deck_486543 Flashcards
Where does the heart lie in situ?
The heart lies in the middle mediastinum
What is the middle mediastinum?
The intervening region in the thoracic cavity between the right and left pleural cavities which are occupied by the lungs
What does the middle mediastinum consist of?
The heart, it’s blood vessels and the roots of the aorta, superior and inferior vena cava and pulmonary vessels
Give a more detailed description of where the heart sits in the chester
Posterior to the sternum and the lungs, anterior to the verterbral column, oesohphagus and trachea
What are the two components of the pericardium?
Fibrous pericardiumSerous pericardium
What is the structure of the pericardium?
A tough connective tissue outerlayer
What is the function of the pericardium?
Helps to retain heart in position, due to its attachment to diaphragm and sternumTough sac limits cardiac distension
What is the structure of the serosa?
Parietal layer: lines the inner surface of the fibrous pericardiumVisceral layer: adheres to the heart and forms its outer covering
What is the function of the serosa?
Space between the parietal and visceral layer lubricates the heart and allows for the relatively uninhibited movement of the heart
What is the clincal relevance of the the pericardium?
reflections of serous pericardium create the oblique and transverse pericardial sinuses. During a coronary bypass, a finger can be placed into the transverse sinus in order to separate arteries from the veins.
What is the function of the phrenic nerve? Where does it originate?
The phrenic nerves, which innervate the diaphragm and originate from C3, C4 and C5, pass through the pericardium and also innervates it.
What is the clinical relevance of the phrenic nerve?
C3 and C4 also innervate the shoulder, pain carried from the pericardium (pericarditis) can cause shoulder pain.
Whip out a diagram of the heart and label the coronary arteries
Do it!
Describe the course of blood in and out of the heart
IN1.Blood enters the right atrium via the superior and inferior vena cavae as well as via the coronary sinus, which returns blood from the walls of the heart itself.2.The left atrium receives blood from the four pulmonary veinsOUT1.The aorta (ascending, arch and thoracic) receives oxygenated blood from the left ventricle for systemic circulation.2.The pulmonary artery receives deoxygenated blood from the right ventricle for pulmonary circulation.
Where is the heart situated on a subject?
Upper margin of the heart is level with the 3rd costal cartilage on the RHS of the sternum, and the 2nd intercostal space on the LHS of the sternum.Lower margin of the heart is level with the 6th costal carilage on the RHS of the sternum and the 5th intercostal space on the LHS of the sternum.
What does the right coronary artery do?
supplies the right atrium and ventricle and the SAN and AVN
What does the left coronary artery do?
supplies the left atrium and ventricles and the septum, bundle of his and purkinje fibres.
When do the coronary arteries fill?
Filled during diastole as semi-lunar valves are closed
What does increased heart rate mean for coronary arteries and why?
Filled during diastole so increased heart rate > decreased blood flow to coronary arteries.
What does accumulation of fluid in pericardial sac cause?
Compression of heart and decreased cardiac output
Where does the right coronary artery originate from?
the right aortic sinus of the ascending aorta
What is the path of the right coronary artery?
Moves anteriorly to the right and descends vertically in the coronary sulcus between the right atrium and ventricle
What happens to right coronary artery at inferior margin of the heart?
it turns posteriorly and continues in the base of the heart where it divides to give several branches
Where does the left coronary artery originate from?
Originates from the left aortic sinus of the ascending aorta
What happens to left coronary artery?
While posterior to the pulmonary trunk it divides into two terminal branches
What happens to the Left Anterior Descending branch of the coronary artery?
descends towards to the apex of the heart in the anterior interventricular sulcus
What happens to the circumflex branch of the left coronary artery?
1.courses to the left in the coronary sulcus. A large branch, the left marginal artery, usually arises from it and continues across the rounded obtuse margin of the heart.
Where do the coronary arteries drain into?
The great cardiac vein and the coronary sinus
Give process of muscle contraction
Stage 1 of contraction – AttachmentRigor configuration: myosin head is tightly bound to actin molecule. In death, lack of ATP perpetuates this binding (rigor mortis).Stage 2 of contraction – ReleaseATP binds the myosin head causing it to uncouple from the actin filament.Stage 3 of contraction – BendingHydrolysis of ATP causes the uncoupled myosin head to bend & advance a short distance (5nm)Stage 4 of contraction – Force GenerationThe myosin head binds weakly to the actin filament causing release of inorganic phosphate, which strengthens binding, and causes the ‘power stroke’ in which the myosin head returns to its former position.Stage 5 of contraction – ReattachmentThe myosin head binds tightly again and the cycle can repeat. Individual myosin heads attach and flex at different times causing movement.
Give six features of cardiac muscle
StriationsBranching of muscle fibresCentrally positioned nuclei (1 or 2 per cell)Intercalated discs between muscle fibres for electrical and mechanical couplingGap junctions (for electrical coupling)T tubules inline with Z line
Give five features of skeletal muscle
StriatedT tubles in line with A-I band junctionMultinucleated at periphery of cellsVoluntary controlRapid, forceful
Give five features of smooth muscle
Not striated, no sarcomeres, no t tubulesCells are spindle shapedContraction is slower and more sustainedResponds to stimuli in form of never signals, hormones, drugs and blood gassesThick and thin filaments arranged diagonally in cell Capable of being stretched
Can cardiac muscle repair themselves? What occurs after damage?
Incapable of regenerationFollowing damage, fibroblasts invade, divide and lay down scar tissue.
What do purkinje fibres do?
transmit action potentials to the ventricles
Describe structure of purkinje fibres
arge cells with:Abundant glycogenSparse myofilamentsExtensive gap junction sites
Why are purkinje fibres important?
They conduct action potentials rapidly compared to regular cardiac muscle. This rapid conduction enables the ventricles to contract in a synchronous manner.
