The Heart Flashcards
Function of heart
to pump blood around the body. It is made of a special type of muscle called cardiac muscle.
Cardiac muscle
The walls of the heart are composed of cardiac muscle which has its own inherent rhythm and does not get tired. it contracts and relaxes regularly, throughout life.
divisions
The heart is divided into four chambers. The two on the right contain deoxygenated blood and are completely separated from the two on the left which contain oxygenated blood, by the septum.
atria
top two chambers, have thin walls and they collect blood entering the heart.
ventricles
The bottom two chambers, have thick walls and they pump blood out of the heart.
valves
present between each atrium and ventricle and in the pulmonary artery and aorta as they leave the ventricles to ensure that blood flows through the heart in one direction.
pulmonary artery
carries deoxygenated blood to the lungs
aorta
carries oxygenated blood to the body
left atrium
collects oxygenated blood from the lungs
pulmonary veins
carry oxygenated blood from the lungs
semi-lunar valves
prevent the backflow of blood into the ventricles when they relax
bicuspid valve
prevents the blood flowing
back into the atrium when
the ventricle contracts..has two parts
tendons
prevent the valve turning inside out
left ventricle
thicker walled than the right ventricle to pump oxygenated blood longer distances around the body
septum
thick, muscular, separates the left and right ventricles
cardiac muscle
thick, own inherent muscle
right ventricle
pumps deoxygenated blood to
the lungs
tricuspid valve
prevents the blood flowing
back into the atrium when
the ventricle contracts…has three parts
posterior vena cava
carries deoxygenated
blood from the body
right atrium
collects
deoxygenated blood from
the head and body
anterior vena cava
carries deoxygenated
blood from the head
name of diagram
Longitudinal section through the human heart showing the function of the parts
Atrioventricular valves
the valve between the left atrium and the left ventricle, and the other between the right atrium and the right ventricle
systole
the heart beats as the cardiac muscles in its walls contract and relax. When they contract, the heart becomes smaller, squeezing blood out. This is called systole.
diastole
when they relax, the heart becomes larger, allowing the blood to flow into the atria and ventricles. This is called diastole.
pacemaker/sinoatrial node
the heart beat begins in the wall of the right atrium, then spreads throughout the heart.
The heart beats on average 75 times per minute. This rate is maintained by a group of specialised cardiac muscle cells in the right atrium called the pacemaker and can be modified by nerve impulses,e.g. the rate increases with exercise.
Diastole; all muscles are relaxed blood flows into the heart
The atria and ventricles relax together (diastole), the semi-lunar valves close, the atria fill up with blood from the anterior and posterior vena cavae and pulmonary vein, and the blood flows into the ventricles. This takes 0.4 seconds.
atrial systole
The muscles of the atria contract together (atrial systole) forcing any remaining blood into the ventricles. the semi-lunar valves remain shut. The valves in the vein are shut by the pressure of blood, stopping the backflow of blood.
This takes 0.1 seconds.
ventricular systole
The semilunar valves are forced open by the pressure of the blood.The ventricles contract together, the tricuspid and bicuspid valves close and blood is forced into the pulmonary artery and aorta. This takes 0.3 seconds.
In the pulmonary circulation
,blood travels from the right ventricle through the pulmonary artery to the lungs to pick up oxygen and lose carbon dioxide, i.e. it becomes oxygenated. It then travels back via the pulmonary vein to the left atrium
In the systemic (body) circulation
the blood travels from the left ventricle through the aorta to the body where it gives up oxygen to the body cells and picks up carbon dioxide, i.e. it becomes deoxygenated. It then travels back via the anterior or posterior vena cava to the right atrium.
double circulatory system
because blood passes through the heart twice per circuit.
Why is a double circulatory system necessary
because blood loses pressure when it passes through the lungs, so it goes back to the heart to be given enough pressure to reach body organs to supply them with oxygen. As it loses pressure passing through organs, the blood goes back to the heart again to be given enough pressure to reach the lungs to get rid of waste carbon dioxide and pick up more oxygen.
