Heart Anatomy

Questions and Answers

Which of the following is NOT a palpable landmark of the thoracic cage used to locate underlying structures?

Thoracic duct (correct)

Sternal angle

Anterior axillary fold

Jugular notch

What is the significance of the sternal angle in relation to the heart?

It is where the superior vena cava enters the heart.

It indicates the level of the bifurcation of the trachea and the origin of the pulmonary trunk. (correct)

It provides a reference point for the location of the heart's valves.

It marks the level where the heart's apex is located.

Which of the following structures does NOT pass through the sternal angle?

Pulmonary trunk

Aortic arch (correct)

Ligamentum arteriosum

Thoracic duct

The acronym "RATPLANT" is used to describe structures that lie at the sternal angle. What does the "T" stand for?

Tracheal bifurcation Signup and view all the answers

What is the clinical significance of understanding the surface anatomy of the thorax?

All of the above. Signup and view all the answers

Which of the following landmarks is NOT used to orient oneself in the thorax?

Diaphragm Signup and view all the answers

The ability to visualize how anatomical structures in the thorax relate to surface features is essential for:

All of the above. Signup and view all the answers

Which of the following is NOT a surface landmark that can be observed on the thorax?

Sternal angle Signup and view all the answers

What is the primary function of the heart?

To pump blood throughout the body. Signup and view all the answers

Where is the heart typically located in the thoracic cavity?

Between ribs 2 and 5. Signup and view all the answers

What is the name of the fibroserous sac that encloses the heart?

Pericardium Signup and view all the answers

Which of the following structures is NOT found in the superior mediastinum?

Heart Signup and view all the answers

What is the main content of the middle mediastinum?

The heart Signup and view all the answers

Which structure separates the superior and inferior mediastinum?

Sternal angle Signup and view all the answers

Which of the following structures blends with the parietal pleura of the lungs laterally?

Mediastinal pleura Signup and view all the answers

What is the name of the imaginary line used to locate the apex of the heart?

Midclavicular line Signup and view all the answers

What is the main function of the 'safe triangle'?

To guide the insertion of chest drains. Signup and view all the answers

What is the most important structure in the anterior mediastinum?

Lymph nodes Signup and view all the answers

Which of the following is NOT a source of deoxygenated blood entering the right atrium?

Pulmonary veins Signup and view all the answers

What is the function of the pericardial fluid?

To lubricate the heart and reduce friction during contractions Signup and view all the answers

What is the name of the structure that separates the right atrium from the left atrium?

Interatrial septum Signup and view all the answers

What is the name of the valve that regulates blood flow between the right atrium and the right ventricle?

Tricuspid valve Signup and view all the answers

Which of the following is a potential cause of pericardial effusion?

Aortic aneurysm Signup and view all the answers

What is the name of the smooth, posterior portion of the right atrium where the vena cava drain?

Sinus venarum Signup and view all the answers

What is the name of the remnant of the foramen ovale in the right atrium?

Fossa ovalis Signup and view all the answers

Which of the following is NOT a characteristic of cardiac tamponade?

Increased heart rate Signup and view all the answers

Which of the following is a common treatment for pericardial effusion?

Pericardial tap/pericardiocentesis Signup and view all the answers

What is the name of the structure that helps the right atrium hold more blood during increased exertion?

Auricle Signup and view all the answers

What is the primary function of the coronary circulation?

To provide nutrients to the heart muscle itself. Signup and view all the answers

What is the name of the artery that originates from the left coronary artery and supplies the left ventricle?

Left anterior descending artery Signup and view all the answers

What is the term used to describe the variation in the origin of the posterior interventricular artery?

Coronary dominance Signup and view all the answers

What is the location of the coronary sinus in relation to the heart?

On the posterior aspect of the heart in the coronary sulcus Signup and view all the answers

What is the function of the chordae tendineae in the heart valves?

To prevent the valves from prolapsing into the atria Signup and view all the answers

What is the term used to describe the layers of tissue that make up the heart valves?

Fibroelastic-fibrocollagenous Signup and view all the answers

What is the name of the artery that arises from the right coronary artery and supplies the right atrium and ventricle?

Right marginal artery Signup and view all the answers

What is the purpose of the elastic tissue in the heart valves?

To allow for flexibility and movement of the valves Signup and view all the answers

What is the direction of the right coronary artery in relation to the heart?

