum?
The vagus and phrenic nerves both descend through the superior mediastinum to reach the inferior mediastinum.
List the three major arterial branches coming off the arch of the aorta in the superior mediastinum.
The three major branches are: Brachiocephalic trunk (which further divides into the right common carotid and right subclavian arteries), Left common carotid arteryLeft subclavian artery.
What is the typical order in which the three major branches arise from the arch of the aorta?
The branches always arise in the same order: Brachiocephalic trunkLeft common carotid arteryLeft subclavian artery
Besides the brachiocephalic trunk, what are the other two major branches of the aortic arch?
The left common carotid artery and the left subclavian artery.
What is the name of the first branch that comes off the arch of the aorta?
The brachiocephalic trunk.
Where do the right and left brachiocephalic veins form?
Immediately posterior to the sternoclavicular joint on each side.
Where does the thoracic duct drain into the venous system?
At the junction of the left internal jugular vein and the left subclavian vein.
What three major branches come off the arch of the aorta?
The brachiocephalic trunkLeft common carotid arteryLeft subclavian artery.
How can the location of structures in the mediastinum impact the symptoms a patient presents with?
Pathology in one structure can affect nearby structures, leading to seemingly unrelated symptoms.
Why is the superficial location of veins in the superior mediastinum important?
It allows for easy access for procedures such as administering fluids or medication, drawing blood, or inserting dialysis lines.
What anatomical landmark marks the division between the superior and inferior mediastinum?
The sternal angle.
Where is the superior mediastinum located in relation to the sternal angle?
The superior mediastinum is located above the sternal angle.
What demarcates the superior boundary of the superior mediastinum?
The superior thoracic aperture marks the superior boundary of the superior mediastinum.
Name three major structures found within the superior mediastinum, besides vessels.
The tracheaThe Oesophagus,The vagus and phrenic nerves
In the superior mediastinum, are the veins generally located anterior or posterior to the arteries?
The veins of the superior mediastinum sit more anteriorly (superficially) compared to the arteries.
What is the clinical significance of the anterior location of the veins in the superior mediastinum?
The anterior position of the veins makes them ideal targets for procedures requiring fast access to the venous system, such as central venous access.
Where do the right and left brachiocephalic veins form in relation to a palpable landmark?
The right and left brachiocephalic veins form immediately posterior to the sternoclavicular joints.
Behind which anatomical structure does the superior vena cava form?
The superior vena cava is formed behind the right costal cartilage of rib 2.
What structure drains into the junction of the left internal jugular vein and the left subclavian vein?
The thoracic duct, which drains lymph from most of the body
Besides administering fluids and drugs, what is another common use for central lines placed in the superior mediastinum?
DialysisAllowing aspiration and reinfusion of large volumes of blood.
Describe the path a guide wire could take to access the inferior vena cava from the superior vena cava. What clinical procedures utilise this pathway?
Due to the vertical orientation of the superior and inferior vena cava, a guide wire can be passed from the Superior vena cava, Through the right atrium, Into the inferior vena cava.This pathway can be used for procedures like transjugular liver biopsies or the insertion of an inferior vena cava filter.
What is a common route for procedures like a transjugular liver biopsy?
Passing a guide wire from the superior vena cava, through the right atrium, and into the inferior vena cava.
Where is the ligamentum arteriosum located?
At the bottom of the superior mediastinumConnecting the pulmonary trunk to the arch of the aorta.
What is the function of the ligamentum arteriosum in adults?
The ligamentum arteriosum serves as a fibrous remnant of the ductus arteriosus, which was crucial for fetal circulation but closes after birth.
What embryonic structure connected the pulmonary trunk to the arch of the aorta?
The ductus arteriosus.
During embryonic development, what function did the ductus arteriosus serve?
It shunted blood from the pulmonary trunk to the aorta, bypassing the lungs, which were not yet functional.
What is patent ductus arteriosus, and what are its consequences?
Patent ductus arteriosus is a condition where the ductus arteriosus fails to close after birth, leading to the mixing of oxygenated and deoxygenated blood and a decrease in the oxygen content going into systemic circulation.
What can happen if the ductus arteriosus fails to close after birth?
Mixing of low oxygenated blood from the pulmonary trunk into the aorta, decreasing oxygen content in the systemic circulation.
What happens to the oxygen content of blood in the aorta if the ductus arteriosus fails to close after birth?
The oxygen content decreases because low-oxygenated blood from the pulmonary trunk mixes with the high-oxygenated blood in the aorta.
What is contained within the anterior mediastinum?
Remnants of the thymus glandInternal thoracic arteriesSome connective tissue.
Where do the internal thoracic arteries originate?
From the right and left subclavian arteries in the superior mediastinum.
What is the path of the internal thoracic arteries?
They travel inferiorly on either side of the sternum, lateral to the sternum itself.
What are the internal thoracic arteries also sometimes called?
Internal mammary arteries.
What branches do the internal thoracic arteries give off, and what is their significance?
They give off anterior intercostal arteries that anastomose with posterior intercostal arteries from the aorta, ensuring blood supply to the thoracic wall.
Why are internal thoracic arteries clinically significant for procedures like coronary artery bypass grafting (CABG)?
They can be harvested for use in CABG because their anastomotic connections allow them to be removed without compromising blood supply to the thoracic wall.
Besides their use in CABG procedures, what is notable about the internal thoracic arteries?
They have extensive anastomotic connections, meaning they can be harvested for use elsewhere without compromising blood supply to the thoracic wall.
What unique characteristic makes the internal thoracic artery particularly well-suited for CABG?
It is resistant to atherosclerotic plaque build-up, making it a durable choice for grafting.
How are internal thoracic arteries used in coronary artery bypass graft surgery?
They are harvested and used to bypass blocked or damaged coronary arteries, effectively restoring blood flow to the heart muscle. The internal thoracic arteries are particularly well-suited for this procedure due to their resistance to plaque build-up.
What is the role of the thymus gland, and how does it change with age?
The thymus is involved in the early development of the immune systemIt atrophies after puberty, leaving behind fatty tissue remnants.
How does the thymus appear on medical images of children, and what is this called?
In children, the thymus can appear as a large opacity in the upper thorax on X-rays, often resembling a sail; this is known as the “thymic sail sign”.
What is the thymic sail sign?
A normal opacity on a chest X-ray in children, caused by the relatively large thymus gland.
Why is it important to recognise the thymic sail sign in children?
Recognising this sign as normal is crucial to avoid misinterpreting it as a tumour or other pathology.
What major structures are located in the posterior mediastinum?
The posterior mediastinum contains:The oesophagusVagus nerves and their plexusesThe descending aortaThe sympathetic chainsThe thoracic ductThe azygos venous system.
What major vessels originate in the middle mediastinum?
The superior vena cavaPulmonary trunkAscending aorta.
How do the vagus nerves course through the posterior mediastinum?
The vagus nerves descend through the mediastinum, with the vagal plexuses wrapping around the oesophagus.
What do the vagus nerves form as they enter the abdomen?
They continue into the abdomen as the left and right vagal trunks.
What spinal nerves contribute to the phrenic nerves?
C3C4C5
Where is the thoracic duct located in the posterior mediastinum?
The thoracic duct is found close to the vertebral bodies along the midline.
What is transoesophageal echocardiography and how does it utilise the anatomical relationship between the oesophagus and the heart?
It is a technique where an ultrasound probe is inserted down the oesophagus to obtain clear images of the left atrium. This is possible because the oesophagus lies in close proximity to the heart.
How can the anatomical relationship between the oesophagus and the heart be utilised clinically?
An ultrasound probe can be passed down the oesophagus to visualise the left atrium, taking advantage of their close proximity.
What is the function of the azygos venous system?
It helps to drain the thoracic wall and the overlying tissues.
What constitutes the majority of the middle mediastinum’s contents?
The heart and its coverings, including the fibrous pericardium.
What is the fibrous pericardium, and where is it anchored?
It is the fibrous outer sac of the heart and is anchored to the central tendon of the diaphragm.
What is the fibrous pericardium anchored to, and why is this important?
It is anchored to the central tendon of the diaphragm. This provides support to the heart as this part of the diaphragm does not change shape significantly during respiration.
What is the significance of the central tendon of the diaphragm in relation to the fibrous pericardium?
The fibrous pericardium is anchored to the central tendon of the diaphragm, which provides support to the heart because this tendinous portion of the diaphragm does not change shape significantly during respiration.
Why is the fibrous pericardium anchored to the central tendon, rather than the muscular part of the diaphragm?
The central tendon experiences minimal shape changes during respiration, providing stable support for the heart.
What nerves provide sensory innervation to the fibrous pericardium?
The phrenic nerves.
