CH16 The heart Flashcards
Describe the size of the heart and it’s location in the thorax
Hollow cone shaped.
14cm/5” long. 9cm/3.5”wide
300g
Lies inside thoracic cavity. Within mediastinum resting on diaphragm
Posterior border near vertebral column
Anterior border near sternum
2/3 lies to left of mid sternal line
Partially obscured laterally by lungs
What are the layers of the heart wall
What are their functions
Epicardium. Outer
Myocardium. Middle
Endocardium. Inner
Epicardium protects the heart reducing friction.
Thick myocardium pumps blood out of chambers.
Endocardium has elastic and collagenous fibres. Contains blood vessels and purkinje fibres.
Lines chambers and covers fibrous tissue that forms valves. Continuous with endothelial linings Of hearts blood vessel
How does blood flow through the heart
Right atrium receives blood from superior/inferior vena cava (veins).
And from smaller vein (coronary sinus) that drains blood into right atrium from myocardium.
Blood from lungs enter pulmonary veins and into left atrium.
Blood travels from right ventricle to pulmonary trunk then pulmonary arteries.
The left ventricle sends blood into aorta and its branches (right and left coronary arteries)
Name the four heart valves
Where do the valves lie
2 AV Valves
2 semilunar valves
AV valves include tricuspid and bicuspid (mitral)
Semilunar include aortic and pulmonary
(AV between atria and ventricles)
Tricuspid between right atrium and right ventricle
Bicuspid (mitral) between left atrium and left ventricle.
(Semilunar valves lie between ventricles and large arteries that emerge from them.)
Aortic valve lies between left ventricle and aorta.
Pulmonary valve lies between right ventricle and pulmonary trunk and arteries
Describe the vascular supply to the heart
What are the first two aortic branches called
What is the job of the coronary arteries (2)
First two aortic branches = right and left coronary arteries
Deliver blood when heart is relaxed. Have less functioning while ventricles contracting because they are compressed by the myocardium
Enclose the heart in the coronary sulcus and provide arterial supply of coronary circulation.
Vascular supply of heart continued…
What is the anterior interventricular artery also known as and what is its job
Left anterior descending artery
Supplies blood to anterior walls of ventricles and to interventricular septum
Vascular supply of heart continued…
What does the circumflex artery supply
What is the job of the coronary artery branches
Posterior walls of left ventricle and atrium
Supply many capillaries in the myocardium
Vascular supply to heart continued…
Coronary artery branches have smaller branches with connections known as what, where and what do they provide
What is this known as
Anastomoses between vessels providing alternate blood pathways
Collateral circulation
Vascular supply continued…
The coronary veins join to form what and what does it do
What does the coronary sinus do
Several anterior cardiac veins empty into what
The enlarged coronary sinus emptying into the right atrium
Empties into the great cardiac vein, middle cardiac vein, small cardiac vein.
Right atrium anterior portion
Identify the electrical events that relate to the ECG
P shows depolarisation of atrial fibres causing atrial contraction
QRS depolarisation of ventricle fibres before ventricular contraction
T repolarisation of ventricles
Draw a normal ECG include U wave
P
QRS
T
U
Define cardiac output
How is it calculated
What are the factors that influence cardiac output
Volume discharged from ventricle per minute
SV X HR in BPM
Increase or decrease in SV air HR
What is happening when the first thump of the heartbeat is heard. Describe the sound
What is happening when the second thump is heard. Describe the sound
What are abnormal heart sounds called and who are they common in. What do they indicate
The ventricles contracting and AV valves close
First thump is loudest longest and most resonant
Ventricular relaxation when pulmonary and aortic (semilunar) valves close. Shorter and sharper
Heart murmurs. Common in young children and elderly. Valve problems
What causes a swishing sound of the heart
Blood back flow or regurgitation through a valve that remains partially open when it should be closed
What happens when the sympathetic part of ANS is stimulated
What happens as a result of this
Related nerve fibres release norepinephrine at cardiac synapses.
This binds to beta adrenergic receptors in heart and threshold can be reached faster
SA node fires more quickly and heart beats faster
