Cardiovascular Flashcards
Which germ layer does the cardiovascular system originate from?
Haemangioblasts which form in ‘blood islands’ in the splanchnic mesoderm
What embryological process puts the veins of the heart behind the arteries?
Looping of the primitive heart tube
What primitive structures develop into the right atrium?
Most of the primitive atrium and the sinus venosus
What primitive structures develop into the left atrium?
Sinus venosus and some of the primitive atrium.
Where is the oblique pericardial sinus found?
The cul de sac of the pericardium underneath the heart formed by the process of looping.
Where is the transverse pericardial sinus found and what is it useful for clinically?
Where the pericardial sac meets at the top of the heart, between the superior vena cava and the aorta/pulmonary artery.
Clamp to put the heart on bypass.
What is the ductus arteriosus and where can it be found?
It is a fetal shunt that allows blood to bypass the lungs during gestation. It connects the pulmonary artery to the proximal descending aorta.
Which embryological aortic arch develops into the mature aortic arch?
Arch 4
Why does the laryngeal nerve descend further down on the left than the right?
Descends to t4/5 on the left and only t1/2 on the right because on the left it has to go around the ductus arteriosus but on the right apoptosis of the primitive aortic arches allows it to be shorter.
Name the three types of artery and how you would identify them in a histological slide.
Elastic - thick Tunica media with lots of elastin
Muscular - thick tunica media with lots of smooth muscle
Arterioles - thin tunica media
Name three types of capillary and give an example of where they can be found.
Continuous - skeletal muscle
Fenestrated - endocrine glands
Sinusoidal - liver, spleen
What are the layers of a blood vessel from superficial to deep?
Tunica adventitia - connective tissue
Tunica media - extra cellular elastic
Tunica intima - 1 cell thick with internal elastic lamina
Which type of blood vessels contain valves?
Veins and venules
What are venae comitantes and give an example of where they can be found?
A pair of veins that follow an artery, encapsulated in a sheath of fascia eg brachial artery
What are vasa vasorum?
Blood vessels that supply and drain other large vessels such as the aorta. Found in the tunica adventitia.
What are the atrioventricular valves called?
Left - mitral, bicuspid valve
Right - tricuspid valve
Describe the seven phases of the cardiac cycle.
1. Atrial contraction SA node fires to AV node 2. Isovolumetric contraction Septum, bundle of His, inner to outer surface of the ventricles contract 3. Rapid ejection 4. Reduced ejection 5. Isovolumetric relaxation 6. Rapid ventricular filling 7. Reduced ventricular filling
Distinguish systole from diastole.
Systole - contraction
Diastole - relaxation
During which phases are both the mitral valve and the aortic valve closed?
Isovolumetric contraction and isovolumetric relaxation.
Why is a small amount of valve regurgitation normal?
A small amount of blood must regurgitate back to close the valve.
At what stage of the cardiac cycle does the aortic valve open?
Rapid ejection
At what stage of the cardiac cycle does the mitral valve open?
Rapid ventricular filling
What is the first stage of septation in the development of the cvs and where does it occur?
Formation of emdocardial cushions in the atrioventricular canal
Describe the process of septation of the atria.
- Growth of septum primum and the hole underneath it - the ostium primum
- Before this is complete, the ostium secundum forms within it by apoptosis.
- The septum secundum forms behind it with a hole in it known as the foramen ovale
The process allows blood to constantly flow from right to left which is necessary for intrauterine life. After septation blood flows from the right atrium to through the foramen ovale to the left atrium through the ostium secundum
Describe the process of septation of the ventricles.
- Muscular growth of the primary inter ventricular foramen
2. Membranous growth of connective tissue, proliferating from the endocardial cushions to fill the gap.
What is the name of the fetal shunt which bypasses the liver and what is the name of its remnant in the adult?
Ductus venosus - ligamentum venosum
What is the name of the fetal shunt which bypasses the lungs to prevent deoxy blood missing with oxy. And what is the name of its remnant in the adult?
Ductus arteriosus - ligamentum arteriosum
What is the name of the fetal shunt which allows blood flow between the atria in order to bypass the lungs, and what is the name of its remnant in the adult?
Foramen ovale - fossa ovalis
What is the name of the fetal shunt which provides nutrients to the fetus and what is the name of its remnant in the adult?
Umbilical vein - ligamentum teres
Which arteries originate at the aortic trunk?
Right to left
Brachiocephalic
Common carotid
Subclavian
Describe the layout of the coronary arteries.
Right coronary - right marginal
Left coronary - left anterior descending, left marginal, left circumflex
What are the names, locations and functions of the two vascular sinuses?
Aortic sinus
Opening in the aorta behind the aortic valve
Allows coronary arteries to fill during diastole
Coronary sinus
Drains to the right atrium on the posterior surface
Drainage of the coronary veins
What embryological feature do the cardiac auricles originate from? What is their function in the adult?
Embryological atria
Can expand the capacity of the adult atria if required
What causes heart looping to occur?
Continual growth of the heart tube in the pericardial cavity which does not stretch or grow.
What is the embryological derivative of the left ventricle?
Primitive ventricle
What is the embryological derivative of the right ventricle?
Bulbus cordis
What does the process of septation achieve?
Divides right and left heart, keeping blood flowing right to left at all times.
Describe the cardiac action potential.
- Voltage gated Na channels open - depolarisation
- Na channels start to inactivate - pointy bit on graph
- Voltage gated Ca channels open, balanced with leak K channels - plateau
- Ca channels inactivate, delayed voltage gated k channels open - hyperpolarisation
Describe the action potential at the SA node.