What important vascular structures originate in the middle mediastinum?
The great vessels:The superior vena cavaPulmonary trunkAscending aorta
How do the phrenic nerves course in relation to the middle mediastinum?
The phrenic nerves run alongside the fibrous pericardium on each side of the middle mediastinum.
Besides innervating the diaphragm, what other function do the phrenic nerves serve in the middle mediastinum?
They provide sensory innervation to the fibrous pericardium.
What serious condition can result from a blockage of the superior vena cava due to a mediastinal mass or clot?
Superior vena cava syndromeCharacterized by impaired venous return from the upper body.
What is the clinical significance of the phrenic nerves in relation to the heart?
As they pass by the fibrous pericardium on their way to the diaphragm, they provide sensory innervation to it.
Why is it clinically important to understand the positional anatomy of the mediastinum?
The close proximity of structures in the mediastinum means that a pathology in one structure can impact nearby structures, leading to a complex presentation of symptoms that might seem unrelated.
What is superior vena cava syndrome?
Partial or complete blockage of the superior vena cava leading to congestion in the areas draining into it.
What are the common causes of superior vena cava syndrome?
A mass in the mediastinum, such as a tumour or enlarged lymph nodes, can compress the superior vena cava. Additionally, a blood clot lodging within the superior vena cava itself can also obstruct blood flow and lead to the syndrome.
Where might a mediastinal mass be located to cause superior vena cava syndrome?
Tumours or clots situated near the hilum of the lungs can compress the superior vena cava, leading to the syndrome.
How do the vagus nerves course in relation to the hila of the lungs, and what other key structures do they pass in the thorax?
The vagus nerves pass posterior to the hila of the lungs. They also pass anterior to the subclavian arteries on both sides.
What important branch does the right vagus nerve give off, and where does this occur?
The right recurrent laryngeal nerve in the root of the neck.
Describe the path of the right recurrent laryngeal nerve.
The right recurrent laryngeal nerve loops under the right subclavian artery. It then ascends, passing over the apex of the lung’s pleura to reach the right side of the internal larynx.
What clinical implication is associated with the course of the right recurrent laryngeal nerve?
A Pancoast tumour in the apex of the right lung can compress the right recurrent laryngeal nerve due to its course over the lung apex. This can lead to right vocal cord palsy and hoarseness.
Where does the left recurrent laryngeal nerve branch off, and what is notable about its course?
The left recurrent laryngeal nerve branches from the left vagus nerve and passes through the Aorta Pulmonary Window, the space between the pulmonary artery and the aortic arch.
What clinical significance is linked to the left recurrent laryngeal nerve’s location?
The left recurrent laryngeal nerve, due to its passage through the Aorta Pulmonary Window, is vulnerable to compression by structures in this region. This can lead to left vocal cord paralysis and hoarseness. Hilar lymph node enlargement, commonly associated with lung cancer spread, is a frequent cause of such compression.
Why is a chest radiograph a standard investigation for patients with hoarseness?
Hoarseness can be caused by various conditions, some related to the vagus and recurrent laryngeal nerves in the thorax. A chest radiograph helps visualise structures in this area, possibly revealing abnormalities like tumours or enlarged lymph nodes that could be compressing these nerves.
What happens to the vagus nerves after they branch into the recurrent laryngeal nerves?
The vagus nerves continue to descend and splay out, forming a right and left plexus around the trachea and, further down, the oesophagus.
Where do the vagus nerve plexuses ultimately lead, and what is their function there?
The plexuses pass through the diaphragm into the abdominal cavity to provide parasympathetic (vagal) innervation to the abdominal organs (gut viscera).
In relation to the lungs, how do the phrenic and vagus nerves descend?
The phrenic nerve descends anteriorly to the hilum of the lungsThe vagus nerve descends posteriorly.
What anatomical landmarks can be used to locate the vagus nerves?
The hilum of the lungs and the subclavian arteries.The vagus nerves pass anterior to the subclavian arteries.
Which vagus nerve gives off the recurrent laryngeal nerve?
The right vagus nerve.
How does the right recurrent laryngeal nerve reach the larynx?
It recurs under the right subclavian artery and passes over the apex of the lung’s pleura as it ascends towards the right side of the internal larynx.
What might a hoarse voice and right vocal cord palsy indicate, and why?
It could indicate a potential Pancoast tumour in the right lung’s apex. This is because the right recurrent laryngeal nerve, which innervates the right vocal cord, passes over this area and can be compressed by a tumour.
How does the course of the left recurrent laryngeal nerve differ from the right?
The left recurrent laryngeal nerve passes between the pulmonary artery and the aortic arch (a region known as the Aorta Pulmonary Window).
What happens to the vagus nerves after they give off the recurrent laryngeal nerves?
They continue to descend and splay out into a right and left plexus surrounding the trachea and oesophagus. They then pass through the diaphragm to provide parasympathetic innervation to the abdominal viscera.
Where do most of the cardiac branches of the vagus nerves arise?
In the thorax.
The left recurrent laryngeal nerve can be compressed by pathology in the Aorta Pulmonary Window. What is a key example of such pathology?
Hilar lymph node enlargementOften associated with lung cancer spread.
Vagus nerves descend into the abdominal cavity. What is the purpose of their innervation in this region?
They provide parasympathetic autonomic nerve supply to the gut viscera, influencing functions like digestion.
What is the clinical significance of the right recurrent laryngeal nerve passing over the apex of the lung’s pleura?
A Pancoast tumour in this region could compress the nerve, leading to hoarseness and right vocal cord palsy.
Why is the Aorta Pulmonary Window clinically significant?
Pathologies in this region, such as hilar lymph node enlargement, can compress the left recurrent laryngeal nerve, resulting in left vocal cord paralysis and hoarseness.
What is the significance of cardiac visceral sensory nerves entering the spinal cord at the T1 to T4 levels?
This explains why cardiac pain can be referred to the T1 to T4 dermatomes.
What specific pair of symptoms, related to the right recurrent laryngeal nerve, might indicate a potential Pancoast tumour?
HoarsenessRight vocal cord palsy
What is the role of the cardiac plexus in regulating heart function?
It integrates input from both the parasympathetic and sympathetic nervous systems to modulate heart rate and contractility.
What is the source of parasympathetic nerve supply to the heart?
The right and left vagus nerves
Where do most of the cardiac branches of the vagus nerves arise?
Within the thorax.
Where are the ganglia located from which postganglionic parasympathetic fibres to the heart arise?
On the heart itself.
What is the overall effect of parasympathetic stimulation on the heart?
Parasympathetic activation, associated with ‘rest and digest’ states, leads to a reduction in heart rate.
What is the cardiac plexus, and where is it located?
The cardiac plexus is a network of both parasympathetic and sympathetic nerve fibresLocated between the aorta and trachea.
What is the function of the cardiac plexus?
The cardiac plexus receives input from both the vagus nerves (parasympathetic) and sympathetic nerves. It then sends nerve fibres out to innervate the heart.
From which spinal cord segments do the sympathetic nerve fibres that supply the heart originate?
T1-T4 spinal nerve levelsPrimarily on the left side
What are the effects of sympathetic stimulation on the heart?
Sympathetic activation, associated with ‘fight or flight’ responses, causes an increase in heart rate and contractility.
How do cardiac sympathetic nerves reach the cardiac plexus?
Via the sympathetic trunk.
Where do preganglionic sympathetic fibres synapse in the context of cardiac innervation?
Preganglionic fibres synapse in multiple cervical or upper thoracic sympathetic ganglia.
How do postganglionic sympathetic fibres reach the cardiac plexus?
They travel as branches from the sympathetic trunk to the cardiac plexus.
How do cardiac visceral sensory nerves travel back to the central nervous system?
They travel alongside sympathetic fibresEntering the spinal cord at the T1 to T4 levels, mainly on the left.
Why might cardiac pain, such as that from myocardial infarction, be referred to the T1 to T4 dermatomes?
Cardiac visceral sensory nerves carrying pain signals travel with sympathetic fibres and enter the spinal cord at the T1 to T4 levels. The brain can misinterpret the origin of this pain, perceiving it as coming from the corresponding dermatomes.
What is the effect of parasympathetic activation on the heart rate?
It reduces the heart rate.
Where are the sympathetic chains mainly found?
Within the thorax and lumbar region.
Which spinal nerve levels provide sympathetic innervation to the heart?
T1-T4.
What is the effect of sympathetic activation on the heart?
It increases heart rate and contractility.
Preganglionic sympathetic fibres synapse in multiple cervical or upper thoracic sympathetic ganglia. What happens after they synapse?
Postganglionic sympathetic fibres continue as branches from the sympathetic trunk to the cardiac plexus, ultimately acting on the heart.
