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
- main part: firm, dark red muscle = cardiac muscle
- 2 main pumping chambers = ventricles
- above ventricles, there are 2 thin-walled chambers = atria
–> much smaller - over surface of heart = coronary arteries (supply oxygenated blood to heart)
- top of heart = no. of tubular blood vessels (veins which carry blood to atria & arteries carrying blood away)
what can restricted 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 –> oxygenated blood/deoxygenated blood are kept separate
- 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 - prevents blood to heart as ventricles relax
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
- numerous 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
