Cardiothoracics Flashcards
What causes a valve to open?
Pressure in greater in the given chamber in comparison to the next chamber or artery.
What are septal defects?
A whole in the heart, reducing the efficiency of the heart.
Can cause long-term structural changes due to pressure changes and resulting hypertrophy (to make up for changes in pressure)
Can be atrial or ventricular
What are calcification of valves and what do they cause?
Calcium build up on the valves of the heart.
Common, especially in elderly
Valve may not close properly, which will allow backflow of blood during diastole.
Can cause hypertrophy as heart has to work harder
What are the heart sounds you listen to within the heart?
1st is AV valves closing, ventricular pressure would then increase. Should just hear one sound as the two valves should close at the same time.
2nd sound is the pulmonary and aortic valves closing. Should be one sound as they close at the same time.
What are Korotkoff sounds?
Sound of turbulent blood flow, related to taking blood pressure
What controls blood flow?
Valves opening and shutting
What way do ventricles contract?
From the apex of the heart so they can push blood in the correct direction
What is the stroke volume of the heart?
Amount ejected per beat
How can you increase the stroke volume of the heart?
Strenuous activity increases contractility which will increase amount being ejected as well as increasing heart rate
How do you calculate cardiac output?
Stroke volume x Heart rate per minute
Stroke volume normally ~5L/min
Each side pumps about 5L
What is Starling’s law?
The more you stretch the heart, the harder it contracts
What determines the heart rate?
SA Node
Wants to work at 100bpm, but it is kept under control
What does the AV node do?
It slows conduction and can act as secondary pacemaker
What causes fibrillation?
SA node??
Lack of equal conduction to either side of heart, no coordination
Ventricular fibrillation will kill you
What does an ECG do?
Detects phasic changes in potential difference between two electrodes
Allows you to track heart rhythm and electrical activity
What does a P wave measure
Atrial depolarization
What does the QRS complex measure?
Ventricular depolarization
this is when they should start to contract
What does the T wave measure?
Ventricular repolarization
What does an ECG NOT tell you?
Does not tell you how well the heart is contracting
Why dont we see atrial repolarization?
It is hidden by the QRS complex
What is the PR interval indicating?
A delay in electrical transmission through the AV node
What does the ST segment represent, and how can it be used in diagnosis?
The time between depolarization and repolarization of the ventricles.
Important in diagnosing myocardial ischemia
What does the R-R interval on an ECG measure?
Time between heart beats
Can indicatin brady/tachycardia
What phase (0-4) of cellular action potential is represented by the ST segment?
Phase 2- inward movement of calcium leading to the plateau phase (balance of Ca and K movement), seen as the ST segment (i.e. may change in patients with an MI)
Refractory period stops us from continually activating the heart, and is the plateau phase
Important in diagnosing myocardial ischemia (it is changed, and can be depressed or elevated on an ECG in comparison to the PR segment)
What does the R-R interval measure?
Time between heart beats
Can indicating brady/tachycardia
Describe the phases of action potential in a cardiac myocyte.
Phase 0- Rapid Na influx causing depolarization
Phase 1- minor repolarization (initial K efflux while Ca channels slowly open)
Phase 2- influx of calcium leading to the plateau phase (balance of Ca and K movement), seen as the ST segment
Phase 3- efflux of K causing repolarization (Ca channels closing)
Phase 4- Ca/Na gradually leaks into cell reducing permeability of potassium so less moves out, more Ca moves in, resulting in small creep up to the threshold
How does input from the Vagus nerve change heart rate? Include ions in your answer
Acetylcholine release from Vagus nerve binds to M2 and keeps heart rate lower by increasing permeability to potassium so it is able to leak out, taking longer time to reach threshold
How does the SNS increase heart rate?
Noradrenaline release from SNS binds which increases calcium influx into the SA node, reaching threshold sooner
What causes muscles in the heart to contract?
Calcium influx through T-tubules
Can cause calcium-induced calcium release, which will cause the myocyte to contract
What is digoxin?
A drug that increases intracellular calcium causing the heart to contract more strongly.
Explain the movement of ions during the membrane potential plateau in the action potential of cardiac cells.
Sodium moves in causing depolarization which switches on potassium currents causing K to move out, causing repolarization.
This opens Calcium channels, which moves Ca in, causing a balance (outflux K vs Ca influx) out giving plateau.
Ca will eventually shut, and K will continue to exit, causing repolarization
What is inotropy
Strength of contraction
What is the dromotropy?