It descends vertically in the coronary sulcus Signup and view all the answers

What is the term used to describe the pattern of blood supply to the heart muscle?

Coronary circulation Signup and view all the answers

What is the function of the chordae tendineae in the right ventricle?

They attach to the papillary muscles and prevent the tricuspid valve from prolapsing into the right atrium during ventricular contraction. Signup and view all the answers

Which of the following structures is responsible for dividing the right and left ventricles?

Interventricular septum Signup and view all the answers

Which structure in the left ventricle serves as a smooth pathway leading towards the ascending aorta?

Aortic vestibule Signup and view all the answers

What is the function of the semilunar valve in the left ventricle?

To prevent backflow of blood from the aorta into the left ventricle. Signup and view all the answers

Why is the left ventricle thicker and larger than the right ventricle?

The left ventricle pumps blood to the entire body, which requires more force than pumping blood to the lungs. Signup and view all the answers

Which of the following is NOT a feature of the right ventricle's internal aspect?

Bicuspid valve Signup and view all the answers

Which sulcus separates the atria from the ventricles externally?

Coronary sulcus Signup and view all the answers

What is the function of the valve of the foramen ovale in the left atrium?

It is a remnant of a fetal structure that allowed blood to bypass the lungs. Signup and view all the answers

Which of the following structures is responsible for the attachment of the chordae tendineae in the left ventricle?

Papillary muscles Signup and view all the answers

What is the primary function of the cardiac skeleton?

To provide a framework for muscle attachment and support for the heart valves. Signup and view all the answers

What structure acts as a landmark dividing the base from the inferior surface of the heart?

Coronary sinus Signup and view all the answers

Which surface of the heart is primarily in contact with the diaphragm?

Inferior surface Signup and view all the answers

Which of the following statements about the apex of the heart is true?

It indicates cardiomegaly when displaced towards the axilla. Signup and view all the answers

What is the function of the pericardial fluid?

To reduce friction between the heart and the pericardium Signup and view all the answers

Which part of the heart's structure is primarily made up of the left ventricle?

Inferior surface Signup and view all the answers

What comprises the base surface of the heart?

Left atrium and part of the right atrium Signup and view all the answers

Which structure is in direct contact with the anterior surface of the heart?

Sternum Signup and view all the answers

What component of the heart's structure is responsible for covering the heart and the origins of the great vessels?

Pericardium Signup and view all the answers

The right pulmonary surface of the heart is primarily made up of which chamber?

Right atrium Signup and view all the answers

What is the primary role of the fibrous pericardium?

To anchor the heart and prevent over-distension Signup and view all the answers

What is the primary function of the AV node in the heart's conduction system?

To pass electrical signals from the atria to the ventricles Signup and view all the answers

Which structure originates in the medulla oblongata and is responsible for parasympathetic innervation of the heart?

Vagus nerve Signup and view all the answers

What role do Purkinje fibers play in the heart?

Stimulating contraction of the heart muscle cells Signup and view all the answers

What neurotransmitter is released by sympathetic fibers to increase heart rate?

Noradrenaline Signup and view all the answers

Which statement accurately describes the AV node's structure compared to the SA node?

Both nodes have similar network arrangements Signup and view all the answers

During which phase of the cardiac cycle does the heart undergo contraction and pump blood?

Systole Signup and view all the answers

What is the primary output of the sympathetic nervous system's influence on the heart?

Increased conduction rate and force of contraction Signup and view all the answers

Which portion of the heart's conduction system emerges from the AV node?

Bundle of His Signup and view all the answers

What effect does the vagus nerve have on the heart?

Inhibits impulse conduction in the AV node Signup and view all the answers

Which of the following best describes the relationship between the left and right bundle branches?

They branch out from the Bundle of His Signup and view all the answers

What causes referred pain from the heart to areas of the skin?

Overlapping spinal cord segments for visceral and somatic sensory nerves Signup and view all the answers

Which spinal cord segments are responsible for visceral sensory input from the heart?

T1-T4 Signup and view all the answers

Where does the visceral sensory input from the heart enter the spinal cord?

At the thoracic region Signup and view all the answers

What is one reason why the brain may misinterpret heart pain as skin pain?

There is a lack of distinct pathways for visceral and somatic sensory input Signup and view all the answers

Which areas of skin correspond to the T1-T4 dermatomes, relevant for referred pain from the heart?

Chest, neck, shoulder, back, and arms Signup and view all the answers

What is left dominance in coronary circulation characterized by?

