cardiac anatomy and embryology

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Questions and Answers

Which structure primarily separates the left and right ventricles during embryonic development?

Foramen ovale

Neural crest cells

Endocardial cushions (correct)

Bulbus cordis

What is the primary function of Purkinje fibers in the heart?

Provide structural support

Facilitate blood flow

Regulate heart rate

Conduct electrical impulses (correct)

Which of the following correctly describes the role of gap junctions in cardiac tissue?

To allow electrical communication between cells (correct)

To provide mechanical strength between cells

To regulate heart rate

To facilitate vascular growth

In the context of congenital cardiac disorders, which condition is characterized by an opening between the atria?

Atrial septal defect Signup and view all the answers

Which coronary artery is responsible for supplying blood to the sinoatrial node?

Right coronary artery Signup and view all the answers

What physiological change occurs in fetal shunts after birth?

They close to redirect blood flow through the lungs Signup and view all the answers

Which embryonic structure is primarily responsible for forming the aorta and main pulmonary artery?

Truncus arteriosus Signup and view all the answers

Which process involves the formation of brand-new blood vessels from mesodermal cells?

Vasculogenesis Signup and view all the answers

What is the role of mesenchyme in the development of blood vessels?

It develops into the muscular and connective tissue of a blood vessel. Signup and view all the answers

By which week does primitive circulation develop in the embryo?

By week 3 Signup and view all the answers

Which vein carries poorly oxygenated blood from the umbilical vesicle to the embryonic heart?

Vitelline vein Signup and view all the answers

What occurs during angiogenesis?

Existing blood vessels sprout and fuse with other vessels. Signup and view all the answers

Which cardiac structure can be auscultated at the 2nd right intercostal space at the sternal border?

The aortic valve Signup and view all the answers

What is the primary structure responsible for bringing oxygenated blood to the embryonic heart?

The umbilical vein Signup and view all the answers

The papillary muscles in the heart are primarily attached to which structure?

The chordae tendinae of an atrioventricular valve Signup and view all the answers

Which subdivision of the mediastinum is situated posterior to the heart?

Posterior mediastinum Signup and view all the answers

Where is the approximate position of the heart in relation to the median plane?

Primarily to the left of the median plane Signup and view all the answers

What is the primary remnant in the heart connecting the aorta and pulmonary arteries once present in embryos?

Ductus arteriosus Signup and view all the answers

What anatomical feature separates the superior and inferior mediastinum?

The base of the heart Signup and view all the answers

Which of the following arteries does NOT bring blood from the body to the embryonic heart?

The pulmonary arteries Signup and view all the answers

What structure is located at the lower border of the 2nd left costal cartilage?

The apex of the heart Signup and view all the answers

What feature distinguishes the myocardial walls of the right side from those of the left side?

The right side is more trabeculated Signup and view all the answers

Which of the following statements about the AV valves is correct?

The mitral valve has two sets of papillary muscles Signup and view all the answers

What is the primary function of the SA node in the heart?

To serve as a pacemaker Signup and view all the answers

What separates the right and left ventricles?

Inferior IV septum Signup and view all the answers

Where is the AV node located in the heart?

On the floor of the right atrium Signup and view all the answers

What role does the autonomic nervous system play in the conduction system of the heart?

Modulates cardiac rhythm through sympathetic and parasympathetic stimulation Signup and view all the answers

What structure arises from the AV bundle to stimulate the ventricles?

Purkinje fibers Signup and view all the answers

What is unique about the interventricular septum?

It has both muscular and membranous components Signup and view all the answers

Which physiological effect does sympathetic stimulation have on the conduction system?

Speeds up conduction Signup and view all the answers

Which structure is responsible for increasing the capacity of the atrium?

Auricles Signup and view all the answers

What is the function of the fibrous pericardium?

Anchors the heart and prevents overfilling Signup and view all the answers

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

Myocardium Signup and view all the answers

Where is the mitral valve auscultation location found?

5th intercostal space at the midclavicular line Signup and view all the answers

Which layer of the pericardium is involved in the formation of the outer surface of the heart?

Epicardium Signup and view all the answers

What type of cells are Purkinje fibers?

Specialized cardiac muscle fibers for conduction Signup and view all the answers

Which structure allows the heart to work in a friction-free environment?