Cardiac visceral sensory nerves are not part of the sympathetic fibres. How do they differ in function?
Cardiac visceral sensory nerves carry sensory information like stretch, inflammation, or hypoxia from the heart to the central nervous systemSympathetic fibres are motor fibres that regulate heart function.
How do the sympathetic and parasympathetic nervous systems work together to control heart function?
The sympathetic nervous system increases heart rate and contractility (“fight or flight”), while the parasympathetic nervous system decreases heart rate (“rest and digest”).
What type of information do cardiac visceral sensory nerves transmit?
Sensory information from the heart, including sensations of StretchInflammationHypoxia (low oxygen).
Do cardiac visceral sensory nerves travel within sympathetic fibres?
No, they do not become part of the sympathetic nerves. They travel alongside sympathetic fibres to reach the central nervous system.
Where do cardiac visceral sensory nerves enter the spinal cord?
T1 to T4 levelsPredominantly on the left sideReflecting the heart’s position.
How does the pathway of cardiac visceral sensory nerves relate to referred pain?
Because these nerves travel with sympathetic fibres and enter the spinal cord at the T1 to T4 levels, pain signals from the heart can be misinterpreted by the brain as originating in the corresponding dermatomes (skin areas supplied by those spinal nerves). This is why cardiac pain, such as that experienced during a myocardial infarction, can be felt in areas like the chest, shoulder, or arm.
Why might cardiac pain, such as that from ischaemia following a myocardial infarction, be referred to the T1 to T4 dermatomes?
Because cardiac visceral sensory nerves enter the spinal cord at these levels.
What is the general shape of the heart?
The heart is shaped like a lopsided door wedge that points towards the anatomical left.
What is the name of the pointed bottom portion of the heart?
Cardiac apex.
What is the name of the surfaces of the heart that faces the lungs?
Right and left pulmonary surfaces.
Where is the anterior surface of the heart located?
The anterior surface of the heart is located right up against the anterior mediastinum, or just deep to the body of the sternum.
Which structures comprise the base of the heart, and where is it located?
The base of the heart, primarily composed of the left atrium, sits posteriorly and rests against the oesophagus.
What is the inferior surface of the heart like, and where is it located?
The inferior surface of the heart is relatively flat and sits on the diaphragm.
Why does the heart have its unusual shape?
Embryological developmentThe heart develops as a midline tube that folds, rotates, and shifts towards the left.
Which side of the heart primarily faces anteriorly?
Most of the right-sided structures, including the right atrium and right ventricle, are located anteriorly.
Where are the left-sided structures of the heart primarily located?
Most of the left-sided structures sit more posteriorly, with the entire left atrium situated at the back.
Which chamber of the heart primarily composes the base?
The base of the heart is primarily composed of the left atrium.
What can be said about the position of right-sided heart structures when viewing the heart anteriorly?
When viewing the heart anteriorly, most of the right-sided structures sit more anteriorly.
Where is the left atrium situated in relation to the other chambers of the heart?
The left atrium sits posteriorly to the other chambers of the heart.
What structure does the inferior surface of the heart rest on?
The inferior surface of the heart rests on the diaphragm.
How can you see the oblique pericardial sinus?
The oblique pericardial sinus can be seen in images where the heart has been removed.
What two spaces are near the heart?
The transverse pericardial sinus and the oblique pericardial sinus
What is the pericardium?
The pericardium is a double-layered sac that surrounds the heart and the roots of the great vessels.
What are the two main components of the pericardium?
Tough, outer fibrous pericardiumInner serous pericardium.
What is the name of the tough outer layer of the pericardium?
Fibrous pericardium.
Describe the structure of the serous pericardium.
The serous pericardium is composed of two layers: The parietal layer lining the fibrous pericardiumThe visceral layer, also known as the epicardium, directly covering the heart.
What is the name of the space between the visceral and parietal layers of the serous pericardium?
Pericardial cavity.
What is the pericardial cavity, and what does it contain?
The pericardial cavity is the space between the parietal and visceral layers of the serous pericardium; it contains a small amount of pericardial fluid, which is thin and clear to reduce friction.
What is the function of the serous pericardial layer?
Reduces friction between the heart’s epicardium and surrounding layers.
What is the function of the fibrous pericardium?
The fibrous pericardium is tough, inflexible, and quite “fibrousy”. It prevents rapid changes in heart size and volume and does not allow sudden, fast changes in heart size or volume within the pericardial cavity.
What happens in pericarditis?
Pericarditis is the inflammation of the pericardiumCan cause pain with each heartbeat, as the phrenic nerve supplying the pericardium also carries sensory fibres.
What is the relationship between the phrenic nerve and pericarditis?
The phrenic nerve passes by the fibrous pericardium and provides it with sensory innervation. When the pericardium is inflamed, as in pericarditis, each heartbeat can be incredibly painful.
What is a pericardial effusion?
A pericardial effusion is the abnormal accumulation of fluid in the pericardial sac.
Name three types of pericardial effusion.
serous pericardial effusionhaemopericardiumpurulent pericarditis.
What are some potential causes of pericardial effusion?
Pericardial effusion can be caused by a variety of factors:Heart failureBlunt chest traumaMalignancyMyocardial infarctionAortic dissectionLymphatic obstruction.
What is the clinical significance of a slowly accumulating pericardial effusion?
A slowly accumulating pericardial effusion allows the pericardium time to stretch, accommodating larger volumes of fluid (up to 500cc) without significantly impairing cardiac function. The only clinical sign of this may be an enlarged heart shadow on a chest radiograph.
What is the potential danger of a rapidly developing pericardial effusion?
A rapid accumulation of fluid, even as little as 200-300cc, can compress the heart chambers, restricting cardiac filling and potentially leading to cardiac tamponade. The rapid increase in pressure can compress the atria and vena cava as the pericardial sac has not had time to expand.
What is cardiac tamponade?
Cardiac tamponade is a life-threatening condition where the heart is compressed by fluid in the pericardial sac, preventing it from filling properly.
What is another name for the visceral layer of the serous pericardium?
The visceral layer of the serous pericardium is also known as the epicardium.
Why doesn’t the fibrous pericardium allow for sudden, fast changes in the heart’s size?
The fibrous pericardium is tough and inflexible, so it does not allow the heart to rapidly change size.
What is the clinical significance of the phrenic nerve in relation to the pericardium?
The phrenic nerve provides sensory innervation to the fibrous pericardiumHence inflammation of the pericardium (pericarditis) can cause pain, especially with each heartbeat.
What is pericarditis?
Pericarditis is the inflammation of the pericardial coverings of the heart.
How much fluid does the pericardial sac normally contain?
The pericardial sac typically contains less than 50 cc of thin, clear pericardial fluid.
What is a pericardial effusion?
A pericardial effusion is a condition where the pericardial sac becomes distended by the accumulation of various types of serous fluids.
Give three examples of fluids that can accumulate in the pericardial sac.
A serous pericardial effusionBlood (Haemopericardium)Pus (purulent pericarditis).
What are some causes of pericardial effusions?
Pericardial effusions can be caused by:Congestive heart failureBlunt chest traumaMalignancy,A ruptured myocardial infarctionAortic dissectionMediastinal lymphatic obstruction.
What is the clinical significance of a slowly accumulating pericardial effusion?
If fluid accumulates slowly, the pericardium can stretch and accommodate large volumes (up to 500 cc) without impairing cardiac function. The main clinical sign is an enlarged heart shadow on a chest x-ray.
What can happen when a pericardial effusion develops rapidly?
A rapidly developing effusion, even as little as 200-300 cc, can compress the heart, restricting filling and potentially leading to cardiac tamponade.
What is cardiac tamponade?
Cardiac tamponade is a life-threatening condition where fluid in the pericardial sac compresses the heart, preventing proper filling.
Why is cardiac tamponade dangerous?
The rapid pressure increase compresses the atria and vena cava because the pericardial sac has not had time to expand to accommodate the fluid. The ventricles can also become compressed, restricting cardiac filling.
During surgery, how can the transverse pericardial sinus be used?
A surgeon can insert a finger into the transverse pericardial sinus to separate and clamp the aorta and pulmonary trunk, allowing the heart to be placed on a bypass machine for procedures such as coronary artery bypass grafting.
How does the transverse pericardial sinus form embryologically?
During development, the heart tube is surrounded by the pericardial sac, which reflects back on itself at the base of the great vessels. This reflection creates the transverse pericardial sinus. As the heart tube folds and develops, it pulls the pericardial covering with it, forming the transverse pericardial sinus.
What is the name of the condition in which the pericardium becomes inflamed?
Pericarditis.
Why is pericarditis painful?
