the structure and function of the heart Flashcards
what are the atrioventricular valves
valves between the atria and the ventricles which ensure blood flows in the right direction
what is cardiac muscle
specialised muscles found in the walls of the heart chamber
what are semilunar valves
valves that prevent blood re entering the heart from the arteries
what is the heart and where is it located
the heart is a muscular organ located between the lungs in the centre of the chest (thorax) it continuously pumps blood around the body
what can happen if the brain is deprived of blood
an organism can lose consciousness within a few seconds
when does the heart begin to beat in a foetus
about 5-6 weeks after conception
how many pumps does the heart have
two
describe the two pumps
- deoxygenated blood from the body flows into the right side of the heart which pumps it to the lungs to be oxygenated
- oxygenated blood from the lungs returns to the left side of the heart which pumps it to the rest of the body
do the blood from the two sides mix
no
what happens on both sides of the heart
the heart squeezes the blood putting it under pressure
what does blood pressure do
forces the blood along the arteries and through the circulatory system
where is the heart located in humans
just off centre towards the left of the chest cavity
what does the main part of the heart consist of
cardiac muscle
how does cardiac muscle contract
involuntarily like smooth muscle and does not get fatigued like skeletal muscle
what is the function of the cardiac muscle
contracts and relaxes in a regular rhythm
what is the structure of the cardiac muscle
- made up of cells that are conncected by cytoplasmic bridges - consists of fibres that branch producing cross-bridges
- numerous mitochondria
- muscle cells are separated by intercalated discs
- each cell has a nucleus and is divided into contractile units called sacromeres
- contains large numbers of myoglobin molecules
what is the function of the cytoplasmic bridges
enable electrical impulses to pass through tissues
what does the mitochondria do for the cardiac muscle
supply energy for contraction
what do the intercalated discs do
facilitate synchronised contraction
what supplies the cardiac muscle with oxygenated blood
the coronary arteries
what is the heart surrounded by
inelastic pericordial membranes which help prevent the heart from over distending with blood
how many chambers does the heart have
4
what are the two main pumping chambers
the ventricles
what are above the ventricles
the two main thin walled chambers - the atria
what lie over the surface of the heart
coronary arteries that supply oxygenated blood to the heart muscle
what would happen if the coronary arteries became constricted
it would restrict blood flow to the heart muscle reducing the delivery of oxygen and nutrients such as fatty acids and glucose
what can damaged coronary arteries lead to
angina or a heart attack
another word for heart attack
myocardial infarction
what is angina
type of chest pain caused by not enough blood going to the muscles of the heart
what is the function of the blood vessels
the veins carry blood to the heart and the arteries carry blood away from the heart
what is the atrioventricular valve on the right side of the heart
tricuspid valve
what is the atriventricular valve on the left side of the heart
bicuspid valve/mitral valve
what is the role of the tendinous cords
prevents valves from turning inside out when the ventricle walls contract
what is the role of the septum
separates the ventricles from each other and ensures that the oxygenated blood in the left side and the deoxygenated blood in the right side are kept separate
how does deoxygenated blood enter the heart
- deoxygenated blood enters the right atrium of the heart from the upper body and head in the superior vena cava and from the lower body in the inferior vena cava at relatively low pressures
where does the deoxygenated blood travel to in the right atrium
- the atria have thin muscular walls. as blood flows in, slight pressure builds until the tricuspid valve opens to let blood pass into the right ventricle
when does the blood enter the right ventricle
- when both the atrium and ventricle are filled with blood the atrium contracts forcing all the blood into the right ventricle and stretching the ventricle walls
when and why do the tricuspid valves close
- as the right ventricle starts to contract, the tricuspid valves closes preventing any backflow of blood to the atrium.
what do the tendinous cords do
the tendinous cords make sure the valves are not turned inside out by the pressures exerted when the ventricles contract
what happens when the right ventricle contracts
- the right ventricles contracts fully and pumps deoxygenated blood through the semilunar valves into the pulmonary artery which transports it to the capillary beds of the lungs. the semilunar valves prevent the backflow of blood back to the heart
where does the oxygenated blood travel to simultaneously
oxygenated blood from the lungs enter the left atrium from the pulmonary vein. as pressure in the atrium builds, the bicuspid valve opens between the left atrium and left ventricle so the ventricle fills with oxygenated blood aswell
what happens to the oxygenated blood once the left atrium and ventricle are full
- when they are both full, the atrium contracts forcing all the oxygenated blood into the left ventricle
- the left ventricle contracts and pumps oxygenated blood through semilunar valves into the aorta and around the body
- as the ventricle contracts, the tricuspid valve closes preventing any backflow of blood
why is the muscular wall of the left side of the heart much thicker than the right side
the lungs are closer to the heart and the lungs are also much smaller than the rest of the body so the right side of the heart has to pump the blood a relatively short distance and only has to overcome the resistance of the pulmonary circulation.
what does the left side of the heart have to do to ensure efficient transport of blood around the body
the left side has to produce sufficient force to overcome the resistance of the aorta and the arterial systems of the whole body and move the blood under pressure to all the extremities of the body
do the left and right side of the heart fill together
yes
how is pressure created in the blood
cardiac muscle in the wall of each chamber contracts to create pressure in the blood.
higher pressure created in the heart =
= the further it pushes the blood
why don’t the atria need to create much pressure
they have thin walls. they recieve blood from the veins and push it into the ventricles
why is the right ventricle thicker than the atria
they pump deoxygenated blood out of the heart into the lungs. they dont need to travel far so pressure isnt that high. the alveoli could be damaged by the high pressure
why is the left ventricle thicker than the right ventricle
it needs sufficient pressure to overcome resistance of systematic circulation