Serous pericardium Signup and view all the answers

What is the primary composition of the coronary vessels found in the heart?

Loose connective tissue Signup and view all the answers

Which intercostal space is associated with the aortic valve?

2nd right intercostal space Signup and view all the answers

Which layer has a thin internal structure that covers the valves of the heart?

Endocardium Signup and view all the answers

What distinguishes the myocardial cells from other muscle cells?

They are striated, uninucleated, and may branch Signup and view all the answers

Study Notes

Cardiovascular Embryology

Cardiovascular embryology is the study of heart development.
Learning outcomes include relating the histology and anatomy of each cardiac structure to its function.
This also includes the Endocardium, myocardium, Purkinje fibers
Atrioventricular valves, semi-lunar valves, chordae tendinae, fibrous skeleton
And the left and right trigones and fibrous rings
Describing the vascular distribution of coronary arteries and veins/sinuses.
Right coronary artery, SA-nodal artery, right marginal artery, posterior interventricular artery
Left coronary artery, circumflex artery, left marginal artery, Coronary sinus, great cardiac vein, middle cardiac vein.
Briefly describing the nervous innervation of the heart.
Describing the physiologic function of the following subcellular structures: Gap junctions, desmosomes, fascia adherens
Relating the surface anatomy of the precordium to the following cardiac structures: Cardiac apex, base of the heart, mitral valve, tricuspid valve, aortic valve, pulmonic valve, right ventricle, right atrium.
Describing the process of vasculogenesis and angiogenesis in the embryo.
Relating the processes of lateral folding, cephalic folding, and cardiac bending to the development of cardiac structures in the early embryo.
Describing the development of the truncus arteriosus, bulbus cordis, sinus venosus, umbilical vessels, vitelline vessels, dorsal aorta, and cardinal veins.
Describing the contribution of the endocardial cushions and neural crest cells to septal, valvular, and outflow structures in the embryonic heart.
Describing the development of the atrial and ventricular septae and the foramen ovale.
Describing the anatomy of the fetal shunts and the changes they undergo immediately after parturition.
Describing the basic epidemiology, embryological pathogenesis, clinical features, and prognosis of congenital cardiac disorders. Such as: Atrial septal defects, ventricular septal defects, coarctation of the aorta, patent ductus arteriosus.
A clinical case study on a 4-month-old baby presenting with a systolic murmur over the precordium.

Pre-Assessment Questions

If you place a stethoscope at the 2nd right intercostal space at the sternal border, what cardiac structure are you likely listening to? (Aortic valve)
What structure brings oxygenated blood to the embryonic heart? (Umbilical vein)
What is the papillary muscle attached to? (Chordae tendinae of an atrioventricular valve)

Mediastinum

The mediastinum is the middle of the thorax.
It is located between the mediastinal pleura, posterior to the sternum, anterior to the vertebrae, and superior to the diaphragm.
This structure separates the two lateral pleural cavities.
Subdivisions include superior, anterior, middle, and posterior.
The base of the heart separates the superior and inferior mediastinum.

Heart

The heart and pericardial sac are approximately 2/3rds to the left and 1/3rd to the right of the median plane (middle mediastinum).
The upper border of the third right costal cartilage is 1 cm from the sternal line.
The lower border of the second left costal cartilage is 2.5 cm from the left sternal line.
The apex is approximately 9 cm left of the midsternal line.
The 7th right sternocostal articulation.

Heart - Anterior and Posterior Views

Illustrations describing the various structures of the heart, including major vessels and chambers, are included in both anterior and posterior views.

Heart - Open

An anterior or posterior view of the open heart, showcasing internal structures and pathways.
Diagrams included in this section show the heart's structures, such as the superior vena cava, right and left pulmonary arteries and veins, right and left atria, mitral and tricuspid valves, aortic valve, pulmonary valve, right and left ventricles, chordae tendineae, trabeculae carneae, and moderator band, as well as the inferior vena cava.

Auscultatory Locations - Heart

Mitral valve (apex): 5th intercostal space at the midclavicular line.
Tricuspid valve: lower left sternal border in the 4th/5th intercostal space.
Aortic valve: 2nd right intercostal space near the right sternal border.
Pulmonic valve: 2nd left intercostal space near the left sternal border.