Speed of electrical impulses within heart
What cells line the vessels and inside of heart chamber?
Endothelial cells
Why are endothelial cells important in the vessels?
Prevent platelet aggregation (nitric oxide and prostacyclin)
Local blood pressure
Angiogenesis
Permeability barrier for nutrients/fluid
,
.
How does calcification of vessels impact blood pressure?
High calcification score will increase chance of coronary event.
It reduces elasticity, increasing blood pressure within the vessel.
How do you measure the mean arterial blood pressure?
Diastolic BP + 1/3 Pulse Pressure (systolic - diastolic)
This is the average pressure throughout the system
OR MAP= cardiac output x total peripheral resistance
OR MAP =( (2xDBP) + SBP ) / 3
How much of total blood volume in found in capillaries?
5%
~25000 mLs
What is colloid and hydrostatic pressure?
Osmotic (colloid) pressure drawing fluid back into capillaries (same on arteriole and venule side, overall pressure changes)
Hydrostatic is the pressure of blood being pushed through small area, pushing fluid out of capillaries, higher at arteriole end
What is an exception to the starling pressure forces in circulation?
Pulmonary hydrostatic pressure is much lower (colloid is the same), resulting in net transfer
How can heart failure cause oedema?
Backup of blood in pulmonary circulation, pulmonary hydrostatic pressure goes up pushing fluid into the lungs.
In combination with gravity when lying down, fluid will accumulate, resulting in pulmonary oedema (especially at night).
Can give nitrates, ACE inhibitors to treat.
How can elevation cause high altitude pulmonary oedema?
Low oxygen at high altitudes can cause hypoxic volume vasoconstriction which raises the blood pressure in the vessels, causing fluid to accumulate in the lungs
How do we modify Total peripheral resistance with the use of antagonists?
Selective antagonists
-block alpha 1 adrenoreceptors using antagonists
-Decrease vasoconstrictor tone
-Don’t DIRECTLY change the HR or Cardiac Output
-Prazosin
Non-Selective antagonists (bind alpha 1 and 2)
-Not a great idea cause drugs will feedback on alpha 2 receptor
-Phentolamine
What muscles is used for inspiration?
Diaphragm contracts down, pushing abdominal contents down.
External Intercostal muscles pull ribs up and out
During strenuous inspiration/expiration, what muscles are used?
Diaphragm contracts even more
Inspiratory accessory muscles used (sternocleidomastoid, alae nasi, genioglossus)
Expiration: Abdominal Muscles (rectus abdominus, internal/external obliques, transversus abdominus), and internal intercostals (oppose external intercostals)
How does pressure change with inhalation? Touch on alveolar, pleural, barometric, and transpulmonary pressures.
Breathing in decreases the negative pleural pressure more due to an increase in space.
There is a greater difference in pressure between the pleural and alveolar sacs (increased transpulmonary pressure).
Lungs expand, increasing the volume, alveolar volume increases, and alveolar pressure becomes negative, making it different from the barometric pressure outside, which results in flow of air outside moving inwards in the lungs.
When alveolar and barometric pressure are equal (because of volume (air) moving into alveoli), inhalation is complete.
What is in the upper respiratory system?
Larynx and up
What is the role of the upper respiratory tract?
Warms air, cleans air, and humidify air
How does the upper respiratory tract complete its tasks?
Goblet cells produce mucous that sits on top of cilia and causes particles to stick to it, cilia than move mucous up and out
What receptors are responsible for the cough reflex?
Rapidly Adapting Pulmonary Stretch Receptors (RARS) on epithelium.
What causes the cough reflex?
When sensory neurons (RARs) are activated by particles, signal is passed through vagus sensory nerve to the brain, then information is passed down phrenic nerve causing strong contraction
What makes up the respiratory unit?
Respiratory bronchioles, alveolar ducts, alveoli
What are important characteristics about alveoli?
Polygonal in shape
300-400 million in a person
Type 1 and type 2 epithelial cells
What cells are found at the alveoli?
Type 1 pneumocytes - 97%, primary site of gas exchange
Type 2 pneumocytes- septal cells, produce surfactant which reduces surface tension
Alveolar macrophages- clear up debris
What is bronchial circulation?
Systemic circulation
Bring oxygenated blood to parenchyma of lungs
How much blood is found in the pulmonary circulation?
500mLs
10% of blood
How are arteries in pulmonary circulation different from systemic?