The left coronary artery supplies most of the posterior wall. Signup and view all the answers

Which structure primarily drains the cardiac veins?

Coronary sinus Signup and view all the answers

Which artery typically supplies the sinoatrial (SA) node in 60% of individuals?

Right coronary artery Signup and view all the answers

What is the purpose of an arteriogram/angiogram in cardiac medicine?

To detect blockages in coronary arteries Signup and view all the answers

Which of the following veins directly drains into the right atrium?

Small cardiac vein Signup and view all the answers

What is angiogenesis?

The generation of new blood vessels Signup and view all the answers

Which of the following arteries is known as the left anterior descending artery?

Anterior interventricular artery Signup and view all the answers

Which pathway does the electrical impulse take after originating from the SA node?

Through the AV node and then to the ventricles Signup and view all the answers

Which of the following veins begins as the anterior interventricular vein?

Great cardiac vein Signup and view all the answers

What layer of the heart wall is directly responsible for the heart's contraction?

Myocardium Signup and view all the answers

What is the impact of potential obstructions in the coronary arteries?

They can affect ECG readings. Signup and view all the answers

Which layer of the heart wall is in direct contact with circulating blood?

Endocardium Signup and view all the answers

What is the primary function of epicardial fat?

To protect and insulate the heart Signup and view all the answers

Which of the following is NOT a characteristic of the myocardium?

It is responsible for the heart's electrical activity Signup and view all the answers

What is the significance of the trabeculae carneae in the ventricles?

They provide attachment points for the chordae tendineae Signup and view all the answers

Which layer of the endocardium is directly in contact with the myocardium?

Outermost layer Signup and view all the answers

Which of the following is NOT a factor associated with an increase in epicardial fat?

Hypertension Signup and view all the answers

Which layer of the heart wall contains Purkinje fibers?

Endocardium Signup and view all the answers

Why is the middle layer of the endocardium thicker in the atria than in the ventricles?

The atria need to expand more than the ventricles Signup and view all the answers

What is the clinical significance of the location of coronary vessels in the fibrocollagenous layer of the epicardium?

It allows for easier access during coronary bypass surgery Signup and view all the answers

Study Notes

Part 1: Heart Location

Surface anatomy: ability to visualize anatomical structures in the thorax related to surface features is essential for physical examinations
Palpable landmarks:
- Bony palpable landmarks of the thoracic cage are useful to locate underlying structures
- Outline of the heart can be traced on the anterior surface of the thorax
Sternal angle:
- Also known as Angle of Louis
- Structures that lie at the sternal angle:
  - Rib 2
  - Aortic arch
  - Tracheal bifurcation (Carina)
  - Pulmonary trunk
  - Ligamentum arteriosum
  - Azygous vein drains into SVC
  - Nerves (Cardiac plexus, loop of recurrent laryngeal n.)
  - Thoracic duct (right-to-left movement before exiting thoracic inlet)
Observable landmarks:
- Anterior axillary fold
- Posterior axillary fold
- Axillary fossa/Axilla
- Jugular notch
- Pectoralis major and other muscles
Imaginary lines:
- Can be drawn on the surface of the thorax to orientate oneself
- Useful for procedures and knowing what anatomical structures lie below
- Example: "Safe Triangle" for chest drains

Part 1: Heart Location (continued)

Heart location:
- Usually between ribs 2 and 5th intercostal space
- Extends from right medial border of the sternum to having its apex at the midclavicular line on the left
- Can change due to pathology (e.g., cardiomegaly or displaced by mediastinal or lung conditions)
- When displaced, the heart moves inferiorly and laterally towards the axilla
Heart location in relation to vertebrae:
- When supine: T4/T5 - T8
- When standing: T6 - T9
Structures that change the location of the heart:
- Think about what structures are in motion within the thorax region that can change the location of the heart

Part 1: Heart Location (continued)

Heart attached to the diaphragm via its pericardium
Borders of the heart are variable depending on the position of the diaphragm (i.e., during respiration)
Pericardium: fibroserous sac that covers the heart and the roots of the great vessels

