The Heart and vessels💘 Flashcards
(37 cards)
Heart sinuses
Transverse is behind aorta and is continuous
Oblique is in back wall of heart
Cardiac surfaces
Apex is lowest point in heart Surfaces include left and right Posterior/base Sternocostal Diaphragmatic Auricle is the provision of surface wall in each atrium right one bigger and they look like ears
Chambers of heart
Crista terminals separates rough and smooth walls
Right valve tricuspid left mitral
Blood goes from right ventricle to pulmonary artery via infundibulhm
Also pulmonary and aortic valve
Coronary arteries
Fill during diastole
Connected to aorta
Right coronary supplies right side and San and avn nodes and third of septum
Marginal artery branches off forming L shape
Also a posterior descending artery
Left artery is larger but shorter
Branched info left anterior descending and left circumflex
Supples left side and two thirds of septum
Also has anterior descending aka widow maker
Venous drainage
Cardiac veins accompany the arteries Great middle small and oblique All drain into coronary sinus Anterior one collects blood from right ventricle and drains to right atrium Smallest returns blood to heart chambers
Layers of heart
Endocardium is membrane of simple squamous
Myocardium is muscle layer
Epicardium is serous membrane of simple squamous
Muscle structure
Myosin has two heads which contain myosin atpase and each thick filament surrounded by six thin filaments
Actin and myosin interaction called cross bridge
Rod shaped proteins called troomyosjn and have a troponin regulatory complex attached to them at regular intervals
Three types of troponin T (attaches to tropomyosin)
C (acts as binding site for ca2+) and I (inhibits myosin coupling until ca binds to c)
Contraction regulation
Release of adrenaline and noradrenaline causing ca channels to open causing ca to enter causing ca release from sarcoplasmic reticulum this is called calcium induced calcium release the ca then bonds to tropnin and cross bridge cycling occurs
For relaxation SERCA returns ca to sr
Na ca exchanger in sarcolemma transports ca out of cell
Action potential
Voltage changes due to depolarisation and polarisation it is fast in myocytes
Spontaneous but slow in pacemaker cells
For repolarisation fluxes of k+ na+ and ca2+ return to cell membrane to testing potential and no further stimulus responses at this time
Conduction pathway
SAN
AVN
BUNDLE OF HIS
PURKINJE FIBRES
Cardiac output
Heart rate x stroke volume
Stroke volume is end diastolic volume subtracted by end systolic volume (so volume ejected by each ventricle during contraction)
Fraction of edv ejected out by each beat is ejection fraction (sc/edv x 100)
Frank stahling effect
Increased end diastolic volume will
increased velocity of contraction/ contractile strength of ventricles so increased stroke volume
This is because the muscle fibres become longer due to being more stretched so increased sarcomere length so increased sensitivity to ca
Muscle cell structure
Made of striated uninuclear cells joined together to form a network
Joined by inter elated discs and have gap junctions
Cardiogram features ECG
P wave is depolarisation from sa node to atria (atrial depolarisation)
QRS complex is ventricular depolarisation
T wave is ventricular depolarisation
QT interval total time taken for depolarisation and repolarisation of ventricles
Heart rate and rhythm
Determined by SA node
Pacemaker cells depolarise slowly reach threshold tigger action potential then return its initial membrane potential and being slow depolarisation this is called pacemaker potential and determines san firing rate
Action potential occurs spontaneously and aps travel through conducting pathway
<60 is bradychardia >100 is tachycardia
Atrial fibrillation
Commonest form of arrhythmia and jd caused by multiple re entrant circuits sweeping around atrial myocardium
Causes irregular ventricular contractions from time to time overwhelming the regular impulses
On an ecg the p waves will be absent
Digoxin
Derived from digitalis
Cardiac glycosides
Reduces na gradient and increases extra cellular ca
Increased force of contraction (intropy )
Decreased conduction of AVN (negative chronotropy
Slows heart rate
Automaticity not affected and augments vagal tone
Adrenaline
Acts b1 adrenoreceptors via cAMP on SAN to increase chronotropy/ heart rate Atrial muscle to increase force AVN yo increase automaticity Ventricular muscle to increase automaticity and inotropy
Types of cardiac cells
Myocardial - responsible for generating pumping pressure to pump blood around body cells connected via intercalated dics and have gap junctions
Conduction cells - responsible for spreading electrical signals to myocardial cells in order to coordinate pumping they are pacemaker cells (SAN AND AVN) and conduction pathway cells ( bundle of his and purkinje fibres)
Heart cell development
Progenitor heart cells migrate from primitive streak and go through mesoderm into the cranial area forming a primary heart field which has a somatotropin arrangement laterally
Vasculogenesis
Formation of new vessels by coalescence of angioblasts forming dorsal aortas and cardinal veins
Angiogenesis
Formation of new vessels by branching and budding of existing vessels
Development of arterial system
Main sources are pharyngeal arch arteries and dorsal aorta
Aortic arteries turn into arteries of head and neck dorsal turns to rest of body
Ventral aortae fuse partially to form aortic sac
Five artery arches on each side
Development of veins
Three pairs veins drain into primordial heart tube
Common cardinal brings poorly oxygenated blood from body of embryo
Viteline brings poorly oxygenated blood from umbilical vessel (yolk sac)
Umbilical brings well oxygenated blood from chorionic sac (placenta)
