PHTY142 Heart Flashcards
shape, position, size of the heart
Size of the closed fist
Heart rests on the diaphragm
In the mediastinum and 2 thirds lies to left of midline
Shaped like an inverted cone
What is the mediastinum
an anatomical region that extends from the sternum to the vertebral column.
From the first rib to the diaphragm.
Between the lungs
base of the heart
Formed by the atria, mostly the left atrium
Apex of the heart
tip of the left ventricle and rests on the diaphragm
Describe the right atrium
receives blood from superior and inferior Vena Cava, Coronary Sinus
2-3mm in thickness
Tricuspid Valve
Describe the right ventricle
4-5mm thickness
cusps of tricuspid valve are connected to Chordae Tendineae
Pulmonary semilunar valve into pulmonary trunk
What separates the Right and Left Atrium
interatrial septum
What separates’ the Right and Left Ventricles
Interventricular Septum
Describe the Left Atrium
2-3 mm thick
Forms most of the base of the heart
Blood from pulmonary veins
Bicuspid valve
What is the bicuspid valve also known as
Mitral valve
Describe the left ventricle
thickest chamber of the heart
chordae tendineae to papillary muscles
aortic semilunar valve into aorta
Pathway of blood from the left ventricle
Through aortic valve
into aorta
Some to coronary arteries which branch from ascending aorta
The rest goes to arch of aorta and descending aorta to be carried to rest of the body
What is the pericardium
Membrane that surrounds and protects the heart.
It consists of 2 main parts the Fibrous Pericardium and the serous pericardium
What is the role of the pericardium
Confines the heart in the mediastinum
Allows for movement for vigorous, rapid contraction
The Fibrous Pericardium
Tough, inelastic, dense, irregular connective tissue
Rests and attaches to diaphragm
Prevents overstretching of the heart
Anchors heart to mediastinum
movement of diaphragm facilitates movement of the heart
Serous Pericardium
Deeper layer
thinner, more delicate that forms a double layer
around the heart
Outer parietal layer - fused to fibrous pericardium
Inner visceral layer - has pericardial cavity with lubricating serous fluid which reduces friction between the layers as the heart moves
name 3 layers of the heart
epicardium
Myocardium
endocardium
Endocardium
Thin layer of endothelium
Provides smooth lining for chambers
minimises surface friction as blood passes through the heart
Epicardium
outer layer is the Visceral layer of the serous pericardium
Beneath mesothelium is a variable layer of delicate fibroelastic tissue and adipose tissue
Contains blood vessels and lymphatics that supply the heart
Myocardium
Pumping action of the heart
Cardiac muscle tissue. Muscle fibres are wrapped and bundles with connective tissue sheaths
Fibres organised in swirls moving diagonally
What is the fibrous skeleton of the heart
4 dense connective tissue rings that surround the valves of the heart and merge with interventricular septum
Prevents overstretching of the valves
A point of insertion for bundles of cardiac muscle
Acts as electrical insulator between atria and ventricles
Atrioventricular valves
When they open the ends of cusps project into ventricles
When ventricles are relaxed the paillary muscles are relaxed and chordae tendineae are slack
When ventricles contract pressure drives cusps upwards and close the valve. Papillary muscles contract and chordae tendineae tighten preventing evertion
Semilunar Valves
3 crescent moon shaped cusps each attaching to a arterial wall
When ventricles contract pressure increases higher than in valves so valves open
As ventricles relax blood starts to flow back tot he heart and fill cusps acusing them to contract and close the opening
How are the AV valves and SL valves similar
Both prevent backflow
both facilitate unidirectional blood flow
open and close at the right time
Differences between AV valves and SL valves
Different locations
Names different
Av Valves allow blood flow from atria to ventricles and prevent backflow during systole
SL valves pump blood outward and prevent backflow from form arteries to ventricles
Function of coronary arteries
supply blood to myocardium
Left and right deliver to heart
Aortic sinuses are found in aorta. when the heart is relaxed backflow fills the valve pockets allowing blood to enter coronary arteries
Right coronary artery
Supplies right atrium and right ventricle
Right marginal artery
right ventricle and apex
posterior interventricular artery
right and left ventricles
Interventricular septum
Left circumflex artery
left atrium and left ventricle
left marginal artery
left ventricle
left anterior descending artery
right ventricle left ventricle and interventricular septum
what are Autorhythmic fibres
Cardiac muscle fibres
Self excitable
repeatedly generate action potentials
Conducting system of heart
SAN - right atrium wall
Right and left atria contract at the same time
AVN passes information to bundle of His but there is a slight delay
Bundle of His splits into purkinje fibres so left and right ventricles simultaneously contract
What does ECG stand for
Electrocardiogram
A recording of action potentials at the heart
Describe an ECG
P wave - upward deflection representing atrial depolarisation form SA node
QRS complex - upright triangular wave representing rapid ventricular depolarisation
T Wave - Dome shaped and upwards representing ventricular repolarisation occurring just as ventricles start to relax
Systole
period of contraction where blood is pumped into circulation
diastole
Period of relaxation when chambers fill with blood
Outline cardiac cycle
Passive filling - both relaxed but AV open
Atrial systole
Ventricular isovolumetric contraction
Ventricular systole
relaxation period
Atrial Systole
atria contract, ventricles relaxed
Depolarisation at SA Node so pressure increases as blood volume increases
AV valves open and blood forced into ventricles
ventricles contain 130 ml of blood at end diastolic volume
Ventricular systole
Ventricles contract and pressure against AV valves
For about 0.5 seconds both AV and SL valves are closed - isovolumetric period - isometric contraction
When ventricular pressure is higher than aortic pressure SL valve opens and ejection begins
Relaxation in cardiac cycle
Both atria and ventricles are relaxed
Ventricular repolarisation causes ventricular diastole
As pressure decreases blood starts to move back and enters cusps so SL valves close
There is a brief period where all 4 valves are closed
Blood enters atria, so by end of relaxation period ventricles are 3/4 full - passive filling
Cardiac output
Volume of blood ejected from the left ventricle into the aorta each minute
CO= SV X HR
In adults 5.25 litres/minute = 75 X 70