Mediastinum

Thorax divisions:
- Right pleural cavity
- Left pleural cavity
- Mediastinum
Mediastinal pleura:
- Encapsulates most of the mediastinum
- Blends with the parietal pleura of the lungs laterally
- Blends with the pericardium internally
Location of the mediastinum:
- A-P: Extends from sternum to the bodies of the vertebrae (T1-T12)
- S-I: Superior thoracic aperture to the diaphragm
- Lateral (R & L): Mediastinal pleurae
Divisions of the mediastinum:
- Superior and inferior mediastinum divided by the sternal angle
- Inferior mediastinum further subdivided into anterior, middle, and posterior mediastinum

Orientation

Heart shape: wedge or pyramid that has fallen over
Surfaces of the heart:
- Base surface (posterior surface)
- Inferior surface (diaphragmatic surface)
- Anterior surface (sternocostal surface)
- Right pulmonary surface
- Left pulmonary surface
Base surface:
- Made up of the whole of the left atrium and part of the right atrium
- Majority of great heart vessels exit/enter the heart in this location
Inferior surface:
- Projects from the base of the heart towards the apex of the heart
- In contact with the diaphragm via the pericardium
- The coronary sinus acts as a landmark to divide the base from the inferior surface of the heart
Apex:
- Part of the inferolateral portion of the left ventricle
- Lies deep to the 5th intercostal space along the midclavicular line
- Apex beat is the outermost and lowermost palpable cardiac impulse on the chest wall

Part 2: Heart Structure

Pericardium

Overview:
- Fibrous membrane covering the heart and the origin of the great vessels
- Divided into 3 layers:
  - Fibrous pericardium
  - Serous pericardium (parietal and visceral layers)
  - Pericardial cavity
Fibrous pericardium:
- Extends from its inferior apex attachment at the diaphragm, all around the heart, and then blends with the adventitia (blood vessel layer) of the great vessels superiorly
- Attached anteriorly to the sternum
- Attached loosely posteriorly to structures within the posterior mediastinum
Serous pericardium:
- Divided into two layers that are continuous around the roots of the great vessels
- Parietal pericardium: lines the inner surface of the fibrous pericardium
- Visceral layer: adheres to the heart and forms its outer covering (also known as the epicardium)
Pericardial cavity:
- Space between the parietal and visceral layers of the serous pericardium
- Typically has 15-50ml of pericardial fluid
- Function of pericardial fluid: lubrication and reduction of friction between the pericardial layers

Pericardium (continued)

Clinical correlates:
- Pericardial effusion: fluid (including blood) buildup in the pericardial sac
- Puts pressure on the heart and impairs heart function
- Can lead to cardiac tamponade
- Treatment: pericardial tap/pericardiocentesis

The Heart

Chambers:
- Right atrium
- Right ventricle
- Left atrium
- Left ventricle
Blood flow through the heart:
1. Right atrium collects deoxygenated blood from the body
2. Right atrium contracts to pass blood through the AV valve into the right ventricle
3. Right ventricle contracts and blood passes through the semilunar valve into the pulmonary trunk
4. Left atrium collects oxygenated blood from the lungs
5. Left atrium contracts to pass blood through the AV valve into the left ventricle
6. Left ventricle contracts and blood passes through the semilunar valve into the aorta

Heart Chambers

Right atrium:
- Receives venous blood from 4 sources:
  - Superior vena cava
  - Inferior vena cava
  - Coronary sinus
  - Anterior cardiac veins
- Internal aspect:
  - Sinus venarum (smooth posterior portion)
  - Pectinate muscle (rough anterior portion)
  - Crista terminalis
  - Auricle
  - Interatrial septum
  - Fossa ovalis
Right ventricle:
- Internal aspect:
  - Trabeculae carneae
  - Papillary muscles
  - Chorda tendineae
  - Septomarginal trabecula (moderator band)
  - Interventricular septum
  - Conus arteriosus
  - Semilunar valve (pulmonary valve)
Left atrium:
- Internal aspect:
  - Similar to right atrium, but with no distinct structure to divide the two surfaces
  - Auricle
  - Interatrial septum
  - Valve of the foramen ovale
  - Bicuspid valve (mitral valve)
Left ventricle:
- Internal aspect:
  - Trabeculae carneae
  - Papillary muscles
  - Chorda tendineae
  - Interventricular septum
  - Aortic vestibule
  - Semilunar valve (aortic valve)