Thin walled, low resistance, high compliance, large diameter
In the pulmonary capillaries, what is alveolar and venous partial pressure of O2 and CO2?
Alveolar
O2- 40 mmHg
CO2- 46 mmHg
Venous
O2- 102
CO2- 40
Alveoli
O2- 102
CO2- 40
In the systemic capillaries, what is tissue and arterial partial pressure of O2 and CO2?
Arterial
O2- 100 mmHg
CO2- 40 mmHg
Tissue
O2- <40
CO2- >46
What is in the respiratory tree?
Conducting airways and respiratory airways
What is the mediastinum, as well as its superior and inferior components
Thoracic cavity, apart from the lungs.
Superior- T1 to top of manubrium, down to sternal angle to t5
Inferior- Sternal angle down to diaphragm
What components make up the inferior mediastinum?
Posterior (aorta, oesophagus)
Middle (heart)
Anterior (fat and bottom remanence of thymus)
What is the difference in laminar and turbulent blood flow?
Turbulent flow can increase with age, and can be caused by increases in blood viscosity or speed
Laminar is when the blood flows parallel, in concentric layers, down a vessel.
What are the layers of the serous pericardium?
Parietal, pericardial space (with serous fluid, to reduce friction), and then visceral layer (deeper)
Following movement of blood returning to the heart from systemic circulation, describe the chambers and major structures it will pass
Superior/Inferior Vena Cava -> right atrium -> tricuspid valve -> right ventricle -> pulmonary valve -> lungs -> left atrium -> bicuspid (mitral) valve -> left ventricle -> aortic valve -> aorta
What are the first four branches of the aorta, and what do they supply?
1st- Coronary Artery (supplies heart)
2nd- Brachiocephalic trunk (divides into right subclavian and right carotid, both supply brain)
3rd- Left carotid (supplied brain)
4th- Left subclavian (brain)
How does blood pass through foetal circulation?
From mother, through placenta, follows along umbilical vein bypassing foetal liver, ductus venosus conjoins with inferior vena cava and enters right atrium
What is the Foramen Ovalle?
Allows blood that passes into foetal right atrium to move directly into the left atrium
Becomes Fossa Ovalis once born (remanence)
What is the coronary sinus?
Where venous blood from the heart enters
What are the aortic sinuses?
Dilations above the aortic valve.
3 in total, from 2 the right and left coronary arteries stem.
What is the right atrial appendage?
Extra portion of right atrium, where a pacemaker would be placed
What is the crista terminalis?
At the opening of the right atrial appendage
The site of origin for the musculi pectinali
They allow for stretch and improve volume
Where does the musculi pectinati muscle originate?
The cristae terminalis
What is a septal defect?
The septum (between left/right atrium and left/right ventricle) can have a whole.
Can be atrial, atrioventricular, and/or ventricular.
Causes blood to move freely between chambers (typically moving right as left side is stronger), forces heart and lungs to work harder.
Can spontaneously heal, or may require surgery (especially is atrioventricular)
Moving anterior to posterior, what are the heart valves?
Pulmonary semilunar, aortic semilunar, tricuspid, mitral.
What are chordae tendinae?
Joined to the cuspid leaflets of the valves and stop the valves from flipping back into the atrium.
Attached to papillary muscles which contracts to help prevent moving back into atrium.
Pressure build up is what causes them to open, and ventricular pressure causes them to close.
Not on the semilunar valves
What supplies the heart with blood?
Right and left coronary arteries which extend from aorta.
Right gives rise to marginal
Left moves behind pulmonary trunk, and becomes circumflex artery which moves behind the heart to anastomose with arteries behind the heart, and eventually give rise to the posterior interventricular artery (moves around right aspect of heart to meet with right coronary arteries).
Left also branches into the anterior interventricular artery, which moves to the posterior to meet with the posterior interventricular artery.
What veins drain the heart?
Coronary Sinus vein drains into the right atrium.
Small cardiac vein (right inferior aspect), middle cardiac vein (posterior, middle), anterior cardiac veins (right, anterior) all meet up with the great cardiac vein which drains into the coronary sinus.
What diseases impact coronary arteries?
Coronary Artery Disease
Narrowing and/or blocking of vessels suppling the heart.
They are “end” arteries, meaning they only supply one specific area, therefore, if blocked, parts of the heart may die.
What is ischemia
A reduction in blood oxygen
can result in collateral circulation (development of new blood vessels that moves around the area of blocking)
What is angina?
Pain of the chest
Related to Coronary artery disease
In terms of cardiac infarction, what areas are typically affected at what percentage?
