3.2.4 structure of the heart Flashcards
atrio-ventricular valves
valves between atria & ventricles - ensure blood flows in correct direction
cardiac muscle
specialised muscle found in walls of heart chambers
semilunar valves
valves that prevent blood re-entering heart from arteries
in a mammalian heart, describe the overall features of the heart
- muscular pump
- divided into 2 sides
- right pumps deoxygenated blood to lungs
- left pumps oxygenated blood to rest of body
- heart squeezes blood = pressure
external features of the heart
- firm, dark red muscle = cardiac muscle
- 2 main pumping chambers = ventricles
- 2 thin-walled chambers = atria (much smaller)
- over surface of heart = coronary arteries (supply oxygenated blood to heart)
- top of heart = tubular blood vessels (veins which carry blood to atria & arteries carrying blood away)
what can restrict blood flow to the heart cause
angina or heart attack (myocardial infarction)
internal features of mammalian heart
- deoxygenated blood from body flows through vena cava into right atrium
- oxygenated blood from lungs flows through pulmonary vein into left atrium
- blood flows through the atrio-ventricular valves from the atria to the ventricles
- attached to the valves are tendinous cords
- wall of muscle called the septum separates ventricles
- deoxygenated blood leaving the right ventricle flows into pulmonary artery to the lungs
- oxygenated blood leaving left ventricle flows into aorta
- at base of major arteries = semi-lunar valve
what do the tendinous cords do
prevent valves turning inside out when ventricle walls contract
blood pressure in the atria
- muscle of atrial walls = thin
- chambers don’t require much pressure
- function = receive blood from veins & push into ventricles
blood pressure in the right ventricle
- walls = thicker than atria
- enables it to pump blood out of heart
- pumps deoxygenated blood to lungs
- blood doesn’t need to travel very far
- alveoli = delicate & could be damaged by high pressure
blood pressure in the left ventricle
- walls = 2-3x thicker than right ventricle
- blood pumped via aorta
- needs sufficient pressure to overcome resistance of systemic circulation
structure/properties of cardiac muscle
- consists of fibres which branch = cross-bridges
- mitochondria between muscle fibrils (myofibrils)
- muscle cells separated by intercalated discs
- each cell has nucleus & is divided into contractile units called sarcomeres
why does cardiac muscle require cross-bridges
spread stimulus around heart & ensure muscle can produce squeezing action
another word for muscle fibrils
myofibrils
reasoning for myofibrils in cardiac muscle
to supply energy for contraction
why are cardiac muscle cells separated by intercalated discs
facilitate synchronised contraction