Pericarditis is painful because the phrenic nerve, which provides sensory innervation to the fibrous pericardium, becomes irritated by the inflammation.
How much fluid does the pericardial sac normally contain?
Normally less than 50 cc of pericardial fluid.
What is the term for an accumulation of fluid in the pericardial sac?
Pericardial effusion.
What is purulent pericarditis?
Purulent pericarditis is a condition in which pus develops in the pericardial cavity.
What does a large pericardial effusion look like on an x-ray?
On an x-ray, a large pericardial effusion will present as a massive pericardial sac.
Describe the embryological development of the heart’s shape.
The heart develops from a midline tube that folds, rotates, and shifts leftward, resulting in its lopsided, wedge-like shape.
What is the impact of the heart’s embryological development on its structure?
The folding and twisting during development causes most right-sided heart structures to be positioned anteriorly and most left-sided structures posteriorly.
How does the pericardium form during heart development?
The early heart tube is enveloped by the pericardial sac, which then reflects at the base of the great vessels.
How does the formation of the pericardium impact the final anatomical structures?
As the heart tube folds and develops, it pulls the pericardial covering with it, creating two spaces or passageways near the heart: the transverse pericardial sinus and the oblique pericardial sinus.
What is the surgical significance of the transverse pericardial sinus?
The transverse pericardial sinus allows surgeons to insert a finger and separate the aorta and pulmonary trunk to clamp them, facilitating procedures like coronary artery bypass grafting.
Why is the transverse pericardial sinus well-suited for this surgical manoeuvre?
This space exists because of the embryological origin of the arterial outflow of the heart.
How does the development of the pericardial sac relate to the development of the heart?
The early heart tube is surrounded by the pericardial sac, and as the heart folds and develops, it drags the pericardial covering with it.
What are the names of the two spaces near the heart formed by the reflection of the pericardial covering?
Transverse pericardial sinus and the oblique pericardial sinus.
What is a surgical application of the transverse pericardial sinus?
The transverse pericardial sinus can be used in surgery to separate and clamp the aorta and pulmonary trunk, allowing for procedures such as coronary artery bypass grafting.
What type of blood enters the right atrium, and through which vessels?
Venous blood, which is low in oxygen, enters the right atrium through three main vessels: the superior vena cava, the inferior vena cava, and the coronary sinus.
After entering the right atrium, where does the blood flow next?
Blood in the right atrium passes through the tricuspid valve opening into the right ventricle.
What are the three vessels that return blood to the right atrium?
The superior vena cava, the inferior vena cava, and the coronary sinus.
What is the role of the pulmonary trunk, and what type of blood does it carry?
The pulmonary trunk carries deoxygenated arterial blood from the right ventricle to the lungs to be oxygenated.
How and where does blood return to the heart from the lungs?
Oxygenated blood returns from the lungs to the left atrium via four pulmonary veins.
What happens to the blood in the left atrium?
The oxygenated blood in the left atrium flows through the mitral valve into the left ventricle.
What is the final step in the flow of blood through the heart before it enters the systemic circulation?
The left ventricle ejects the oxygenated blood into the systemic circulation via the aorta, the largest artery in the body.
What happens to the blood after it circulates throughout the body?
After delivering oxygen and nutrients to the body’s tissues, the blood, now deoxygenated, returns to the right atrium through the venae cavae to start the cycle again.
How does the shape of the heart relate to blood flow?
The heart’s shape, similar to a lopsided door wedge, influences the spatial arrangement of its chambers, affecting the direction and efficiency of blood flow.
What is the path of blood flow through the heart?
Venous blood enters the right atrium, flows through the tricuspid valve to the right ventricle, then through the pulmonary semilunar valve to the pulmonary trunk and lungs. Oxygenated blood returns to the left atrium via pulmonary veins, passes through the mitral valve to the left ventricle, and is finally pumped through the aortic semilunar valve into the aorta.
What is the function of the right atrium and where is it situated in the heart?
The right atrium forms the vertical right border of the heart and receives venous blood from the upper and lower body, as well as the heart muscle itself.
Besides the superior and inferior vena cava, what other vessel delivers blood to the right atrium?
The coronary sinus
What is the function of the coronary sinus?
It returns deoxygenated blood from the heart muscle itself back to the right atrium.
What structure does blood pass through to move from the right atrium to the right ventricle?
Blood flows from the right atrium into the right ventricle through the tricuspid valve opening.
What is the orientation and function of the tricuspid valve?
The tricuspid valve faces forward and medially, closing during ventricular contraction (systole) to prevent backflow of blood into the right atrium.
What external feature marks the division of the inferior right atrium into two spaces?
The Sulcus Terminalis, a shallow vertical groove, externally marks the division of the inferior right atrium.
What is the name of the shallow vertical groove that marks the division of the inferior right atrium?
The Sulcus Terminalis.
What internal feature divides the inferior right atrium, and how is it described?
The Crista Terminalis, a smooth, muscular ridge, internally divides the inferior right atrium.
What is the name of the muscular ridge that divides the interior of the right atrium?
The Crista terminalis.
What is the origin and characteristics of the space posterior to the Crista Terminalis?
The space posterior to the Crista Terminalis is derived from the sinus venosis and has smooth, thin walls. Both vena cavae empty into this space.
How does the space anterior to the Crista Terminalis differ in appearance?
The space anterior (in front) to the Crista Terminalis is covered with ridges of muscles called pectinate muscles, which fan out like the teeth of a comb.
Where else are pectinate muscles found within the right atrium?
Pectinate muscles are also found in the right auricle (atrial appendage), an ear-like muscular pouch that overlaps the ascending aorta.
Why does the posterior wall of the right atrium have smooth walls while the anterior part has rough walls with pectinate muscles?
The right atrium develops from two embryological structures. The smooth-walled posterior portion is derived from the sinus venosus, while the anterior part with pectinate muscles develops separately.
What is a potential risk associated with the right auricle?
The right auricle can be a potential site for blood clots to form, particularly in individuals with irregular heartbeats.
What does the source say about the potential formation of blood clots in the heart?
The right auricle, due to its ear-like shape and potential for slow blood flow, is mentioned as a possible location for blood clot formation, particularly in individuals with irregular heartbeats.
What is the function and location of the coronary sinus?
The coronary sinus receives blood from most of the cardiac veins draining the heart muscle itself and opens medially just in front of the inferior vena cava.
What structure separates the right atrium from the left atrium, and what is its orientation?
The interatrial septum separates the right atrium from the left atrium. It faces forward and to the right.
What is the name of the depression in the interatrial septum that marks the location of the embryonic foramen ovale?
Fossa ovalis.
What is the fossa ovalis, and where is it located?
The fossa ovalis is a depression in the interatrial septum located just above the opening of the inferior vena cava. It marks the location of the embryonic foramen ovale.
What is the significance of the fossa ovalis?
It represents the closed foramen ovale, an opening in the interatrial septum that allows blood to bypass the non-functional lungs during fetal circulation.
What was the function of the foramen ovale during foetal development?
The foramen ovale, a hole in the interatrial septum during foetal development, allowed oxygenated blood entering the right atrium from the inferior vena cava to bypass the lungs and flow directly to the left atrium.
What important components of the heart’s conduction system are embedded in the superior right atrium?
The sinoatrial (SA) node and the atrioventricular (AV) node, key parts of the heart’s conduction system, are embedded in the superior right atrium.
What are the ridges of muscle found in the right atrium and auricle called?
Pectinate muscles.
Describe the precise location and path of the crista terminalis within the right atrium.
The crista terminalis is a smooth, muscular ridge that begins on the roof of the right atrium, just anterior to the opening of the superior vena cava. It extends down the lateral wall of the atrium to the anterior lip of the inferior vena cava opening.
What is the embryological origin of the smooth-walled space in the right atrium, posterior to the crista terminalis?
This area of the right atrium is derived from the sinus venosus, an embryonic structure that contributes to the heart’s development.
Why is the right auricle clinically significant, especially in individuals with irregular heartbeats?
Due to its ear-like shape and potential for slow blood flow, the right auricle can be a site for blood clot formation, particularly in those with irregular heartbeats.
What is the position of the right ventricle in the anatomical position, and what surface does it mostly form?
In the anatomical position, the right ventricle forms most of the anterior surface of the heart.
Which chamber of the heart forms most of the anterior surface?
The right ventricle.
Where is the right ventricle situated in relation to the right atrium and the atrioventricular orifice?
The right ventricle is situated to the left of the atrioventricular orifice and to the right of the right atrium.
Describe the direction of blood flow as it enters the right ventricle from the right atrium.
Blood entering the right ventricle from the right atrium moves in a horizontal and forward direction.
Why is the direction of blood flow when entering the right ventricle significant?