External Features

Sulci/Grooves of the heart:
- Structures that separate the chambers of the heart internally create impressions on the external surface of the heart
- Provides external demarcations that correspond to the internal partitions that divide the heart into its chambers
- Creates a passageway for the coronary arteries and veins and their main branches
There are 3 main sulci:
- Coronary sulcus (Atrioventricular sulcus)
- Anterior interventricular sulcus
- Posterior interventricular sulcus### Heart Valves
Heart valves function similar to valves in veins
Closure of valves creates the second heart sound (‘DUB’)
There are two main types of abnormalities: stenosis (narrowing) and regurgitation (compromised closure)
Treatment for abnormalities is through heart valve replacement surgery
Heart valves are generally auscultated close to their location, not directly above

Heart Structure

Heart wall has multiple layers:
- Epicardium (outermost layer)
- Myocardium (middle layer, muscular wall responsible for contraction)
- Endocardium (inner layer, smooth lining in contact with blood)
Epicardial fat is a common occurrence on the heart surface, acting to protect and support the heart
Epicardial fat is more abundant in certain areas (atrioventricular and interventricular grooves) and increases with age, obesity, diabetes, and cardiovascular disease

Histology: Epicardium

Pericardial sac encapsulates the heart
Serous pericardium is composed of compact fibrocollagenous and elastic tissue
Epicardium/visceral pericardium lies over the surface of the heart

Histology: Myocardium

Myocardium is the middle and largest layer of the heart
Composed of specialized striated muscle fibres (cardiac muscle)
Amount of myocardium and diameter of muscle fibres vary between chamber and cardiac workload
Outer surface is smooth, inner surface is raised into trabeculation
Papillary muscles serve as attachment for chordae tendineae

Histology: Endocardium

Endocardium is the internal layer of the heart wall in direct contact with blood
Composed of three layers:
1. Layer in contact with myocardium
2. Middle layer with collagen fibres and elastic fibres
3. Innermost layer of flat endothelial cells
Endocardium is thicker in atria than ventricles due to elastic fibres needed for expansion

Histology: Heart Valves

Heart valves originate from the cardiac skeleton
Central plate is fibrocollagenous, superior and inferior surfaces are covered in fibroelastic tissue and flat endothelial cells
Thickness of layers varies between valves and areas of each valve, and with age and disease

Coronary Circulation

Heart receives oxygenated blood from coronary circulation
Coronary circulation has two main coronary arteries (right and left) that circle the heart
Arteries give off multiple branches in and around the interventricular sulci, converging towards the apex of the heart
Cardiac veins drain blood and empty into the coronary sinus
Coronary sinus lies on the posterior aspect of the heart in the coronary sulcus and drains into the right atrium

Coronary Circulation: Right Coronary Artery

Right coronary artery descends vertically in the coronary sulcus
Gives off multiple branches, including sinoatrial nodal or atrial artery, right marginal artery, and posterior interventricular artery

Coronary Circulation: Left Coronary Artery

Left coronary artery enters the coronary sulcus and divides into two branches: anterior interventricular and circumflex
Anterior interventricular artery continues towards the apex of the heart in the anterior interventricular sulcus
Circumflex artery curves around the left in the coronary sulcus and ends just before the posterior interventricular sulcus

Coronary Circulation: Coronary Dominance & Variation

Coronary dominance depends on the origin of the posterior interventricular artery
Three main types of dominance: right dominance (~80-85%), left dominance (~10%), and co-dominance (~20%)

Conduction System

Conduction system starts at the sinoatrial (SA) node, located in the right atrium near the entrance of the SVC
SA node and internodal branches stimulate contraction of the right atrium and left atrium
Atrioventricular (AV) node sends impulses into the interventricular septum to stimulate contraction of the ventricles
Bundle of His divides into main left and right branches, giving off many smaller terminal branches called Purkinje fibres

Histology: Conduction System

SA node is located within fibrocollagenous stroma
AV node has a similar setup, but more arranged
Right and left bundle branches run beneath the endocardium and then connect with large muscle fibres (Purkinje fibres)

Innervation of the Heart

Heart has parasympathetic (vagus nerve) and sympathetic innervation
Parasympathetic innervation slows heart rate, while sympathetic innervation increases heart rate
Visceral afferent fibres transmit noxious stimuli originating from the heart

Cardiac Cycle

Cardiac cycle begins with atrial systole and ends with ventricular diastole
Systole is the period of contraction, while diastole is the period of relaxation

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Description

Quiz on palpable landmarks of the thoracic cage, sternal angle, and surface anatomy of the thorax. Understand the significance of these structures in relation to the heart and other underlying structures.