The Heart

Question 1

Where is the heart located?

Answer 1

Anterior portion of the mediastinum; immediately posterior to the sternum

Question 2

What is the Mediastinum?

Answer 2

Region between the 2 pleural cavities. Contains the great vessels, thymus, esophagus and trachea

Question 3

What are the 3 layers of the heart? (1)

Answer 3

Pericardium: the pericardial sac surrounds the heart. Consists of a dense network of collagen fibres. It stabilises the position of the heart and associated vessels within the mediastinum.

Pericardium is lined by a serous membrane that can be divided into 2 portions:

1) Visceral pericardium/epicardium: covers and adheres closely to the outer surface of the heart
2) Parietal pericardium: Lines the inner surface of the tough pericardial sac surrounding the heart

Question 4

What is the pericardial cavity?

Answer 4

The space between the visceral and parietal layers of the pericardium.

Contains pericardial fluid; secreted by the pericardial membrane. Acts as a lubricant, reducing friction between the opposing surfaces of the heart beats.

Question 5

Whats an infection of the pericardium called?

Answer 5

Pericarditis: inflammation of the pericardial surface - causes them to rub against one-another, making a distinctive scratching noise

Question 6

What is the epicardium?

Answer 6

The visceral pericardium that covers the outer surface of the heart. This serous membrane consists of an exposed mesothelium and an underlying layer of loose areolar CT that is attached to the myocardium.

Question 7

What is the myocardium?

Answer 7

The muscle wall of the heart, forms the atria and ventricles. It consists of concentric layers of cardiac muscle tissue.

Question 8

What is the endocardium?

Answer 8

Layer covering the inner surfaces of the heart, including those of the heart valves. A layer of simple squamous epithelium is continuous with the endothelium of the attached great vessels.

Question 9

Where is the apex beat found?

Answer 9

Left 5th intercostal space (important for measuring heart beat)

Question 10

What are the functions and characteristics of the right atrium?

Answer 10

Function: Receives blood from the systemic circuit through the 2 great veins (superior and inferior vena cava)

Superior vena cava: opens into the posterior and superior portion of the right atrium : delivers blood from the head, neck, upper limbs and chest.

Inferior vena cava: opens into the posterior and inferior portion of the right atrium : delivers blood from the rest of the trunk, viscera and lower limbs

Posterior walls and interatrial septum are smooth. Anterior atrial wall and inner surface of the auricle contain prominent muscular ridges = PECTINATE MUSCLES

Question 11

What is the Coronary sinus?

Answer 11

A large thin-walled vein that opens into the right atrium inferior to the connection with the superior vena cava.

The cardiac veins draining the myocardium return blood to the coronary sinus.

Question 12

Whats the role of the right ventricle and what are its features?

Answer 12

Blood travels from the right atrium into the right ventricle through a broad opening bordered by 3 fibrous flaps (cusps) and they are part of the right atrioventricular valve (tricuspid valve)

The tricuspid valve closes when the right ventricle contracts, preventing the backflow of blood into the right atrium.

Its internal surface contains papillary muscles, conical muscular projections that arise from the inner surface of the right ventricle.

Contains a series of irregular muscular ridges: the trabeculae carneae.

The moderator band is a muscular ridge that extends horizontally from the inferior portion of the interventricular septum and connects to the anterior papillary muscle - contains part of the conducting system - delivers the stimulus for contraction to the papillary muscles - they begin tensing the chordae tendineae before the rest of the ventricle contracts.

Superior end of the right ventricle tapers to the conus arteriosus (cone-shaped pouch) that ends at the PULMONARY VALVE/PULMONARY SEMILUNAR VALVE

Question 13

What are chordae tendineae? What are is their importance in regards to blood flow?

Answer 13

The free edges of the tricuspid and bicuspid valves are attached to CT fibres called chordae tendineae; fibres which originate at the papillary muscles.

Papillary muscles are conical muscular projections that arise from the inner surface of the ventricles - without them, the cusps would be like swingin doors that permit bloodflow in both directions. The musles contract and begin tensing the chordae tendineae - preventing backflow.

Question 14

What are the right and left ventricles separated by?

Answer 14

Interventricular septum

Question 15

Where does the blood in the right ventricle flow to when it contracts?

Answer 15

As it contracts the pulmonary valve (3 semilunar cusps of think CT) passes through this valve and into the pulmonary trunk, the start of the pulmonary circuit.

Once in the trunk, blood flows into the left pulmonary left and right pulmonary arteries (deoxygenated). These vessels branch repeatedly within the lungs before supplying capillaries, where gas exchange occurs.