The horizontal and forward direction of blood flow as it enters the right ventricle is important for listening to (auscultating) the sounds of the tricuspid valve.
What structure does the outflow track of the right ventricle lead to, and via what valve?
The outflow track of the right ventricle leads to the pulmonary trunk via the pulmonary semilunar valve.
What is the Conus arteriosus (infundibulum), and where is it located?
The Conus arteriosus, also called the infundibulum, is a smooth portion of the superior right ventriclealong the outflow track leading to the pulmonary trunk.
What is the name of the smooth portion of the right ventricle that leads to the pulmonary trunk?
Conus arteriosus, or sometimes infandibulum.
What are the muscular, irregular structures in the walls of the ventricles called?
Trabeculae carnae.
What are trabeculae carnae, and how are they typically attached in the right ventricle?
Trabeculae carnae are numerous muscular, irregular structures on the walls of the right ventricle. Most are either attached to the ventricular walls throughout their length or form bridges or ridges across the walls.
What are papillary muscles, and what is their function?
Papillary muscles are specialised trabeculae carnae with one end attached to the ventricular surface and the other serving as an attachment point for chordae tendinae. These muscles help anchor the cusps of the tricuspid valve.
What is the function of the chordae tendinae?
They connect to the free edges of the cusps of the tricuspid and mitral valves, preventing the valves from inverting during ventricular contraction.
How are papillary muscles typically named?
Papillary muscles are named relative to their point of origin on the ventricular surface.
What is the function of the papillary muscles and chordae tendinae?
The papillary muscles anchor the chordae tendinae, which are fibrous cords attached to the cusps of the tricuspid and mitral valves. This arrangement prevents the valves from inverting (prolapsing) into the atria during ventricular contraction, ensuring one-way blood flow.
What is the moderator band, and what is its significance?
The moderator band is a specialised trabeculum that bridges the lower interventricular septum and carries a portion of the cardiac conduction system, specifically the right bundle of the atrioventricular bundle, to the anterior wall of the right ventricle.
What is the role of the moderator band in the right ventricle?
It’s a specialized trabecula carrying part of the cardiac conduction system (the right bundle of the atrioventricular bundle) to the anterior wall of the right ventricle.
What is the specialised trabeculum that forms a bridge between the interventricular septum and the anterior wall of the right ventricle called?
Moderator band.
Beyond its structural presence, what is the key functional role of the moderator band in the right ventricle?
The moderator band carries a significant portion of the heart’s electrical conduction system, specifically the right bundle branch of the atrioventricular bundle. It transmits these signals to the anterior wall of the right ventricle, coordinating its contraction.
How does the structure of the right ventricle direct blood flow?
Blood enters the right ventricle horizontally and forward from the right atrium. It then follows the outflow tract, a smooth area called the conus arteriosus (or infundibulum), leading to the pulmonary trunk via the pulmonary semilunar valve.
Which chamber of the heart forms most of the base?
The left atrium.
What surface of the heart does the left atrium primarily form?
The left atrium forms most of the base, or posterior surface, of the heart.
Why is the left atrium described as forming the “base” of the heart?
The left atrium is the most posterior chamber of the heart. Its location contributes to the heart’s overall shape, which is described as a lopsided door wedge, with the left atrium forming the wider, posterior base.
From what two structures is the left atrium derived?
Like the right atrium, the left atrium is derived from two embryological structures, resulting in some areas with smooth walls and others being more muscular.
What structures deliver oxygenated blood to the left atrium, and how many are there?
Four pulmonary veins, two on the right and two on the left, deliver oxygenated blood from the lungs to the left atrium.
Why does the posterior half, or inflow portion, of the left atrium have smooth walls?
The proximal parts of the pulmonary veins are incorporated into the left atrium during development, leading to smooth walls in the area where they enter.
Why does the area where the pulmonary veins enter the left atrium have smooth walls?
During embryonic development, the proximal parts of the pulmonary veins become incorporated into the left atrium, resulting in smooth walls at their entry point.
What is contained within the anterior half of the left atrium?
The anterior half of the left atrium is continuous with the left atrial appendage, which contains pectinate muscles.
Through which valve does blood pass from the left atrium to the left ventricle?
Blood flows from the left atrium to the left ventricle through the mitral valve, also known as the bicuspid valve.
What is the name of the valve that separates the left atrium from the left ventricle?
The mitral valve (also sometimes called the bicuspid valve).
From what perspective can the fossa ovalis be observed in the context of the left atrium?
The fossa ovalis can be observed on the interatrial septum when viewed from the left atrium.
What is the significance of the fossa ovalis in the left atrium?
It marks the location of the embryonic foramen ovale, which allowed blood to bypass the non-functional lungs during foetal development.
Which chamber of the heart has the thickest layer of myocardium?
The left ventricle.
What surfaces of the heart does the left ventricle contribute to, and what prominent feature does it help form?
The left ventricle contributes to the anterior, inferior, and left pulmonary surfaces of the heart and helps form the apex.
Describe the path of blood flow as it enters and exits the left ventricle.
Blood enters through the mitral valve, flows towards the apex, turns superiorly, and exits through the aortic semilunar valve.
How does the wall thickness of the left ventricle compare to other chambers, and what does this reflect about its function?
The left ventricle has the thickest layer of myocardium of all the chambers, reflecting its function of ejecting blood with force into the aorta for systemic circulation.
How do the trabeculae carnae in the left ventricle compare to those in the right ventricle?
The trabeculae carnae, with their muscular ridges and bridges, appear similar in both ventricles.
What is the role of papillary muscles and chordae tendinae in the left ventricle?
Papillary muscles extend from the trabeculae carnae and anchor to the chordae tendinae, which in turn secure the cusps of the mitral valve.
How does the thickness of the myocardium in the left ventricle compare to other heart chambers, and why?
The left ventricle has the thickest myocardium of all chambers. This is because it needs to generate enough force to pump blood into the aorta and throughout the entire body.
What are the two chambers of the heart primarily responsible for pumping blood?
The ventricles are the two chambers of the heart responsible for pumping blood.
What is the function of heart valves?
Heart valves ensure the unidirectional flow of blood through the heart.
What are the two types of heart valves?
The two types of heart valves are atrioventricular (AV) valves and semilunar valves.
What are the two atrioventricular (AV) valves, and where are they located?
The tricuspid valve is located between the right atrium and right ventricleThe mitral valve is between the left atrium and left ventricle.
What are the two atrioventricular valves in the heart?
The two atrioventricular valves are the tricuspid valve and the mitral valve.
What structures anchor the atrioventricular valve cusps to the ventricle wall?
The cusps are anchored to the ventricle wall by the chordae tendinae tendons.
How many cusps does each AV valve have, and what anchors them?
The tricuspid valve has three cusps, and the mitral valve has two. Chordae tendinae, which are tendons, anchor the cusps to the ventricle wall. The chordae tendinae are themselves secured to the bottom of the ventricle via the papillary muscles.
What is the function of the papillary muscles?
The papillary muscles are extensions of the ventricular wall and contract during ventricular systole to put tension on the chordae tendinae, preventing inversion of the AV valve cusps.They do not contract to open valves - valves open passively
What can happen if the papillary muscles are damaged?
Damage to the papillary muscles can lead to AV valve incompetence or regurgitation, potentially causing a cardiac murmur.
How do the AV valves open?
AV valves open passively when the atria contract and force blood downwards into the ventricles. The valves are simply pushed against the ventricle walls.
What is the role of the papillary muscles during ventricular systole?
During ventricular systole, the papillary muscles contract to put tension on the chordae tendinae. This prevents the AV valve cusps from inverting or prolapsing back into the atria.
What can happen if the papillary muscles are damaged?
Damage to the papillary muscles, such as from a myocardial infarction, can lead to AV valve incompetence or regurgitation. This means the valve doesn’t close properly, allowing backflow of blood, which can cause a cardiac murmur.
What is the fibrous skeleton of the heart?
It is a dense, fibrous connective tissue framework surrounding the edges of the heart valves.
What is the fibrous skeleton of the heart, and what are its functions?
The fibrous skeleton is a dense, fibrous connective tissue framework that surrounds the heart valves. It provides:Structural support for the valves.An attachment point for cardiac muscle and the valve cusps.Electrical insulation between the atria and ventricles, ensuring the electrical signal passes in an orderly fashion through the atrioventricular node.
Besides providing structural support, what is another important function of the fibrous skeleton of the heart?
The fibrous skeleton also provides electrical insulation, preventing the free conduction of electrical signals through the heart.
Besides the atrioventricular valves, what other types of valves are found in the heart?
The heart also contains the aortic and pulmonary semi-lunar valves, located between the ventricles and the aorta and pulmonary trunk, respectively.