Anterior interventricular branch of Left Coronary Artery (40-50%)
Right Coronary Artery (30-40%)
Circumflex branch of the Left Coronary Artery (15-20%)
So 70% are due to left coronary artery block.
What veins can be used for a CABG?
Saphenous vein (lower limb) Internal mammary artery (by sternum)
What is the modulator band and what is its purpose?
Also called septomarginal trabecula
Allows for more rapid conduction across to anterior papillary muscle
Starting at the SA node, describe the movement of electrical conduction.
SA node -> AV node -> AV bundle -> split at top of interventricular septum -> R/L bundle of His -> septomarginal trabecula -> Purkinje fibres (help form synchronous contraction)
What portions make up the pharynx?
Nasopharynx (soft palate, nose)
Oropharynx (from soft palate down to epiglottis),
Laryngopharynx (epiglottis down to bifurcation to trachea and oesophagus)
Paranasal Sinuses- air filled cavities beside the nose
If a foreign body entered the trachea, what bronchus is it more likely to enter and why?
The right
It is more vertical, has a greater diameter, shorter, and is more of a continuation of the trachea.
How many lobes are on each side of the lung?
3 on right
2 on left
What are the tracheal respiratory epithelium?
Pseudostratified ciliated columnar epithelium with goblet cells
How do epithelial cells change, moving from the trachea, to lobular, to terminal, to respiratory bronchiole, and finally the alveolar ducts?
Trachea- ciliated columnar epithelium
Lobular- Ciliated cuboidal
Terminal-ciliated and non-ciliated cuboidal
Respiratory- ciliated and non-ciliated cuboidal epithelial cells with type 1 pneumocytes
Alveolar ducts- Type 1 (95%) and Type 2 pneumocytes
What cells are present in each of the following areas of the respiratory tract; Trachea, lobular, to terminal, to respiratory bronchiole, and finally the alveolar ducts?
Trachea- Goblet cells, basal cells, seromucous gland cells, neuroendocrine cells, and brush cells
Lobular- Basal cells, Brush Cells, seromucous gland cells (only upper portion)
Terminal- Clara cells, Brush cells
Respiratory- Clara cells, Type 1 pneumocytes
Alveolar ducts- Type 1 and Type 2 pneumocytes (5%)
What is the purpose of type 2 pneumocytes?
Surfactant production- it increases compliance, prevents collapse (called atelectasis) at end of respiration. Premature babies (before 34 weeks) may not produce this, and are therefore at risk for lung collapse (may be given it)
What is the purpose of type 1 pneumocytes?
Gas exchange
What separates the 3 lobes of the right lung?
Oblique fissure- separates inferior lobe from middle and top lobes
Horizontal - Separates superior lobe from middle lobe
Where do you listen to the apex of the lungs?
Rises about an inch above the medial 1/3 of the first clavicle
What factors impact blood flow?
Pressure gradient in vessel Length of vessel Viscosity of fluid in vessel Diameter of vessel Resistance (as vessel branching increases, so does resistance, reducing flow)
When investigating circulation, what factors impact susceptibility to deep vein thrombosis?
High altitude
Immobility- pooling of blood
Dehydration (and alcohol consumption)- increases viscosity and reduces blood flow
How do vein and artery vessels differ in terms of layers and components?
Veins -valves -larger lumen -thicker tunica externa Arteries -thicker tunica media -higher pressure -internal and external elastic lamina surrounding tunica media
What is preload?
Amount of blood moving back into the right atrium
-this can be a problem in people with heart failure, or in people with angina as the heart needs to work harder to increase output
How can you reduce preload using drugs?
Nitro-glycerine (glyceride tri-nitrate)
Causes venodilation, reducing central venous pressure, causing a reduction in pre-load/LVEDV, reducing cardiac output, work, and O2 consumptions (relieving angina).
Increase flow to head and can cause headaches.
You spray it under tongue (avoids first past metabolism), its absorbed quickly, and alleviates anginal attack quickly
What are the typical histological features of a cardiac myocyte?
Mononuclear, striated, high numbers of mitochondria, intercalated discs and gap junctions (coupling of metabolic and electrochemical functioning)
What nerves supply the heart?
Vagus nerve (parasympathetic) and sympathetic nerves
What is the moderator band?
It is a thickening of muscle present in the right ventricle and carries the right bundle branch to the anterior papillary musculature
What is the smooth muscle in the posterior aspect of the trachea called?
Trachealis