Question 16

What are the features of the left ventricle and what is its role?

Answer 16

From the respiratory capillaries, blood collects into small veins (oxygenated) that unite to form the 4 pulmonary veins.

The posterior wall of the left atrium receives oxygenated blood from 2 left and 2 right pulmonary veins.

• It has an auricle
• it has a left atrioventricular valve (bicuspid/mitral valve), which guards the entrance to the left ventricle. Allows blood flow into the left ventricle and prevents backflow when the left ventricle contracts.

Question 17

What are the features of the left atrium and what is its role?

Answer 17

From the respiratory capillaries, blood collects into small veins (oxygenated) that unite to form the 4 pulmonary veins.

The posterior wall of the left atrium receives oxygenated blood from 2 left and 2 right pulmonary veins.

• It has an auricle
• it has a left atrioventricular valve (bicuspid/mitral valve), which guards the entrance to the left ventricle. Allows blood flow into the left ventricle and prevents backflow when the left ventricle contracts.
• Forms most of the base of the heart

Question 18

What are the features of the left ventricle and what is its role?

Answer 18

Even though the ventricles hold and pump the same amount of blood, the left ventricle has thicker walls - due to having to push blood through the large systemic circuit.

• Doesn’t have a moderator band
• Trabeculae carneae are prominent
• 2 large papillary muscles tense the chordae tendineae that anchor the bicuspid valve and prevent blood backflowing into the left atrium

Question 19

Where does the blood go after left ventricle contraction?

Answer 19

Blood leaves the ventricle through the Aortic valve and goes into the ascending aorta.

Once its left for the systemic circuit, the aortic valve prevents blackflow into the left ventricle - from here it flows into the aortic arch and into the descending aorta

Question 20

What is Atrial and Ventricular septal defect (ASD & VSD)?

Answer 20

Holes in the septum between the two atrium or two ventricles - leads to insufficient blood circulation

Question 21

What does Automaticity mean?

Answer 21

Contracting without neural or hormonal stimulation. The cardiac muscle possesses this property.

The cells that initiate and distribute the stimulus to contract are part of the heart’s conducting system aka the cardiac conduction system or nodal system

Question 22

What are the 3 main elements of the conducting system? (1)

Answer 22

Sinoatrial (SA) node: located in the wall of the right atrium

Question 23

What are the 3 main elements of the conducting system? (2)

Answer 23

Atrioventricular (AV) node: located at the junction between the atria and ventricles

The AV node is a collection of specialised cells that form the beginning of the atrioventricular bundle; extends the excitatory impulse to all ventricular musculature.

Atrioventricular Bundle:

• Follows along the lower border of the membranous part of the interventricular septum before splitting into right and left bundles.

Right bundle branch = continues on the right side of the interventricular septum toward the apex of the right ventricle. From the septum, it enters the septomarginal trabecula to reach the base of the anterior papillary muscle. It then divides and is continuous with the final component of the cardiac conduction system, the Purkinje fibres

Left bundle branch = Passes to the left of the muscular interventricular septum and descends to the apex of the left ventricle. Gives off branches which eventually become continuous with the purkinje fibres.

Question 24

What are the 3 main elements of the conducting system? (3)

Answer 24

Conducting cells: Interconnect the two nodes and distribute the contractile stimulus throughout the myocardium. Thought to be specialised myocytes

In the Atria, conducting cells are found in INTERNODAL PATHWAYS, which distributes the contractile stimulus to atrial muscle cells as this electrical impulse travels from the SA node to the AV node.

Question 25

Cardiac Innervation: The autonomic division of the peripheral nervous system is directly responsible for regulating?

Answer 25

1. Heart rate
2. Force of each contraction
3. Cardiac output

Question 26

What’s the parasympathetic innervation of the cardiac system?

Answer 26

Stimulation of the parasympathetic nervous system causes:

1. heart rate decrease
2. reduces the force of contraction
3. constricts the coronary arteries

Preganglionic parasympathetic fibres reach the heart as cardiac branches from the right and left vagus nerves. They entre the cardiac plexus and synapse in ganglia located either within the plexus or in the walls of the atria.

Question 27

What’s the sympathetic innervation of the cardiac system?

Answer 27

Stimulation of the sympathetic system causes:

1. increases heart rate
2. increases the force of contraction

Sympathetic fibres reach the cardiac plexus through the cardiac nerves from the sympathetic trunk. Preganglionic sympathetic fibres from the upper 4 or 5 segments of the thoracic spinal cord enter and move through the sympathetic trunk.