How many cusps do semilunar valves have?
Both the aortic and pulmonary semilunar valves have three cusps.
Where are the semilunar valves located?
The semilunar valves are located between the ventricles and the great vessels leaving the heart: the aortic semilunar valve is between the left ventricle and the aorta, and the pulmonary semilunar valve is between the right ventricle and the pulmonary trunk.
What are the sinuses of the semilunar valves?
The sinuses are pocket-like spaces located behind each cusp of the semilunar valves.
How do the semi-lunar valves open and close?
They open when the ventricles contract, pushing blood out of the heart. When the ventricles relax, blood flows back slightly, filling the valve cusps and causing them to slam shut.
Describe the mechanism of semilunar valve opening and closing.
Opening: When the ventricles contract, blood is ejected out, pushing the semilunar valve cusps against the vessel walls, allowing blood to flow through.Closing: When the ventricles relax, blood in the aorta and pulmonary trunk slightly reverses, filling the sinus pockets behind each cusp. This causes the cusps to slam together, closing the valve.
How are the individual cusps of the aortic and pulmonary semi-lunar valves named?
They are named for their relative position to the coronary arteries.
What is the relationship between the coronary arteries and the aortic sinuses?
The openings for the right and left coronary arteries are located within the right and left aortic sinuses, respectively.
How are the coronary arteries perfused?
During ventricular diastole, when the aortic valve closes and the sinuses fill with blood, that blood flows into the coronary arteries, perfusing the heart muscle.
How are the cusps of the aortic and pulmonary semi-lunar valves named, and how does this relate to their function?
The cusps are named for their relative position to the coronary arteries: right coronary leaflet, left coronary leaflet, and non-adjacent leaflet. This naming is significant because during ventricular diastole, blood fills the sinuses behind the cusps and flows into the coronary arteries, perfusing the heart muscle.
When does coronary artery perfusion occur, and how?
Coronary artery perfusion occurs during ventricular diastole. When the aortic valve closes, blood fills the sinuses behind the cusps, and this blood then flows into the openings of the coronary arteries.
What are the two basic types of heart valve defects?
The two basic types are valve stenosis (failure to open fully) and valve insufficiency (failure to close completely).
What is valvular insufficiency?
Valvular insufficiency is when a valve does not close completely, allowing blood to leak back into the chamber it was just ejected from
What can cause valvular insufficiency?
Scarring or contraction of the cusps, preventing the edges from lining up properly.
What is valve stenosis, and what is its effect on blood flow?
Valve stenosis occurs when a valve cannot fully open, which restricts blood flow exiting a chamber of the heart.
Which heart valves are most commonly affected by valve disease?
The mitral and aortic valves are most commonly affected by valve disease.
What are some specific examples of causes for mitral stenosis and mitral regurgitation?
Mitral stenosis can be caused by calcification, making the valve stiff. Mitral regurgitation can be caused by a floppy valve and valve prolapse, preventing the valve from closing properly.
What is mitral valve prolapse?
Mitral valve prolapse is a common type of congenital heart disease where one or both of the mitral valve leaflets become enlarged, causing them to extend back into the left atrium during ventricular systole.
What happens to the valve leaflets during ventricular systole in mitral valve prolapse?
During ventricular systole, the floppy leaflets of a prolapsed mitral valve can extend back into the left atrium, causing blood regurgitation and a late systolic murmur.
How does mitral valve prolapse impact the pulmonary system?
Mitral valve prolapse can cause blood to backflow into the left atrium, increasing pressure in the pulmonary veins and capillaries. This can lead to increased pulmonary pressures, pulmonary oedema, and eventually pulmonary hypertension.
What are some potential consequences of mitral valve prolapse?
Mitral valve prolapse can cause blood to regurgitate back into the left atrium, leading to a late systolic murmur, left ventricular hypertrophy, left atrial hypertrophy, increased pulmonary pressures, pulmonary oedema, and potentially even right ventricular hypertrophy.
What is the most common valve defect affecting the aortic valve?
Aortic stenosis, often caused by calcified build-up on the valve, is the most common aortic valve defect.
What is aortic stenosis, and what is a common cause?
Aortic stenosis occurs when the aortic valve cannot fully open, often due to calcified build-up on the valve leaflets.
What is aortic stenosis often caused by?
Aortic stenosis is often caused by a calcified build-up on the aortic valve, preventing it from opening fully.
How does aortic stenosis affect the left ventricle?
Aortic stenosis forces the left ventricle to work harder to pump blood out to the body, often resulting in left ventricular hypertrophy.
What are some symptoms a patient with aortic stenosis might experience?
Patients with aortic stenosis may experience dizziness, syncope (fainting), angina (chest pain), and potentially heart failure.
What are some causes of right-sided valve disease affecting the tricuspid or pulmonary semilunar valves?
Right-sided valve disease can be caused by infections such as rheumatic fever or infective endocarditis.
What is a common cause of right-sided valve disease?
Infections like rheumatic fever or infective endocarditis.
What are splinter haemorrhages?
Splinter haemorrhages are tiny haemorrhages that appear as black splinters under the finger or toenails, often associated with infective endocarditis.
What is a classic clinical presentation of right-sided valve disease?
Splinter haemorrhages, appearing as small black lines under the finger or toenails, can be a sign of right-sided valve disease, particularly infective endocarditis.
What is a possible clinical sign of right-sided valve disease?
A possible clinical sign of right-sided valve disease is the presence of splinter haemorrhages, which appear as tiny black splinters under the finger or toenails.
What causes splinter haemorrhages in patients with right-sided valve disease?
In patients with right-sided valve disease, splinter haemorrhages are caused by microdamage to the vessels in the heart as a result of infection. This microdamage leads to the formation of tiny clots (emboli), which damage the small capillaries under the nails.
What is a potential consequence of pulmonary semilunar valve stenosis?
Pulmonary semilunar valve stenosis can lead to the valve cusps fusing together, forming a dome with a narrow opening. This can cause right ventricular hypertrophy and potentially cardiac failure.
What can happen if the pulmonary semi-lunar valve is affected by stenosis?
Stenosis of the pulmonary semi-lunar valve can lead to the cusps fusing together, forming a dome shape with a narrow central opening. This can cause right ventricular hypertrophy and potentially cardiac failure.
Besides infection, what else can cause damage to the heart valves?
Rheumatic fever can also damage the heart valves.
What is the primary goal of aortic aneurysm repair surgery?
The surgery aims to repair a weakened and enlarged section of the aorta (an aneurysm) before it ruptures, which can be life-threatening.
What surgical procedure is used to treat atrial fibrillation, and how does it work?
The maze procedure is used to treat atrial fibrillation. This procedure creates scar tissue in the heart, which interrupts the abnormal electrical circuits that cause irregular heartbeats.
What is the first step in the surgical procedure?
The surgeon makes an incision in the skin and divides the breastbone (sternotomy) to access the heart.
What structure surrounding the heart is opened to expose the aorta?
The pericardium, the sac that encloses the heart, is opened to reveal the aorta and the aneurysm.
What device takes over the function of the heart and lungs during surgery?
A heart-lung machine, also known as a cardiopulmonary bypass machine, temporarily performs the roles of the heart and lungs.
Why is it necessary to stop the bypass machine and empty the patient of blood during aortic aneurysm repair?
It’s necessary to stop the bypass machine and empty the patient of blood to operate on a section of the aorta that is inaccessible while blood is flowing through it. To achieve this, the patient’s temperature is lowered, and a high dose of anaesthesia is administered to reduce brain metabolism to a minimum.
Why is it necessary to temporarily stop the bypass machine and drain the patient’s blood during surgery?
This step is necessary to access and repair a portion of the aorta that is unreachable when blood flow is present.
Why is the heart stopped during surgery?
Stopping the heart allows the surgeon to safely operate on the delicate structures of the aorta and heart valves.
How is the heart protected during the period when it is stopped?
A cold solution is poured around the heart to cool it down, protecting it from damage while it is not beating.
The patient has atrial fibrillation, what are its characteristics?
The patient has atrial fibrillation, a condition characterized by abnormal electrical circuits in the heart, leading to irregular heartbeats and an increased risk of stroke.
What instrument is used to create scar tissue in the maze procedure?
A cryo probe, which reaches temperatures as low as -150 degrees Celsius, is used to freeze and create scar lesions.
What material is used to replace the weakened section of the aorta?
A Dacron graft, made of woven polyester and shaped like a tube, is used to replace the aneurysmal section of the aorta.
What issue with the aortic valve often accompanies an aortic aneurysm and requires surgical repair?
Aortic valve insufficiency, where the valve leaflets do not close properly, allowing blood to leak back into the heart, is often addressed during surgery.