- Hyperpolarisation triggers HCN channels Na slow influx - depolarises to threshold
- Voltage gated Ca channels open - full depolarisation
- Voltage gated k open - hyperpolisation
What causes the natural automacity of the SA node?
The funny current
When the action potential reaches cardiac myocytes, what is the molecular process that causes contraction?
- Ach release
- Beta 1 adrenoceptors - Gs protein - camp pathway - pka activates ca channels - Ca release
- Ca - Ca positive feedback via ryanodine receptor
- Ca binds to troponin - moves tropomyosin
- Myosin binds to actin heads
When the action potential reaches blood vessel smooth muscle cells, what is the molecular process that causes vasoconstriction?
- Ach release
- Alpha 1 adrenoceptor - Gq protein - IP3 pathway - Ca release
- Ca activates myosin light chain kinase
- MLCK phosphorylates myosin
- Myosin binds to actin heads
Which type of heart defects are acyanotic? Which are cyanotic?
Acyanotic - left to right shunts
Cyanotic - right to left shunts
Give three examples of congenital heart defects which cause a left to right shunt.
Just a hole-
Atrial septal defects - eg patent foramen ovale
Ventricular septal defects
Patent ductus arteriosus
Give an example of a congenital heart defect which causes a right to left shunt.
Tetralogy of Fallot
What needs to go wrong in the heart for there to be a right to left shunt defect?
Hole + increased pressure from the right eg pulmonary stenosis or right sided hypertrophy in heart failure
What are the consequences of a left to right shunt defect?
ASD - Blood goes to the lungs twice so increase in pulmonary pressure
Increased preload on right heart. Eventual right heart failure
VSD - (as above plus…) High pressure blood goes to the lungs twice so lung damage and the left heart’s effort is wasted. Cardiac output has to increase so left heart fails.
Describe the 4 defects associated with tetralogy of fallot.
- Ventricular septal defect
- Aorta stems from both ventricles
- Pulmonary artery squashed
- Right ventricular hypertrophy
Why do people with tetralogy of fallout tend to live for years without diagnosis?
Squashed pulmonary artery increases pressure on the right. This balances out the ventricular defect and prevents left to right shunt.
What would be the prognosis for a patient with tetralogy of fallot left untreated? What is the treatment given to a baby?
Blood bypasses the lungs, so cyanotic, exercise intolerance, potential for hypoxia and sudden death
Prostaglandin e1 to keep the ductus arteriosus open
Which arteries branch off the celiac trunk? Which vertebra is it level with? What does it supply?
Splenic artery
Left gastric artery
Common hepatic artery
At level of t12 to supply the foregut
What is the main process which maintains the venous pressure?
Starling’s law - increase vp, increase Stoke volume. More in more out.
What are the main processes which determine the arterial pressure.
Total peripheral resistance
Baroreceptors in carotid sinus
Outline Starlings law of the heart.
Increase venous pressure, increase filling, increase stroke volume. More is removed from the veins each beat, regulating the venous pressure back down to normal.
Define contractility of the heart.
The inherent ability to contract caused by the strength and stretch of bonds between actin and myosin fibres.
Increase contractility with the same venous pressure, increase stroke volume.
But only till the point where the ventricle has been stretched to its maximum.
How do the baroreceptors in the carotid sinus work?
Carotid sinus is a weaker wider area of arterial wall that is sensitive to pressure.
Decrease pressure signals to the medulla - increase sympathetic to increase contractility (b1 adrenoceptors) and decrease parasympathetic to increase heart rate (m2 muscarinic)
What is cardiac output made up of?
Stroke volume and heart rate
Define total peripheral resistance. Which factors can influence it?
Total force opposing blood flow in the vasculature. Mainly produced in the arterioles.
Viscosity of blood, diameter of vessel, turbulent flow.
If my heart rate (only) was artificially increased, how would my body return it to normal?
Increase cardiac output, decrease venous pressure, decrease stroke volume, decrease heart rate (starlings law that in equals out)
How does the body regulate against postural hypotension (normally)?
Decrease venous pressure, decrease cardiac output, decrease arterial pressure, baroreceptors increase heart rate and increase resistance by vasoconstriction.
Give an example of a situation when the baroreceptors reflex is not beneficial. How does the body deal with that situation?
Haemorrhage. Decrease arterial pressure makes the baroreceptors increase hr and vasoconstrict so there is an increase in blood loss.
Instead auto transfusion (shunted out of capacitance vessels) from nearby tissue and veno constriction can help temporarily.
How does the body self regulate blood pressure after light activity or digestion which increase local vasodilation?
Increase in local vasodilation, decrease in total peripheral resistance, increase venous pressure and decrease arterial pressure
Increase cardiac output
Decrease venous pressure and increase arterial pressure
How would an increase in total peripheral resistance affect venous and arterial blood pressures?
Arterial pressure increase
Venous pressure decrease
How would an increase in cardiac output affect venous and arterial blood pressures?
Increase arterial pressure
Decrease venous pressure
Why can the body not self regulate long term hypertension?
Increase venous pressure, increase cardiac output, increase arterial pressure, increase total peripheral resistance, increase arterial pressure, self perpetuating.
What is a normal bp in the aorta?
120/80
What is a normal bp in the right atrium?
5 (no systolic pressure)
What is a normal bp in the right ventricle?
20/5
What is a normal bp in the pulmonary artery?
20/10
What is a normal bp in the left atrium?
5 (no systolic)