Pericardium

A fibrous membrane that encloses the heart and the roots of the great vessels, anchoring and protecting the heart, preventing overfilling, and allowing for friction-free movement.
Two layers: outer fibrous pericardium (tough, inelastic CT) and inner serous pericardium.
Parietal layer (inner surface of the pericardium)
Visceral layer (lines outer surface of the heart = epicardium)
Continuous with the central tendon of the diaphragm (pericardiophrenic ligament).

Myocardium Components

Contains contractile and impulse-generating cells
Cardiomyocytes: individual muscle cells forming the myocardium.
Striated, uninuclear, often with one or two branches.
Full of myofibrils and mitochondria.
Purkinje fibers are specialized cardiac fibers involved in signal conduction.
Glycogen-filled, large diameter fibres, gap junctions, few myofibrils or mitochondria.
Pale-staining
Papillary muscles: located in the ventricles, connected to AV valves by chordae tendineae.
Pectinate muscles: muscular structures in the atrial walls, contributing to atrial contraction.
Trabeculae carneae: irregular ridges on the ventricular walls, providing structural support.
Intercalated discs have desmosomes and gap junctions.

Endocardium

The endocardium is the inner lining of the atria and ventricles.
Simple squamous epithelium (endothelium).
Underlying layer of fibroelastic connective tissue with scattered fibroblasts.
Deeper layer of subendothelial fibroelastic CT.
Contains small blood vessels, nerves, and Purkinje fibers.
Specialized cells forming the inner lining of AV and semilunar valves.

Histology – Purkinje Fibres

Detailed histological features of Purkinje fibers.

Histology – Valve

Histology and structural details of heart valves.

Cardiac Muscle Fibers

Cardiac muscle cells: striated, short, branched, uninuclear.
Nucleus situated at the center of the cell body.
Connected at intercalated discs populated with many gap junctions.
Contain numerous large mitochondria for resistance to fatigue.
Z discs, A bands, and I bands present.
T tubules and cisternae present.
Sarcoplasmic reticulum is simpler compared to skeletal muscle.
Larger T-tubules.

Fibrous Skeleton

Cardiac muscle fibers are anchored to the fibrous skeleton.
A complex framework of dense collagen/fibroblastic tissue surrounding the valve orifices, and associated right and left fibrous trigones.
Trigones connect rings and the membranous part of interventricular septa.
Functions: maintaining valve patency, providing attachments for valve leaflets and cusps, providing attachments for myocardium, acting as an electrical insulator to separate atrial and ventricular impulses.

Left vs Right Sides

Myocardial walls: Right side is more trabeculated, less muscle mass, thinner vs Left side is less trabeculated, more muscle mass, thicker.
AV Valves: Tricuspid (3 leaflets, 3 sets of papillary muscles: anterior, posterior, septal) vs Mitral/Bicuspid (2 leaflets, 2 sets of papillary muscles: anterior and posterior).
Conduction System: SA node and AV nodes are in the right atrium.

Features of the Heart

Interatrial septum: separates the right and left atria (Note: Fossa Ovalis)
Interventricular septum: separates the right and left ventricles
Auricles: increase atrial capacity.

Conduct System

SA Node: The heart’s pacemaker located near the opening of the SVC in the RA, sending ~70 impulses/minute, myogenically spreads in both atria and is innervated by the sympathetic and parasympathetic division.
AV Node is located on the floor of the RA near the opening of the coronary sinus at the junction with IV septum and distributes the signal through the AV bundle (of His).
Sympathetic stimulation speeds up conduction, and parasympathetic stimulation slows it down.

Innervation of the Heart

The heart is supplied by autonomic nerve fibres from the cardiac plexus which divides into superficial and deep portions.
Located on the anterior surface of the bifurcation of trachea and the posterior aspect of the aorta and pulmonary trunk.
The cardiac plexus formed of both sympathetic, parasympathetic and visceral afferent fibres.

Vasculature of the Heart

Coronary arteries/ cardiac veins supply and drain the myocardium.
End circulation.
Note: The endocardium and some of the subendocardial tissue receive oxygen and nutrients through diffusion or microvasculature.
Vessels are typically embedded in fat and run beneath the epicardium.
Parts of these blood vessels are embedded within the myocardium to ensure the myocardium receives oxygen and nutrients.
The blood vessels of the heart are under autonomic control.

