The Heart and vessels💘 Flashcards
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)
Early heart development
Angioplasties cords canalise into heart tubes which then fuse to form single heart tube
Heart tube develops five sections (top to bottom)
Truncus arteriosus
Bulbous cordis
Primitive ventricle
Primitive atrium
Sinus venosus
Umbilical veins drain into horns of sinus venosus
What the five heart sections turn into
Truncus arteriosus - ascending aorta and pulmonary trunk
Bulbous cordis-smooth parts of ventricles RIGHT VENTRICLE
Primitive ventricle-trabeculated portions of right and left ventricles LEFT VENTRICLE
Primitive atrium-rough parts of atria
Sinus venosus- smoothie parts of right atrium coronary sinus and oblique vein of left atrium
Foremen ovals
Septum secundum grows towards cushion and leaves a hole called foremen ovale
Septum priming deteriorates and leaves a flap like structure called foremen ovales valve this valve fuses with septum when baby breathes and pressure in left atrium increases
Atrial septal defects
Abnormal gives openings on atrial septum caused by incomplete tissue formation creating passage between left and right atrium
Usually aysmptomatic til adulthood
Symptoms include difficulty breathing (dyspnoea) respiration infecting feeling heart beat(palpitations) and shortness of breath with activity
The three layers in blood vessels
Tunica interna- inner lining composed of epithelial and connective tissue layers
Tunica media contains smooth muscles and elastic fibres . Regulates vasoconstriction etc
Tunica externa sheath of connective tissue composed mainly of collagenous fibres
Vasa vasorum
Nervi vasorum
Vessels that supply blood vessels with blood
Nerves of the blood vessel
Aorta arteries and. Arterioles
Aorta and larger arteries are rich in elastin and have lots of vasa vasorum due to poor oxygen diffusion
Smaller arteries and srterioles have more smooth muscle to regulate flow control
Venues and veins
Low pressure collecting system And have no internal elastic lamina underlying endothelium
Movement involves a muscle pump
Three types of capillaries
Continuous is least leaky found in skin and muscles in change occurs through flattened out cytoplasm
Fenestrsted has pores for exchange found in high exchange tissues such as small intestine and kidneys
Sinusoid/discontinuous has gaps between endothelial cells and irregular fenestrations so are most leaky found in cell and molecule exchange tissues eg liver and bone marrow
Hart muscle
Made of uninuclear cardiac myoctytes joined via intercalated disks containing gap junctions
Skeletal muscle has a larger multinuclear structure
Blood pressure
Factors that influence include volume cardiac output resistance and elasticity of vessel
Hematocrit is percentage of red blood cells in blood and affects Viscosity more viscous so more resistance so higher bp
Arteries and elasticity
A healthy elastic artery expands absorbing shock of systolic pressure
Wells tic recoil then maintains continues flow during diastole
Arteriosclerosis causes arteries to become calcified and rigid so they can’t expand so they experience a higher pressure and become weaker
Branches on aorta linked to embryological origins
Celiac gut= foregut
Midgut=superior messenger if artery
Hindgut=inferior mesenteric artery