What specific measures are taken to access a particular section of the aorta during surgical repair of an aortic aneurysm?
To reach a section of the aorta that is inaccessible while blood is flowing through it, the surgical team must stop the bypass machine and empty the patient of all their blood. The patient’s temperature is lowered, and a high dose of anaesthesia is administered to minimise brain metabolism during this process.
Why are the aortic valve leaflets adjusted during the repair?
The aortic valve leaflets are overstretched due to the aneurysm, so their length must be reduced to ensure proper valve function after the repair.
How is the patient’s body managed during the period of circulatory arrest?
The patient’s body temperature is lowered, and anaesthesia is deepened to reduce brain metabolism to a minimum, protecting the brain during circulatory arrest.
How are the coronary arteries reconnected after the graft placement?
The surgeon meticulously attaches the coronary arteries back onto the Dacron graft, ensuring blood flow to the heart muscle.
What is used to restart the heart after the repair is complete?
A solution is administered to help stimulate the heart to beat again, and an electric shock (defibrillation) may be needed if the heart does not resume a regular rhythm.
What imaging technique is used to assess the success of the valve repair?
Trans-oesophageal echocardiography (TEE) is used to visualise the repaired aortic valve and confirm that it is functioning correctly and that the leak is resolved.
How is the success of an aortic valve repair assessed?
The success of an aortic valve repair is assessed using trans-oesophageal echocardiography, which allows the surgeon to see the valve functioning in a physiologic state and to confirm that the aortic leaking has been resolved.
What are the names of the two arteries that supply the myocardium of the heart?
The left and right coronary arteries.
When do the coronary arteries fill with blood and perfuse the heart muscle?
During ventricular diastole, when the cusps of the aortic semilunar valve are closed.
During which phase of the cardiac cycle are the coronary arteries perfused?
The coronary arteries are perfused during ventricular diastole, when the aortic valve cusps are closed and blood briefly flows back into the sinuses.
What event causes the aortic valve cusps to close shut?
As the ventricles relax, blood within the aorta briefly reverses, filling the aortic valve cusps and forcing them to close.
What happens to the coronary arteries during ventricular systole?
During ventricular systole, the coronary arteries are occluded as the aortic valve cusps are pushed against the coronary ostia by the force of blood being ejected from the left ventricle.
What happens to coronary blood flow during ventricular systole?
During ventricular systole, blood is ejected into the aorta and pulmonary trunk pushing open the semilunar valves. The cusps of the aortic valve push against the openings of the coronary arteries, temporarily occluding them.
Why is coronary perfusion less effective during systole, even if the coronary arteries weren’t occluded?
During systole, the contraction of the myocardial muscle compresses the vascular beds within the heart, making perfusion less effective.
Why is the temporary occlusion of the coronary arteries during systole advantageous?
It is not beneficial to perfuse the heart muscle during systole while it is contracting, as the vascular beds within the muscle are also contracted. The occlusion of the coronary arteries during this period prevents blood flow to the myocardium.
Why is it advantageous for coronary perfusion to occur during diastole?
During systole, the myocardium and its vasculature are contracted. Therefore, diastole, when the myocardium and its vasculature are relaxed, is a more physiologically appropriate time for blood to perfuse the heart tissue.
When does most of the blood flow to the myocardium occur?
Most coronary blood flow occurs during ventricular diastole. When the ventricles relax, blood briefly flows backward, filling the coronary sinuses and allowing blood to enter the coronary arteries.
What are the two main coronary arteries?
The two main coronary arteries are the left coronary artery (LCA) and the right coronary artery (RCA).
Where do the coronary arteries originate?
The coronary arteries originate from the coronary sinuses located just above the left and right coronary cusps of the aortic valve.
Where do the coronary arteries originate?
The coronary arteries arise from the coronary sinuses which are located just above the left and right coronary cusps of the aortic semilunar valve.
How is coronary artery dominance determined?
Coronary artery dominance is determined by which coronary artery gives rise to the posterior interventricular artery (PDA).
How does blood fill the coronary arteries during diastole?
During diastole, the ventricles relax and there is a brief backflow of blood in the aorta and pulmonary trunk. This backflow fills the coronary sinuses, located above the cusps of the aortic semilunar valve. The blood then flows from the coronary sinuses into the right and left coronary arteries, perfusing the heart muscle.
What does it mean if a heart is “right coronary artery dominant”?
In a right coronary artery dominant heart, the right coronary artery extends around the back of the heart and gives rise to the inferior interventricular artery. This anatomical variation is present in about 60% of the population.
What is the term for a heart in which the right coronary artery gives rise to the inferior interventricular artery?
A right coronary dominant heart.
What percentage of individuals have a right coronary artery dominant heart?
About 60%.
Which artery typically gives off the sinuatrial nodal artery?
The right coronary artery.
Besides the Posterior interventricular artery (PDA), what other branches typically arise from the RCA?
The RCA also typically gives rise to the sinuatrial nodal artery, anterior ventricular arteries, and the right marginal artery.
Besides the sinuatrial nodal artery, what other arteries does the right coronary artery typically give off?
The anterior ventricular arteries and the right marginal artery.
What parts of the heart does the right coronary artery supply?
The RCA supplies the:right atriumright ventriclea large part of the cardiac conduction system, including the SA node and AV nodthe posterior third of the interventricular septum.
What are the two main branches of the LCA?
The LCA divides into two branches: the circumflex artery and the anterior interventricular artery (AIA) (also known as the left anterior descending artery or LAD).
What does it mean if a heart is “left coronary artery dominant”?
In a left coronary artery dominant heart, it is the left coronary artery that gives rise to the inferior interventricular artery. This variation is seen in about 40% of individuals.
What is the term for a heart in which the left coronary artery gives rise to the inferior interventricular artery?
A left coronary artery dominant heart.
What percentage of individuals have a left coronary artery dominant heart?
About 40%.
What are the two major branches of the left coronary artery?
The circumflex artery and the anterior interventricular artery (also called the left anterior descending or LAD).
What parts of the heart does the anterior interventricular artery supply?
Much of the right and left ventricles and the anterior two-thirds of the interventricular septum.
What cardiac structures are supplied by the circumflex artery?
The circumflex artery supplies much of the left atrium and ventricle. In individuals with left coronary artery dominance, it also gives rise to the PDA.
What parts of the heart does the circumflex artery supply?
Much of the left atrium and ventricle and can continue on to terminate as the inferior interventricular artery in left coronary artery dominant hearts.
What is the clinical significance of the AIA supplying the anterior two-thirds of the interventricular septum?
The atrioventricular bundle and the right and left bundle branches are situated within the anterior two-thirds of the interventricular septum. Blockage of the AIA can therefore disrupt the propagation of electrical signals through the heart.
Give an example of how understanding coronary artery anatomy can be useful in clinical practice.
A blockage in the AIA can lead to necrosis of the papillary muscles due to loss of blood supply, resulting in mitral valve regurgitation.
What are the three large cardiac veins that drain the heart?
The great, middle, and small cardiac veins.
How are the cardiac veins anatomically related to the coronary arteries?
The three major cardiac veins (great, middle, and small) run alongside the coronary arteries, following a similar pattern. This arrangement facilitates efficient drainage of deoxygenated blood from the myocardium.
Describe the path of the left coronary artery.
The left coronary artery arises from the left coronary sinus, then travels behind the pulmonary trunk and under the left atrial appendage before dividing into its two main branches, the circumflex artery and the anterior interventricular artery.
What can be concluded about the impact of a myocardial infarction (MI) based on which coronary artery is affected?
Knowing which coronary artery is affected in an MI allows clinicians to predict which areas of the heart may have compromised function.
Give a specific example of how a blockage in the AIA could affect cardiac function.
A blockage in the AIA can lead to necrosis of the papillary muscles, which are responsible for the proper functioning of the mitral valve. This can result in mitral valve regurgitation.
What might be a consequence of a myocardial infarction in the right coronary artery on the electrical activity of the heart?
The right coronary artery supplies the SA and AV nodes, which are important for the conduction of electrical signals through the heart. A myocardial infarction in this area could disrupt the conduction of these signals, potentially leading to arrhythmias.
What might be a consequence of a myocardial infarction in the left coronary artery affecting the anterior two-thirds of the interventricular septum?
The anterior two-thirds of the interventricular septum contains the atrioventricular bundle and its branches, which are essential for electrical signal propagation in the heart. A myocardial infarction in this region could block these signals, leading to serious conduction disturbances.
If a patient has a blockage in the anterior interventricular artery, what specific heart damage might occur and why?