Coronary Arteries

Right and left coronary arteries, first branches of the aorta.
Supply the myocardium and epicardium.
Arise from aortic sinuses, superior to the aortic valve and pass around opposing sides of the pulmonary trunk.

Right Coronary Artery (RCA)

The RCA runs in the coronary sulcus, with ascending SA nodal branches.
It gives branches to the right marginal branch and gives posterior descending branches.
Posterior descending branch arises near the posterior junction of interatrial and interventricular septa and gives rise to AV nodal branches

Left Coronary Artery (LCA)

The LCA arises from the left aortic sinus of the ascending aorta.
Passes between the left auricle and left side of the pulmonary trunk, running in the AV sulcus.
Splits into the anterior IV and circumflex branches.
Anterior IV branch: supplies walls of the ventricles, provides a diagonal branch.
Circumflex branch: provides a marginal branch and supplies the walls of the LV and LA.

Dominance

The dominance of the coronary arterial system is defined by the artery that gives rise to the posterior interventricular branch.

Cardiac Veins

Cardiac veins empty into the coronary sinus and eventually into the right atrium.
The coronary sinus is the main heart vein, which runs from left to right, in the posterior part of the coronary sulsus.
The coronary sinus receives the great cardiac vein, the middle cardiac vein, and small cardiac veins.
The left posterior ventricular vein and left marginal vein also open into the coronary sinus.

BMS 150 Review

Vasculogenesis = development of brand-new blood vessels from mesodermal cells.
Angiogenesis = "sprouting" of existing blood vessels.
Connects blood vessels to each other.
Development of embryonic vessels.
Laterality is related to PHF and SHF cells, which contribute to the outflow tract, on the right and left sides.
Cardiac loop (outflow tract bends on day 23).
Formation of the common atrium, trabeculated part of the right ventricle, outflow tracts of both ventricles, roots of aorta and pulmonary artery from bulbus cordis and truncus arteriosus.
Atrial and ventricular partitioning, with descriptions of structures like septum primum, foramen secundum, septum secundum etc.
Endocardial cushions, and their role in AV canal formation.

Summary

Summary descriptions of different embryonic structures and their adult counterparts.

Early Development of the Heart

Blood flow from the sinus venosus to the primordial atrium, and ventricle.
Ventricle contracts, pushing blood into the bulbus cordis and truncus arteriosus.
Passes through pharyngeal arch and dorsal aorta to the rest of the embryo.

Congenital Heart Disease - Overview

Prevalence of different congenital heart diseases.

Atrial Septal Defect (ASD)

Most are septum secundum ASDs (90%).
Usually shunts blood from the left atrium to the right atrium.
Patent foramen ovale
Increased intrathoracic pressure.
Can be asymptomatic to significant symptoms.

Ventricular Septal Defect (VSD)

Incomplete closure of the ventricular septum causes left-to-right shunting.
Common anomaly at birth.
Larger VSDs can lead to symptoms such as rapid breathing, poor feeding, failure to thrive, recurrence respiratory infections, and right-sided heart enlargement.

Patent Ductus Arteriosus (PDA)

The ductus arteriosus remains open.
Pressure differences between aorta and pulmonary trunk increase blood flow through the ductus arteriosus.
Shunts blood from aorta to the pulmonary artery.

Coarctation of Aorta

The aortic lumen below the origin of the left subclavian artery is narrowed.
Classic clinical signs include hypertension in the right arm concomitant with lowered blood pressure in the legs.

Factors Leading to Embryological Defects

Interference with left-right determination (e.g., dextrocardia, situs inversus).
Improper migration of precursor cells (e.g., neural crest cells).
Improper regression of embryological structures (e.g., Patent Ductus Arteriosus).

Class Discussion

A case study involving a 4-month-old baby presenting with a systolic murmur.
Further questions, such as possible embryological disorders, and investigations.

References

Key references for the information provided.

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Description

Test your knowledge on the structures and functions associated with the embryonic development of the heart. This quiz covers key concepts including Purkinje fibers, gap junctions, congenital disorders, and the physiological changes that occur at birth. Perfect for students studying cardiac biology or embryology.