UNIT 2 - KA6
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What is the heart
The heart is a muscular pump which keeps blood flowing continuously in one direction round the body
What are the four chambers through which blood flows
The tow upper chambers are called atria, while the lower chambers are known as ventricles
What do valves within the heart prevent
There are valves within the blood which prevent blood flowing backwards
In which parts of the heart does de/oxygenated blood flow through
Deoxygenated blood flows through the right side of the heart, while oxygenated blood flows through the left side
Which wall in the heart ensures deoxygenated and oxygenated blood never mix
Both sides of the heart beat in rhythm, but a muscular dividing wall in the centre of the heart called the septum ensures that oxygenated and deoxygenated blood never mixes
Describe the process of deoxygenated blood entering and leaving the heart
Deoxygenated blood enters the right atrium through the two main veins of the body, the vena cavae. It is then pushed through the tricuspid (atrio-ventricular or AV valve) into the right ventricle. When the right ventricle contracts blood is forced out of the heart through a semi-lunar valve into the pulmonary arteries. These arteries carry the blood to the lungs where it releases carbon dioxide and picks up oxygen.
Describe the process of oxygenated blood entering and leaving the heart
Oxygenated blood then returns to the left atrium along the pulmonary veins. Contraction of the left atrium pushes the blood through the bicuspid (atrio-ventricular or AV valve) into the left ventricle. When the left ventricle contracts, blood is forced out of the heart through a semi-lunar valve into the aorta. The aorta is the main artery of the body and it carries oxygenated blood to all the body organs.
Where does the right half of the heart receive blood from
The right half of the heart receives deoxygenated blood from all parts of the body through the veins called the VENA CAVAE
Where does the left side of the heart receive blood from
The left half receives oxygenated blood returning from the lungs via the pulmonary veins
What is the purpose of the Atrio-ventricular valves linking the atria to the ventricles
The purpose of these is to prevent back flow of blood and keep it moving in one direction
What is the purpose of semi lunar valves
Semi lunar valves open only during contraction to ensure blood flows in one direction as it leaves the heart
Why is the left ventricle thicker than the right
The left ventricle forces blood from the heart to the rest of the body so it is thicker than the right ventricle that know takes blood to the lungs
Cardiac output (CO)
Volume of blood pumped through each ventricle per minute (1/min)
Heart rate (HR)
Number of heartbeats that occur per minute (bpm)
Stroke volume (SV)
volume of blood pumped through each ventricle per contraction (ml)
What are the three distinct stages in the cardiac cycle
• atrial systole • ventricular systole • diastole
Atrial systole
(0.1s) - when the atria contract sending blood through the bicuspid and tricuspid valves (AV valves) into the ventricles
Ventricular (systole)
(0.3s) - when the ventricles contract and blood is pushed out of the heart through the Semi-lunar valves
Diastole
(0.4s) when the heart muscles relax and atria fill with blood
Describe the action of the heart during atrial systole
During atrial systole the atria are contracting and ventricles are in diastole (relaxed) the AV valves are open and the SL valves are closed
Describe the action of the heart during ventricular systole
During ventricular systole the ventricles are contracting and the atria are in diastole (relaxed) the AV valves are closed and SL valves are open
Describe the action of the heart during full diastole
During diastole the atria are in diastole (relaxed) the ventricles are in diastole (relaxed) the AV valves are (closed) opening and the SL valves are closed
What valves are responsible for the heart sounds heard with a stethoscope
The opening and closing of the AV and SL valves are responsible for the heart sounds heard with a stethoscope
What is the heart beat sounds
‘Lubb’ ‘dupp’