The papillary muscles, responsible for proper mitral valve function, are located distal to the anterior interventricular artery and rely on it for blood supply. If a blockage occurs, these muscles may become necrotic due to lack of blood flow. This can lead to mitral valve regurgitation as the damaged papillary muscles can no longer effectively control the valve’s closure.
What imaging technique is used to visualise the coronary arteries?
Coronary angiography is an x-ray imaging technique used to visualise the coronary arteries.
What is a coronary angiogram?
A coronary angiogram is an X-ray imaging technique used to visualise the coronary arteries. A contrast agent is injected into the arteries, allowing them to be seen on X-ray.
How does coronary angiography work?
Coronary angiography involves injecting a contrast dye into the coronary arteries and using x-rays to create images of the arteries and assess their perfusion patterns.
How are coronary angiograms used to examine the coronary arteries?
A coronary angiogram uses X-ray imaging and a contrast agent to visualise the coronary arteries. The contrast agent is injected into the arteries, allowing them to be clearly seen on X-ray images. This helps clinicians identify blockages or other abnormalities.
Provide some examples of coronary artery branches that can be observed in a coronary angiogram.
Coronary angiograms can visualise branches like the sinuatrial nodal artery, anterior ventricular arteries, right marginal artery, and the inferior interventricular artery.
Aside from the coronary arteries, what other vascular structures are important for maintaining heart function?
The heart also relies on venous drainage for proper function.
What are the major cardiac veins responsible for venous drainage of the heart, and how are they structured in relation to the arteries?
The three large cardiac veins are the great, middle, and small cardiac veins. They run alongside the arteries in a similar pattern.
Where do the great, middle, and small cardiac veins drain into?
The coronary sinus.
Where do the cardiac veins drain?
All three cardiac veins drain into the coronary sinus.
Describe the location and function of the coronary sinus.
The coronary sinus is a large vein located on the inferior surface of the heart, under the left atrium. It receives deoxygenated blood from the cardiac veins and drains into the right atrium.
Where does the coronary sinus drain into?
The right atrium.
What approach is used to define the heart’s borders within the chest?
Finding the heart’s edges involves mapping out four key points on the chest wall, similar to how we use three key points to locate the liver.
Which anatomical landmark serves as a guide for rib counting and locating heart anatomy?
The sternal angle, where the manubrium of the sternum connects with the body of the sternum, is crucial for identifying the second rib and subsequently counting other ribs. This is essential for locating the heart’s anatomical landmarks.
What is the significance of the sternal angle?
It is used to locate the second rib, which is key to identifying other anatomical landmarks.
How do you locate the junction of the superior vena cava and the right atrium?
It is found just lateral (1cm) to the sternum at the third rib’s costal cartilage.
Where can the sternal angle be found?
Where the manubrium of the sternum meets the body of the sternum.
What marks the junction of the right atrium and the inferior vena cava?
The sixth rib’s costal cartilage on the right (1cm lateral to sternum)
Describe the location and significance of the first key point in mapping the heart’s edges.
Situated just lateral to the sternum at the level of the third rib’s costal cartilage on the right side, this point signifies the junction where the superior vena cava meets the right atrium.
What anatomical landmark does the second key point represent, and where is it found?
Located at the sixth rib’s costal cartilage on the right side , this point marks the meeting point of the right atrium and the inferior vena cava.
Where is the junction of the left atrial appendage and the pulmonary trunk?
At the second costal cartilage on the left, just lateral (1cm) to the sternum.
What insight can be gained about the right side of the heart by observing the positions of the first and second key points?
The alignment of these points along a straight vertical line indicates that the right side of the heart, predominantly the right atrium, has a vertical orientation within the chest.
Where is the third key point situated, and what does it indicate anatomically?
Found at the second costal cartilage on the left side, just lateral (1cm) to the sternum, this point marks the junction of the left atrial appendage and the pulmonary trunk.
Explain the importance of the fourth key point and its location.
Located in the fifth intercostal space on the left side, at the mid-clavicular line, this point pinpoints the site of the cardiac apex, representing the lowermost tip of the left ventricle.
What marks the site of the cardiac apex and the left ventricle?
The fifth intercostal space on the left, at the mid-clavicular line.
What are the four key points used to map the edges of the heart?
Right side: Junction of the superior vena cava and right atrium (third rib’s costal cartilage)Junction of the right atrium and inferior vena cava (sixth rib’s costal cartilage). Left side: Junction of the left atrial appendage and the pulmonary trunk (second costal cartilage)Cardiac apex/left ventricle (fifth intercostal space at the mid-clavicular line).
Why is the stethoscope placement for listening to heart valves not directly over the valve itself?
To hear the sound of blood flow through the valve, auscultation is performed slightly downstream from the valve, where the sound is loudest. This also allows for better detection of any murmurs or abnormalities.
Why is the placement of the stethoscope important when listening to heart valves?
The stethoscope should be placed slightly downstream from the valve being examined because the sound of blood flow, and any potential abnormalities, is most audible in the direction of blood flow after passing through the valve.
Why is a stethoscope placed slightly downstream from a heart valve to listen to it?
To hear the sound of the blood flowing through the valve, including any murmurs or other abnormalities.
Where should the stethoscope be placed to auscultate the aortic valve, and why?
The aortic valve is best heard in the second intercostal space on the right, just lateral to the sternum. This is because blood flows from the aortic valve upwards and to the right.
Describe the optimal stethoscope placement for listening to the pulmonary valve and the reasoning behind it.
The stethoscope should be positioned in the second intercostal space on the left, just lateral to the sternum. This placement aligns with the upward and leftward direction of blood flow through the pulmonary valve.
Explain the stethoscope placement for auscultating the tricuspid valve and the rationale for this location.
The tricuspid valve is best heard in the fifth intercostal space on the left, just next to the sternum. This is because the valve’s oblique orientation directs blood flow downwards and slightly towards the left.
Where should the stethoscope be placed to listen to the mitral valve, and why is this location chosen?
The mitral valve is auscultated in the fifth intercostal space on the left, at the mid-clavicular line. This position is chosen because the mitral valve’s oblique angle directs blood flow downwards and towards the left.
What is the function of the heart’s conduction system?
It ensures the rapid and coordinated transmission of electrical impulses to the atrial and ventricular muscles, enabling synchronised contractions.
What is considered the pacemaker of the heart?
The sinoatrial (SA) node.
Where do these electrical impulses typically originate?
They typically originate in the sinoatrial (SA) node, often referred to as the heart’s pacemaker.
How does the signal travel from the SA node to the ventricles?
The signal spreads from the SA node to the atrioventricular (AV) node, then through the AV bundle (bundle of His), branching into right and left bundle branches, and finally reaching the ventricular muscle via Purkinje fibres.
What role does the cardiac skeleton play in the conduction system?
It acts as an electrical insulator between the atria and ventricles, ensuring that the electrical signal passes to the ventricles only through the AV node and bundle.
How does understanding the conduction system relate to clinical situations like myocardial infarction?
Knowledge of the conduction system helps us understand how damage to a specific area, such as the interventricular septum, can disrupt the heart’s electrical activity. For example, a myocardial infarction affecting the left coronary artery, which supplies the anterior two-thirds of the interventricular septum, can impede the coordinated spread of the electrical signal to the ventricles, potentially leading to heart failure.
What is the pathway of the electrical signal through the ventricles?
AV bundle of His, right and left bundle branches, Purkinje fibres.
Why is understanding the heart’s conduction system clinically important?
Understanding the heart’s conduction system helps explain how issues like myocardial infarctions or ventricular septal defects can impact the heart’s ability to contract efficiently.
How can a myocardial infarction affect the conduction system?
If a myocardial infarction damages the interventricular septum where the bundle branches are located, it can disrupt the smooth flow of the electrical signal to the ventricles, leading to uncoordinated contractions and potentially heart failure.
Why is damage to the interventricular septum, particularly where the bundle branches are located, especially concerning?
Damage in this area is particularly concerning because it can directly disrupt the bundle branches, which are essential for carrying the electrical signal to the ventricles. This disruption can lead to serious heart dysfunction.
Provide an example of how a specific coronary artery blockage can impact the conduction system.
A blockage of the left coronary artery, responsible for supplying the anterior two-thirds of the interventricular septum, can impede the conduction system’s electrical pathway. This disruption can result in severe issues with heart function.
How could a ventricular septal defect affect the heart’s contractions?
A ventricular septal defect could disrupt the electrical signals that control heart contractions, potentially leading to serious issues with the heart’s ability to beat and circulate blood effectively.
What is the clinical significance of the left coronary artery supplying the anterior two-thirds of the interventricular septum?
If the left coronary artery is blocked, such as in a myocardial infarction, the electrical signals travelling down the ventricles may be disrupted, leading to uncoordinated contractions and potential heart failure.