They synapse in cervical and upper thoracic sympathetic ganglia, and postganglionic fibres proceed as bilateral branches from the sympathetic trunk to the cardiac plexus

Question 28

Where to listen for heart sounds?

Answer 28

To listen for valve sounds, position the stethoscope downstream from the flow of blood through the valves.

Question 29

Where do you listen to the tricuspid valve?

Answer 29

Just left of the lower part of the sternum near the 5th intercostal space

Question 30

Where do you listen to the mitral/bicuspid valve?

Answer 30

Over the apex of the heart in the left 5th intercostal space at the midclavicular line

Question 31

Where do you listen to the pulmonary valve?

Answer 31

Over the medial end of the left 2nd intercostal space

Question 32

Where do you listen to the aortic valve?

Answer 32

Over the medal end of the right 2nd intercostal space

Question 33

Whats the pulmonary trunk?

Answer 33

Contained within the pericardial sac; covered by the visceral layer of serous pericardium

Associated with the ascending aorta in a common sheath. Divides into the:

1) right pulmonary artery - passes to the right, posterior to the ascending aorta and the superior vena cava, to enter the right lung
2) left pulmonary artery- passes inferiorly to the arch of the aorta and anteriorly to the descending aorta to enter the left lung

Question 34

What’s the ascending aorta?

Answer 34

Contained within the pericardial sac and is covered by a visceral layer of serous pericardium, which also surrounds the pulmonary trunk in a common heath.

Origin of ascending aorta is the aortic orifice at the base of the left ventricle, at the level of the lower edge of the 3rd left costal cartilage, posterior to the left half of the sternum

Moving superiorly, slightly forward and to the right, the ascending aorta continues to the level of the 2nd right costal cartilage

At this point, it enters the superior mediastium = ARCH OF THE AORTA

Question 35

Arch of aorta and its 3 branches

Answer 35

1) Brachiocephalic trunk: Beginning of the right, the 1st branch of the arch.

Largest of the 3 branches and, at its point of origin behind the manubrium of the sternum, is slightly anterior to the other 2 branches.

Ascends slightly posteriorly and to the right. At the level of the upper edge of the right sternoclavicular joint, the brachiocephalic trunk divides into:

• Right subclavian artery
• Right Common carotid artery

2) Left Common carotid artery
3) Left subclavian artery

Question 36

Where does the subclavian artery go?

Answer 36

(1st division) Right vertebral = supplies spinal cord, cervical vertebrae (right side); fuses with left vertebral = BASILAR ARTERY after entering cranium through FORAMEN MAGNUM

(2nd division) Right thyrocervical trunk = supplies muscles, skin, tissue of the neck, thyroid gland, shoulders, and upper back (right side)

(3rd division) Right internal thoracic = supplies skin and muscles of chest and abdomen, mammary gland (right side), pericardium

Right axillary: supplies muscles of the right pectoral region and axilla

Right branchial: supplies structures of the arm

• Right Radial = supplies forearm, radial side
• Right Ulnar = supplies forearm, ulnar side

Question 37

Where does the common carotid artery go?

Answer 37

(1st division) Carotid sinus + Internal carotid:

The carotid sinus may extend along a portion of the common carotid; the internal carotid enters the skull through the carotid canals of the temporal bones, delivering blood to the brain.

Ascends to the level of optic nerves, then divides into 3 branches:

1) opthalmic artery = supplies the eye
2) Anterior cerebral artery = supplies frontal and parietal lobes of the brain
3) Middle cerebral artery = supplies the mid-brain and lateral surfaces of the cerebral hemispheres.

Question 38

What is an abdominal aortic aneurysm?

Answer 38

Localised enlargement of the aorta

Deep palpation of mid-abdomen can detect aneurysm

Question 39

What are the 6 limb plus points?

Answer 39

Radial artery - Distal radius

Brachial artery - Medial to the tendon of biceps

Femoral artery - Midlinguinal point

Popliteal artery - Popliteal fossa

Posterior tibial artery - mediway between achilis tendon & heel bone

Dorsal artery of foot - midway between two malleoli (dorsum of foot)

Question 40

What are the 4 head, neck and abdomen pulse points?

Answer 40

Carotid pulse - upper margin of adam’s apple (thyroid cartilage)

Abdominal aorta - medline, left of umbilicus

Facial artery - ramus of mandible (anterior to lower part of masseter muscle)

Superficial temportl - in from of tragus (ear skin fold)